There was an interesting story in the Las Vegas Journal Review on August 20th. which had a passage and quote from California Senator Diane Feinstein (emphasis mine):
Both U.S. Sen. Dianne Feinstein, D-Calif., and Ensign announced that they and other members of their delegations will reintroduce a bill in Congress to provide $390 million for additional preservation projects at Lake Tahoe.
Ensign said some have called the summits “publicity gimmicks,” but they are an important way to focus at what still needs to be done.
He said he has noticed how the dense forest around the Nevada side of the lake has been thinned dramatically in an effort to prevent forest fires. Feinstein praised Nevada for its efforts to stop fires, adding she wishes she saw the same results in California.
Unlike other officials, Feinstein blamed global warming for the degradation of Lake Tahoe.
“The real culprit in my mind is global warming,” she said.
Since 1970, the water temperature of the lake has risen by about three degrees, according to scientists.
I have no dispute about the temperature rise, but I do have a dispute with her assignment of blame, especially since she is my senate representative. I’ve found something interesting that leads me to think that global warming and Lake Tahoe’s water temperature are not significantly connected.
First about her statement. Perhaps Senator Feinstein is recalling this article on Lake Tahoe from 2004 in the San Francisco Chronicle.
There was a weak caveat in that article that Feinstein likely ignored if she read it:
No one can be certain if any given change is due to human activity, but the widely held assumption is that emissions of carbon dioxide and other heat-trapping greenhouse gases are involved.
I’d like to add a reason of my own for Senator Feinstein and the Chron: turbidity.
For those who don’t know, water turbidity is defined by the EPA as:
Turbidity is a principal physical characteristic of water and is an expression of the optical property that causes light to be scattered and absorbed by particles and molecules rather than transmitted in straight lines through a water sample. It is caused by suspended matter or impurities that interfere with the clarity of the water. These impurities may include clay, silt, finely divided inorganic and organic matter, soluble colored organic compounds, and plankton and other microscopic organisms.
The EPA definition comes from the publication American Society for Testing and Materials, ASTM (2000) D1899-00 Standard test method for turbidity of water. Annual Book of ASTM Standards, Vol. 11.01.
Water clarity and turbidity has been a big issue with Lake Tahoe for many years, and there have been campaigns to reduce the amount of runoff into Lake Tahoe that is a direct consequence of the building boom that has occurred around the Lake in the last century. “Keep Tahoe Blue” is one of those and you’ll see these bumper stickers all over California:
Senator Feinstein is certainly aware of this effort to reduce turbidity and maintain clarity in Lake Tahoe, in fact she is one of the champions of the cause. She drafted the Lake Tahoe Restoration Act in 1999
Her own website has quite a section on it:
http://feinstein.senate.gov/tahoe_restoration_act.html
In that web page is this passage and graph related to it:
Sediment and algae-causing phosphorus and nitrogen, all of which contaminate the water in the lake, continue to flow into Lake Tahoe from a variety of sources. Destruction of wetlands, wet meadows and stream habitat has compromised Lake Tahoe’s ability to cleanse itself of pollutants.
There’s not one word on Feinstein’s Lake Tahoe Restoration Act web page about global warming or climate change. Zilch, nada, zero. I’ll also point out that it looks like the page has not been updated in quite some time. Perhaps after passing the act in 1999 her interest waned.
The graph above can also be found in a different form from the 2009 State of the Lake Report from the UC Davis Tahoe Environmental Research Center (TERC):
TERC writes about the clarity as defined by the Secchi depth measurement:
Secchi depth (the point below the lake surface at which a 10-inch white disk disappears from view) is the longest continuous measurement of Lake Tahoe clarity. The annual Secchi depth is the average of 20 to 25 readings made throughout the year. While lake clarity has improved for brief periods since 1968, the overall long-term trend has shown a significant decline. In the last eight years, Secchi depth measurements have been better than predicted by the long-term linear trend. Statistical analysis suggests that the decline in Lake Tahoe’s clarity has slowed, and is now better represented by the curve below than a straight line. In 2008, the Secchi depth was 69.6 feet and virtually the same as 2007. With the exception of 2005 and 2006, precipitation has been low during the past 8 years. The response of the Secchi depth to a series of normal and above normal years will be very instructive.
What is interesting is that the top two values of the TERC graph occurred in 1997 and 1998, the years of the super El Nino and massive amounts of rainfall (and runoff) in California. I wasn’t surprised to see those years as the peak of low clarity of the last 40, but I was surprised that TERC does not mention it in the report. Perhaps it is counter to the TERC mission to blame nature for peak values.
So we’ve established two things:
1) The water temperature of Lake Tahoe has been increasing. From the LVJR news article:
Since 1970, the water temperature of the lake has risen by about three degrees, according to scientists.
2) As measured by TERC, the turbidity of Lake Tahoe has been increasing, thus reducing the clarity.
While lake clarity has improved for brief periods since 1968, the overall long-term trend has shown a significant decline.
I should add, I think it is a good thing to reduce the runoff issues that contribute to the reduced clarity of Lake Tahoe. This is a clear case where human activities have made a measurable impact on an ecosystem. That said, I believe that same human impact affects the lake temperature. As Dr. Roger Pielke Senior argues, land use and land cover changes have significant local and regional impacts. Lake Tahoe’s clarity decline has been established to be a result of increased runoff and pollutants resulting from the local population increase around Lake Tahoe in the last century.
This USGS publication, Stream and Ground-Water Monitoring Program, Lake Tahoe Basin, Nevada and California, defines the issue:
Lake Tahoe has long been admired for its alpine setting and the clarity of its water. During the last half-century, however, human activity in the lake basin has increased while the lake has been losing water clarity at a rate of about 1 foot (ft) per year.
Now, for a look at what I believe to be a significant contributor to the water temperature increase in Lake Tahoe.
One thing nobody seems to be talking about is the relationship between water turbidity and temperature. It is a quite simple physical mechanism, and quite well established.
For example, here is a peer reviewed study, published in International Journal of Biometeorology on mosquito larvae and increased turbidity contributing to increased water temperature.
The effect of water turbidity on the near-surface water temperature of larval habitats of the malaria mosquito Anopheles gambiae
K. P. Paaijmans &W. Takken & A. K. Githeko & A. F. G. Jacobs (full PDF here)
In that study they write in the abstract:
Water turbidity affects water temperature, as suspended particles in a water column absorb and scatter sunlight and hence determine the extinction of solar radiation. To get a better understanding of the relationship between water turbidity and water temperature, a series of semi-natural larval habitats (diameter 0.32 m, water depth 0.16 m) with increasing water turbidity was created. Here we show that at midday (1300 hours) the upper water layer (thickness of 10 mm) of the water pool with the highest turbidity was on average 2.8°C warmer than the same layer of the clearest water pool. Suspended soil particles increase the water temperature and furthermore change the temperature dynamics of small water collections during daytime, exposing malaria mosquito larvae, which live in the top water layer, longer to higher temperatures.
That is a small scale experiment in shallow water. On a larger scale there are lots of other scientific references available that demonstrate a relationship between increased water turbidity and increased water temperature. Here’s one published in BAMS from the Naval Research Lab looking at turbidity in the Black Sea and water temperature relationships. (Kara et al 2005, PDF here)
The K.P. Paaijmans et al study above writes about the Kara et al 2005 Black Sea Study:
In larger water systems, turbidity is known to change the water temperature. In seas, for example, a high turbidity changes the sea surface temperature (SST), and model simulations of the SST should include turbidity to account for variations in solar radiation extinction (Kara et al. 2004). Kara et al. (2005) demonstrated that using a clear-water constant attenuation depth assumption as opposed to turbid water type to model the SST of the Black Sea, resulted in monthly SST biases as large as 3°C in the summer period.
What I find amazing is that Senator Feinstein, who championed a bill to save Lake Tahoe from reduced clarity, apparently has no idea of the relationship between water clarity and water temperature. Apparently TERC doesn’t see it either, and prefers to blame increased water temperatures on climate change.
Of course, if we take the “global warming” route followed by Senator Feinstein, it can be argued that Lake Tahoe’s increasing air temperature is a significant contributing factor to the Lake Water temperature:
Source: NASA GISTEMP
But then you see what the measurement station looks like. Then of course that station’s data purity is brought into question for reasons of siting as well as local development nearby in Tahoe City.
Of course, we don’t know exactly what the magnitude of contribution to warmer temperatures at this station from those siting issues are, and the burn barrel has since been removed from the USHCN station enclosure shortly after I highlighted it in June 2007. The tennis courts surfaces nearby may have an effect on air temperature also.
What is important to note though, and this fact is lost on many politicians, is that the lake itself, as a large solar insolation heat sink, has more effect on local air temperatures than the other way around. The reduced clarity contributing to increased water temperature issue likely is a factor in the USHCN weather station data, given it is just a few feet from the lake.
And that brings us back to the quote from the original newspaper article:
Since 1970, the water temperature of the lake has risen by about three degrees, according to scientists.
Eyeballing our Tahoe City USHCN station graph from GISS above, it looks like we have a trend since 1970 not far from that value. Using air temperature from our world renowned center for global warming data, NASA GISS, one can certainly draw a correlation between the air temperature of the Tahoe City station and the water temperature of the lake.
But as we’ve heard so many times, correlation is not causation.
Feinstein appears to completely miss the physical connection between increased water temperature and the Lake Tahoe water clarity cause she championed. Now the need for an additional $390 million. Before she spends more citizen’s money chasing this global warming issue, let us hope she gets some “clarity” on the issue soon.
Ever wonder where some of that money goes? See TERC’s headquarters. Nice digs for studying a lake. The field station is not too shabby either.
While TERC has a really nice LEED certified HQ, I can’t find a single publication on their website about water temperature and turbidity. Unfortunately I can’t scan the content of the papers on their website since so few are posted in full text form, just titles.
Given the huge public relations effort to preserve Lake Tahoe’s clarity and, by the view of the lake’s most famous patron, Diane Feinstein, and the apparent connection to global warming, one would think that a water turbidity-temperature study would be something they would want to pursue. Either to confirm it, or to rule it out.
If I’ve missed such a study, please feel free to post it in comments.
Addendum: Additional References on turbidity (originally from comments)
Here is one where reflectivity is examined in the context of turbidity.
Citation: Witte, W. G., C. H. Whitlock, R. C. Harriss, J. W. Usry, L. R. Poole, W. M. Houghton, W. D. Morris, and E. A. Gurganus (1982), Influence of Dissolved Organic Materials on Turbid Water Optical Properties and Remote-Sensing Reflectance, J. Geophys. Res., 87(C1), 441–446.
http://www.agu.org/pubs/crossref/1982/JC087iC01p00441.shtml
“From these data it is clear that dissolved organic materials decrease upwelled reflectance from turbid waters. ”
Here is a primer on suspended solids in water from the City of Boulder Water Quality Monitoring:
http://bcn.boulder.co.us/basin/data/BACT/info/TSS.html
“High TSS (total suspended solids) can also cause an increase in surface water temperature, because the suspended particles absorb heat from sunlight.”
Here is another identical passage from the New York Harbor Survey that cites TSS and water temperature:
http://www.nynjcoast.org/NYCDEPHarbor_survey/docs/water_clarity/total.htm
“High TSS can also cause an increase in surface water temperature, because the suspended particles absorb heat from sunlight.”
From Brockport University
http://vortex.weather.brockport.edu/~jzollweg/oakorchard/docs/waterquality.pdf
On page 1 under TDS (Total Dissolved Solids):
“Similar to TSS, high concentrations of TDS may also reduce water clarity, contribute to a decrease in photosynthesis, combine with toxic compounds and heavy metals, and lead to an increase in water temperature.”
For a fairly recent and mostly comprehensive study of Lake Tahoe’s warming, see Coats et al 2006
http://www.springerlink.com/content/6384855p5513l393/fulltext.pdf
1 Quote – I have no dispute about the temperature rise, but I do have a dispute with her assignment of blame, especially since she is ***my*** senate representative (my emphasis).
2 Quote – If I’ve missed such a study…
I’m sorry to say that but you missed other important issues. Search google for “senator feinstein conflict of interests”. She’s not about science, she’s about money.
BTW. And such Madam is ***your*** senate reprepresentative?
Regards
Since I no longer live in California, I have come up with some ways to reduce ghg emissions for California. Where we now live we have two things not found in California, clean air and coal.
Clearly we should regulate going to places for recreation in California and Nevada.
Nicely done Anthony.
What planet do people like her hail from? Oh, yeah. I forgot. She’s from InSaneFrancisco.
This is another amazing story and the fact that Senator Feinstein is “your Senator”, almost makes it personal.
I really hope this story breaks big and will hit the blogs World Wide and I really hope you can save the already stressed public budget the 390 million dollar Feinstein applied for and further discredit the Global Warming Madness and the incredible spending frenzy of the current administration.
Very nice job Anthony.
Lake Tahoe is on average 1000 feet deep. When these people speak of Lake Tahoe being 3 degrees warmer, I expect they only mean the surface temp. The bottom of the lake will ony be 4 Centigrade
One other thing, while I’m thinking about it. Hey ECONUTS! We’ve saved Love Canal, cleaned up all kinds of lakes and rivers (including the Great Lakes ), cut smog to nearly nothing in the US, scrubbed our chimneys, put catalytic thingies in our cars ( and seat belts ), taken care of nuke waste ( if you’d let us ), figured out how to feed 7 billion people, saved the damn whales, baby seals, salmon, lizards, rats, and freaking SPOTTED OWLS! GIVE IT A REST ALREADY! You freaking WON! Now shut the hell up and leave us alone!
I like your photographic example of data turbidity, Anthony … which also causes warming 🙂
It simply befuddles the mind how many edumacated people actually think that a warmer atmosphere “heats” the ocean (or lake, in this instance) without considering how high the atmospheric temperature would have to get in order to “heat up” an ocean of any depth.
Is there a relatively simple mathematical process which would illustrate this fallac?
Anthony,
Excellent point.
I wonder if the turbidity of the ocean is tracked?
REPLY: As a whole, probably not, I’m not aware of any database for the whole ocean. We should probably have one. But, in places where pollution laden outflow occurs, such as river outlets, most likely. Satellite imaging certainly shows the near shore turbidity issue clearly:
http://www.eosnap.com/public/media/2009/01/india/20090120-rivers-full.jpg
http://www.eosnap.com/public/media/2009/05/korea/20090518-korea-full.jpg
http://cimss.ssec.wisc.edu/goes/blog/wp-content/uploads/2008/03/080308_modis_truecolor_250m.jpg
and
http://www.nasa.gov/vision/earth/environment/dead_zone.html
It would be interesting to correlate SST’s with turbidity measurements if they exist.
– Anthony
Mark I found this study that may be of interest. SST’s correlated against turbidity using buoy measurements
http://www.stormingmedia.us/94/9443/A944324.html
A small study, only 12 buoys, but the effect appeared in 11 out of 12 – Anthony
When our Wisconsin Demorat politicians begins a sentence with “I really think”
or “In my mud” it always means what they are about to say is backed up by no facts or even logic.
They get away with it because a freindly audience or reporters will not say “Wait a minute, where are the facts to back up what you just said.
That is exactly why the Town Hall meetings are ratteling them. The questioners have the proposed health care bill in there hands and they’ve read it.
The politiciand haven’t read it and aren’t used to people saying “THAT’S NOT WHAT IS SAYS RIGHT HERE”.
Feinstein suffers from the same stupidity.
I read the title incorrectly and had a good laugh.
My $.02 on what may be happening is that surface phosphate levels have trended upwards from a variety of sources. More phosphates seem to be linked to algae blooms in summer months. The algae seems to act like a magnet for other pollutants to attach and float near the surface. And I agree from personal observation that there is a correlation of turbidity to temperature.
And this is where I believe that mankind is ‘somewhat’ responsible for “CLIMATE CHANGE”. The holding back of meltwaters in lakes and reservoirs only to be released later into the oceans that control the climate a whole lotta degrees warmer has got to have a large effect. Even if’n ya doan believe the sun heating up 95% of reflective matter in a thin band that the planets go through as part of “nature”, the sun do shurely warm up them lakes.
Sorry, personal rant. No comment required.
As an environmental engineer specializing in stormwater treatment and quality I know full well the impact of turbidity on water temperature well. A perfect example is a crystal clear river with very low turbidity is always cold, even in summer on a hot day, without particles suspended in the water it can absorb very little heat, the sun instead hits the river bed and tries to warm the rocks at the bottom. A murky river, particularly slow moving ones, will instead be warm in summer.
As a boy I always knew to avoid the clear rivers (though they look the most inviting!) as they were the coldest.
Again, its seems scientists and policy makers cannot see the glasses on the end of their noses and instead blame a real and well documented issue on a unproven hypothesis. This is why few engineers believe in AGW and look down on many modern scientists who appear to have lost the ability to use observation and use logic in place of making toy models and talking green theology
“…the dense forest around the Nevada side of the lake has been thinned dramatically…” It would be interesting to see a plot of this activity as it relates to groundwater runoff quantity, turbidity and temperature.
I believe there have been some papers published on the relationship between algae blooms and increasing temperature within Chesapeake Bay- can’t find at the moment
I realize the burn barrel has been moved and maybe no longer used but I wonder what they burned there. Our county in Washington State no longer allows burn barrels, in part, because folks tend to try to burn all sorts of things that are better sent to a landfill and because the barrels are usually not constructed to facilitate complete combustion. I’m surprised to see they have (had, 2007) them in the Tahoe basin.
Don’t worry about her being your senator – most are just as clueless.
A 1995 paper by Escartin and Aubrey “Flow Structure and Dispersion within Algal Mats” demonstrates that temperature increases of 1.5C are possible in near shore waters as the result of eutrophication
Jeff F (16:55:58) : “…the dense forest around the Nevada side of the lake has been thinned dramatically…” It would be interesting to see a plot of this activity as it relates to groundwater runoff quantity, turbidity and temperature.
Do not be so hasty to blame thinning for turbidity. In the absence of thinning, forest fuels build up, increasing the likelihood of catastrophic forest fire — such as the Angora Fire (June, 2007) which incinerated 3,100 acres of public forest and 254 private homes.
From “Conserve Water at the Source — What We Do, or Don’t Do, in Forests Has a Tremendous Impact on Our Water” by Norman Pillsbury, Ph.D., professor of forest hydrology and watershed management at Cal Poly – San Luis Obispo, in California Forests (Summer 2008, Vol 12 No. 1):
.
Feinstein and Harry Reid have set up a program whereby the US Treasury is used to purchase building lots in Lake Tahoe, for the purpose of allowing them to fester in unmanaged condition. The US Forest Service is now the confused owner of some 3,800 “urban intermix” lots, 1/4 acre mini-wildernesses in the otherwise privately-owned strip of land surrounding the lake. This useless waste of your money has created firetraps in every residential neighborhood, waiting to explode into flames. Furthermore, the Tahoe Regional Planning Agency and the Lahontan Regional Water Quality Control Board have prevented any fire hazard reduction on the “urban intermix” lots by concerned residents who are willing to do it for free, just to save their own homes from impending firestorms.
The USFS is also the confused non-manager of the millions of acres of national forest surrounding the privately-owned strip of land surrounding the lake. They no longer control fuels and so that public forest land is poised for future severe fires which will incinerate whole watersheds. Again, thanks to politicians such as Feinstein and Harry Reid.
How facile and disingenuous of Feinstein and Reid to blame global warming for a problem of their own making! Moreover, the “new preservation projects” will exacerbate the fire hazard and lead to more severe fires, and by extension worsen the turbidity problem and ergo the lake water warming “problem” (if said problem is a problem).
The real problem at Lake Tahoe is a lack of responsible land and forest stewardship on the part of an authoritarian, power-mad government run by a political elite made up of dunderheads.
PS — Note to Curiousgeorge (15:38:08): 15 years ago the Clinton Admin set aside 25 million acres for the northern spotted owl. Since then catastrophic fires have denuded a few million of those acres and the owl population has crashed by 60% or more. The species is being extirpated by non-management on the part of… [see preceding paragraph].
“He said he has noticed how the dense forest around the Nevada side of the lake has been thinned dramatically in an effort to prevent forest fires. Feinstein praised Nevada for its efforts to stop fires, adding she wishes she saw the same results in California.”
But I thought fires were caused by global warming, not bad forest management?
(BTW, LOL, she’s praising clear cutting, as long as it is done by the government to “prevent fires” and not “for profit” by loggers.)
I lived in South Lake Tahoe in the early 1960s. I am today an unabashed capitalist. But Lake Tahoe is not just another body of water. If you have never been there, you should visit. It is a thing of incredible beauty. Emerald Bay is breathtaking.
This is one (of many) very special places where we should go the extra mile and beyond to preserve. As a kid, my family would marvel that you could swim out a few hundred yards into the lake and see the bottom as tho it was just below your feet. Yet, you could dive, and never reach the bottom. You could walk directly into the lake and begin drinking in earnest. I once crouched in shallow water and opened my eyes, and looked upon a surreal underwater landscape. visibility was spectacular. My father died in a tragic accident, and we moved into the central valley. When we then ran water in the kitchen sink, the foul odor chased us from the kitchen. We had become so conditioned.
Some Cool Lake Tahoe Facts: 12 Miles Wide by 22 Miles Long, Lake Tahoe is the 2nd deepest lake in the US at 1645 ft deep. Volume of water in Lake Tahoe is 39 Trillion Gallons. The only outlet is the Truckee river (and on the bridge over that river near it’s origin at the lake, you can see (and feed) trout of gargantuan size. If completely drained, Lake Tahoe could cover the entire state of California in 14 inches of water, and would need 700 years to refill. So much water evaporates from the lake, that its daily evaporation would supply a city the size of Los Angeles. The largest Lake Trout ever caught in the lake was 37lb 6 oz in 1974. The largest Cutthroat was over 31lb and the largest Brown over 26lb.
I will never forget this place with its shockingly deep snowfall and unimaginable beauty. What a place for a little boy to grow up.
$390 million
They approve use of large amounts of our money so seemingly flippantly. They aren’t reducing spending in a recession like all of us have had to do. This $390 million shouldn’t even be considered for years, is ever.
As long as Americans don’t pay attention to who they are voting for we will continue to have more of this. We can yell at the politicians we have now to try to make them change. Or, we can just pay attention from now on and vote better ones in.
I live in Reno. I would like to sue the state of California because they refuse to take any reasonable steps to clear brush and deadfall to prevent wildfires. In the summer it is not uncommon for our air to be brown because there is a fire somewhere in the Sierras. Last year on my yearly 4WD expedition from the Utah border to the California border, the sky turned brown all the way out near Owyhee (hundreds of miles from California) because of California wildfires. At 5pm it might as well have been night. Although I have not calculated it, I would guess that the amount of CO2 released into the atmosphere during the California wildfire season exceeds manmade emissions for the entire US for the entire year.
Marty (16:33:22),
The reality is the reverse of what you state. Generally, reservoirs discharge water that is far colder and clearer than what passed through before the dam went up. When water enters the newly formed lake it slows down and drops its sediment (eventually filling the reservoir with dirt, usually after many, many years, but there are rare exceptions where they fill up quite quickly due to poor watershed management and/or catastophic erosion associated with fires and landslides). The remaining water tends to be clear and cold, even colder where the intakes for the power turbines are.
Even in a reservoir like Lake Powell, on the Colorado River, where water temperatures near the surface can be quite warm (above 85F) in the Summer, the water below the dam supports one of the best trout fisheries in the nation (I don’t know how the recent artificial floods have impacted the trout, but they do seem to be helping the humpback chub, which was the intent).
I work monitoring wildlife in the Tahoe National Forest. I look at annual changes in snow pack as part of my analysis on the changes in bird populations. I also like to swim the lakes in the Lake Basin area. It is very obvious that the lake waters stay cool while being fed by snowmelt but then will warm quite quickly once the snow has melted. The highly publicized study did never took into account the affect of snow pack. They simply assumed AGW attribution. If you look at the 100 year record of snow pack for the month of April on nearby Mt Rose, you will find the peak year for snow pack was 1970 with a declining trend over the past 35 years ( 1970 to present was the time of the warming study). The snow pack correlation would explain Lake Tahoe’s warming trend just as readily as Tahoe City’s rising temperature trend. The article emphasize the warming was spreading to the depths of the lake. The mechanism for this warming is harder to explain if you attribute it to atmospheric warming, but more readily explained by less cold water is feeding the lake depths.
When the article was first written I emailed a few challenges to it but never heard from the authors. The SF Chronicle editor responded to my email but was content to accept the attribution of AGW. Judging from the low snowpack in the early 1900’s I would expect any water temperature trends would actually show cooling from 1900 to 1970, but I didn’t readily find the data to test my hypothesis.
I would assume that turbidity would be a result of warming and increased alagal growth.
Hope this post was sent to Fenstein…
Sadly, Feinstein is also my US Senator.
It is the forest practices of clear-cutting followed by the shutdown of most legitimate logging, coupled with 100 years of forest fire suppression that has led to the ugly conditions of our forests.
The same interests that leveled the forests in Oregon waltzed on in to Calif. and proceeded to ravage the place. We HAD sustainable yields and excellent trees.
Not any more.
Feinstein needs to look in the mirror.
Where was she when the forests were being leveled, and where was she when the burnt areas were lawsuited into non-recoverable tinder-box brush patches?
Out to lunch.
I’ve been on (and in) and over Tahoe for years. From my own Sailor’s and Pilot’s eye the
turbidity issue is real. Also what about UHE ? Iknow the place has got to have some issues there. a warm summer day and the radiation of all that asphalt….
With more population around any lake and the increased runoff which most likely has phoshates from sewers and agricultural activities the algae population in the lake will shoot up proportionaly. The increased algae will make the temperature of the surface water go up since they absorb much solar radiation (lots of non-photonic deactivation mechanisms in plants… thermal deactivation). An algae layer will also give a stagnant water above that does not get mixed well with the bulk water of the lake. On one hand you get a low local CO2 concentration and higher O2. However, due to the increased temperature, the actual concentration of oxygen in the water is low… this is why fish die in lakes with algae bloom problems. The algae and hot water layer keeps the deeper water from getting oxygen. On the other hand, a cristal clear lake without any algae could be a sign of acidification, which is also bad for aquatic life.
Robert Wood (15:31:48) :
I visited the US in 1993 with a mate of mine. We went to Lake Tahoe and had a greatood time. We played a round of golf there and by the time we were on the last green, it was just about pitch black. We heard a shout from the tee: “is there anyone on the green?”
We met a local guy there who had a boat and he took us on a trip on the Lake the next day – a great hangover cure that was. He told us that the local Indians used to ‘bury’ their dead on the Lake because the water was so deep. He also told us that on occasion a body will still float up to the surface.
Jimmy Haigh (23:59:51)
“greatood”? Sorry – I wrote “good” initially then changed it to “great” but my keyboard is a bit dodgy. My mouse has seen better days as well…
excellent article Anthony…. Good explanation of cause and effect.
The lake’s surface water warming due to turbidity, the local atmosphere warming due to the heat released by the warm lake surface water, then being recorded by the nearby temperature station. The results then being deliberatly misrepresented or confused by the naive Senator Feinstein.
It is impossible for the temperature of the water in the lake to have a 3 degree rise due to a transfer of heat from CO2 in the atmosphere. It would be interesting to see if an AGW proponent could show that mechanism…. do any wish to try?
Storm induced turbidity currents are important mechanisms for introducing sands into water. The following picture is an example of deep water ‘turbidite’ sands from Anzoategui State in Venezuela. The rocks here are Upper Cretacous in age, approximately 75 million years old. In general the sands ‘fine upwards’ and a typical sequence goes from coarse sand through to silt. After the turbidite has been deposited, background sedimentation of mudstone continues.
http://i919.photobucket.com/albums/ad34/Jimmy1960/Taguayasands.jpg
Turbidite sand bodies are important oil/gas reservoirs. The Paleocene Forties Formation of The North Sea is a good example.
I seem to recall that the Grand Banks of Newfoundland earthquake of 1929 caused a turbidity current which severed several undersea communication lines. I’d look for a link but the baby has just woken up and normal service has to resume…
Mike D. (18:00:04)
Someone once said the government is the problem.
$390,000,000.00, hmmm, how much senior health could that buy?
For a discussion of the greenhouse gas emissions from forest fires, see Bonnicksen, Thomas M. The Forest Carbon And Emissions Model. 2008. The Forest Foundation, Auburn, CA, here:
http://westinstenv.org/ffsci/2008/03/14/the-forest-carbon-and-emissions-model-fcem/
FCEM is a model (what else?) but it is useful making rough calculations. For instance, one acre of forest burned severely emits the GHG equivalent of 9 to 15 cars driven all year. Then as the fire-killed (but not consumed) wood rots, an addition 3 to 4 times that much is emitted (over the next few decades).
Considering that 5 to 10 million acres of forest is burned in wildfires in the U.S. each year, the GHG equivalent of 150 to 600 million cars is emitted.
Using FCEM I calculated that in 2007 in Oregon 56 teragrams of CO2 was emitted by forest fires (a teragram is 10^12 grams, or one million megagrams; a megagram is one million grams and is also called a metric tonne). That was approximately the same amount emitted by the transportation, waste, residential, commercial, industrial, and agriculture sectors combined (in Oregon). Reducing forest fire acreage by half would reduce total CO2 emissions by 25% in our state.
Personally, I am not all afliver to reduce CO2 emissions because I am a climate realist. However, reducing forest fire acreage would benefit watersheds, soils, wildlife, public health and safety, and the economy, as well as dozens of other natural and human environmental resources (such as reducing erosion and improving water runoff quality).
Ref Sea Turbidity Question
You may not have seen this http://www.aslo.org/lo/toc/vol_46/issue_5/1100.pdf
Regarding turbidity currents, I should also point out that not only can they redistribute sand and silt from shallow water or continental environments into deeper water, be it lacustrine (as in the case of Lake Tahoe) or marine environments but they also introduce land based or shallow water biota into deeper environments. They also redistribute warm surface waters into cold deep environments. Storms are the major source of turbidity currents but earthquakes can also cause them.
Here’s another photo from the Pliocene age outcrops on the south coast of Trinidad of a possible earthquake induced coarse water deposit of Pliocene age in Trinidad. Some of the sediment blocks here were up to 100m in size! Here, coals and fluvial flood plain mudstiones sit in a very deep water marine environment; perhaps several hundreds of meters. This particular deposit was possibly caused by a tsunami of the same magnitude of the 2004 Indonesian event. It may also have been caused by a hurricane.
In the photo, (in which yours truly appears!), we can see a chaotic extremely coarse grained and poorly sorted unit. The large block above my head is a clast of shallow marine sandstone and the smaller blocks are a mixture of shallow and non marine sediments. The depositional environment of the unit was deep water – in the order of a couple of hundred metres as evidenced by deep water microfossils.
http://i919.photobucket.com/albums/ad34/Jimmy1960/mdb2.jpg
It is MUCH easier (and more popular) to blame it on Global Warming that to actually tackle the problem. How do you think this would go over: Completely eliminate all towns around Lake Tahoe. Take out all the concrete and asphalt, replant trees. Remove all storm drain systems. Oh, and you have to make that a joint project with Nevada.
Once that is done, both the turbidity and lake level issues will have been (temporarily) addressed. Lake levels because instead of seeing huge amounts of water running into storm drains, into the lake, raising the level to spill down the Truckee River, the water will percolate into the ground and slowly filter out over the course of the summer from springs maintaining the lake level by being added to the lake gradually rather than being channeled through concrete pipes to the lake immediately.
But there is another issue. In general, Lake Tahoe and other Sierra Nevada lakes are at record high levels in a geological timescale. There are trees submerged under tens of meters of water where they once grew on dry land. What we consider “normal” rainfall patterns are actually quite wet by long-term standards. The Sierras have experienced what we would call “mega droughts” that have lasted centuries during this interglacial period. So our idea of what is “normal” is based on about a century and a half of people actually living there during an abnormally wet couple of centuries.
Politicians have no sense of scope on a geological timescale. Their scope is limited to the time to the next election. But I suppose that is OK because most people have no idea they have been living in a rainfall boom time and when things get back to more “normal” patterns, they are going to have to blame someone for it.
DiFi just wants to make sure they don’t blame her.
Just one comment/question. Where do these clueless politicians keep coming from? Is there a college to teach dropouts/idiots to become politicians? One thing is certain; none of them could hold down a real job.
@ “van is from the maintenance man”: I guess before 1960, here was no maintenance-man-van to influence the temperature.
Why not go the whole hog and say:
‘These folks are spending millions of my tax dollars fuelling the construction boom, talking about global warming, but not actually doing the studies they are tasked to carry out to understand the CAUSES of recent temperature rises at Tahoe?’
Or am I being a tad brutal for our understated American friends?
Excellent post, Anthony. You have the nose of a super detective on the trail of evidence to determine the science of the matter. $390 million smackeroos for “additional preservation projects” at Lake Tahoe, hmmm. Perhaps more cushy buildings where academic “researchers” into global warming can do their stuff. I like the following two sentences:
“Unlike other officials, Feinstein blamed global warming for the degradation of Lake Tahoe.
“The real culprit in my mind is global warming,” she said.
We all know by now that Sen Feinstein has funneled billions of dollars to her husband Richard C. Blum, chair of the board of CB Richard Ellis Group (CBRE), “the world’s largest services firm”; “a multinational real estate corporation”; “a global leader in commercial real estate services”. The latest was legislation for $25 billion in taxpayer money to a government agency that had just awarded her husband’s real estate firm a lucrative contract to sell foreclosed properties (not in CBRE’s “commercial” expertise) at compensation rates higher than the industry norms. Lots more: http://www.washingtontimes.com/news/2009/apr/21/senate-husbands-firm-cashes-in-on-crisis. See more goodies on the crash of CBRE’s share prices; Blum buying at the bottom when CBRE’s contract was approved; prices have increased around 300%.
I am hoping that other readers have information on this couple’s sleaze in the carbon trading market. UC Berkeley now has a Richard C Blum Center for Developing Economies. Dr. Stephen Chu is a Blum Center Trustee. Al Gore was a keynote speaker in April of this year. One aspect is Live Climate, a “growing [voluntary] commodity market [in carbon offset purchase] represents a valuable new source of financing for sustainable development.”
Furthermore, the sixth annual Brookings Blum Roundtable for leaders from the climate change and global development communities convened 7/30-8/1 in preparation for Copenhagen in December. “Policy-makers must now think creatively to realize their goal of revitalizing the global economy through low carbon growth models….the roundtable forged sustainable solutions to solve the climate crisis in a way that revitalizes the global economy and lifts the lives of the poor.”
“Turbid” in its figurative meaning is “confused, muddled”. These global corporate types who have taken over the U.S. government, the U.S. media, and academia want to keep us confused and muddled about their real intentions — unimaginable wealth for themselves under the guise of helping those in poverty and saving the world from GHGs while throwing a few bones — $390 million — to their lackeys.
http://earthobservatory.nasa.gov/IOTD/view.php?id=39891
John F. Hultquist (17:24:12) :
“I realize the burn barrel has been moved and maybe no longer used but I wonder what they burned there. Our county in Washington State no longer allows burn barrels, in part, because folks tend to try to burn all sorts of things that are better sent to a landfill and because the barrels are usually not constructed to facilitate complete combustion. ”
Notice that the barrel is sitting on a wooden pallet. Clearly it was not used for burning within the enclosure, but merely stored there.
I have no idea of the size of the lake you are talking about but another problem that I have not seen discussed is stratification. The temperature of the top layer will alter quite rapidly in accordance with the weather – sunshine, wind, rain, season. Temperature then drops quite dramatically at greater depths and becomes anaerobic. When the air temperature drops significantly after a hot spell, there is a corresponding drop in temp of the top layer. If this falls below the temp of the water below, this can cause inversion with anaerobic water coming to the surface causing dramatic fish kill.
There is a simple method to alleviate this by drawing the water from depth to the surface where it is naturally oxygenated. If this is done slowly but constantly, the water will be more healthy at much greater depth and the turbidity will be considerably reduced. There are simple wind powered machines that can do this. It floats on the water, suitably anchored, with a vertical pipe, say 12 inches in diameter, going down to the required depth. A propellor at the top just below the water surface is driven by the wind drawing the initially anaerobic water to the surface. A large lake would naturally need quite a few of these but I believe that one unit can successfully transform a 2 acre lake. Lake Aid is based in the USA and provides these products – or did so a few years ago.
All the best solutions are the simplest and cheapest!
On the other hand, turbidity is also caused by the natural process whereby necessary nutrients (iron rich dust) being injected (or nutrient rich sediment being brought up) into surface layers so that the food chain can be maintained. Clear lakes that stay clear usually have few fish at hand. Why? No food source. High glacier lakes in the Wallowas are stocked with fish every year to enhance tourism (when the budget allows) because otherwise, there is no possible way for fish to get there and there is not enough of a food chain to sustain a fishable lake.
It is quite possible that natural forest cycles (decadal growth and burn) create the necessary wash of nutrient rich soil into large bodies of lakes which in turn maintains its food chain. Fire supression, or logging practices that do not mimic natural fire cycles, reduce and disrupt the food chain.
In summary, natural turbidity cycles are a necessary food chain mechanism. To disrupt that by over-enthusiastic control measures, or to overwhelm it by using the lake as a constant water runoff garbage dump, will result in a disrupted food chain with consequences throughout the flora and fauna ecosystem.
After reading clarity and heat Buffalo Springfield comes to mind–and I enjoy reinterpreting their masterwork for the climate change saga:
“There’s something happening here
What it is ain’t exactly clear
…
What a field-day for the heat
A thousand people in the street
Singing songs and carrying signs
Mostly say, hooray for our side”
Listen to the whole thing, if you got it. Or Youtube it:
– Mike
After Yellowstone was allowed to burn naturally, much understanding was developed about fire behavior. Where fuel loads were high, the fire clearcut the forest into meadows. Where fuel loads were low, the fire cleared the forest floor but did not harm as many trees. It appears in natural cycles that clear cutting fires are as necessary as forest floor fires. Both seem to enhance the natural meadow and forest combinations seen in untouched and allowed to burn forests. These cycles should be studied and mimicked in managed forests.
To do this, I think that all federal forests should be returned to the states and the federal budget sent with the forests. Each state should then be allowed to create a state forestry department that works with specific forest managers and loggers to develop logging practices unique to each forest type and that both sustains and utilizes forestry products for the benefit of forest product companies, loggers and the surrounding communities.
Disband any and all Federal forestry departments, including oversite of national parks, and return lands and control to states.
Perhaps the real problem for Lake Tahoe is that she has not found a way to funnel cleanup money to her family’s defense contractor corporation?
http://www.indybay.org/newsitems/2009/05/14/18594789.php
enduser,
The pallet does not mean that the barrel was never used at the location.
And, the heating of the barrel during the day assures that the temp sensor is receiving the heat from the barrel’s cooling during the evening. And what is one of the tenets of AGW?
That night time temps are a *proof* of AGW.
Have any of you wonder that this is a psychological “projection” of your senator?
We can not stop the unavoidable course of time….
Robert Wood (15:31:48) :
“When these people speak of Lake Tahoe being 3 degrees warmer, I expect they only mean the surface temp.”
Good point. Has anyone done a water temp vs depth study? (I suspect not) SST’s are a factor, but represent only a minute fraction of the total energy content of the water. What has happened 1,10,100 meters down? And where did they measure the water temperature? Near the shore? All over? Without additional information, the “3 degrees warmer” is not useful.
Not to defend Sen. Feinstein as a whole, since she has done plenty to sensationalize the AGW cause while ignoring good published science, but I think that she needs to be cut a little slack here. I work as a water resource engineer, and when I began reading the article that turbidity was somehow involved in warming, I was dubious, since I had never considered the impact of turbidity on water temperature. My initial thought was “what kind of brownies has Anthony been eating this morning?” But after reading the article, I agree that he may be on to something, and that this is a valid hypothesis worth testing.
However, the point must be made very clearly: this hypothesis has not yet been tested. I think that it is entirely unreasonable to blame a politician for not making this connection, especially when it has not been documented in any peer-reviewed journals or properly sanctioned and controlled studies. Notwithstanding the fact that she has championed the “Keep Tahoe Blue” cause in the past, I think it is entirely unfair to blame her for not understanding the scientific correlation between turbidity and water temperature.
Rowland Pantling (UK) (07:35:45) : Tahoe is over 1,500 feet deep and the deepest or one of the deepest in the USA. I fished on it once and wondered if fish would be at the bottom.
The physics of the article is totally wrong.
The transmittance coef. air-water is 95-97%,(depends on the angle)and does NOT depend on the turbidity.The incoming flux of energy does not change.
In fact the mean temperature of a lake DIMINISHES with the increasing turbidity because the heat is trapped in the first centimeters of water increasing the night cooling by thermal radiation.
(The article cited is about the 2 mm water near surface and thus has no relevance)
Retired Engineer (09:20:47) :
Robert Wood (15:31:48) :
“When these people speak of Lake Tahoe being 3 degrees warmer, I expect they only mean the surface temp.”
Good point. Has anyone done a water temp vs depth study? (I suspect not) SST’s are a factor, but represent only a minute fraction of the total energy content of the water. What has happened 1,10,100 meters down? And where did they measure the water temperature? Near the shore? All over? Without additional information, the “3 degrees warmer” is not useful.
Anyone interested in understanding the link between climate warming and Lake Tahoe temperature should read the Robert Coats et al. (2006) paper which is available for everyone as a PDF (try Coats and Lake Tahoe) in Google scholar. Of course, the temperature profiles from 0-400 m have been measured at at least monthly intervals over the last 30+ years. Such data are available for most of the large lakes in the world.
One of the main issues is the effects of both turbidity and temperature on the stabililty of stratification and thickness of the upper mixed layer of homogenious temperature. In small lakes, a thinner mixed lake due to increased turbidity and less solar penetration can lead to greater solar heating of the thinner surface layer (See paper by Mazumder in Science among others). However, in large lakes, such as Tahoe, the mixing depth is mainly determined by the effect of lake size on wind fetch. For Lake Tahoe, the surface layer with uniformly warm temperature during the warm seasons is the upper 20-30 m. For this reason, results from mosquite ponds are not useful for understanding the temperature budgets of lakes and oceans. If you read the Coats paper, you learn that the upper 30 m of Lake Tahoe has heated the most quickly, but that heating is occuring in the upper 400 m.
The best data on effects of climate effects on lake temperatures is work on David Livingsone on European lakes. Some of his papers are directly available as PDFs. Papers in Limnology and Oceanogrphy before 2005 are also available at the http://www.ASLO.org website. You can find free pdfs of papers on the heat budgets and thermal stratification of Lake Tahoe and other lakes by searching for the pre 2005 papers in Limnology and Oceanography.
I’m surprised they haven’t blamed the boom in house building on global warming…
Alexandriu, I’ve triple checked this. Increased water turbidity equals increased water temperatures, and the effect is not limited to 2mm of the surface.
Pamela Gray (08:31:27) :
Before Europeans came, the natives on the East coast would regularly burn out the underbrush. The forests in the area I have in mind were mostly chestnut and able to withstand fire quite well. The forest floors would then be used to plant various things such as squash and corn. After a couple of years, another section would be burned out and the planting areas moved.
One interesting fact is that the Eastern forests had no earthworms as we know them prior to Europeans arriving. Those were brought by settlers. Leaf litter would pile up year after year along with the debris from fallen twigs/limbs, etc. Burning the forest floor allowed the nutrients locked up in this debris to be returned in a soluble form to the soil where they could be used by the plants. Once production began to drop at that location, another area was burned (fertilized) and used. Fire was basically a fertilizer used by the native population to increase food production both on the ground and for the chestnut trees that also provided food for both the natives and game.
The really scary thing is Feinstein is the ‘better’ senator form the former golden state.
When you have surface water being directed into the lake in an express fashion by a storm drain system, you end up with a different chemical mix going into the lake than if it is allowed to percolate through the soil and enter slowly via springs.
Pet and bird excrement is one thing that would be washed in at higher concentrations as water is washed off roofs, down driveways, into gutters, down the storm drain and out into the lake.
It also causes boom/bust runoff events where a huge amount of water is washed in. The lake only rises a certain amount because the runoff increases into the Truckee River. Once the level returns to “normal” there is less “sustaining” inflow from springs because the water that would be recharging the ground water has already washed into the lake and down to Reno. Also, water that is filtered through the ground has less nutrient load from things like animal droppings.
We are, in effect, hosing off several towns and directing the runoff directly into the lake with each rainstorm. The lake HAS to get cloudier.
For Watts.
You must check the Fresnel formulas, which are basic physics.
They will tell you that even in a zero impurity water ,practically ALL the energy of a electromagnetic wave penetrates WITHOUT reflection:
-at angle 0-Reflectivity=[(n-1)/(n+1)]^2=(0.3/2.3)^2=1.7%
_at angle 30deg-Reflectivity=(rt+rp)/2
rt=(sin(B-A)/sin(B+A))^2
rp=(tg(B-A)/tg(B+A))^2
B=30 deg
A=22.6 deg
rt=2.6%
rp=2.8%
rt=2.7% which is practically 0
Thus,turbidity cannot influence the light reflectivity because it is already almost zero.
If anybody says different he is not a reliable source
REPLY: My name is Anthony, please. There are several papers which cite a water turbidity to water temperature correlation. Here is one where reflectivity is examined in the context of turbidity.
Citation: Witte, W. G., C. H. Whitlock, R. C. Harriss, J. W. Usry, L. R. Poole, W. M. Houghton, W. D. Morris, and E. A. Gurganus (1982), Influence of Dissolved Organic Materials on Turbid Water Optical Properties and Remote-Sensing Reflectance, J. Geophys. Res., 87(C1), 441–446.
http://www.agu.org/pubs/crossref/1982/JC087iC01p00441.shtml
“From these data it is clear that dissolved organic materials decrease upwelled reflectance from turbid waters. ”
Here is a primer on suspended solids in water from the City of Boulder Water Quality Monitoring:
http://bcn.boulder.co.us/basin/data/BACT/info/TSS.html
Here is another from the New York Harbor Survey thats cites TSS and water temperature:
http://www.nynjcoast.org/NYCDEPHarbor_survey/docs/water_clarity/total.htm
Then there’s this one, from Brockport University
http://vortex.weather.brockport.edu/~jzollweg/oakorchard/docs/waterquality.pdf
On page 1 under TDS:
It seems the water quality people disagree with your assertion. – Anthony
Re:watts:
I did an error of calculation.In fact Rp =0.0098 so R=1.8%
crosspatch (12:34:37) : Ants (some other insects and fungi) on the north American continent would be doing what worms do before their arrival. Much the same thing with honey bees before they arrived around the same time. I think both came with Apple trees.
Interesting question somewhere up there about air heating water. In short, the air cannot heat water, since the heat capacity of water is so great that only shortwave radiation can heat a body of water. On the other hand, oceans can heat the atmosphere, since water retains heat whilst air doesn’t . Air temperature itself cannot penetrate water, particularly so called re-emitted longwave radiation, which, for some odd reason, is the basis of the AGW case
Rowland Pantling (UK) (07:35:45) : You wrote:
“I have no idea of the size of the lake”
Use Google Earth and go here: 39.097641 N, 120.025191 W
then back away to about an altitude of 44 km. which allows you to see the Lake from north to south. At an elevation of about 5 km. you can move to the SE part where the light blue line is the boundary between Calif and Nevada. The major urban area is here. The north end of the lake also has much development.
This Google images link provides a visual tour:
http://images.google.com/images?hl=en&source=hp&q=%22lake+tahoe%22&um=1&ie=UTF-8&ei=R6-RSsnpGIHEsQOStpAM&sa=X&oi=image_result_group&ct=title&resnum=16
“In short, the air cannot heat water, since the heat capacity of water is so great that only shortwave radiation can heat a body of water. ”
But if higher troposphere temperatures inhibited a process that cooled the ocean, namely ITCZ cu-nims, then solar heating would get through to the oceans.
There is almost something of a transistor here. The main heating of the Earth is tropical ocean heating from the sun with a large heat-flux or power. With no tropical clouds for a few months I think everyone would agree that the Earth would warm significantly, conversely a solid tropical cloud belt would cause severe cooling.
Thus tropical cu-nims act like the ‘gate’ in a source-gate-drain field effect transistor, regulating much more energy than they themselves contain.
I first visited Lake Tahoe about 1/2 century ago. Then it was crystal clear. I vaguely remember (heck, I was not yet in kindergarden then…) the story that you could see the bottom (a few hundred feet down?) from a boat in the lake. (Any errors in that statement ought to be attributed to being a kid at the time 😉
So, about 1970 it was getting very turbid, largely due to “people pee and poo” from all the development fertilizing the lake. There was a building moratorium and then some requirements added for better sewage treatment.
Now, we have a bit of an improvement, but it’s still not anything like it was. You can’t have that much development and that much runoff of garden / lawn fertilizers and deposition of sulphates and nitrates from car exhaust and runoff from logging and… without getting some growth in the lake. That, and the stuff that in the lake from the past does not just wash out in a decade…
Yup, I’d call it “turbidity denial”…
BTW, some of that “temperature rise” might come from using Airports in their UHI “correction” as “rural” stations. Out of 2179 records used for “correcting” other stations (a few thousand times) “only” 500 are marked as Air Stations in the v2.inv file…
http://chiefio.wordpress.com/2009/08/23/gistemp-fixes-uhi-using-airports-as-rural/
Maybe DiFi could fly into Truckee-Tahoe airport and check on the status of the thermometer…
Take a look at the graph from the UC Davis Tahoe Environmental Research Center — the one with a boat floating on the surface of Lake Tahoe. Notice where the surface of the lake is, the implied zero point of the graph. Notice the depth calibrations at the sides of the graph. Where should the real zero point of the graph be located? If there’s ever a new edition of Huff’s How to Lie with Statistics, this graph should be included as an example.
Oddly enough, this presentation from a government-funded environmental agency just happens to make an environmental problem look worse than it really is. Yes, it’s still a problem, but wouldn’t it be nice if we could make decisions without being misled?
It is not correct to cite the mosquito experiment(which is completely non-relevant on the issue)
Their pool was only a few cm deep and had p[lastic on the bottom.
The reflectivity of plastic is ~50%.Roughly 49% of the light is coming out of the water if the water is pure.If the water is muddy ,the heat is trapped and the pool will warm up.
In a lake,the opposite occurs:the light coming up from the deep water is practically 0.The backscattering is negligible.The heat will remain in the water and the only difference will be an increasing thermal gradient which will enhance the cooling of the lake by nighttime.So,the assumptions of the article are totally flawed.
REPLY:True, they have an experimental setup versus an in situ, but I’m still not convinced. Since you didn’t mention them, did you not read any other citations on turbidity and water temperature I posted? Please offer some citation of your own that show that increased turbidity equals a cooler water temperature. – Anthony
EM–It’s a bit of exageration to say that Lake Tahoe was getting very turbid when the Secchi depth has always been deeper than 20 m (60 Ft.). Anyone interested in the general relationship between water clarity and solar heating of lake should read the following paper:
Mazumder and Taylor, 1994, Thermal structure of lakes varying in size and water clarity. Limnology and Oceangraphy 968-976.
Variation in lake water temperature is directly related to air temperature and to solar radiation. There is a lot of argument on this blog about issues that have been well know and worked out 15-20 years ago or more. There is lots of information on these topics in the peer reviewed literature and in basic text books on aquatifc ecology and limnology.
It is easy to find 50 peer reviewed articles relevant to these issues.
So if I understand correctly from what you’ve written:
(1) the lake is warmer by about 3 degrees due to increased turbidity of the water;
(2) the air temperature above the lake is about 3 degrees warmer;
(3) the temperature sensor for the area that is used in calculations of global warming hysteria, er, hypothesis is just a few feet from said warmed lake;
Thus one can form a hypothesis for testing that this station’s weather data is skewed upward not by “global warming” but by the increased turbidity of the water in Lake Tahoe.
While correlation might not be causation correlation can sure be a huge hint of causation that should be taken seriously and tested by scientists.
I wonder how much this Lake Tahoe station contributes to the overall trend of the global warming hysteria, oh, hypothesis?
How many other stations are in this area?
If this correlation is in fact a causation of human development causes increased turbidity of the water and thus increased lake temperatures and thus increased local air temperatures that caused increased science thermometer temperatures then sure humans are contributing to global warming temperatures WITHOUT C02 emissions! How ironic that bad local data leads to bad science with the illusion of it being global!
I wonder how far the Lake Tahoe air temperatures extend in miles? Any idea? How does it effect the wider region? How local or far reaching is this Lake Tahoe heat island? (A lake being an island how quaint ;-).
Very illuminating and educational article Anthony. Please send a copy to your representatives, U.S. Sen. Dianne Feinstein, D-Calif., and Ensign, and any others.
Oh, might increasing the water turbidity of lakes up here in Canada be a way to cause local warming around human settlements by about 3 degrees? That could be a huge win to reduce energy costs while increasing the local temperatures. Just a thought of turning what is a negative to some into a positive for others.
I’ve adding the additional citations about turbidity to temperature relationships discussed in replies to Alexandriu Doru to the main article.
I’ve also added a sentence, noting that the mosquito experiment was small scale. An an additional passage noting what the authors of the small scale mosquito experiment say about the large scale Kara et al 2005 study.
Kara et al 2005 shows that in Figure 1, turbidity decreases the shortwave radiation penetration depth, and thus concentrates the solar energy in the nearer the surface rather than distributing it to greater depth. More solar energy extinction near the surface would thus increase the temperature nearer the surface.
Alexandriu suggests that I have the effect backwards, that turbidity actually cools the water surface. I’ve provided some citations from water quality organizations showing increased turbidity equal increased water temperature, and asked him to provide citations that show the opposite, which I will happily investigate if provided.
A very fine report, Anthony. Feinstein has always struck me as rather dense. If Dan White hadn’t shot Harvey Milk and Mayor Moscone, she might have spent her whole political career in San Francisco.
Antony,sorry.
None of your references did say that turbidity increases the mean temperature of any lake.
On the contrary .The study about the Black Sea turbidity(that the author of the article cites)affirms that the simulations (yes,simulations)showed that ,when they introduce the rss turbidity,the simulated temperature DIMINISHES from 2C to 1.04C(compared to the real climatology).
So ,as i argued on my previous post ,the turbidity has a global cooling effect.
REPLY: I disagree. The way I read the Black Sea study is just the opposite. Note they didn’t put a minus sign in front of the 3C bias statement.
And lets not jump off topic, we aren’t discussing a global cooling effect here, we are talking about the water surface temperature of a lake, so lets not get outside of the discussion context. As I asked before, show me a reputable citation anywhere that equates increased water turbidity to lower water surface temperatures. I’ve shown several for water quality in general that demonstrate increased turbidity equals increased water temperature. There were no size caveats about puddles, ponds, lakes, or seas listed, in any of them.
– Anthony
pyromancer76 (03:20:52), per your request about info re: Feinstein & her hubby: click. [The link in the first sentence of the article goes to the original exposé.]
She used her position as Chair of the Senate’s military construction appropriations subcommittee [MILCON] to funnel $Billions in taxpayer loot straight to her husband’s companies in open ended, no-bid contracts. [Since California is a community property state, Feinstein’s wrongdoing amounts to conversion.]
When she was caught, she was forced to resign as committee Chair. But of course, they didn’t have to pay the money back to the U.S. Treasury, and Feinstein wasn’t sent to San Quentin like other thieves.
Betcha didn’t hear anything about that in the media.
Alexandriu,
Here is yet another citation from a water quality agency saying that increased turbidity equals increased water surface temperature.
In this citation, they very clearly mention larger bodies of water, like reservoirs. The state of Kentucky has some very large ones.
http://kywater.org/ww/ramp/rmtss.htm
(Kentucky Water Watch, main page http://www.water.ky.gov/ww/ )
I’ve now quoted several water agencies all saying the same thing about increased turbidity resulting in increased water temperature.
The onus is now on you to provide credible citations showing that this is not true. – Anthony
I don’t know why Anthony and other bloggers and posters would ignore a 28 page peer reviewed article by Coats et al. (2006) titled: The warming of Lake Tahoe. This paper is freely available as a PDF at several sites including the publshers web site:
http://www.springerlink.com/content/6384855p5513l393/fulltext.pdf
The analysis for this paper is based in part on weekly measurements at 2-15 m intervals to 100 m since 1969, biweekly measurements every meter to 125 m since 1996 and less frequent measurments to 400 m. This paper shows that Anthony’s speculation that lake warming is can be atributed to increased turbidity does not hold up.
I would agree that a good part of the increase in turbidity is due to increased runoff and nutrient loading. Anthony’s point about the El Nino effect is well supported . Certainly, when weather or climate results in increased runoff and nutrient loading, this results in increased turbidity, while droughts lead to increased water clarity.
Warming, by reducing the mixing depth, also leads to increased turbidity. These interactions between mixing depth, warming and turbidity, which are quite complex, are discussed in the Coats et al. paper. It does not make sense to ignore a readily available paper that is directly relevant while mixing good points with speculation that can easily be dismissed.
REPLY: Thanks for this, Bill. You make an unsupported assumption that this paper was ignored. I’ve done a lot of searching on turbidity TSS, and TDD and this never came into view. But I’ll have a look now. – Anthony
Follow up: Bill again thanks for this, I’m going to add it to the list of citations at the bottom of the article. A couple of points about your claim of “ignoring” this paper. First, I’m not in the mainstream academic world as you are, I’m in the business world, so things that are “givens” for you being exposed to with periodicals and such (paid for by your university) are not part of my world. 2) Given that you do biology of lakes, (love those daphnia, spent hours loking at them as a kid) I’m sure your were already aware of this study a couple of years ago. This convenience of being in mainstream academics that I don’t have sets you up to unfairly judge me for “ignoring” a paper that I wouldn’t have the same opportunity to be pre-exposed to that you do.
Me, I have to find such things with Internet searches. The word “turbidity” is not mentioned anywhere in the Coats et al paper, so I didn’t find it in searches. Oddly with all the measurements they made, that is the one thing that paper didn’t cover.
There’s a lot of interesting things in the Coats paper, much of which I agree with, some that I don’t, and some that supports my idea. I’ll have more in the next couple of days. – Anthony
1.Anthony
Tahoe lake warmed from top to bottom With 3C.
I agree with you that turbidity is warming the surface of the lakes
But in the same time it cools the bottom(and may generate stratification)
2.From the article you pointed.
“From these data it is clear that dissolved organic materials decrease upwelled reflectance from turbid waters. .. Changes in backscatter coefficient are moderate, indicating minimal changes in particle scattering.”
As i explained ,at the surface ,there is ~zero reflection.
Once in the water,as there is no ‘mirror’, the photons will go down indefinitely.
The only chance for them to go up is the backscatter (who,as you see, does NOT change)
3.the text in the “black sea “article is explicit.
“In particular, when using the clear-water constant attenuation depth as opposed to using spatial and temporal kPAR, basin-averaged rms SST difference with respect to the Pathfinder SST climatology increases ∼46% (from 1.41°C in expt 1 to 2.06°C in expt 3)”
It is clear: when they use clear water(instead of kpar=turbidity) the temperature INCREASES!
4.the physics behind this effect is obvious:more you warm a thinner surface, more you loose the heat.
5.I live in Roumania and the Black Sea is no more what it once was.
Mais ou sont les neiges d,antan?
REPLY: We agree on points 1 and 2. On 2 I never claimed there was a “mirror” that was your argument, I said from the beginning that turbidity increases radiation absorption. On point 3 I still don’t see it your way. Point 3 conflicts with point 1. The logic seems backwards, but then again we are talking a model and a satellite. The question remains though, in the abstract they mention a 3°C bias, but do not give a negative sign, why? I’ll have a look again.
Point 4 I think what you are defining there is a heat sink of lower volume, in which case, yes it would lose heat faster than one of a large volume. In the case of a lake warmer water strata, that would transfer the energy as LWIR into the air above it. This is consistent with point 1.
Point 5. I have no doubt the Black Sea has similar issue to Lake Tahoe.
It seems possible to verify the turbidity question experimentally.
Use two containers, one containing pure distilled water, and the other containing, say, 10% India ink and 90% distilled water.
Place them side by side in direct sunlight for several hours, then compare temps.
It seems intuitive that the darker water would be warmer; an experiment like this would definitively answer the question.
Smokey
For a container is true because the reflection from the bottom is important and the ink will stop the light going up.
For a lake is not: there is no bottom reflection if the lake is deeper than the attenuation length in water.
IF you put ink in a lake you will warm the surface(who will rapidly loose the heat during the night) and you will cool the bottom (who receives less energy).
Globally it will be a cooling effect
About five (??) months ago an AWGer posted here that the increasing temperatures of lake water supported the case for global warming and discredited the oceanic data showing no warming. It appears to me that this increasing lake-turbidity factor is an effective counterpoint to his claim.
Likely the oceans are getting more turbid too, from increased runoff of topsoil, agricultural fertilizers, sewage, etc. There should maybe be a correction for these, showing that the oceans would be cooling in their absence.
Antony
Thank you for the last article citation(Coats& al. 2006)
It is in fact very comprehensive and informative .
May be,one day, you will publish a comment on it .
Pamela Gray (08:16:42) :
The forest practices you speak highly of was called thinning.
It used to be practiced.
That was then.
This is now, 40 years after those practices were dumped in favor of clear cutting and herbicides.
Yellowstone worked because it wasn’t messed with.
The National Forests failed because they were subjected to pure greed (aka overharvesting).
They continued to fail as restoration efforts were subjected to lawsuit gridlock (it’s natural for it all to burn faster than it can recover).
Diane Feinstein stared blankly as it all took place, and still does.
Anthony I agree with you on most things and turbidity might have some affect on temperature. However I think it is slight, It would also be hard to separate cause and effect. Warmer water creates more algae growth and thus more measured turbidity. Land use and residential discharge certainly affect the nutrient availability and thus algal growth. However there is a much more dynamic factor that I hope become more clear from the linked graphs.
What is missing from the Coats et al paper and this discussion is the affect of inflows and outflows from Lake Tahoe. The affect of cold water coming in and warmer surface water leaving certainly seems as if it would be a major contributing factor. The outflow is controlled by a dam also located in Tahoe City. The Coats et al paper shows a definite increasing trend in temperature with a few cooling periods. He goes to great lengths to attribute the cooling of in 82 and 83 to Pinatubo. Much closer to home we see that year had peak snow pack and maximum lake discharge. It is curious that Coats et al would ignore such an obvious factor.
I have linked to a jpeg I made containing 3 graphs. Top is the Lake Tahoe temperatures from Coats et al. Notice the 2 main warming trend that go from 1975-1982 and from 1983-1994. The next graph show the amount of discharge from Lake Tahoe. Notice the 2 periods of very low discharge coincide with the warming trends. The bottom graph shows snow depth anomalies based on the 1970-2002 average and computed from California’s Dept of Water Resources Snow Surveys for 7 Lake Tahoe sites, Squaw Valley and Mt Rose. All available on line. We see the heavier snow packs are during the cooling periods Coats cites. Less cold water entering lake means less warmer surface water being pushed out over the dam. Here is the link . I apologize that the images are a bit small as a result of converting the document into an image.
http://farm3.static.flickr.com/2658/3851020563_550606911e_m.jpg
I would appreciate any comments.
REPLY: Linked images are so small I can’t even see it. Thumbnail sized. – A
Jim Steele (00:37:24) :
Anthony I agree with you on most things and turbidity might have some affect on temperature. However I think it is slight, It would also be hard to separate cause and effect. Warmer water creates more algae growth and thus more measured turbidity. Land use and residential discharge certainly affect the nutrient availability and thus algal growth. However there is a much more dynamic factor that I hope become more clear from the linked graphs.
Jim:
I am not a physical limnologist, but I have looked at quite a few heat budgets for lakes. Except for very shallow lakes with residence times of weeks or months and high flow reservoirs, the effects of water inflows and outflows are negligible for heat budgets. According to a Google search, the water residence time for Lake Tahoe is an exceptionally long 700 years. This confirms that effects of water inflow and outflow on water temperature and total heat are completely negligble.
Very impressive Anthony.
Enjoyed the reminisces and the many fillers supplied by your readers, especially those of Layne Blanchard. Must have been a magic time.
Keep up the good work.
Given a constant atmospheric condition, I would tend to think that if the water surface is warmer from increased turbidity absorbing more solar energy at the surface then it will also radiate more heat back out while blocking more solar energy from reaching the bottom thus making the bottom colder. So increased turbidity should reduce a lake’s total heat energy overall with the bottom utltimately losing more heat than the surface gains.
Wouldn’t temperature measurements at the bottom put this debate to rest?
Better yet… let’s send Dianne down to the bottom with no wet suit to discover how cold it is down there.
Beyond Lake Tahoe: effects turbidity and climate on lake temperatures
One of the big advantages of studying lakes is that there are so many of them. I am privileged to be participating in studies on the effects of climate warming on the food chains of large European subalpine lakes. These lakes experienced high nutrient loading and reduced clarity (increased turbidity) during the 1960s and 1970s due to high phosphorus detergents, increased human populations and poorly treated sewage. This is an environmental success story–large investments in sewage treatment and restricted use of detergents with phosphate has resulted in great reductions in phosphorus, improvements in water quality and, in most cases, substantial increases in water clarity back to pre-1960 values.
These intensive long term monitoring studies that started mostly in the late 70s to assess the effect s of P remediation have proven very important in documenting effects of climate warming on lake water temperature and lake food chains. Lake Constance (Europe’s second largest lake, bordering Germany, Switzerland and Austria) showed probably the biggest decrease in phosphate loading and greatest improvement in water quality (and water clarity) during the 80s and 90s. During this period it also showed a trend of warming very similar to that of Lake Tahoe. Much of the work on the effects of warming on Lake Constance and its food chain has been published by Dietmar Straile of the University of Konstanz (search under Google Scholar under Straile, Lake Constance and Climate change for PDFs).
Direct effects of P loading from a lake’s watershed can have strong effects on water clarity and my guess (after reading only a few specific studies on this lake) is that these effects have probably been dominant in Lake Tahoe, as suggested in Anthony’s original posting.
There is, however, also evidence that warming, through its effects on thermal stratification, mixing depth and food chain interactions can have negative effects on water clarity (increased turbidity). This seems to be the case in Lake Maggiore (Italy and Switzerland) where warming and altered predator-prey interactions may be overriding a 50% reduction in phosphorus. I am coauthor of a study (in press) on Maggiore that looks at effects of warming on a specific predator-prey interaction. Effects of warming on water clarity is not a significant topic of my study. However, my Italian coauthor has presented evidence of a eutrophication-like effect of warming in this lake (search Manca, Maggiore and climate warming).
It’s also clear from the Maggiore data (included on my paper in press) that warmer winters are resulting in shallower water mixing and more algal growth (and increased turbidity) during winter, the period of clearest water. Like Lake Tahoe, Maggiore never freezes. Colder winters lead to mixing at uniformly cold temperatures (about 5oC) to hundreds of meters. Even though the water is relatively clear, few algae can grow under such low average light.
Heads up–A special issue of Limnology and Oceanography titled something like “Lakes as sentinels and integrators of climate change” is in press. A part of the volume focuses on paleolimnology which uses sediment chemistry and fossils to study past climates but many studies present data for the past 20-30 years. Authors of L&O have the option of paying to make their articles open access. Thus, many of these (40 articles or so) and other recent studies are or will be available at the American Society of Limnology and Oceanography web site (www.ASLO.org). You can also find PDFs of all L&O articles between 1947 and 2005 freely accessible.
This posting has lead to comments on how or whether warmer air temperatures can influence water temperature (in lakes and oceans). Work by David Livingstone shows that warming in Lake Zurich over the last 50 years is tied to higher nighttime minimal temperatures rather than an increase in maximal temperature. Thus, lake warming seems to be mainly linked to less heat loss during warmer nights. Here’s a PDF of probably the best study (in my opinion) on effects of climate warming on lake temperatures. (http://homepages.eawag.ch/~living/downloads/2003/Livingstone%202003.pdf.)
I appreciate Anthony’s earlier comment that he does not have ready access to much of the scientific literature, nor does he have the time to read a large number of studies. This does, however, raise the risk of reaching and posting conclusions that are contrary to a substantial body of already published and well documented scientific evidence. I also don’t have the time to read hundreds of original studies outside of my field of expertise. This is the reason that I largely restrict my posting on blogs to areas where I have professional interest.
On a windy day, large lake temperatures are colder due to mixing from wave action. On a still day, large lake temperatures are layered (warm on top with a rather definitive transition to cold). Turbidity is likely both a cause and an effect in bodies of water surrounded by development. However, to say that a lake is in better health because it is clear is very iffy. The very thing that is necessary for the food chain to stay intact from top to bottom will cloud the water.
Well it is my understanding that historically, Lake Tahoe water has had very high clarity, and apparently relatively low biological content; in other words it is/was very clean water; and of course it is very deep.
So as someone else observed it is likely 4 deg C at the bottom.
The clearer thbe water is, the further down the incident sunlight propagates; and the spectral components containing the most sloar energy are the ones that propagate to the greatest depths.
As a result the incident solar energy is distributed throughout a very large volume(mass) of water, so the average temperature rise is quite small. Thjat warm water is going to conduct somewhat to the deeper colder waters, but also the vertical temperature gradient, si going to set up a vertical convection currnet; which might be relatively small because of the great depth over which the incident solar energy is distributed. But the result should be a vertical temperature gradient that is relatively small, because of the water clarity.
So now fast forward to a more turbid present condition, where particulates, and biological materials make the water less clear and mor ehighly scattering.
A direct result of this is that incident soalr energy is going to be more strongly abosrbed at shallower depths. The total absorbed energy isn’t going to be any different; it will be a very good black body approximation (for a natural object), but all that energy is now depoasited in a smaller volume of water; which is still pegged at 4 deg C at the bottom.
With the same flux of solar energy deposited as heat in a smaller shallower volume (mass) of water; the mean temperature of that smaller mass of water has to go up as the turbidity increases.
I still believe that the main heat loss from the lake is through the surface to the atmosphere, because the convection current should trump the downward conduction to the colder depths.
So I believe it is as simple as that; the higher the turbidity/absorptance, the smaller the mass of water over which the constant influx of soalr energy is distributed, so the higher the mean temperature must get.
George
And speaking of the energy (E), and the temperature (T); the two are clearly related.
Everybody is familar with E = mc^2 but that is only part of the story. We could say:-
E = (1/2)mv^2 = mc^2 = hf = kT etc
Here f is a substitute for the Greek “nu” = c/(lambda) in the Einstein relationship between quantum energy and em radiation frequency; (h) of course is Planck’s constant. And then there is that kT where k is Boltzmann’s constant = 1.38066 e-23 J/K (joules per Kelvin), and the (E) in this case is the mean energy per particle in a heated body.
If we multiply k by Na ; Avogadro’s number = 6.0221367 e+23 we of course get R , the Universal Gas Constant (not to be confused with the Rydberg Constant which is something else).
But in any case, it is Boltzmann’s constant which relates energy to Temperature (and hence to “heat” that awful word) ; and just incidently irretrievably links heat to matter, since it specifies the mean energy per particle of matter, directly in terms of the abolute temperature (Kelvins).
From there of course you have to get into the statistical mechanics of the random motion of particles (above zero K), and the Maxwell Boltzmann distribution of particle kinetic energies or velocities.
A classic textbook derivation of the specific heats of solids at low temperatures done by Sir James Jeans starts off by assigning an energy of kT to each degree of freedom of each particle in a system, and computing the total energy for the system. The number of possible modes of oscilaltion in the sytem is astonomical, and in the process of developing his solution Jeans made a simplifying assumption that allows the accurate expression to be reduced to one that is much simpler to understand. That simplifying assumption was to set the value of one of the factors to the value 1. It was a pretty brazen step because the factor that he said was approximately one happened to be Avogardo’s number that is really 6 x 10^23. That is a pretty approximate substitution in anybody’s language; but you have to understand that the quantity of which the Na term was a nuisance factor he wanted to get rid of, also included the term factorial of Avogadro’s number; so really he was just leaving off one number in the factorial.
Somehow I think the factor he approximated as one was only the square root of Avogadro’s number; I seem to recall a term (Na + 1/2) inside a square root term, and that half in there was bloody awkward to say the least.
Hey it was 50 years ago, so I have forgotten exactly how to do the derivation; but that part I remember.
But the important thing is that it closely ties the concept of the mean energy per particle in a system to its heat content, and absolute temperature.
So that discussion with Nassif was not just idle chatter or opinion; important fundamental concepts were at stake.
But we can have such discussions on a forum like this, without upsetting the whole United Nations General Assembly.
George
PS; Don’t forget next time someone asks you; “what’s nu? “, you can smartly answer; ” E/h !”
George’s reasoning above is largely, but not completely correct. A number of studies have shown that in small lakes, increased turbidity leads to stronger heating of a thinner upper layer through which light from the sun is attenuated.
However, Mazumder and Taylor show that this turbidity effect mainly applies to small to medium-sized lakes <12.5 km2 in surface area. It would not apply to great lakes or Lake Tahoe (about 500 km2) or oceans. This is because the greater wind fetch and greater turbulent mixing of large water bodies is such that the mixed depth is determined by wave action and turbulent mixing and is independent of turbidity and light penetration. For larger lakes, mixing by wind trumps heating by the sun in determining the thickness of the upper warm, mixed layer. This is shown in several studies, including one paper in Science. The following paper in Limnology and Oceanography is available as free access from the ASLO.org web site.
http://aslo.org/lo/toc/vol_39/issue_4/0968.pdf
feinstein has been in office way too long. the problem is not global warming, the problem is the kind of industrialization the world participates in. what is feinstein’s “carbon footprint” over the years?
A great and interesting article and thread. I cant help reaching the conclusion, from just visitng the place a few times, that the problems with Lake Tahoe are directly related to the homes and businesses built around it (Some right on
the shores) and the huge year round tourism from the Bay area and elsewhere. Perhaps I missed something, but I assume there have been no long term
studies related to the effects of this.
Every time I saw that Tahoe sticker on the backs of cars (it’s amazing which states it turns up in and once or twice in Mexico) I could’nt help thinking what … why dont you stop living or going there if you cared so much about it!
“”” BillD (11:09:45) :
George’s reasoning above is largely, but not completely correct. A number of studies have shown that in small lakes, increased turbidity leads to stronger heating of a thinner upper layer through which light from the sun is attenuated.
However, Mazumder and Taylor show that this turbidity effect mainly applies to small to medium-sized lakes <12.5 km2 in surface area. It would not apply to great lakes or Lake Tahoe (about 500 km2) or oceans. This is because the greater wind fetch and greater turbulent mixing of large water bodies is such that the mixed depth is determined by wave action and turbulent mixing and is independent of turbidity and light penetration. For larger lakes, mixing by wind trumps heating by the sun in determining the thickness of the upper warm, mixed layer. This is shown in several studies, including one paper in Science. The following paper in Limnology and Oceanography is available as free access from the ASLO.org web site. """
Bill, I don't have any disagreement with your point that stirring the lake up will spread the heat around and complicate the simplified picture I drew.
But is there data on how significant an effect that would be in lake Tahoe. It seems to me that Tahoe is a relatively calm lake. Maybe that's a bad assumption on my part. I would actually be quite surprised if in fact wind driven surface turbulence can effect more than a fraction of the depth which I believe gets direct solar heated.
I guess if Tahoe is 500 squ km that puts it around 25 km diameter; so it certainly is large compared to its depth; but then it also has mountain peaks all around.
But I'm sure you are correct, that wind driven mixing somewhat counters the process I described.
But lets say that wind driven mixing completely obliterates any trace of the effect I mentioned.
Bottom line is that deep lakes and oceans are effectively black body absorbers, since the total Fresnel reflection from the surface is 2% at normal incidence, and maybe 3% integrated over the hemisphere; so the total solar energy input would be the same turbidity or no.
So what sort of Secchi disk data or history do they have for Tahoe to give some actual quantitative turbidity measurements.
It's amazing how speculative one gets in the absence of data; I couldn't even begin to guess at the long wave ir heating from the atmosphere over Tahoe; given its altitude; don't know a thing about the humidity history to guess about evaporative cooling.
I would place my bets on the increased population and activities; if looking for extra energy input. One thing is for sure that the water turbidity would have no effect whatsoever on the long wave IR heating; which wouldn't make it deep enough to discover there was any turbidity. That pretty much leaves local atmospheric or surface heating due to climate change if any.
But I wouldn't sign on to the Feinstein bandwagon; that's just a photo-op for her.
George:
The pictures that I have seen of Lake Tahoe suggest a relatively calm lake. However, since its surface area is 40X greater than the empirically derived boundry between lakes where there is a shift from turbidty to turbulent mixing being more important, then is safe to assume that turbulent mixing by wind is more important.
I am also skeptical about Feinstein’s comment about causes of increased turbidty in Lake Tahoe.
Looking at the Coats et al paper, I believe that the mixed upper layer (epilimnion) of Lake Tahoe is about 30 m thick in fall. Evidently the lower depth (30 m) is deeper than significant heating by light. I don’t know the details of the Lake Tahoe sampling regime. If they have been measuring temperature over the upper 30 m every two weeks for the last 40+ years, as the Coat’s paper notes, it seems safe to assume that the research group also has regular Secchi measurements and also measured light transmission with depth using a light meter, probably also over the upper 100 m. It’s a well funded research programs and Charles Goldman for UC Davis has been the research leader for all or most of the 40 years.
George:
The pictures that I have seen of Lake Tahoe suggest a relatively calm lake. However, since its surface area is 40X greater than the empirically derived boundry between lakes where there is a shift from turbidty to turbulent mixing being more important, then is safe to assume that turbulent mixing by wind is more important.
I am also skeptical about Feinstein’s comment about causes of increased turbidty in Lake Tahoe.
Looking at the Coats et al paper, I believe that the mixed upper layer (epilimnion) of Lake Tahoe is about 30 m thick in fall. Evidently the lower depth (30 m) is deeper than significant heating by light. I don’t know the details of the Lake Tahoe sampling regime. If they have been measuring temperature over the upper 100 m every two weeks for the last 40+ years, as the Coat’s paper notes, it seems safe to assume that the research group also has regular Secchi measurements and also measured light transmission with depth using a light meter, probably also over the upper 100 m. It’s a well funded research programs and Charles Goldman for UC Davis has been the research leader for all or most of the 40 years.
Hey thanks Bill for your expert insights. This sort of question is one where the hand waving stick scratching on a sandy beach approach doesn’t lead to much enlightenment; and actual quantitative data is needed.
I happen to be aquainted with a somewhat Kooky guy who lives up in the Truckee area, and is an avid Tahoe supporter. He’s also probably the most knoweldgeable individual on California trout, and has spent hours sitting underwater in lakes and streams watching what trout actually do under there (for the interest of fly fishermen).
Six months ago I’d never even heard of a Secchi disk; but he clued me in with a discussion about why his horizontal visibility was less than when he looked down from a boat; and yes he had measured the visibility with a Secchi disk, both vertically and horizontally so he knew the effect was real.
I surmised that it was the lighted bright background he was looking at horizontally, that obscured the Secchi pattern much faster than when there was no light returned from below the disk in the vertical measurement case.
It’s a bloody clever gizmo for essentially making Optical Modulation Transfer Function estimates with a single observation; and six months ago, I’d never heard of such a thing. I still plan to get one to take on my fishing jaunts to play with.
A problem with making light measurments with a light meter (down there), is that very turbidity is going to result in both forward scatter and back scatter, so if you pointed the light sensor upwards, in addition to reading the light reaching there from the surface, you are going to have downward back scatter of light that was already scattered upwards from below the sensor.
And frankly, I don’t quite know how you can isolate the direct forward scattered light from the indirect back scattered; you need the optical equivalent of the microwave directional coupler; and one that works with incoherent light.
I wonder if Goldman’s team have a method of doing that; or if they even care about that issue.
Same problem occurs if trying to read infrared long wave emissions from a surface say the south polar ice surface, when the sensor is embedded in a sea of scattered ir from every which direction.
George