Well here we go again, you know the drill. Global warming at fault, other possibilities ignored, multiple press releases. Lake Tanganyika is the second largest lake in the world for fresh water, so naturally any change it is cause for “alarm”. Unfortunately in these press releases there is no mention of a possible increase in turbidity due to human action on and around the lake, decreasing the albedo to absorb more sunlight on the lake surface, warming it. At least somebody has already asked that question previously in peer reviewed literature where they describe the Lake Tanganyika problem as “watershed deforestation, road building, and other anthropogenic activities result in sediment inundation…“.
But in our current press releases, there is this hat tip to anthropogenic: “The team attributes the lake’s increased temperature and the decreased productivity during the 20th century to human-caused global warming.”
First from Brown University:
Brown Geologists Show Unprecedented Warming in Lake Tanganyika
PROVIDENCE, R.I. [Brown University] — Lake Tanganyika, the second oldest and the second-deepest lake in the world, could be in for some rough waters.
Geologists led by Brown University have determined the east African rift lake has experienced unprecedented warming during the last century, and its surface waters are the warmest on record. That finding is important, the scientists write in the journal Nature Geoscience, because the warm surface waters likely will affect fish stocks upon which millions of people in the region depend.
The team took core samples from the lakebed that laid out a 1,500-year history of the lake’s surface temperature. The data showed the lake’s surface temperature, 26 degrees Celsius (78.8°F), last measured in 2003, is the warmest the lake has been for a millennium and a half. The team also documented that Lake Tanganyika experienced its biggest temperature change in the 20th century, which has affected its unique ecosystem that relies upon the natural conveyance of nutrients from the depths to jumpstart the food chain upon which the fish survive.
“Our data show a consistent relationship between lake surface temperature and productivity (such as fish stocks),” said Jessica Tierney, a Brown graduate student who this spring earned her Ph.D. and is the paper’s lead author. “As the lake gets warmer, we expect productivity to decline, and we expect that it will affect the [fishing] industry.”
The research grew out of two coring expeditions sponsored by the Nyanza Project in 2001 and 2004. Cores were taken by Andrew Cohen, professor of geological sciences at the University of Arizona and director of the Nyanza project, and James Russell, professor of geological sciences at Brown, who is also Tierney’s adviser.
Lake Tanganyika is bordered by Burundi, the Democratic Republic of Congo, Tanzania, and Zambia — four of the poorest countries in the world, according to the United Nations Human Development Index. An estimated 10 million people live near the lake, and they depend upon it for drinking water and for food. Fishing is a crucial component for the region’s diet and livelihood: Up to 200,000 tons of sardines and four other fish species are harvested annually from Lake Tanganyika, a haul that makes up a significant portion of local residents’ diets, according to a 2001 report by the Lake Tanganyika Biodiversity Project.
Lake Tanganyika, one of the richest freshwater ecosystems in the world, is divided into two general levels. Most of the animal species live in the upper 100 meters, including the valuable sardines. Below that, the lake holds less and less oxygen, and at certain depths, it is anoxic, meaning it has no oxygen at all. What this all means is the lake is highly stratified and depends on wind to churn the waters and send nutrients from the depths toward the surface as food for algae, which supports the entire food web of the lake. But as Lake Tanganyika warms, the mixing of waters is lessened, the scientists find, meaning less nutrients are funneled from the depths toward the surface. Worse, more warming at the surface magnifies the difference in density between the two levels; even more wind is needed to churn the waters enough to ferry the nutrients toward the fish-dwelling upper layer.
The researchers’ data show that during the last 1,500 years, intervals of prolonged warming and cooling are linked with low and high algal productivity, respectively, indicating a clear link between past temperature changes and biological productivity in the lake.
“The people throughout southcentral Africa depend on the fish from Lake Tanganyika as a crucial source of protein,” noted Cohen, an author on the paper. “This resource is likely threatened by the lake’s unprecedented warming since the late 19th century and the associated loss of lake productivity.”
Climate change models show a general warming in the region, which, if accurate, would cause even greater warming of the Lake Tanganyika’s surface waters and more stratification in the lake as a whole. “So, as you move forward, you can imagine that density gradient increasing,” said Russell, an author on the paper.
Some researchers have posited that the declining fish stocks in Lake Tanganyika can be attributed mainly to overfishing, and Tierney and Russell say that may be a reason. But they note that the warming in the lake, and the lessened mixing of critical nutrients is exacerbating the stocks’ decline, if not causing it in the first place. “It’s almost impossible for it not to,” Russell said.
Other authors on the paper are Brown graduates Marc Mayes and Natacha Meyer; Christopher Johnson at the University of California, Los Angeles; and Peter Swarzenski, with the United States Geological Survey. The National Science Foundation and the Nyanza Project funded the research.
=======================================
Here is the University of Arizona version
=======================================
Twentieth-Century Warming in Lake Tanganyika is Unprecedented
Warming in the last century threatens one of Africa’s largest inland fisheries.
Lake Tanganyika’s surface waters are warmer than at any time in the previous 1,500 years, a University of Arizona researcher and his colleagues report online in Nature Geoscience.
The rise in temperature during the 20th century is driving a decline in the productivity of the lake, which hosts the second-largest inland fishery in Africa.
“People throughout south-central Africa depend on the fish from Lake Tanganyika as a crucial source of protein,” said study co-author Andrew S. Cohen, a UA professor of geosciences. “This resource is likely threatened by the lake’s unprecedented warming since the late 19th century and the associated loss of lake productivity.”
This is the first detailed record of temperature and its impacts on a tropical African ecosystem that allows scientists to compare the last 100 years with the previous 1,400 years, Cohen said.
The team attributes the lake’s increased temperature and the decreased productivity during the 20th century to human-caused global warming.
“We’ve got a global phenomenon driving something local that has a huge potential impact on the people that live in the region and on the animals that live in the lake,” he said.
The annual catch of the Lake Tanganyika fishery is estimated at about 198,000 tons per year, more than 20 times greater than the U.S. commercial fishery in the Great Lakes, he said. The nations of Burundi, Tanzania, Zambia and the Democratic Republic of Congo border the lake, which is the longest lake in the world and the second deepest.
The surface waters of Lake Tanganyika are the most biologically productive part of the lake. For the 1,400 years before 1900, those waters were no warmer than 75.7 F (24.3 degrees C). Since 1900, the lake’s surface waters warmed 3 degrees F, reaching 78.8 degrees F (26 degrees C) in 2003, the date of the researchers’ last measurement.
The researchers used sediment cores from the lake bed to reconstruct the 1,500-year history of the lake. The scientists analyzed the cores for chemicals produced by microbes and left in the sediments to determine the lake’s past temperature and productivity.
Because sediment is deposited in the lake in annual layers, the cores provide a detailed record of Lake Tanganyika’s past temperatures and productivity and of the regional wildfires.
The instrument record of lake temperatures from the 20th century agrees with the temperature analyses from the cores, Cohen said.
The cores were extracted as part of the UA’s Nyanza Project, a research training program that brought together U.S. and African scientists and students to study tropical lakes. The National Science Foundation funded the project.
“A big part of our mandate for the Nyanza Project was looking at the interconnectivity between climate, human activity, resources and biodiversity,” said Cohen, who directed the multi-year project.
Lake Tanganyika and similar tropical lakes are divided into two general levels. Most of the fish and other organisms live in the upper 300 feet (about 100 meters). At depths below that, the lake waters contain less and less oxygen. Below approximately 600 feet, the lake water, although nutrient-rich, has no oxygen and fish cannot live there.
During the region’s windy season, the winds make the lake’s surface waters slosh back and forth, mixing some of the deep water with the upper layers. This annual mixing resupplies the lake’s food web with nutrients and drives the lake’s productivity cycle, Cohen said.
However, as Lake Tanganyika warms, the upper waters of the lake become less dense. Therefore, stronger winds are required to churn the lake waters enough to mix the deeper waters with the upper layer. As a result, the upper layers of the lake are becoming increasingly nutrient-poor, reducing the lake’s productivity.
In addition, warmer water contains less dissolved oxygen, reducing the quality of the habitat for some fish species.
Other lakes in Africa are showing similar effects to those the team found in Lake Tanganyika, he said.
The finding has implications for lakes in more temperate climates.
“Increasingly, lakes in the U.S. are warming and they’re behaving more like these African lakes,” Cohen said. “There’s a potential for learning a lot about where we’re going by seeing where those lakes already are.”
The team’s article, “Late twentieth-century warming in Lake Tanganyika unprecedented since AD 500,” will be published in the June issue of Nature Geoscience.
Cohen’s co-authors on the paper are first author Jessica E. Tierney of Brown University in Providence, R.I.; Marc T. Mayes, Natacha Meyer and James M. Russell, also at Brown University; Christopher Johnson, a former University of Arizona student now at the University of California, Los Angeles; and Peter W. Swarzenski of the U.S. Geological Survey in Santa Cruz, Calif. The National Science Foundation funded the research.
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
one to watch, tho i haven’t checked the reader’s comment on accuweather:
19 May: UK Daily Mail: Blazing in, the 80f weekend: But we’ll soon be cooling down again
(Met Office forecaster Helen Chivers) ‘A temperature of 25c (77f) is possible on Friday and temperatures might reach 26c (79f) on Friday or Saturday,’ Miss Chivers said…
COMMENT BY READER: AccuWeather gives a maximum of 16C today with rain at 0800 and again at 1100 in the North West of England – and a MAXIMUM temperature of 12C on Sunday.
What a shame the Met Office cannot agree on the forecasts projected by AccuWeather and others of that ilk.
http://www.dailymail.co.uk/news/article-1279270/Get-ready-long-barbecue-summer-temperatures-forecast-hit-39C.html#comments
Even if the claims are true, which they aren’t, wouldn’t it be cheaper to buy each of the 10 million local residents their own restaurant chain than implode the economies of the entire industrialized world?
—
@ur momisugly Tom Jones, regarding temperature gradient findings (or the lack thereof), not having full online access to Nature Geoscience – and certainly unwilling to pay $18 for such access to this single letter – I cannot say for sure that the perpetrators of this study harvested any information on water temperatures at varying levels or other sites in Lake Tanganyika.
Who knows? Perhaps such information is being reserved for later baloney-slicing. Those of us who have published on any sort of research are familiar with the need to get as many entries in our curricula vitae as possible out of the expenditures we oversee.
But speaking from the perspective of a trained biologist who spent some rather miserable time on the water decades ago dunking a Nansen bottle and recording temperatures at varying depths by way of a thermocouple attached to the gadget, I’m aware of the fact that whenever you drop any weight on a line into a body of fluid, you can sure as hell do a bit of rough-and-ready bathythermography.
Measuring nothing but surface temperatures offers no insight into the total heat being accumulated by the waters of Lake Tanganyika, not so? Moreover, if surface water turbidity – as the result of agriculture-promoted sediment run-off from the tributaries’ drainage areas – is increasing solar heat absorption and leading to increased stratification (meaning that there is less updwelling of colder, nutrient-rich bottom waters), there is a more immediate, much more powerful causative mechanism that must be considered and ruled out before anthropogenic global warming is trumpeted.
—
—
Addendum. If there’s anyone reading here who does have access to Nature Geoscience, could there be some examination of this letter to see whether or not the investigators performed nephelometric evaluations of surface waters and samples taken at depths within the range at which freshwater phytoplankton might customarily be expected to populate Lake Tanganyika?
I would think that some such method – to assess the degree of reduction in the intensity of incident light after passing sequentially through waters ranging down from the surface as the result of turbidity – together with analyses of the chemical compositions of these samples, the microflora contained therein, and determination of the nature and levels of such particulates as might be suspended in the water at these shallow and easily accessed depths would be part of any examination of Lake Tanganyika as a physical phenomenon.
Or couldn’t these clowns get a biologist or two to come along with them?
—
Al Gored 7:36 pm
It may have something to do with the 1500 year climate cycle they found in the ice cores. Perhaps the Dark Ages that followed wasn’t really as bad as itz rumored to have been.
Anyone actually read the paper? I wouldn’t just rely on the media coverage. From the first press release shown here, it seems they are mostly talking about fluctuation in productivity linked to temperature. In the second, they mention a link to GHGs. What does the actual paper say? I think until you actually READ the paper rather than these press releases you really don’t have anything to say.
Uhhhh……. isn’t Lake Tanganyika located over a “mantle plume” which is thought to heat the crust, causing a lot of the geological activity in this portion of Africa?
Anyone know how these researchers used core sediment samples to determine a 1.7C increase in SURFACE temperatures over a 1400 year period from a lake with mean depth of 570 meters? They also say the rapid warming started in the late 19th century- can we say end of LIA?
So why isn’t my inground pool 3 degrees warmer? I’ve been recording the temperature daily every summer. Last summer it was the coldest of the prior five years. This year I haven’t even opened it yet. It’s been far too cold. Why does global warming only seem to occur in far away places like the arctic, central Africa, or the top of the Himalayas, but not here in Philadelphia?
An article from Nat. Geog. 2000.
“Allen compared Baikal to the U.S.-Canadian Great Lakes, now believed on
the rebound after years of abuse. As a worst-case outcome, she cited Lake Tanganyika which, unlike teeming Baikal, is all but lifeless. ”
http://news.nationalgeographic.com/news/2000/12/1201_russianlake.html
Is this “Schrodinger’s lake” – dead one minute, and alive the next?
“anoxic, meaning it has no oxygen at all”……….uhmm, at the risk of displaying my ignorance…..yet again, how does H2O contain no O?
Reply: Anoxic means depleted of dissolved Oxygen. ~ ctm
The Brown University geology department has been doing some very PC “research” lately. I hope they recover.
I too am depressed by the constant release of half baked papers offering no more than an alarmist headline. My question is where are the papers/letters/statements refuting this garbage? We have ben told often that geologists by and large don’t buy the AGW line yet we rarely hear or see such statements.
Just today the president of the Australian Council of Trade Unions is calling for the creation of 3.6 million green jobs over the next two decades. Maybe she hasn’t heard of the green economies of Spain or California and the associated deterioration in those economies. The warmers, generally leftists, are hell bent on curbing CO2 and are totally ignorant of alternative explanations for perceived climate change. The danger of Trading schemes and hairbrained green technologies is alive and well.
@ur momisugly barefootgirl, see http://tinyurl.com/37gm7wh for online access to Nature Geoscience‘s early promulgation of this letter. If you want full access, they expect you either to be a subscriber or to cough up eighteen bucks.
Got your credit card handy?
@ur momisugly Gary, on the possibility of an underlying mantle plume or similar geothermal factor which might conceivably account for any heating of the waters of Lake Tanganyika, I don’t believe that any mention has been made. Warmist True Believers I’ve thus far encountered elsewhere causelessly dismiss this possibility.
Frankly, I would dismiss it, too. To the best of my limited understanding, this study has incorporated precisely no bathythermographic assessment (easy as that would have been to conduct as part of the geologists’ sediment core sampling activity, you’d think) and therefore not even the simple consideration of the heat content increases required to raise the temperature of Lake Tanganyika’s contents as a whole to any reliably mensurable extent.
I’m willing to go (for the nonce) with the notion that the surface waters may have increased in temperature, and that there has been the induction of a degree of stratification hitherto not observed in the lake. What does this tell, however, about the temperature of the waters deeper down? Have the investigators in this study even bothered to consider that question? Present deponent answereth not.
Without some idea of temperature increases (if any) within the depths of Lake Tanganyika, speculations about geothermal contributions are (to quote a line from Blazing Saddles) “…just jerking off.”
They claim that the core data agree with the instrument data. What instrument data? I cannot find any instrument data near Lake Tanganyika. There are no weather station with a continous record near the lake, even if you stretch the meaning of “near” to be rather far away. Most that existed seem to have close. At least they don’t report data anymore. For example, the weather station in Harare stopped reporting in 1991. Before that, the temperature had dropped slightly compared to 1915.
Decoded : stop African development. Keep blacks poor. Better to be a noble savage. Keep all energy resources for the superpowers.
It is well known that fertilizers used in modern agriculture leaking into lakes cause algeae to bloom, in turn the algeae will deplet the oxygen in the lake. Very common problem in lakes surrounded by farmland and/or unfiltered sewers.
A slight warming in the surface layers of a lake that represents some promilles of the earths area is a proof of co2-induced global warming ? Uh, ok.
Meanwhile, just a couple of days slow train ride down the track “Bankruptcy threat as SA farmers produce a mountain of maize” (Business Day 18/5/2010). “South African maize farmers, bouyed by unexpectedly good rains,,,,,,,,are preparing to reap their biggest crop in 28 years. The reward for their success may be bankruptcy …………Overplanting, after the national meteorological agency warned of a drought that did not materialise also helped cause this year’s bumper harvest.”
It seems we are likely to have a surplus of 6 million tons of grain, with no market for it. I don’t know but would hazard a guess that the drought scare was caused by global warming and the good rains were the true result of global warming.
At least there is no need for the ’10 million people living near the lake’ to starve – their governments can buy them half a ton each and we will still have a surplus. (But governments and greenies don’t think that way, do they?)
This any good?
“Hydrothermal vents in Lake Tanganyika, East African, Rift system”
http://geology.geoscienceworld.org/cgi/content/abstract/21/6/499
Sardines in fresh water? I suspect they mean small tilapia (Sarotheradon species, or cichlids).
… reaching 78.8 degrees F (26 degrees C) in 2003,
the date of the researchers’ last measurement. …
Breaking news…. on seven year old data,
nothing to see here, move on.
1500 years ago there were probably 10,000 people living there and they didn’t cut down the forest to do their cooking. This is a different sort of UHI.
Lake Tanganyika is approx 3,000,000 years old, the sample of derived proxy temperature from sediment record is 1,500 years.. thats 0.05% of the lifespan of the lake.. and it’s ‘unprecedented’ ?? so we can discount the other 99.95% of it’s lifespan?
They did how many cores for a lake approx. 32,000 sq k in area?
(Magic boremometer perhaps).