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.
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Here is the University of Arizona version
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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.
And of Course Greenland is melting away — see CBC…
http://www.cbc.ca/technology/story/2010/05/18/greenland-land-rising.html
The GPS determined that the increases in land elevation began in the mid-1990s.
Clever GPS…
Can the authors come over to this leading science blog and explain this?
They wrote a story but offer no actual facts?
This story is getting fishy. What are they thinking? The temps last measured in 2003. There is no excuse for this. If a real team went out there and measured it today and found it had dropped, what would they say?
The other fish tale portion is the catch doesn’t really prove much. If the fishing methods are not identical, she has no way of proving there are more or less sardines packed in water.
OK. Let’s pretend the results are accurate, to 2003, and that all the carefully ignored other factors don’t matter. Why was it as warm in 500 A.D.?
What the … is indunation? Covering with dunes? Or inundation perhaps?
Reply: Fixed. ~ ctm
Picking nits:
“Lake Tanganyika is the second largest lake in the world for fresh water, …”
Lake Tanganyika is the second largest lake in Africa, not the world. It is the sixth largest (freshwater) lake in the world by area.
Reply: Second or third in the world by volume. I’ll amend for clarity. ~ ctm
I wonder if they bothered to measure the thickness of the annual layers in the cores? Increased turbidity would increase the annual layers, right? But that would disprove their theory, wouldn’t it? Very bad science!
“…increasing the albedo to absorb more sunlight on the lake …”
Uh, high albedos reflect more light. You mean increasing the absorptivity.
Reply: Fixed, but in a different way. ~ ctm
Another ‘what else could it be’ warming story.
Where’s the data?
Has anyone checked on rift action, since it is in Africa’s Rift Zone?
OK, so Lake Tangyanika stretches from 3 degrees S latitude to 8 degrees S latitude. turning to GISS for the latitude band 0-24S, the temperature change from 1900 to 2003 is 0.5 degrees C. Researchers claim the lake has warmed 3 degrees F. Why is the lake experiencing a temperature anomaly 3 times that of the rest of the planet at that latitude? And what warms it? Certainly not CO2, since LW from CO2 only penetrates a millimeter or less of water and just evaporates back up into the atmosphere… Oh yeah, there were those posts on WUWT about decreased storm intensity in opposition to what the climate models predicted… Oh yeah, the article talks about storm activity sloshing the lake around and bringing water up from the bottom…. cold water…. less storms…. less mixing…. I know I’m really close to figuring this out…. just can’t quite put my finger on it…. less storms, less cold water coming to top, almost got it…. GOT IT! The LW is heating up the boats on the lake which in turn heat the lake! Itz AGW! And global warming reduces storm activity which makes it even worse because the boats can spend more time on the lake! Itz a feedback loop!
Fertilizer.
O/T but this waste of taxpayers’ money has received very little media attention since it sank last Saturday:
wikipedia: Oceanlinx
Oceanlinx is a Wave Energy Converter device , that is a device which uses wave energy and converts it into electrical energy operating on the oscillating water column principle. The Oceanlinx was developed in Australia. The technology has developed greatly in the past ten years thanks to the large amount of international funds it has received.
http://en.wikipedia.org/wiki/Oceanlinx
wiki also lists all the funding, plus the countries and US States that are spending on the technology.
the following are from Illawarra Mercury, Australia:
15 May: $5m Port Kembla wave generator wrecked
It will be a blow to Oceanlinx, which had been keen to prove the project was commercially viable.
The wave-to-energy barge, known as the Mk3, was at the forefront of marine renewable technology and has operated for four years.
Launched at a ceremony on March 29 by Federal Environment Minister Peter Garrett, it is feeding power into the Integral Energy grid.
The mishap caused a 45-minute power outage to nearby areas
http://www.illawarramercury.com.au/news/local/news/general/5m-port-kembla-wave-generator-wrecked/1830582.aspx
17 May: Port Kembla wave generator on sea floor
Throsby MP Jennie George said the sinking of the prototype was devastating news.
“There had been mooring problems with earlier models and the company was confident these had been ironed out,” Ms George said.
“But companies and governments needs to keep persevering … renewable energy is an important part of the energy mix in reducing carbon emissions in the future. I’m sure Oceanlinx will overcome this setback.”
http://www.illawarramercury.com.au/news/local/news/general/port-kembla-wave-generator-on-sea-floor/1831275.aspx
19 May: Barge’s watery grave
Hopes of saving the ill-fated Oceanlinx barge were dashed yesterday after it was discovered smashed to 40 pieces and scattered across the seabed at Port Kembla.
A dive team inspecting the 170-tonne wreck spent hours searching for the damaged metal remnants, combing through masses of thick seaweed at the base of the eastern break wall…
The barge was at the forefront of renewable marine technology and had fed power back to the Integral Energy grid since March this year..
Last year Oceanlinx won a $3 million Climate Ready federal grant to help develop the device, all of which had been allocated.
http://www.illawarramercury.com.au/news/local/news/general/bargeswatery-grave/1834461.aspx
I defy any scientist to measure the temperature of the water at 78.8 deg F with uncerainty that allows the digit after the decimal. I’d put the error, unashamedly subjectively, at about +/- 5 deg F. That’s about what I feel when I take a dip in the pool. For L. Tanganyika, how deep, sun angle, cloud or not, how calm, day or night, season, influence of Rift valley volcanism, mixing, oxidation/reduction of biomass variations with nutrient input/output … Many, many factors.
Several publications show that fish productivity increases with temperature, see e.g. the graph on page 61 and several others which follow (including sardines that this study mentions):
http://www.klimarealistene.com/09VaageV8R.pdf
They could have measured fish scales in the sediments as these authors did for a more direct indicator of fish productivity rather than using “chemicals produced by microbes” and apparently didn’t consider that the lake may be “over-fished” now compared to the last 1500 years.
sorry wrong link above
here is correct link:
http://alexeylyubushin.narod.ru/Climate_Changes_and_Fish_Productivity.pdf
200,000 tons of fish per year? That’s 2000 rail cars!
The results stretching back to 500AD are essentially based on interpretation of core from ONE borehole.
Perhaps a look back at the doomsday claims made by the USGS for a 100 year wasteland in the wake of St Helens eruption would show some similarities. Today it is a thriving system that shows little sign of anything having occurred. Acid rain was going to reduce everything to a gooey slop, but that never happened either. My favorite, Killer Bees, were going to mercilessly attack women and small children but that too didn’t pan out. Now they claim lakes are heating out of control due to a combination of acidic killer bees with volcanic temperament that will kill us all if we don’t run about on bent knees wailing about our terrible ways and go back to living in caves.
What a load of horse pucky!
It would seem like the temperature gradient due to solar heating due to increase turbidity is going to be very different than the temperature gradient due to warming of the atmosphere. There is no mention of trying to measure the thermal gradient at all.
In one interview I read the paper author told the interviewer that several warming and cooling cycles were seen in the sediment data but this one is warmer then the others. I am not a limnologist but the link to AGW is weak to non existent at best. The major concern in this and other lakes is overfishing. If the water temperature effects fish productivity and it does, as far as I know, the sustainable yields will change and that is not good if you need that food source. That said, as others pointed out above many things influence yields besides temperature. A complex situation with unfortunately not simple answers.
Thanks for this illuminating article. But it leaves me a little confused.
Was it that a thousand years ago, when according to African stalagmites the temperature was more than 1 deg C warmer, the lake was nonexistent?
Or was it that the lake was there, but there were no fish in it?
Or have all the fish evolved in the last 8000 years, since the end of the last glaciation, and they’re having trouble with the recent cooling?
Please explain.
Sincerely, Confused
No surprise that it is published in Nature. Good science articles should always address and discuss the confounding factors. But it seems that Nature encourages articles on Global Warming that avoids discussing confounding variables. It is degrading the scientific process. I have seen it in so many “blame global warming for changes” in butterflies, amphibians, etc . Climate-gate and Josh Demming exposed the gatekeeper effect that restricted articles that contradicted AGW. But I think even worse is that Nature puts out articles with very weak evidence that is often contradicted by other good scientific papers about how AGW is disrupting nature, like Pounds’ paper claiming 99% certainty a la IPCC that AGW caused the frog extinctions. Then those papers and ideas go viral, which I suspect is their strategy.
/rant on
Ok, my pet hate, wheres the preceding….’We estimate that….’ or the polite, ‘the data appears to show that…’, i’ll even settle for ‘We interpret the data as…’
Nah.
Nada, thanks to the French business school of management, no uncertainty is permisable. BUT! uncertainty is the foundation of science, it prompts a questioning mind in action. How many poorly reported stories must we endure? Always straight to a statement of fact,…”Lake Tanganyika’s surface waters are warmer than at any time in the previous 1,500 years.” Thanks DR WHO, must be handy, time travellin’ an all.
A proxy ain’t mecury observed and logged, its a “what if”, underlined with a “perhaps” and punctuated with a “maybe.”
To illustrate:
“What if” the AGW-biased Tanganyika research is !#$@*&%$ wrong, and “Perhaps” there is another [Self-Snip]ing answer, “maybe” you could do some actual science that doesn’t rely on a barney the dinosaur level of comprehension.
/rant off.
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For general information, the report is published in the form of a letter (Tierney, Mayes, Meyer, et al, “Late-twentieth-century warming in Lake Tanganyika unprecedented since AD 500”). Links I have noted are:
1) Brown University press release at http://tinyurl.com/3y789dv
2) Online journal citation at http://tinyurl.com/37gm7wh (full access available only to subscribers of Nature Geoscience)
3) Supplemental information (in PDF) at http://tinyurl.com/27tfgx3 (fully accessible at the time of this posting)
The usual warmist crap is being spouted and supported by the True Believers online at The Independent (UK) regarding this study.
Whenever I encounter the AGW cabal chicken-dancing like this, I am minded of my youngest granddaughter (now a lordly five years of age) some several years ago falling upon an Easter egg in the back yard and yelping self-righteously to her older brother that here was proof positive that the Easter Bunny really does exist.
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The real evil of climate change is the systematic hostage taking of all environmental problems. We can solve no problem if the answer is not climate change and as such we solve few problems. This fishery feeds millions of dependent people- to put climate change as the primary driver is at best reckless.
We have an estimate from the 2003 Nature article that the lake’s anchovy biomass is 300,000 metric tons and the current research saying the harvest is 200,000 metric tons. Overfishing? How accurate are the fishery records? The 2003 Nature study says we don’t know the true harvest:
“But the data on the lake is poor and no one really even knows how many people are fishing on the lake. Half of the Tanganyika shore belongs to the Democratic Republic of the Congo, but a long-standing civil war there means fishing records are hard to get.”
A 1991 study by Coulter found other fishery statistic problems:
“The lack of a comprehensive study compounds the continuing problem created
by the frequent confusion between their ‘true’ abundance and their seasonal/annual catchability, which strongly depends on their feeding/spawning habits and impacted on by fishing strategies/efficiencies .”
The comparisons made to the US Great lakes commercial catch is disingenuous at best. The US fishery collapsed some 60 years ago from overfishing. The Great Lakes are now managed as a recreational fishery with a very limited commercial take. The researchers make the statement about Lake Tanganyika’s relatively higher productivity (20X catch)- but fail to appreciate the irony of the Great Lakes being much colder.