From the University of Cincinnati: Long-Lost Lake Offers Clues to Climate Change
What caused water levels to drop in an immense yet long-vanished lake? Research by a University of Cincinnati geologist suggests that conditions 12,000 years ago encouraged evaporation.
Not long ago, geologically speaking, a now-vanished lake covered a huge expanse of today’s Canadian prairie. As big as Hudson Bay, the lake was fed by melting glaciers as they receded at the end of the last ice age. At its largest, Glacial Lake Agassiz, as it is known, covered most of the Canadian province of Manitoba, plus a good part of western Ontario. A southern arm straddled the Minnesota-North Dakota border.
Not far from the ancient shore of Lake Agassiz, University of Cincinnati Professor of Geology Thomas Lowell will present a paper about the lake to the Geological Society of America annual meeting in Minneapolis. Lowell’s paper is one of 14 to be presented Oct. 10 in a session titled: “Glacial Lake Agassiz—Its History and Influence on North America and on Global Systems: In Honor of James T. Teller.”
Although Lake Agassiz is gone, questions about its origin and disappearance remain. Answers to those questions may provide clues to our future climate. One question involves Lake Agassiz’ role in a thousand-year cold snap known as the Younger Dryas.
As the last ice age ended, thousands of years of warming temperatures were interrupted by an abrupt shift to cold. Tundra conditions expanded southward, to cover the land exposed as the forests retreated. This colder climate is marked in the fossil record by a flowering plant known as Dryas, which gives the period its name.
“My work focuses on abrupt or rapid climate change,” Lowell said. “The Younger Dryas offers an opportunity to study such change. The climate then went from warming to cooling very rapidly, in less than 30 years or so.”
Scientists noted that the Younger Dryas cold spell seemed to coincide with lower water levels in Lake Agassiz. Had the lake drained? And, if so, had the fresh water of the lake caused this climate change by disrupting ocean currents? This is the view of many scientists, Lowell said.
Lowell investigated a long-standing mystery involving Lake Agassiz – a significant drop in water level known as the Moorhead Low. It has long been believed that the Moorehead Low when water drained from Lake Agassiz through a new drainage pathway. Could this drainage have flowed through the St. Lawrence Seaway into the North Atlantic Ocean?
“The most common hypothesis for catastrophic lowering is a change in drainage pathways,” Lowell said.
The problem is, better dating of lake levels and associated organic materials do not support a rapid outflow at the right time.
“An alternative explanation is needed,” he said.
Lowell’s research shows that, although water levels did drop, the surface area of the lake increased more than seven-fold at the same time. His research suggests that the lower water levels were caused by increased evaporation, not outflow. While the melting glacier produced a lot of water, Lowell notes that the Moorhead Low was roughly contemporaneous with the Younger Dryas cold interval, when the atmosphere was drier and there was increased solar radiation.
“The dry air would reduce rainfall and enhance evaporation,” Lowell said. “The cold would reduce meltwater production, and shortwave radiation would enhance evaporation when the lake was not frozen and sublimation when the lake was ice-covered.”
Further research will attempt a clearer picture of this ancient episode, but researchers will have to incorporate various factors including humidity, yearly duration of lake ice, annual temperature, and a better understanding of how and where meltwater flowed from the receding glaciers.
Lowell’s efforts to understand changes in ancient climates have taken him from Alaska to Peru, throughout northern Canada and Greenland.
In Greenland, Lowell and a team of graduate students pulled cores of sediment from lakes that are still ice-covered for most of the year. Buried in those sediments are clues to long-ago climate.
“We look at the mineralogy of the sediments,” Lowell said, “and also the chironomids. They’re a type of midge and they’re very temperature sensitive. The exact species and the abundance of midges in our cores can help pinpoint temperature when these sediments were deposited.”
Lowell’s research was initially funded by the Comer Foundation. In recent years, the National Science Foundation has provided funding for this work.
When the Geological Society of America meets this year the University of Cincinnati will be well represented, with more than two dozen papers and presentations. Topics range from ice-age climate to the health effects of corrosion in drinking water pipes.
Photos By: Lisa Ventre
Big Al says:
October 5, 2011 at 2:36 pm
I’ve been a fan of Lake Agassiz since growing up in Minnesota. I actually find the whole idea of evaporation hard to grasp. The only present day equivalent I can think of is the Aral Sea, and it has been caused by humanoids!
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I don’t know if it is a valid comparison, but you might look at the pluvial lakes of the Great Basin — Lake Manley, Lake Bonneville, etc. The innumerable mountain ranges in the area complicate things, but basically. the handful of lakes that remained by the time that Europeans reached the area — Great Salt Lake, Owens Lake, etc are the remains of much larger lakes that shrunk through evaporation.
To aire is human…..
But direct transformation from solid to gas is sublime.
There are valleys in Saskatchewan that once flowed much more water than they do now. In the Qu’Appelle valley once ran a great river. Similarly the Saskatchewan once obviously flowed much more water than it does now. The natural drainage existed and you don’t need evaporation to explain how Lake Agassiz drained.
Gail Combs says:
October 5, 2011 at 3:24 pm
One possibility is as you indicate but if the water is removed quickly then the succession will differ:
http://blog.midwestlakes.org/07-06/what-is-lake-succession.html
http://en.wikipedia.org/wiki/Pioneer_species
To all those questioning how the lake could have increased surface area while draining : the lake level could have been high relative to nearby lowlands, and a breach (due to whatever) could have caused the lake to drain into nearby lowlands – thus lowering its level (height) while increasing surface area. Think of a tall, narrow glass of water with a small exposed surface suddenly spilled on the countertop – the glass might be quickly picked up and remain partially filled – meanwhile the entire countertop is now covered in water – resulting in a tremendous increase in liquid surface area for a comparitively small reduction in level (height) within the glass.
The last Y-D theory I heard was that the lake normally drained via the Mississippi but a meteor
impact struck the glacier and (without details) ultimately redirected meltwater, of which now there was a new immense quantity, into the St. Lawrence river system via the Great Lakes. And this sudden immense influx of glacial water into the NA interupted the Gulf Stream and shut down the AMOC.
Good theory with good supporting vidence, but still not conclusive.
Anyone else notice that Lowell looks just like Leif Svaalgard ?
GW
Don K says:
October 5, 2011 at 6:16 pm
Great Salt Lake . . . shrunk through evaporation.
Yes, but . . .
Read about Red Rock Pass here:
http://www.hugefloods.com/Bonneville.html
The lake expanded because the extreme amount of sediment in the melt waters. There are hundreds of feet of sediment over the bedrock here. Here at my house I can dig down 50 feet and you find nothing but the most wonderful small grained beach sand you could ever want. The largest rocks are no bigger than the eraser on a pencil… which occur in sporadic lenses throughout the layers. When we dug in a well, we had to deal with sand in the water blasting our dishes and then getting baked on by the heating element in the dish washer for about a year. The lake was “filling in” so fast that even though it got shallower, it expanded greatly in size.
This is why the Red River Valley area along the border of ND and MN is one of the flattest areas on earth. In any case, evaporation or not… some of the lake most definitely drained into Hudson Bay.. as the river systems do today. I’ve never heard of it draining into the St. Lawrence Seaway… there is no evidence of rivers moving from Agassiz to Lake Superior. The continental divide runs just south of the lake shore in northern Minnesota and would have kept the water from flowing that way. Instead, it seems most of the water flowed either through the glacial river Warren into the modern day Mississippi or through the current channel into Hudson Bay.
Lowell’s paper is one of 14 to be presented Oct. 10 in a session titled: “Glacial Lake Agassiz—Its History and Influence on North America and on Global Systems: In Honor of James T. Teller.”
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14 papers to be presented, five days from now.
Geology is fascinating to me, there is still so much to be understood.
The present-day map at the top doesn’t give the proper context. These claim to show the Dryas era:
http://hot-topic.co.nz/wp-content/uploads/2010/04/Dryas1.gif
http://www.nature.com/news/2010/100331/images/dryas-big.jpg
The lake may not be as deep now, but it is still wet.
I have long wondered if the Younger Dryas “needs” a special explanation. By this, I mean to ask if it was really any different fundamentally from the rapid cooling following earlier Dansgaard-Oeschger warm periods during the last glacial period. Was the warm period before the Younger Dryas just a larger D-O event?
It seems entirely plausible to me that D-O events can “kick” the climate from a glacial state to a non-glacial state, much like impulses that try to push a pendulum over the top and into a different cycle. There were many D-O events in the last glacial period that ended in a fully cold climate; possibly the D-O event before the Younger Dryas just failed to make it “over the top”.
Of course, even if correct, this just pushes the question back one level: what caused the start and end of the D-O events?
Some 5.9 million years ago the Straits of Gibralter opened and closed its access to the Atlantic Ocean, and the Mediterranean Sea evaporated several times. This left a scorchingly hot valley up to three miles deep. This tremendous depth resulted in an atomspheric pressure up to 1.7 times that of today’s mean sea level. The massive increase in air density heated the air and made it far more forceful along the evaporite valley floor. As the opening to the Atlantic Ocean reopened and reclosed, the repeated cycles of evaporation deposited evermore salt and other evaporites. One news report claimed a human footprint had been discovered in this evaporite.
I’ve often wondered how the depositon of the evaporites may have affected the oceanic salinity, thernal currents, and the Miocene climate?
Uhm… have a look at the Souris River highlighted in this map:
http://en.wikipedia.org/wiki/File:Sourisrivermap.png
Today the Souris flows into the Assiniboine which flows into the Red River which empties into Lake Winnipeg, the remants of Lake Aggasiz. Note the proximity of the southern bend in the Souris River to the Missouri River.
Note we’re talking the prairies here. Flat. You can watch your dog run away…for three days. You can see Regina from Winnipeg. Stand on a can of tuna, and you can see Calgary. Stand on a foot stool, and you can see the Rockies. When you go for a drive in the country, there’s a tree on the horizon. Where? Which part of “horizon” are you not understanding? Turn slowly in a circle and you’ll see it at some point.
The 1997 “Flood of the Century” was (if I recall correctly) about 10 meters above flood level and created a lake larger than some of the Great Lakes – in area. It doesn’t take much extra water (or a bit of isostatic rebound) to cause the water to spread out to 7 times its normal area. I grew up on the Souris and recall high school geography classes where evidence that the Souris once emptied into the Missouri being discussed. Seems to me that’s a more likely drainage point than evaporation or the St Lawrence.
I mapped Precambrian geology in central-northern Manitoba in the late 50s and early 60s and came across a hitherto undiiscovered beach strandline that was a chain of dunes eerily standing in the silence of a boreal forest. This must have been the last stand of Agassiz before it rushed out into Hudsons Bay. The numerous concentric lowered beaches are unmistakable evidence of periodic rapid outflows. Evaporation would not produce these features. You would rather get broad flats as with the present remains of Lake Bonneville, that of Great Salt Lake. Sorry Dr. Tyrell, you are wrong. Never mind Greenland, go to Carbery, Manitoba and look at the large abandonned sand delta high and dry in the middle of the prairie wehre the Assinniboine used to enter L. Agassiz. Stop destroying knowledge.
The same fate which struck Lake Agassiz in Northern America some 12000 years ago might have happened to what is known as Taklamakan Desert in Central Asia today.
If you look closely, this pot-like desert, surrounded by two of the highes mountain-ranges in the world, makes up for a marvellous meltwater-lake at the end of the last Ice Age, once the surrounding glaciers started melting.
But when the melting of these glaciers litterally “dried out”, evaporation got the upper hand and, over milleniums to come, the lake completely evaporated again and finally exposed it’s sandy seafloor, today known as Taklamakan desert.
That would explain several of the mysteries of the development of mankind in Asia, too – as a lot of people came out of nowhere and literally burst into existence from an unknown beginning way out in the East some 8000 years ago, to finally populate eastern and northern Europe – an unresolved mystery, which is driving european anthropologists mad for centuries, already.
Did the ancestors of those people live on the shores of a then-huge and splendid Lake Taklamakan – which might have been more of a freshwater-ocean back then – until it disappeared before their very eyes and made them fugitives before the ensueing drought…?
Is this an impossible scenario? Nope! It happened before – see Lake Agassiz back then – and is happening again right now, while we watch: See the vanishing of Lake Aral in Asia today.
What do you think? Opinions wanted!
Michael Schaefer says:
October 6, 2011 at 1:03 am
Humans are able to watch the Aral Sea vanish, thanks to overweening pride by pesky communists. “Formerly one of the four largest lakes in the world with an area of 68,000 square kilometres (26,300 sq mi), the Aral Sea has been steadily shrinking since the 1960s after the rivers that fed it were diverted by Soviet Union irrigation projects.”
http://en.wikipedia.org/wiki/Aral_sea
The links provided by Bill Illis, John F. Hultquist & davidmhoffer took me on a journey of discovery for 2 hours and as a consequence i believe Professor of Geology Thomas Lowell may be barking up the wrong tree. Nevertheless, his work is to be applauded and I look forward to learning more in a few days.
Shallower with a bigger area?
These two facts do not go together unless an area geomorphological change happened. Isostatic readjustment happens too slowly to have caused this I think.
One of the oft mentioned global warming bogeymen is the possibility of a “Thermohaline Catastrophe”. If too much fresh meltwater was suddenly dumped into the North Atlantic, the “conveyor belt” current would shut down… The so-called Thermohaline Circulation (THC| catastrophe theory.
This “theory” died a decade ago; yet the THC bogeyman lives on I’m the media. In Geological Perspectives of Global Climate Change (2001), Wallace Broecker, the father of the THC catastrophe theory, wrote that “the threat (of an anthropogenic thermohaline catastrophe) will be far smaller than previously envisioned.” Broecker’s epiphany was likely inspired by Gerard Bond’s demonstration that Dansgaard-Oeschger-type events continued throughout the Holocene.
The best evidence for a past THC catastrophe had always been the Younger Dryas mini-ice age during the Pleistocene-Holocene transition. For quite a long time it was believed that the failure of an ice dam holding bake glacial Lake Agassiz in Canada had dumped so much water into the North Atlantic that it shut down the “conveyor belt” and caused a THC catastrophe.
About the same time as Broecker’s epiphany, Gosler et al.(2000) demonstrated the Broecker’s THC “smoking gun” radiocarbon signature was present in lake sediment cores.
In 2005 Thomas Lowell published a paper in Eos, demonstrating that the Agassiz ice dam failed well after the Younger Dryas… Testing the Lake Agassiz Meltwater Trigger for the Younger Dryas, Lowell, EOS, October 4, 2005.
This particular AGW myth lives on, despite having been killed about a dozen times since the mid-1990’s. The Warmists don’t have the slightest clue as to how the pre-industrial climate behaved, yet they are certain that industrial era climate change is unprecedented.
Read about a Glacial Lake in Siberia
http://www.esd.ornl.gov/projects/qen/lake.html
The winds at that latitude blow from west to east. How could a failure of the thermohaline in the Atlantic, cause massive cooling in the middle of the N. American continent?
I’ve read recent studies that claim that the Gulf Stream only adds a small amount of warmth to the European continent, and almost all of that is confined to coastal regions.
My Uncle, a native Minnesotan, pointed out a unique geological feature of that State.
Minnesota has 3 distinctive watersheds.
*The Mississippi headwaters start fairly high up in the state, then wend their way south to the Gulf of Mexico, gathering in the Ohio and Missouri rivers and thereby draining most of the central US.
* The rivers along the upper northeast portion of Minnesota drain east into Lake Superior, and ultimately through the great lakes and out to the Atlantic Ocean through the St Lawrence.
* The Red River of the north forms part of the boundary between Minnesota and North Dakota. This river flows northward into Canada and ultimately into the Hudson Bay (which takes it through the region discussed in the posted article).
I know of no where else in the US that has this unique 3 watershed feature. Which gives some credence to the various proposals and possibilities for Lake Agassiz draining so many different ways.
Interestingly, the spring flooding in parts of North Dakota seem to be related to thawing in the US earlier than farther north, which may still be ice jammed on the way to the Hudson Bay. Makes me wonder if that could have happened on a larger scale as the ice retreated north of Lake Agassiz long ago.
It’s a pleasure to read thoughtfull, polite, replys to information one disagrees with, instead of the blather that usually accomplaies these types of atricles. Thank you gentlemen and ladies, you have restored my faith in the intellectual capacities of us all…..jg
@ur momisugly Bill Illis
Would you explain? Is there a standard explanation for the Younger Dryas that is offered up by warmist?
Bill Parsons says:
October 6, 2011 at 11:44 am
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In the Younger Dryas Event, Greenland temperatures declined by 4.0C, Antarctica declined by 2.0C, the north Atlantic declined by 1.0C and global temperatures declined by 1.0C.
If freshwater outflow from Hudson Bay/Lake Agassiz caused it, then it did it 25 times in the last ice age, not just once. Greenland just had significant climate variability which are commonly called the Dansgaard–Oeschger events and the Younger, Older and Oldest Dryas events were just one of those.
http://en.wikipedia.org/wiki/Dansgaard%E2%80%93Oeschger_event
A certain person is most responsible for overblowing how much temperatures changed in the Younger Dryas.
http://img706.imageshack.us/img706/294/dryasevents.png
http://img836.imageshack.us/img836/9484/lasticeageglant.png
http://img830.imageshack.us/img830/6250/alley2000finaltime.png
I can’t picture a gentle uplift of land, even if the weight of the Laurentide Ice Sheet “gradually” melted. Wouldn’t the rebound have taken place in a series of earthquakes?
From Ferdinand Enlebeen’s post above, it seems the southern terminus of the sheet was some 500 vertical meters, and if only the top 50 meters were above the lake level, glacier calving would have been quite a splash. Wouldn’t these events in summers, along with the icebergs they spawned, have been sufficient to send water cascading over any moraines representing the lake edges?
Windblown icebergs may have scoured the lakebed, leaving some distinctive grooves. Bluemle photographed some of these from the air. Here they show through the patchworks of farmland in the Red River Valley:
https://www.dmr.nd.gov/ndgs/ndnotes/Shelterbelts/shelterbelts.htm
Bill Illis,
Thank you. So… the mechanism they propose is the “thermohaline catastrophe” outlined by David Middleton, 4:03 am, above?