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
@Dave in Delaware October 6, 2011 at 9:46 am:
Cool points about the three watersheds in Minnesota. I would suggest that Pennsylvania also has three watersheds. The NW empties northward into Lake Ontario and Lake Erie, the east empties out to directly to the Atlantic, and the center-west-SW drains to the Gulf of Mexico via the Ohio and the Mississippi. While they all eventually end up in the Atlantic, they do it in three far different ways.
@Steve Garcia
Thanks,
I like your addition about the Pennsylvania watersheds, and will add that to my informal list of interesting trivia.
I assume the glacier melt was world wide? if so I can see other theories in there, maybe this was when the `English channel opened up?? it could be so many things that to postulate a concealed water passage to the sea for just some of the ice cap melt seems a bit like grabbing at straws! and yes the 7 times surface area bit worries me too, but as it says it got colder to the melt would slow and the lake would loose its feed, no real mystery is there?
RE: Steve Garcia says:
October 5, 2011 at 4:15 pm
Thanks for the interesting info, but I tend to wonder how plastic the crust is, and ponder the idea of earthquakes mentioned briefly by
Bill Parsons says:
October 6, 2011 at 12:15 pm
A isostatic rise of four inches a year is no small thing. The fact that this rise, over 900 feet in places, is measured by “strandlines” tends to suggest that things stayed in one place long enough to make a line, before a quake changed the status quo to the level where it stayed as the next line was made.
Even now , thousands of years after the ice is gone, I have experienced weak quakes in both New England and Scotland that were explained as isostatic uplift still occurring. I cannot help but wonder if the quakes back when the land was rising four inches a year might have been quite dramatic.
If the lake bed remained quiet for only three years, tension would build up enough to jolt the lake’s bottom up a foot, all at once. That would have made quite a slosh, I imagine.
If one slosh caused vast amounts of water to drain away, even if it merely drained from one area to another, that would reduce the weight oppressing the crust in the drained area, leading to the next quake. One can even envision a series of quakes and drainings occurring in a compressed period of time, rapid fire, each causing the next.
Boating on Lake Agassiz might have been interesting.
Dude, those are PR press releases by Thomas Lowell prior to the GSA meeting in Minneapolis, promoting a nutty idea. Very few, if any, among the geological community subscribe to this notion.
Any time you read alarmist warnings that global warming could trigger an ice age, they are referring to a thermohaline circulation disruption (AKA THC catastrophe). A THC catastrophe forms the central plot line of The Day After Tomorrow. Dennis Quaid’s character was supposedly very loosely based on Wallace Broecker.
Bill Illis is correct in his characterization of the Younger Dryas stadial and other Dansgaard-Oeschger-related events. The amplitude of these events was greater during the last glacial stage of the Pleistocene than they have been in the Holocene; but the magnitude expressed in the Greenland ice cores is at least four times as large as the global magnitude. The cooling of the Younger Dryas wasn’t that anomalous; but the warmth of the preceding Bølling-Allerød interstadial appears to have been very anomalous… As warm as the Little Ice Age in Central Greenland.
GISP2
During the last Pleistocene glacial stage, the D-O events had a period of ~1,470 years and an amplitude of 10° to 20° C in Central Greenland (~2.5 to ~5.0° C globally). During the Holocene, the D-O equivalent cycle (Bond Events) has had a period of ~1,000 years with an amplitude of 1.0° to 1.5° C in Central Greenland (~0.25 to ~0.50° C globally). The Medieval Warm Period, Little Ice Age and Modern Warming (AKA AGW) are all explained by the Holocene equivalent of the D-O cycle. The warm-up from the nadir of the Little Ice Age has probably been enhanced by ~0.1 to ~0.2° C by anthropogenic activities… Although the temperature drop from the peak of the Medieval Warm Period to the nadir of the Little Ice Age was very sharp and deep. Some of the possible anthropogenic warming may simply be part of the climatic rebound from the Little Ice Age.
HadCRUT3 & Ljungqvist
A very interesting discussion.
Given the size of Lake Agassiz and the fact the glaciers were melting and calving not to mention uplift and possible earthquakes…. What is there to say that the lake was not draining from more than one point all at the same time? Or perhaps a bit of alternating as the glaciers melted and refroze in places.
Seems to me that things would have been rather unstable.
And then there were the Giant Beavers (GASP) I have a beaver dam a good five feet high on my property that has turned a little creek into a decent sized pond and shunted the water into another closeby creek.
“The extinct giant beaver, Castoroides ohioensis, was just one species of large animals, or megafauna, …weighed between 60 and 100 kilograms…
Yansa and University of Wisconsin-Whitewater colleague Peter Jacobs recently analyzed material drilled from the jawbone of a giant beaver that had been unearthed at a farm in southeastern Wisconsin. Carbon dating showed that the creature lived around 14,500 years ago, she reported October 19 at the annual meeting of the Geological Society of America. Pollen and plant fossils from sediments surrounding the jawbone suggest that the environment at the site then was cold and marshy with few trees….
Fossils from younger sediments at the sites reveal that climate in the region became warmer and drier after the ice age lifted, says Yansa. As a result, forests crowded out many of the region’s wetlands, providing prime habitat for modern beavers.” http://news.discovery.com/animals/ancient-giant-beavers-trees.html
The Younger Dryas is somewhere around 12.8 and 11.5 ka BP so that particular beaver would have been prior to the Younger Dryas by a couple thousand years. It does indicate that area of Wisconsin was cold and marshy.
From Steve Garcia on October 6, 2011 at 2:38 pm
Not hardly. The main watershed is the Susquehanna River, which drains into the Chesapeake Bay, which covers the center of the state very well.
Very old, very well-established, sometimes very angry. As a lifelong Pennsylvania resident living near the river, sometimes affected by its moods, I would be remiss in not pointing this out. Thus it may be considered four watersheds, the Susquehanna, the small eastern part that goes into the Deleware River (followed by the Deleware Bay then the Atlantic), with the small western bits draining somewhat like you said.
dave in delaware:
in glacier park in montana there is a peak (naturally named triple divide peak) that according to the highway signs, if a drop of water were to fall precisely on the top of the peak 1/3 of it would flow to the pacific via the columbia, 1/3 of it would make it to the missississisissipppppi river and the gulf of mexico and 1/3 to hudsons’ bay.
C
Thanks David
This study says that Lake Agassiz has drained and refilled more than once and it drained to the south, east and to the north:
SUMMARY
The principal points emphasized here are: 1) that the earliest levels of Lake Agassiz built shorelines on stagnant ice well above the Herman level, 2) that two outlets across the Mesabi Range controlled Lake Agassiz for a portion of its early history, 3) that the highest Herman shoreline was formed as outlets to the Superior basin were uplifted until the southern outlet to the Minnesota River was re-occupied, 4) that Lake Agassiz was lowered from the high level Lockhart Phase to the low Moorhead Phase by the opening of outlets to Thunder Bay and on to the Atlantic from 10.9 to about 10.3 ka, 5) that drainage to the Arctic Ocean via the Clearwater River in Saskatchewan maintained low levels from about 10.3 to 9.9 ka, 6) that a readvance at the start of the Emerson Phase at 9.9 ka, which blocked western and eastern outlets, returned drainage to the southern outlet and hence the Gulf of Mexico by raising Lake Agassiz to the Norcross level, at which time the upper fossiliferous fill of valleys along the western shore was deposited, 7) that the southern outlet was eroded to the Campbell level for the first time during the Emerson Phase, 8) that a brief episode of eastward outflow in late Emerson time ended with a rise to the lower Campbell shoreline and deposition of another alluvial fill, and 9) that the Morris Phase history of the lake, after final abandonment of the southern outlet, involved drainage to Lake Nipigon and, in the very late history of the lake at about 8 ka, a possible brief episode of northwestward drainage through Wollaston Lake, probable direct drainage to northeastern Lake Superior, confluence with Lake Ojibway, and final drainage eastward to Hudson Bay.
http://www.geostrategis.com/PDF/review_lake_agassiz_history.pdf
ES says:
October 8, 2011 at 4:33 am
This study says that Lake Agassiz has drained and refilled more than once and it drained to the south, east and to the north….
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Well, that is pretty clear and passes the “Smell Test”
Perhaps the remnants of Lake Agassiz were dried out by evaporation and sedimentation but to think the entire lake evaporated given evidence of drainage basins is a bit hard to swallow. Especially when you consider it was filled by melting from a continental ice sheet as much as ten thousand feet thick.
Also if a lake of that size was evaporating you would be pumping a huge amount of water into the atmosphere. I do not think the local weather would be all that “dry”.
I did find this about from Indiana Geological Survey
“…Environmental conditions near this ice sheet would have been harsh indeed! Possibly as much as a half-mile to a mile thick, the imposing ice front would have been the scene of frigid cascades of meltwater and icy lakes amidst a landscape of thick, cold mud put in motion by constant freeze-thaw activity and water. The sense of desolation would have been compounded by the constant pounding of katabatic winds—cold blasts of air that roar off of the glacier as air masses passing over the ice surface are abruptly chilled and sink rapidly. In fact, an ice sheet of this scale would have probably made its own local weather. Sudden cooling of warm, moist masses of Gulf air encountering the cold ice sheet would have created torrential summer rains and near-constant “glacier-effect” snow in winter….”
I was also happy to see this on their website:
“…another possibility is that substantially warmer ocean surface temperatures will lead to much higher rates of evaporation, thus resulting in far greater cloud cover than we see today. Clouds reflect back much of the incoming solar radiation, and some models suggest that an increase in cloud cover of as little as 20-30% could actually lower global temperatures significantly. Because our record of detailed observation is so short, such feedback mechanisms are very poorly understood, leading to a very limited ability to predict actual changes in global climate, including the possibility of a resurgence of glacial activity in temperate latitudes. Either way, it seems all but certain that the relatively mild, temperate climate we now enjoy is but a fleeting moment in the vast span of geologic time we refer to as the Ice Ag”
But then you would expect geologist to be down to earth in their views.
I’ve spent some time in recent years exploring and reading about the Salt Lake Valley. The former Lake Bonneville drained out through the Snake, leaving a smaller lake that was still somewhat bigger than the Great Salt Lake of today. You can go around the valley and find geological evidence of the old lake levels. As the climate dried out in the Salt Lake Valley, a process of evaporation set in which resulted in the concentration of minerals in the lake water. In some places where the lake receded altogether, “salt flats” were left. The Bonneville Salt Flats are an example of that.
So, If Lake Agassiz disappeared through evaporation shouldn’t some remnants of the lake, i.e. Lake Winnepeg, Devil’s Lake, etc., have high levels of water soluble minerals (salt, etc.) concentrated in their water, and shouldn’t there be salt flats and other mineral deposits left in places?
Just askin’
I realize I am somewhat late with my commnet. My thanks to Steve Garcia for making me aware of this article. I agree with some here who have sugggested that the shutting down or complete stoppage of the North Atlantic as cause for the Younger Dryas should now be put to rest. For those interested, I wrote a book on this very topic in 2009. I call the book “Sudden Cold An examination of the Younger Dryas