Great Lakes water level sensitive to climate change

Jan 13, 2009

The water level in the Great Lakes has varied by only about two meters during the last century, helping them to play a vital role in the region's shipping, fishing, recreation and power generation industries.

But new evidence by scientists from the University of Rhode Island and colleagues in the U.S. and Canada, published last month in the journal Eos, indicates that the water level in the lake system is highly sensitive to climate changes.

"In the distant past, there were great fluctuations in the water level of the Great Lakes, but it was thought to have been related entirely to the advance and retreat of the glaciers," said URI geological oceanographer John King, who led the study with URI visiting scientist Michael Lewis, emeritus scientist with the Geological Survey of Canada. "But the last time lake levels fell dramatically - down to 20 meters below the basin overflow outlets - it was due to dry climate conditions."

That event, which occurred between 7900 and 7500 years ago in the early Holocene period, caused the lakes to become disconnected as their overflow rivers, including the Niagara River, ran dry.

"People used to say that the oceans are so big, we can dump whatever we want in them and nothing will happen," said King. "They thought of the Great Lakes in the same way, that the system is too large to be sensitive to climate variations. But now we know that to be untrue. We've demonstrated that at least once in the last 10,000 years, climate drove the lake levels down pretty substantially."

Researchers had long assumed that the Great Lakes had been "hydrologically open" and connected since their formation 16,000 years ago during the retreat of the last ice sheet, but recent evidence has found this to be false. Ancient shorelines, submerged beaches, and tree stumps on the floor of some lakes indicate that the water line had been as much as 20 meters below the present lake level.

"We had a multi-proxy approach to this study, and through many lines of evidence we identified this as a dry interval with a climactic cause as opposed to a glacial-related cause," King said.

The climate and water levels in the Great Lakes region are determined by the interplay of three air masses: dry, cold Arctic air from the North, dry warm Pacific air from the West, and warm, moist tropical air from the Gulf of Mexico. The scientists found that during the period when lake levels receded significantly, the dry air from the Arctic and Pacific was dominant. Later, when precipitation from the tropical air mass became more frequent, the Great Lakes began to flow from one to another as they do today.

King worries about the economic impact to the Great Lakes region if the present climate changes lower water levels significantly. Navigation, water usage and hydropower would be severely affected.

"The climate interval that occurred back then is different from what we're going through now," King said. "It would take a pretty big change to close the basins again. But the sorts of temperatures and precipitation amounts that happened then are within the range of what is predicted for 2100. In the worst-case scenarios, a lot of things become possible.

"The range of lake-level changes that are likely to happen in the next 100 years is probably larger than the range of levels observed during the last century," he added.

Source: University of Rhode Island

Explore further: Rising anger as Nicaragua canal to break ground

add to favorites email to friend print save as pdf

Related Stories

Great Lakes water level slump over, future unclear

Dec 10, 2014

Scientists say the longest period on record of abnormally low Great Lakes water levels has ended, but it's uncertain whether the recovery is temporary or the beginning of a new long-term trend.

Reconstructing the African humid period

Dec 05, 2014

During the end of the last ice age, there were dramatic changes in rainfall across a vast swath of Africa. As the world's large ice sheets receded in northern and southern latitudes, rainfall in much of Africa ...

Recommended for you

Rising anger as Nicaragua canal to break ground

15 hours ago

As a conscripted soldier during the Contra War of the 1980s, Esteban Ruiz used to flee from battles because he didn't want to have to kill anyone. But now, as the 47-year-old farmer prepares to fight for ...

Hopes, fears, doubts surround Cuba's oil future

Dec 20, 2014

One of the most prolific oil and gas basins on the planet sits just off Cuba's northwest coast, and the thaw in relations with the United States is giving rise to hopes that Cuba can now get in on the action.

New challenges for ocean acidification research

Dec 19, 2014

Over the past decade, ocean acidification has received growing recognition not only in the scientific area. Decision-makers, stakeholders, and the general public are becoming increasingly aware of "the other carbon dioxide ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.