Via Eurekalert
BUFFALO, N.Y. — Buffalo’s legendary snowfall totals are largely the result of one unlucky geographic reality: the city sits east of the Great Lakes instead of west.
Anyone who has lived through a winter in Buffalo, Cleveland or any snowbelt city knows that prevailing westerly winds pick up moisture from the lakes and dump lake-effect snow on their eastern shores.
But it wasn’t always that way.
University at Buffalo researchers have uncovered new evidence of an Ice Age wind system that likely pushed lake-effect snow toward the western shores instead.
Evidence of this reverse snowbelt lies in thousands of grooves carved into the Great Lakes landscapes by ancient drifting icebergs. The carved landscapes — many now home to beach towns and farm fields — would have been submerged lakebeds about 15,000 years ago, when the lakes were much larger than they are today.
In a study published in Geology, the researchers mapped over 3,300 of these iceberg plowmarks along Lake Erie, Lake Ontario, Lake Huron and the St. Lawrence River, and found that nearly all of them trend from east to west.
Crucially, the west-moving plowmarks span roughly 17 different lake stages — periods when the Great Lakes varied dramatically in size, shoreline and currents.
“Lake currents alone would have moved these icebergs in a variety of directions. The only thing that could have consistently moved them west would be persistent easterly winds,” says first author Sean Grasing, a master’s student in the Department of Earth Sciences within the UB College of Arts and Sciences.
The easterly winds were likely caused by the Laurentide ice sheet, whose retreat northward at the end of the last Ice Age carved out the Great Lakes’ basins and filled them with glacial meltwater. Even after retreating north, the massive ice sheet would have remained large enough to generate a high-pressure anticyclonic wind system, producing persistent easterly winds for thousands of years.
“Climate-model simulations of the Ice Age atmosphere have long pointed to this kind of wind system, but it’s exciting to find hard physical evidence supporting it,” says corresponding author Jason Briner, professor and associate chair in the Department of Earth Sciences.
The west-moving plowmarks span from about 12,000 to 17,000 years ago — a period of roughly five millennia. That means the areas now home to Buffalo and other snowbelt cities likely experienced far less lake-effect snow during that time, while cities along the western shores of the lakes, like Chicago and Milwaukee, likely received more snow than they do today.
“Not only is this fun for Buffalonians to imagine, but it’s also critically important context for paleoclimate researchers looking for clues about future climate patterns,” Briner says.
Use this interactive map to see if there’s an iceberg scratch mark near you
The study is believed to be the most extensive record to date of ancient iceberg plowmarks across the Great Lakes.
The plowmarks range in size from about a third of a mile to more than six miles long. The longest one identified was 11 kilometers long and located in the St. Lawrence Lowlands north of the Adirondack Mountains, near Potsdam.
Most of the marks are nearly impossible to notice with the naked eye — appearing only as a slight divot in the landscape — but become visible using LiDAR, a remote-sensing technology that maps subtle changes in ground elevation.
To identify the plowmarks, Grasing used a technique known as vertical exaggeration, digitally amplifying subtle changes in topography to make the ancient grooves more visible.
The researchers note that their map only includes plowmarks still visible on the surface. Many others have likely been erased by urban development or buried beneath sediment, while countless more probably remain hidden beneath the modern Great Lakes.
“People who have owned their property for decades may never have noticed these plowmarks because they’re very subtle features,” Grasing says. “Maybe a farmer might recognize one as a part of their field where the soil gets particularly wet.”
Despite their modest appearance today, some of the larger plowmarks could only have been carved by enormous icebergs. The researchers estimate the iceberg that created the plowmark near Potsdam may have been roughly the size of Seneca One Tower in downtown Buffalo.
The sheer scale of the ancient landscape was not lost on the researchers.
“These skyscraper-sized icebergs floating in the much larger Great Lakes would have been a backdrop to Paleo-Indians hunting mastodons and other megafauna,” Grasing says. “It creates a very epic image.”
“The beautiful imagery of these iceberg plowmarks that Sean created are fantastic and so fun to look at,” Briner adds. “It’s not every day you get to work on a research project that has such a high giggle factor.”
