University of Alabama professor: Microscopic fossils tell the tale of climate change - Tuscaloosa Magazine

Microscopic fossils tell the tale of climate change, UA professor says

University of Alabama professor: Microscopic fossils tell the tale of climate change
Gary Cosby Jr.

Rebecca Totten, associate professor at the University of Alabama looks into the mud at the bottom of the Amundsen Sea in Antarctica. Totten, a microbiologist studies microscopic fossils of sea creatures found in the layers of sea floor mud to help determine how sea temperature is affecting the critical Thwaites Glacier, dubbed the "Doomsday Glacier" because of it's potential impact on global sea level rise.

"I grew up playing in the mud in south Louisiana and that’s still what I do for a living. I look at the layers of mud extracted from the sea floor that have been deposited since that ice was really expanded 20,000 years ago and grounded out on the continental shelf," Totten said.

As the ice has receded, it has exposed the sea floor and opened it to life. Her study involves taking mud cores to see which creatures lived in each layer of mud during a given period of time. These creatures, Totten says, are extremely sensitive to changes in the ocean's salinity as well as the temperature.

"The cool thing we do as paleo-detectives is we have to figure out what the history of these glaciers are," Totten said.

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Currently, the biggest temperature factor affecting the melting of the Thwaites Glacier and the nearby Pine Island Glacier, is the slight rise in the temperature of the Antarctic Circumpolar Current. As the name implies, the current circles Antarctica and isolates the continent, a fact that enabled glaciers to grow there to begin with.

The Western Antarctic Ice Sheet, of which the Thwaites and Pine Island Glaciers are a part, is about 2 kilometers thick. One the opposite side of the Trans-Antarctic Mountains is the Eastern Antarctic Ice Sheet is up to 4 kilometers thick. When the glaciers melt, tremendous amounts of water can be released into the oceans.

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"It really isn’t that warm. It’s only two degrees above freezing. It’s just above freezing, but if you take that two-degree warmer sea water and put it in contact with ice it’s going to melt it," Totten said.

Scientists now believe that the current melt cycle probably began with the extended El Nino in the 1930s and '40s. From that time, the seawater temperature seems to have increased due to a warmer current flowing into the area and accelerating ice melting. By examining microscopic fossils in the mud layers at the bottom of the sea, Totten can determine the water conditions at those times.

"We go out and collect these sediments with what’s called a sediment coring device. It’s basically like a big metal straw that we send all the way through hundreds, sometimes thousands of meters of water down to the sea floor, drop that on the sea floor, then like a straw in your drink cup we plug the top so we can pull it back up. We open it and we can see all these layers," Totten said.

By counting the fossils and comparing them to the same creatures that exist today, they can compare ocean conditions in various areas and determine what those conditions were like in the past. This helps determine the conditions under which the glacier was receding at various points in history.

Reach Gary Cosby Jr. at gary.cosby@tuscaloosanews.com.