SOME ICE SHEET EXPANSION COULD BE CAUSED BY WARMING TEMPERATURES

SOME ICE SHEET EXPANSION COULD BE CAUSED BY WARMING TEMPERATURES

By Stephanie Fox, Nov. 1, 2018 –

Antarctic ice sheets anchored on land show evidence of expanding even as atmospheric and oceanic warming accelerates, according to research conducted by an undergraduate scientist.

The data shows that the expansion of alpine glaciers, or tall glaciers found within bowl-shaped hollows on mountains, may have been occurring for nearly 3,000 years or possibly more, at the same time as ice sheets anchored in the ocean are melting.

After a 10-day journey from Maine to New Zealand to Antarctica, Laura Mattas—a senior studying Earth and climate science at the University of Maine—arrived in Garwood Valley, Antarctica, accompanied by her thesis adviser, geologist Brenda Hall, and with two other University of Maine students. With Hall’s guidance, Mattas set out to gain further insight on an ongoing debate as to whether Antarctic ice sheets are losing or gaining mass as global temperatures rise.

Laura Mattas stands before miles of Antarctic glaciers.
Laura Mattas stands before miles of Antarctic glaciers. (Tyler Pollock)

“There’s a lot of opposing hypotheses,” said Mattas, while standing in front of a poster presenting her research at the 12th annual Comer Abrupt Climate Change Conference this fall.

Several studies, including a 2015 study conducted by University of Arizona of geophysicist Christopher Harig and Princeton University geoscientist Frederick Simons, concluded that the outer edges of Antarctic ice sheets are melting as temperatures escalate. With rising temperatures, Harig and Simons say, comes rising sea-levels.

Mattas isn’t so sure that’s always the case, she said.

The data gathered by then-sophomore Mattas and her two University of Maine professors, Hall and George Denton, show results similar to those found by NASA science and exploration director Jay Zwally and his team of researchers. Zwally’s data suggests that warming temperatures, which causes an increase in precipitation, also cause ice sheets to thicken.

When Mattas headed to Garwood Valley for the first time in 2016 she decided to take research regarding warming temperature’s impact on Antarctic glaciers one step further by focusing on land-terminating, or land-anchored, glaciers. The majority of Antarctica is covered by two massive glaciers. Mattas is focusing on the mountains and the smaller land-terminating alpine glaciers that form there.

Laura Mattas stands before miles of Antarctic glaciers. (Tyler Pollock)
Antarctic researchers sleep in tents during their fieldwork. (Laura Mattas)

Hall assisted Mattas in choosing Joyce Glacier and Garwood Glacier to conduct her research.

“We picked the best spot based on our knowledge of the area and based on imagery. So, we picked the spot that had the best deposits,” explained Hall. “[Garwood Valley] has the best deposit for that region.”

Garwood Valley ended up being a prime location for Mattas to gather data because glaciers in the valley operate similarly to glaciers in a neighboring valley, which have been correlated to even bigger glaciers called East Antarctic outlet glaciers. The glaciers in that valley are responsible for draining a large part of the East Antarctic Ice Sheet. Mattas’ research provides a proxy for how parts of the larger glaciers might behave.

“My research… shows that Joyce Glacier is actually expanding. And the preliminary dates that I have for Garwood Glacier also shows expanding glaciers,” Mattas said.

Garwood Glacier (left) and Joyce Glacier (right) within Garwood Valley. (Diagram: Laura Mattas)
Garwood Glacier (left) and Joyce Glacier (right) within Garwood Valley. (Diagram: Laura Mattas)

She agrees with Harig and Simons findings that rising temperatures cause melting of ice sheet edges, particularly where the ice sheet ends in the ocean, but she doesn’t think that melting always leads to instability. Instead, her research suggests that increased snowfall, which accumulates on the interior of glaciers could be contributing overall expansion of land-terminated ice sheets.

“[Joyce Glacier is] expanding, which could disprove—” Mattas paused to reconsider her word choice. “Well, not disprove anything, but make us think more about the stability of the Antarctic ice sheet. There’s a strong push right now in science and nature geoscience that the ice sheet is unstable because of this rapid deterioration at the marine limits. But… what [some data suggest] is that these interior glaciers are expanding because of the increased precipitation.”

Not only does Mattas’ data affirm this theory, but through radiocarbon dating, a process which uses carbon-12 and carbon-14 isotopes to determine the age of organic matter such as lacustrine algae samples, and 10Be, a radioactive isotope of Beryllium that can be used to calculate how long a rock has been ice-free she has developed evidence that Garwood Valley’s land-terminated glaciers have expanded since 2,820 years ago. Further research could reveal that the expansion has been occurring for even longer.

For those skeptical of her findings, Mattas said she stands by her data.
“The evidence is the evidence and the facts are what they are. And it is showing that in this system, glaciers are expanding currently,” said Mattas.

Photo at top: Undergraduate Laura Mattas stands before land-terminated glaciers during her fieldwork in the Dry Valleys, Antarctica. (Tyler Pollock)


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