Shifting winds have helped drive West Antarctica’s ice sheet melting for millennia, according to a new analysis that could help scientists better anticipate sea-level rise.
The findings, published yesterday in the journal Nature, show that during the past 11,000 years, wind patterns have driven relatively warm waters from the deep ocean onto Antarctica’s continental shelf, leading to significant and sustained ice loss. That influx of warm water then halted for several millennia before beginning again around 1940.
More data are needed to explain those shifts, but atmospheric temperatures likely played a role, said Claus-Dieter Hillenbrand, the study’s lead author and a senior marine geologist with the British Antarctic Survey. Whatever the reason for shifts, the results demonstrate the importance of climate models accounting for the region’s winds.
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“By understanding the mechanisms that caused the retreat of the [West Antarctic Ice Sheet] over the past several thousand years, we can begin to build a clearer picture of what is happening today,” Hillenbrand said.
Gerhard Kuhn, co-author of the study, said, “Our results provide evidence that in the past, [West Antarctic Ice Sheet} retreat was also predominantly caused by melting through warm ocean water.”
Kuhn, from Germany’s Alfred Wegener Institute, added, “This gives confidence in the predictions of the current generation of ice sheet models which are used to forecast future ice loss from Antarctica and resulting sea-level rise.”
The area studied two of the continent’s largest glaciers, Thwaites and Pine Island, which drain into the sea and contribute to rising sea levels. But scientists have struggled to pinpoint how much—and how quickly—that should affect climate change models, with researchers in the last two years suggesting a U.N. panel had underestimated its impact by half, according toThe New York Times.
The new research draws from sediment samples taken at Pine Island Bay—one of the continent’s most inhospitable areas and, consequently, one of its least understood. The first reliable measurements of the area weren’t taken until 1994, so it’s hard to come by data that are more than a few decades old, said Hillenbrand.
The international research team spent 10 years collecting and analyzing sediment samples in order to find microfossils. Analyzing the chemical composition of those shells “acts like a fingerprinting” for the water’s temperature, Hillenbrand said, enabling researchers to trace the intervals when relatively warm water welled up onto the continental shelf.
The scientists say more research is needed to fine-tune their understanding. For instance, these findings trace the relative difference in water temperature, but more study is needed to ascertain the absolute temperatures from those periods.
“It’s often a hit-or-miss” in that area around the Amundsen Sea, Hillenbrand said, adding that researchers were able to flag areas for sampling but occasionally had to depart. “The conditions were changing, the wind picked up and got stronger, so it was impossible to hold the ship on station, or an iceberg came along so that the ship had to move out of the way.”
Reprinted from Climatewire with permission from E&E News. E&E provides daily coverage of essential energy and environmental news at www.eenews.net.
