Ice (Re) Cap: April 2015

by Timothy Oleson
Monday, March 9, 2015

From Antarctica to the Arctic; from polar caps, permafrost and glaciers to ocean-rafted sea ice; and from burly bears to cold-loving microbes, fascinating science is found in every nook and crevasse of Earth’s cryosphere, and new findings are announced often. Here are a few of the latest updates.

Ice sheets and mountain glaciers shed huge volumes of water into their surrounding environments through melting and calving. In the process they also release large amounts of organic carbon (OC) stored in the ice — roughly 3 million metric tons per year, according to a new study in Nature Geoscience — much of which flows into oceans and lakes. The study, led by Eran Hood of the University of Alaska Southeast, combined existing data on the OC contents of glaciers with glacier mass estimates to look at how the glacial OC budget will change in coming decades. Currently, nearly 90 percent of what’s lost annually is replaced through primary production in and on glaciers — by photosynthesizing organisms, for example — as well as through deposition of soot and other atmospheric OC onto the ice. But if glacial mass loss accelerates globally, as predicted by climate projections, Hood and colleagues estimated a cumulative net loss of about 15 million metric tons of dissolved OC by 2050 — about half the amount of OC the Mississippi River delivers to the ocean each year. Quantifying and projecting glacial OC fluxes is important for understanding how aquatic ecosystems like fisheries might fare locally and globally in the future, the researchers wrote.

Researchers who drilled through 740-meter-thick sea ice near the intersection of the Whillans Ice Stream and the Ross Ice Shelf in West Antarctica came upon an unexpected find: a population of fish and invertebrates living in a thin layer of minus-2-degree-Celsius seawater. At almost 85 degrees south latitude, it’s the farthest south that fish have ever been seen. The scientists, part of the Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project, were studying the grounding zone of the West Antarctic Ice Sheet, a critical juncture where ice, ground and sea meet, and which controls glacial ice dynamics. After boring through the Ross Ice Shelf with a hot-water drill, the team deployed a remotely operated vehicle to explore the roughly 10-meter-deep cavity of ocean water between the base of the ice and seafloor on Jan. 16. And although the waters there are frigid, perpetually dark and thought to be low in the nutrients needed to support complex life, the team observed at least three types of fish, along with shrimp-like crustaceans called amphipods and other invertebrates. Data gathered “will establish for the first time sources of carbon and energy for higher trophic levels in this most southerly marine ecosystem,” said John Priscu, a lead scientist with WISSARD and a professor at Montana State University, in a statement.

Two teams of glaciologists studying Greenland’s ice sheet have recently reported evidence — for the first (and second) time — of large subglacial lakes draining suddenly. Both drainage events occurred in 2011, one in southwest Greenland and the other in the northeast part of the island. Both were discovered by researchers who noticed large depressions in the ice surface — 1.5- to 2-kilometers wide and 70-meters deep — where it had collapsed when the lakes drained. It’s unclear yet whether the drained subglacial lake discovered in the southwest is refilling, according to a study in The Cryosphere led by Ian Howat of Ohio State University. Prior to 2011, it is thought to have been stable since the early 1970s based on past satellite imagery. However, Michael Willis of Cornell University and colleagues reported in Nature that the ice sheet surface above the second lake, discovered in the north, has risen again since 2011, indicating the lake below is filling up again as it captures meltwater seeping down through the glacier. The draining and refilling of the lake suggests that a substantial amount of heat stored in warm surface meltwater is likely being transferred to the glacier’s interior, which may affect how the ice flows locally. Both sets of observations may portend fundamental changes in Greenland’s glacial drainage systems, the researchers wrote.

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