How high will the oceans rise in response to our warming global climate, and how fast will it happen?
Climate scientists have been unable to answer these basic questions with any confidence, mainly because they can't really tell how the ice caps at the poles are going to take the heat.
The good news is that this mystery is a major research focus and ice and climate specialists are coming up with important new details about the melting processes underway. The bad news is that their estimates of the extent and pace of sea level rise is being measured now in terms of feet instead of inches.
Most recently, extensive modeling work by University of Arizona geoscientist Jianjun Yin and colleagues found differences in the rate of subsurface ocean warming beneath the glacial outcroppings of Antarctica and Greenland.
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Because overhanging ice shelves and buoyant fronts of tidewater glaciers can act as dams holding back upstream ice, the temperature of the subsurface seawater can be critical. As Yin notes in a University release, water can carry a lot more heat than air.
"If you put an ice cube in a warm room, it will melt in several hours," he said. "But if you put an ice cube in a cup of warm water, it will disappear in just minutes."
The new study is published in the current issue of the journal Nature Geoscience.
Assuming a "mid-level increase in greenhouse gases," the scientific team analyzed simulations from 19 state-of-the-art climate models and found that by 2100 subsurface ocean water between 650 feet and 1,650 feet down, will increase by 3.6° F off coastal Greenland but only 0.9° F around Antarctica.
Coastal Greenland subsurface waters will warm twice as fast as the global average because the warm subtropical water of the Gulf Stream flow relatively unimpeded into the far north, the scientists observe. To the south, however, warm subtropical water encounters the the Antarctic Circumpolar Current, which blocks it from coastal Antarctica.
Still, co-author Jonathan T. Overpeck notes that ice sheets at both poles are feeling the heat.
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"This does mean that both Greenland and Antarctica are probably going to melt faster than the scientific community previously thought," he said. "This paper adds to the evidence that we could have sea level rise by the end of this century of around 1 meter (3 feet, 4 inches) and a good deal more in succeeding centuries."
IMAGE: This view of the seaward edge of Antarctica’s floating Ross Ice Shelf shows a region where the ice is cracking and may produce an iceberg. CREDIT: Michael Van Woert, NOAA NESDIS, ORA. National Oceanic and Atmospheric Administration/Department of Commerce.
Tags: Antarctica, Climate Change, Glaciers, Global Warming, Meteorology
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