Tuesday, September 11, 2007

Mathematics of ice to aid global warming forecasts

Science Daily: University of Utah mathematicians have arrived at a new understanding of how salt-saturated ocean water flows through sea ice -- a discovery that promises to improve forecasts of how global warming will affect polar icepacks.

University of Utah mathematician Ken Golden stands in front of sea ice melt ponds in the Arctic near Barrow, Alaska. His research on sea ice's permeability to salt water promises to help improve forecasts of the effects of global warming. (Credit: Image courtesy of University of Utah)

In the current issue of the journal Geophysical Research Letters, math Professor Ken Golden and colleagues show that brine moving up or down through floating sea ice follows "universal transport properties."

"It means that almost the exact same formulas describing how water flows through sedimentary rocks in the Earth's crust apply to brine flow in sea ice, even though the microstructural details of the rocks are quite different from sea ice," says Golden, who currently is on an Australian research ship in Antarctica.

The study suggests similar porous materials -- including ice on other worlds, such as Jupiter's icy ocean-covered moon Europa -- should follow the same rules, he adds. Golden has made several trips to Antarctica and the Arctic for his studies.

The American Geophysical Union, which publishes the journal carrying Golden's study, says sea ice is important because it is both "an indicator and regulator of climate change; its thinning and retreat show the effects of climate warming, and its presence greatly reduces solar heating of the polar oceans."

"Sea ice also is a primary habitat for microbial communities, sustaining marine food webs," the group adds. "The permeability of sea ice and its ability to transport brine are important to many problems in geophysics and biology, yet remain poorly understood."

The AGU says Golden's study presents "a unified picture of sea ice permeability," and how that permeability to brine flow varies with the temperature and salinity of the ice.

"One of the most important aspects of the polar sea ice packs is the role they play in Earth's albedo -- whether Earth absorbs or reflects incoming solar radiation," says Golden. "White sea ice reflects; the ocean absorbs. In the late spring, melt ponds [atop the ice] critically affect the albedo of the polar ice packs. The drainage of these melt ponds is again largely controlled by the permeability of the ice."

…The results "can also help in understanding how polar ecosystems respond to climate change," Golden says. "Biological processes in the polar regions depend on brine flow through sea ice. For example, the rich food webs in the polar oceans are based on algae and bacteria living in the ice, and their nutrient intake is controlled by brine flow."…

No comments: