Antarctica -2 Ice making and ice melting
I’m McKensie Daugherty, your host for On the Ocean. Ice is ubiquitous in Antarctica, and many different types of ice are found both over the continent and the Southern Ocean. Snowfall over the Antarctic Ice Sheets adds to the continental ice volume year round, which in turn feeds ice streams terminating in coastal glaciers and floating ice shelves. Sea ice forms as surface seawater freezes from extreme cold temperatures and strong winds. Although seasonal sea ice is only about one meter thick, its insulating layer covers an area much larger than the Antarctic continent by the end of the winter. Ice floes are generally the results of surviving patches of multiyear sea ice, about 3-4 meters thick and topped with lots of snow, that float adrift and change direction as dictated by ocean surface currents. When ice floes collide and rift the pack ice field they produce prominent ridges a few meters tall. Coastal polynyas are known as the true sea ice factories in the Southern Ocean, where extremely cold air from nearby ice shelves is brought down to polynyas by energetic kabatic winds, more effectively freezing seawater and blowing new sea ice to areas farther offshore. Eventually the additional salt left behind during sea ice formation makes the remaining near-freezing surface seawater denser than the waters below and it sinks to the bottom. During the past few decades the atmospheric warming and expanding of mid-latitude regimes has resulted in higher temperatures of the underlying upper ocean. Warmer subtropical waters incorporated to the Antarctic Circumpolar Current could potentially magnify oceanic heat transport toward Antarctic continental and sea ice. Warmer subsurface water upwelled to near the shelf break of certain continental shelves of Antarctica would increase the melt rate of floating ice shelves and glaciers, and therefore current rates of global sea level rise. This has been On the Ocean, a program made possible by the Department of Oceanography and a production of KAMU-FM on the campus of Texas A&M University in College Station. For more information and links, please go to ocean.tamu.edu and click On the Ocean.
Contributing Professor: Dr. Alejandro Orsi
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