Melting icebergs fertilize ocean

Janet Raloff in Science News: Efforts to remove climate-warming carbon dioxide from Earth’s atmosphere appear to be getting a helping hand from a surprising source: the iron in meltwater from Antarctic icebergs.

Icebergs calving off of Antarctica are shedding substantial iron — the equivalent of a growth-boosting vitamin — into waters starved of the mineral, a new set of studies demonstrates. This iron is fertilizing the growth of microscopic plants and algae, transforming the waters adjacent to ice floes into teeming communities of everything from tiny shrimplike krill to fish, birds and sometimes mammals.

To grow, these plants and animals use carbon drawn into the water from carbon dioxide in the atmosphere. Some share of this carbon will eventually be excreted as wastes that fall to the ocean floor, essentially removing it as a near-term climate risk.

“Icebergs should be considered by climate modelers, because the more icebergs that develop [from the breakup of glaciers], the more carbon dioxide you’ll draw out of the atmosphere,” says Ken Smith of the Monterey Bay Aquarium Research Institute in Moss Landing, Calif.

Smith and colleagues first fingered icebergs as hotspots of biological and chemical activity in a 2007 study published in Science. New data from Antarctic cruises in 2008 and 2009 by Smith and other scientists from nine research institutions now appear as 20 papers in the June Deep Sea Research Part II…

An iceberg off the Antarctic coast, shot by Jerzy Strzelecki, Wikimedia Commons, under the Creative Commons Attribution 3.0 Unported license