Icebergs Support Life, May Slow Climate Change

While global warming has been associated with increased abundance of icebergs, a new research article in the journal Science suggests that icebergs may actually stem the rate of climate change.

A team of scientists, lead by Kenneth Smith of the Monterey Bay Aquarium Research Institute and funded by the National Science Foundation, studied two icebergs in the Weddell Sea, near Antarctica. While icebergs as long as 300km have been found, the two chosen for the study were 2km and 21km long, respectively. Researchers evaluated attached and floating communities of phytoplankton and associated animals to depths of 60 meters by trawling and by taking measurements with a remote controlled vehicle.

The researchers found that the icebergs, and waters within several kilometers of them, were "hot-spots" of life when compared to waters further away. The icebergs were found to enrich the waters around them with iron; iron is required for the function of several enzymes, and as such is required for algal growth. Although the amount of iron required by algae is small, the amount of available iron in ocean water is low enough that the addition of small amounts of iron is enough to stimulate growth. The increased algal abundance in turn supports more dense populations of krill and other small animals. Sea birds were also found to be more abundant and diverse near the icebergs. Based on their data for two icebergs and estimates of iceberg density in the Weddell sea, authors estimated that roughly 39% of the sea surface area in the region had increased biological density as a result of icebergs.

By fostering more dense communities of organisms, the icebergs may impact atmospheric carbon dioxide levels. Organic detrius from the algae and animals living on or near icebergs can settle to the bottom of the ocean, where it remains. As the ultimate source of this organic material is photosynthesis, which takes up carbon dioxide from the atmosphere and locks its carbon away in larger molecules, the sequestration of the detrius on the ocean floor leads to a net decrease in atmospheric carbon. According to the study authors, current models of atmospheric carbon dioxide inputs and outputs do not account for iceberg-induced carbon sequestration. As elevated carbon dioxide levels are believed to be the cause of global climate change, a further study of communities of organisms around icebergs may ultimately lead to better understanding of the global warming.

References:

Amber Dance. "Climate may be helped by iceberg ecosystems" http://www.sun-sentinel.com/news/nationworld/sfl-flaicebergs0622nbjun22,0,4713165.story?track=rss

Smith, Kenneth; Robison, Bruce; Helly, John; Kaufmann, Ronald; Ruhl, Henry; Shaw, Timothy; Twining, Benjamin; and Vernet, Maria. 2007. Free-Drifting Icebergs: Hot Spots of Chemical and Biological Enrichment in the Weddell Sea. Science. Published online as a Science Research Express article on June 21, 2007.