Although icebergs are clearly a significant feature of the waters around Antarctica, many people assume that they are barren masses of ice that have little bearing on life, apart from the hazards they pose to unwary seafarers, especially under conditions of darkness, fog, and storm. While the perils of icebergs cannot be denied, as the 2007 sinking of the Antarctic Explorer attests (as well as the Titanic's fate in 1912), these frozen, free-drifting mountains are, nevertheless, hardly devoid of life.
A 2007 article in Science magazine found that icebergs in the Weddell Sea, off the Antarctic Peninsula, were "hot spots of chemical and biological enrichment." The scientific team, led by Kenneth Smith of the Monterey Bay Aquarium Institute, USA, selected two icebergs that were scrutinized in detail from their research vessel, the Laurence M. Gould, and from NASA satellite images. One iceberg, called A-52, was more than thirteen miles long. The second, W-86, had a smaller surface area, but was deeper, extending nearly 1,000 feet below the surface. Smith and his collaborators described the icebergs as moving estuaries that deliver nutrients and minerals from land that might elsewhere be supplied by rivers. Elevated concentrations of these nutrients and minerals boosted, in turn, the abundance of phytoplankton—photosynthetic and generally microscopic organisms—especially diatoms. The availability of diatoms and other forms of phytoplankton, meanwhile, attracted Antarctic krill, jellyfish, and worms, which themselves attracted predators higher up the food chain—various species of fish and seabirds.
The zone of heightened biological activity extended about 2.3 miles from the icebergs, before dropping off significantly. However, given the large number of icebergs in the Weddell Sea, the researchers estimated their "combined area of influence" to be about 40 percent of the surface waters. Raised biological production in the vicinity leads to the removal of more carbon dioxide from the atmosphere, the authors note, and the "sequestration of organic carbon to the deep sea, a process unaccounted for in current global carbon budgets."
"No longer can we look at icebergs as mere passive beauties," writes Jeff Rubin of the American Polar Society. "They are active agents of change, each one an icy oasis, trailing a wake of life as it drifts on its inexorable oceanic journey to melting."