International Polar Year: clear signs of warming

Ice sheets in Greenland and Antarctica are diminishing, contributing to sea level rise, and in the summers of 2007 and 2008, Arctic sea ice shrank to its smallest size since satellite observations began. These are among the findings of a preliminary report released by the World Meteorological Organization.

The report summarizes the findings of the International Polar Year initiative, carried out over two years and  involving thousands of scientists contributing to 200 projects on physical, biological and social science topics focused on the Arctic and Antarctic.

From the report:  

“It now appears certain that both the Greenland and the Antarctic ice sheets are losing mass and thus raising sea level, and that the rate of ice loss from Greenland is growing . . .  Part of the loss is due to increased ice outflow, and the potential for these ice sheets to undergo further rapid ice discharge remains the largest unknown in projections of the rate of sea-level rise by the Intergovernmental Panel on Climate Change. New data also confirm that warming in the Antarctic is much more widespread than was thought prior to IPY.”

Among other findings: 

• Both land and marine species are moving poleward as a result of global warming
• The Southern Ocean has warmed more rapidly than the global ocean average
• Antarctic bottom water has freshened in some places and warmed in others, consistent with increased melting from ice shelves
• In places, Arctic grasses are giving way to shrubs, treeline is shifting, and infestations by insects and fungi are rising with concomitant impacts on grazing animals
• Pools of carbon stored in permafrost are larger than previously thought
• Permafrost is breaking down faster than expected when sea ice disappears
• Substantial amounts of methane, a potent greenhouse gas, are being released from ocean sediments along the Siberian coast

For stories about the report, see Scientific American and Nature.