Warm air temps, shifts in hemispheric winds tabbed as causes for slow freeze-up
By Summit Voice
SUMMIT COUNTY — Arctic sea ice was at an all-time record-low level since the era of satellite tracking started, as air temperatures over the polar region were 4 to 11 degrees above average for the month.
For the second year in a row, climate researchers said a strong negative phase of the Arctic Oscillation (a cyclical shift in air pressure patterns) is part of the reason for the lagging ice development in the region.
In January, ice covered about 5.23 million square miles, which is about a half-million square miles below the 1979 to 2000 average and 19,000 square miles below the previous low, set in 1996.
The National Snow and Ice Data Center explained the status of the ice:
“Ice extent in January 2011 remained unusually low in Hudson Bay, Hudson Strait (between southern Baffin Island and Labrador), and Davis Strait (between Baffin Island and Greenland). Normally, these areas freeze over by late November, but this year Hudson Bay did not completely freeze over until mid-January. The Labrador Sea remains largely ice-free.
“In contrast, regional ice growth has been particularly slow compared to past years. Hudson Bay did not completely freeze up until mid-January, about a month later than normal according to Canadian Ice Service analyses. The Labrador Sea region is still largely free of ice, except in protected bays along the coast. Normally at this time of year, ice extends a few hundred kilometers from the coast all the way from Hudson Strait to Newfoundland.”
The warm temperatures came from unfrozen areas of the ocean that continued to release heat to the atmosphere, and from wind patterns associated with the negative phase of the Arctic Oscillation, that can often bring warm, dry winds to the area.
Some climate researchers are speculating about a link between Arctic warmth and cold weather in the mid-latitudes. Here’s how it may work:
“Warm conditions in the Arctic and cold conditions in northern Europe and the U.S. are linked to the strong negative mode of the Arctic oscillation. Cold air is denser than warmer air, so it sits closer to the surface. Around the North Pole, this dense cold air causes a circular wind pattern called the polar vortex , which helps keep cold air trapped near the poles. When sea ice has not formed during autumn and winter, heat from the ocean escapes and warms the atmosphere. This may weaken the polar vortex and allow air to spill out of the Arctic and into mid-latitude regions in some years, bringing potentially cold winter weather to lower latitudes.”
Is it linked to global warming? Here’s another explanation from the NSIDC:
“Some scientists have speculated that more frequent episodes of a negative Arctic Oscillation, and the stormy winters that result, are linked to the loss of sea ice in the Arctic. Dr. James Overland of NOAA Pacific Marine Environmental Laboratory (PMEL) recently noted a link between low sea ice and a weak polar vortex in 2005, 2008, and the past two winters, all years with very low September sea ice extent. Earlier work by Jennifer Francis of Rutgers University and colleagues also suggested a relationship between autumn sea ice levels and mid-latitude winter conditions. Judah Cohen, at Atmospheric and Environmental Research, Inc., and his colleagues propose another idea—a potential relationship between early snowfall in northern Siberia, a negative phase of the Arctic Oscillation, and more extreme winters elsewhere in the Northern Hemisphere. More research on these ideas may shed light on the connections and have the potential to improve seasonal weather forecasting.”