Figure 4. This graph shows the ice extent in Hudson Bay from late November to the end of January, for the last five years. This year, Hudson Bay froze up substantially later than in previous years. MASIE data



Slow regional ice growth

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.



Figure 5. These images show high and low atmospheric pressure patterns for January 2011 (left) and the January 1968-1996 average (right). Yellows and reds show higher pressures; blues and purples indicate lower pressures, as indicated by the height of the 850 millibar pressure level above the surface, called the pressure surface. Normally, the pressure surface is nearer to the surface around the pole, winds follow the pressure contours around the pole (the polar vortex), and cold air is trapped in the Arctic. This year, the pressure surface is allowing cold air to spill out of the Arctic into the mid-latitudes. —Credit: NSIDC courtesy NOAA/ESRL PSD

High-resolution image



Potential links with mid-latitude weather

While the Arctic has been warm, cold and stormy weather has affected much of the Northeast U.S. and Europe. Last winter also paired an anomalously warm Arctic with cold and snowy weather for the eastern U.S. and northern Europe. Is there a connection?

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.

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.

Further reading

Francis, J.A., Chan, W-H., Leathers, D.J., Miller, J.R., Veron, D.E., 2009. Winter Northern Hemisphere weather patterns remember summer. Geophys. Res. Lett. 36, L07503, doi:10.1029/2009GL037274.

Overland, J.E., Wang, M-Y., 2010. Large-scale atmospheric circulation changes are associated with the recent loss of Arctic sea ice. Tellus 62A, 1-9.

Cohen, J., J. Foster, M. Barlow, K. Saito, and J. Jones, 2010. Winter 2009-2010: A case study of an extreme Arctic Oscillation event. Geophys. Res. Lett., 37, L17707, doi:10.1029/2010GL044256.