photo: NationalGeographic
An unusual trend has marked this winter's temperatures. Although global warming is now a reality few will deny, the current evidence points to a longer winter, or a colder Spring.
Climatologists are now realizing that the ice melt in the Artic might be causing an effect on the sea water. The ice in the Arctic has reached a new minimum this winter, and more current data shows that the sea ice covers, is at its sixth lowest extent in the satellite record.
The melting of the sea ice, alters the circulation of air in the atmosphere. This is turn causes more snow and rain.
Without its ice cover, the winds that batter the Arctic blow unabated. The jet stream then is able to dip lower and lower into the continents, bringing cold air from the Arctic south towards the equator.
The cold Spring then, is a result of this colder air which is stronger and more lasting than normal.
A Chinese scientists from the University of Albany, Prof Liu and his colleagues have intuited the influence of the Arctic melt as the primary cause of the cold spring. In fact in the last few winters, all the north hemisphere continents have experienced these colder conditions, from Asia to Europe. The only possible culprit when looking at past data was the fast dissolution of Arctic ice.
This also explains why this winter has been so wet, and the snow slushy. Arctic ice usually locks up water molecules that would otherwise evaporate and generate rain.
With less ice, more moisture escapes into the atmosphere where it freezes and then returns to earth. The Arctic ice therefore is trasformed into snow.
However, the low sea ice and the ever increasing quantity of greenhouse gases will cause hotter summers too.
The trend, Liu and others believe, will continue to be erratic and in the short term at least, the northern hemisphere will continue to experience longer, wetter winters.
Source: National Geographic 3.31.13
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