The question of the moment is whether global warming had something to do with the size and intensity of hurricane Sandy. Sandy was the largest hurricane on record for the North Atlantic. The amount of damage done by flooding and high winds probably exceed the infamous Long Island Express hurricane of 1938. Most hurricanes that originate in the Atlantic's tropical waters either enter the Gulf of Mexico or follow the warm Gulf Stream up the Atlantic coast only to veer off to the northeast into the open ocean. Sandy was unusual because it did not follow the usual course into the North Atlantic but made a
vicious left hook into the New Jersey coast. Meteorologists say a several factors played a role in this unusual storm track. Sandy combined with an approaching nor'easter cold front as it moved north which fed energy into the cyclonic storm system allowing it to maintain coherence despite entering colder waters. Also, a blocking arctic high pressure off Greenland contributed to steering the storm into the northeastern US coastline. Finally, the jet stream that moves from west to east at high altitude usually pushes a hurricane out to sea, but this time the jet stream was perturbed and weakened. Coupled with the coincidence of a full moon high tide that increased the size and destructiveness of it's storm surge which reached the ancient shoreline of Manhattan at Pearl Street, Sandy became a "frankenstorm" for the record books.
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| Physicsworld.com: Arctic surface temperature trends, 1981-2008 |
It is the weakened jet stream that seems to be directly connected to an indisputable phenomenon of global warming: melting of the Arctic ice cap in summer. During one year, 2007, the minimum summer ice coverage dropped by 26%. Most studies now predict the Arctic Ocean will be ice free in summer by 2020 to 2040, reflecting the much more rapid rate of melting observed by satellites. The previous accepted prediction was ice free by the end of the 21st century.
With the melting ice comes increasing Arctic temperatures double that recorded in the remainder of the world, referred to as "arctic amplification". Higher temperatures increase moisture release from the warming ocean and melting permafrost. In turn, atmospheric pressure in the Arctic increases and temperature gradients decrease. This combination of factors causes the polar vortex and the jet stream to weaken. When the jet stream weakens, it follows a more sinusoidal path around the globe from west to east. Meterologists observed just one such dip in the jet stream when Sandy slammed into the coast.
These jet stream waves can allow weather to get stalled in one place. Readers may recall the "snomaggedon" of 2010 that shut down Washington, DC for a week. The new record setting loss of Arctic sea ice this year enhances the probability of severe winter weather in the United States as cold arctic air is able to push it's way more easily to mid-latitudes. These altered climatic conditions do not bode well for the eastern seaboard which often experiences nor'easter storms in winter that bring very cold temperatures and heavy snow.
In this way, winter storms could be amplified by the effects of global warming.
