Cold Atlantic 'blob' puzzles scientists
(CNN)At
first glance, it stands out like a sore thumb. That blob of blue and
purple on the map. One of the only places on the globe that is
abnormally cold in a year that will likely shatter records as the
warmest globally.
It's being
called the Atlantic "blob." It's a large area in the North Atlantic
that is seeing a pronounced cooling trend. The ocean surface is much
cooler than normal and in fact record cold in some locations.
Scientists
began to notice it developing over the last couple of years, this
cooling in the Atlantic is the complete opposite of the warming over in
the Pacific. Much of the warming is attributed to El Nino, a natural
process where warm water sloshes over the Central Pacific and extends to
South America, but scientists are unable to completely explain what has
been dubbed the Pacific Blob. This pronounced warming over large areas
of the entire Pacific basin has fueled a well above average season for
hurricanes and typhoons over the entire Pacific, and could have
contributed to everything from the California drought, impacts on the
salmon industry, and even tropical sharks seen in waters further north
than ever before.
The Atlantic cold
blob is near Greenland. You may not expect to see such a pronounced
cooling that far north. After all, we know that most of the documented
climate change has impacted the poles much more than equatorial
regions. Greenland is home to an enormous sheet of ice.
In fact, if you combine the ice sheets of Antarctica and Greenland, you
will find 99% of the freshwater ice on earth. Scientists believe it is
the melting of ice in Greenland that is causing the cold anomaly.
A recent study by top climatologists shows massive ice-loss is
occurring over Greenland and is disturbing the normal Atlantic Ocean
circulation, called the Atlantic Meridional Overturning Circulation
(AMOC). You may be familiar with part of this circulation, the Gulf
Stream, which brings warm, tropical surface water northward along the
East Coast of the U.S. and funnels towards the poles. The other main
current in the AMOC is a return flow of deep, cold water that runs
southward from the poles towards the tropics. This current has
dramatic impacts on our weather globally. The heat and cold driven by
the current transfer to the atmosphere and help to drive our weather
patterns.
Normally,
cold salt water in the North Atlantic sinks, because it is denser, and
it is replaced by warm water moving in from the south. It's a similar
process that drives the high and low pressure systems and Jetstream
that drive our weather. In this case, the study suggests that the
massive amounts of freshwater melting into the ocean from Greenland can
prevent the sinking of the dense, cold, salty water and alter the AMOC
circulation.
Believe it or not, this
was the very scenario in the popular movie "The Day After Tomorrow.". In
the movie, the global climate changes in a matter of days, causing
tornadoes in Los Angeles, deadly hail in Tokyo, and a massive blizzard
in New York City.
Fortunately "The
Day After Tomorrow" scenario is Hollywood fiction at its best, and not
based on sound science. That said , there is cause for concern that the
changes we have observed in both the Atlantic and Pacific. While there
is certainly not scientific consensus that either the Pacific or
Atlantic blob is related to climate change, there is evidence that is
the case. The impacts, while not like the movie, could be bad enough.
The loss of the normal ocean circulation could cause drastic shifts in
weather patterns, and continued loss of ice in Greenland will lead to
the continued rise in sea level, threatening coastal cities around the
globe.
end quote from:
http://edition.cnn.com/2015/09/30/weather/atlantic-cold-blob/index.html
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