Thursday, March 23, 2017

Gelo mares Árctico & Antárctico atinge mínimos: o pior resultado de sempre !

Operation IceBridge, NASA’a aerial survey of polar ice, near the Alaskan coast on March 11, 2017
Credits: NASA/Jeremy Harbeck

Os dados do centro de análise da NASA, Colorado, são claros. Mostram que o nível de gelo do Pólo Norte e no Pólo Sul atingiu, este ano, os mínimos de sempre, pelo menos desde que há registos.

A principal surpresa apontada pelos investigadores está na redução do nível de gelo no Pólo Sul onde chegou agora ao fim o verão. 

Mar Árctico, gelo
Arctic sea ice
créditos:NASA Goddard's Scientific Visualization Studio/L. Perkins

Os satélites revelam uma redução do nível de gelo no mar depois de várias décadas com uma expansão moderada.
Março terá sido o pior mês de sempre. Os mínimos foram atingidos a 7 de Março no Árctico, enquanto no Antárctico, o registo foi feito a 3 de Março. 
O vídeo da NASA documenta os dados recolhidos:

Arctic sea ice appears to have reached on March 7 a record low wintertime maximum extent, according to scientists at NASA and the NASA-supported National Snow and Ice Data Center (NSIDC) in Boulder, Colorado. 
On the opposite side of the planet, on March 3 sea ice around Antarctica hit its lowest extent ever recorded by satellites at the end of summer in the Southern Hemisphere, a surprising turn of events after decades of moderate sea ice expansion.

Line graphs plot monthly deviations &overall trends
 in polar sea ice from 1979 to 2017 
Credits: Joshua Stevens/NASA Earth Observatory

The ice floating on top of the Arctic Ocean and surrounding seas shrinks in a seasonal cycle from mid-March until mid-September. 

As the Arctic temperatures drop in the autumn and winter, the ice cover grows again until it reaches its yearly maximum extent, typically in March. 

The ring of sea ice around the Antarctic continent behaves in a similar manner, with the calendar flipped: it usually reaches its maximum in September and its minimum in February.

Antarctic sea ice
Credits: NASA Goddard's Scientific Visualization Studio/L. Perkins

“We started from a low September minimum extent,” said Walt Meier, a sea ice scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “There was a lot of open ocean water and we saw periods of very slow ice growth in late October and into November, because the water had a lot of accumulated heat that had to be dissipated before ice could grow. The ice formation got a late start and everything lagged behind – it was hard for the sea ice cover to catch up.” Read more

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