Bancadas de gelo e permafrost do Ártico infographic
A infografia mostra as variações da extensão das bancadas de gelo do Ártico.


Ártico na linha da frente da mudança climática

By Duncan Mil

September 23, 2019 - O Ártico está a aquecer duas vezes mais depressa que o resto do planeta, com o degelo no mar e a fusão do permafrost Ártico rico em carbono, segundo a agência meteorológica (NOAA) dos EUA.

In 2016, average Arctic surface temperatures were 3.5 degrees Celsius warmer than they were at the start of the 20th century, says NOAA.

When sea ice vanishes, the colour of the Arctic changes. Deep blue waters of the Arctic Ocean absorb more solar energy than ice, which reflects 70 per cent of the sun’s radiation into space. In turn, this heat spiral causes more ice to melt.

The ice recedes to an annual minimum extent every September. The record low was set in 2012 when the ice shrank from 15.2 million square kilometres to 3.4m sq km. This year it is expected to decrease from 14.8m sq km to 4.2m sq km, a close second lowest minimum, according to the National Snow and Ice Data Center. Additionally, the average ice thickness has halved from 1980 to just one metre.

Another chain effect involves the Arctic’s frozen permafrost. Levels of soil organic carbon tend to be around five per cent. The soil in Arctic permafrost regions contains up to 50 per cent. Estimates of organic carbon in the Arctic permafrost range from 1,000 to 1,500 billion tonnes -- almost half of the carbon that the atmosphere holds.

As the Arctic warms, bacteria in the soil consume organic matter faster, releasing carbon dioxide and methane. These gases can then speed up global warming -- thawing more permafrost and causing more emissions.

PUBLISHED: 23/09/2019; STORY: Graphic News
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