Arctic and Antarctica Ice cover

• A new NASA-led study has found the reason behind slight increase in ice cover surrounding Antarctica
• It is in sharp contrast to the drastic loss of sea ice occurring in the Arctic Ocean.

Ice cover increase in Antarctica

• Geology of Antarctica and the Southern Ocean is responsible for this rise.
• Two persistent geological factors — the topography of Antarctica and the depth of the ocean surrounding it — are influencing winds and ocean currents, respectively, to drive the formation and evolution of Antarctica’s sea ice cover and help sustain it.
• Sea ice forms and builds up early in the sea ice growth season, it gets pushed offshore and northward by winds, forming a protective shield of older, thicker ice that circulates around the continent.
• The persistent winds, which flow down slope off the continent and are shaped by Antarctica’s topography, pile ice up against the massive ice shield, enhancing its thickness.
• This band of ice, which varies in width from roughly 100 to 1,000 km, encapsulates and protects younger, thinner ice in the ice pack behind it from being reduced by winds and waves.
• As the sea ice cover expands and ice drifts away from the continent, areas of open water form behind it on the sea surface, creating “ice factories” conducive to rapid sea ice growth.

Ice cover decrease in Arctic :

• Since 1980, the summer sea ice cover over the Arctic has gone into a drastic decline, from 7.8m sq km to 4.4m sq km in 2012.
• There were a number of causes, in addition to the record high temperatures and carry-over effects of earlier ice loss.
• The El Niño weather system produced more warming, and the Arctic saw influxes of exceptionally warm water from the Pacific as well as the Atlantic side.
• The extent of ice cover is a critical indicator of the changes taking place in the Arctic – but the shrinking of the polar ice carries sweeping consequences for lower latitudes as well.
• The bright white snow-covered ice reflects about 85% of sunlight back into the atmosphere, compared to the dark surfaces of the open water which absorb most of the heat energy.

By: Vishal