The area of sea ice in the Arctic fell to a summer minimum of around 5.0 million square kilometres this year. This is the sixth lowest extent in the satellite record and reinforces the long-term downward trend in Arctic ice extent, according to leading international scientific and research bodies.
The findings were released by the U.S. National Snow and Ice Data Center (NSIDC) and the Alfred-Wegener-Institut Helmholtz Centre for Polar and Marine Research.
On September 17, 2014, sea ice extent dropped to 5.02 million square kilometers (1.94 million square miles), according to NSIDC. This appears to have been the lowest extent of the year. In response to the setting sun and falling temperatures, ice extent will now climb through autumn and winter. However, a shift in wind patterns or a period of late season melt could still push the ice extent lower.
This year’s minimum was 1.61 million square kilometers (622,000 square miles) above the record minimum extent in the satellite era, which occurred on September 16, 2012, and 1.20 million square kilometers (463,000 square miles) below the 1981 to 2010 average minimum.
The lowest sea ice extent was in 2012, followed by 2007. In both years, weather phenomena led to a particularly large reduction in sea ice. In 2007, a stable high pressure area in early summer resulted in numerous melt pools forming on the ice. They absorbed energy from the sun, which further intensified the melting. In summer 2012, there was exceptional melting on the underside of the ice, and in August that year there was a severe storm, which stirred up the ice. Such extreme weather was largely absent in 2014.
The long-term decline in Arctic sea ice is the result of climate change, with the Arctic warming about twice as fast as the global average.
Meanwhile, sea ice in the Antarctic has surpassed the previous record maximum extent set in 2013 and is now more than 20 million square kilometers (7.72 million square miles)for the first time in the past thirty-five years. It is too soon to determine if Antarctic sea ice has reached its annual maximum.
The sea ice situation in the Antarctic can not be compared with the conditions in the Arctic, given the differences in their geographical and meteorological circumstances. The Antarctic is an ice-covered continent surrounded by the Southern Ocean. Here the Antarctic Circumpolar Current limits the maximum sea ice expansion. Wind and waves greatly influence the ice edge – and the amounts of precipitation and glacial meltwater determine the percentage of fresh water, which in turn helps to determine how much sea ice forms in winter.
The international scientific community is currently discussing a variety of factors as possible explanations for the major expansion of Antarctic sea ice. For example, the growth in area could have been set off by changed wind currents and rising meltwater.