Sea ice at both poles is at lowest levels on record, again
Wednesday, February 21, 2018, 4:53 PM - There's bad news coming in from the ends of the Earth, as sea ice in both the Arctic and the Antarctic is, once again, setting new records for lowest extent on record.
After global sea ice set a new record low for 2017, conditions in the Arctic and Antarctic started off 2018 less than ideal, and they have no been improving since.
Arctic sea ice extent on January 1, 2018 was 12.34 million square kilometres, over 1.3 million sq km smaller than the long term average, and 230,000 sq km smaller than it was just one year before, when it was setting a previous record low. As of February 20, the ice extent has grown since, reaching 13.95 million sq km in the darkness of the Arctic winter, but only very slowly and even suffering a setback in early February, despite the darkness.
Arctic Sea Ice Extent in 2018 (orange) compared to all years back to 1979. The inset closeup of current extent provides a clearer comparison with last year's record low extents. Credit: NSIDC/Scott Sutherland
According to the US National Snow and Ice Data Center (NSIDC), for the month of January air temperatures above the Arctic Ocean were at least 3oC above normal, for the entire region.
January temperature anomalies, in degrees Celsius, over the Northern Hemisphere, in January 2018. Credit: WeatherBell
From the NSIDC January report on the Arctic: "The warmth over the Arctic Ocean appears to result partly from a pattern of atmospheric circulation bringing in southerly air, and partly from the release of heat into the atmosphere from open water areas."
As of now, while the ice extent continues to tick upward in the Arctic, it is roughly 350,000 sq km behind what was there at this time last year, and we are seeing a rate of growth now that is significantly slower. Unless something fairly significant happens in the next few weeks, to freeze more than half a million square kilometres of ice in the Arctic Ocean, 2018 will become the fourth year in a row that sets a new record low for maximum winter sea ice extent in the Arctic. This is certainly possible.
In the Antarctic, where sea ice around the continent is approaching its summer minimum for the year, the ice extent is also setting a new record low, at this time. As of February 20, ice extent was at 2.181 million sq km, just 48,000 sq km behind the 2017 extent on that day.
Antarctic Sea Ice Extent in 2018 (orange) compared to all years back to 1979. The inset closeup of current extent provides a clearer comparison with last year's record low extents. Credit: NSIDC/Scott Sutherland
Throughout the month of January, sea ice extent in the Southern Ocean was tracking at slightly above 2017 levels, and thus second lowest on record. Just in the past week or so, however, the daily extents have dropped below where they were for the same dates in 2017, thus setting new record lows.
As of their January 2018 report, NSIDC scientists were puzzling over the low sea ice extents in the Southern Ocean for that month, as air temperatures in the region were roughly average or slightly below the 1981-2010 average. Subsurface ocean temperatures or currents may hold the key, but are more difficult to measure and track.
If the Antarctic melt season ends earlier than last year, we may avoid a new record low summer minimum in 2018, but ice extent there only needs to drop by another 81,000 sq km to set a new low, and the Southern Ocean lost that much ice in just the past seven days.
These results from both ends of the Earth keeps the planet on track for even lower global sea ice extents, and it continues a long-term trend of sea ice loss that hasn't been seen in at least 1,500 years!
The last 1,500 years of global ice extent data, taken from proxies such as ice cores, tree rings, etc for the period before satellite measurements. The dotted line indicates the approximate start of the Industrial Revolution. Credit: NOAA