Global sea ice closes out 2016 at new record low level
Meteorologist/Science Writer
Thursday, January 5, 2017, 5:51 PM - With 2016 soon to rank as the warmest year on the books, it took its toll on sea ice around the world, leaving global and Arctic extents at their lowest yearly levels ever recorded and with absolutely no help from the Antarctic.
Agencies around are in the midst of tallying 2016 weather records, and they are already finding that the year was the hottest on record, by quite a wide margin over previous years.
One way the year took its toll on the planet was with sea ice, not just in the Arctic, but everywhere.
In the Arctic
Sea ice extent across the Arctic reached the lowest winter maximum extent on record, on March 2, 2016, which did not bode well for the rest of the year.
Arctic sea ice extent, 1979-2016. 2016 is highlighted for clarity. Credit: NSIDC/Scott Sutherland
Although it managed to avoid becoming a new lowest summer minimum extent on record, it ended up in a statistical tie with 2007 for 2nd lowest extent on the books. What that means is, although by the actual satellite measurements - catalogued by the US National Snow and Ice Data Center (NSIDC) - 2016 was lower by around 17,000 km2, when you take the inherent errors in the measurements into account, 2016's and 2007's values overlap enough that either one could be the real 2nd lowest on record. Thus, the tie.
According to the NSIDC:
That September 2016 did not see a new record low is likely due to the unusually stormy atmospheric pattern that set up over the Arctic Ocean in the summer. Storm after storm moved into the central Arctic Ocean, including a pair of very deep low pressure systems in late August. While a stormy pattern will tend to chew up the ice cover, it also spreads the ice out to cover a larger area and typically brings cloudy and, in summer, relatively cool conditions, inhibiting melt. Sometimes these deep lows act to reduce extent by mixing warm ocean waters upwards, but at present there is no compelling evidence that this occurred in 2016.
2016 surpassed all previous years in one way, though. Due to sea ice remaining near or at record low levels throughout the entire year, it resulted in an annual average for Arctic sea ice extent that was lower than any other year on the books. Lower than 2007. Lower than even 2012, which currently holds the record for lowest summer minimum extent.
Annual average Arctic sea ice extents, in millions of square kilometres, from 1979 to 2016. Data from NSIDC. Credit: Scott Sutherland
In the Antarctic
The Arctic and Antarctic are very different regions of the planet, and thus respond to climate change in different ways. With little to directly replenish it other than simply the onset of cold winter weather, sea ice has been declining rapidly in the north. In the south, with glaciers melting on the coastlines of Antarctica, this has been feeding cold, fresh water into the surface layer of the ocean around the continent, promoting the development of fresh sea ice. This, coupled with stronger winds and possibly with the addition of changing ocean currents, has resulted in higher than average sea ice extents in the southern ocean.
This year has been quite different, however. Antarctic sea ice extent ran at average to slightly below-average levels for much of the year, and then starting in October, sea ice extent dipped to record lows and stayed there for the rest of the year.
Antarctic sea ice extent, 1979-2016. 2016 is highlighted for clarity. Credit: NSIDC/Scott Sutherland
According to the NSIDC:
The cause of the rapid drop in Antarctic sea ice in the second half of 2016 remains elusive. Significant changes in Southern Ocean wind patterns were observed in August, September, and November, but air temperatures and ocean conditions were not highly unusual.
The overall pattern caused the yearly average for 2016 to plummet.
Annual average Antarctic sea ice extents in millions of square kilometres, from 1979 to 2016. Data from NSIDC. Credit: Scott Sutherland
The yearly average didn't quite reach the lowest on record. That still belongs to 1986, during a time when sea ice extents surrounding Antarctic generally remained at or below the 1981-2010 average. Even so, 2016 now ranks as the 2nd lowest annual average for Antarctic sea ice extent on record.
Globally
Taken together, the Arctic and Antarctic sea ice extents for the year have resulted in the lowest global annual average sea ice extent on record.
Annual average global sea ice extents, in millions of square kilometres, from 1979 to 2016. Data from NSIDC. Credit: Scott Sutherland
Looking ahead
As of the first week of January, daily sea ice extents in both the Arctic and Antarctic are still running at record low levels.
The Arctic is headed towards its yearly winter maximum, while the Antarctic is now on its way towards its yearly summer minimum. Both tend to occur sometime in late February or early March. A close eye will be kept on both over the next two months, to see if we are witnessing new record lows in the making. Let's hope for chilly weather near the poles to keep that from happening.
Source: NSIDC
