We are about 4 days away from the annual Arctic ice extent minimum, which typically occurs on or about day 260 (mid September). Some take any year’s slightly lower minimum as proof that Arctic ice is dying, but the image below shows day 260 over the last 10 years. The Arctic heart is beating clear and strong.
Recent posts noted that 2017 Arctic ice extents were stabilizing and then coasting to a halt. Now we are seeing a reversal with ice growing in all but one region. While the daily average extent over the last 10 years bottomed out on day 260, years like 2016 and 2009 hit minimum on day 254. This year’s extent was at 4.7M km2 for a week, hit bottom at 4.6M on day 253, and 3 days later is now up to 4.8M km2. SII (Sea Ice Index) 2017 is similar to MASIE, though a bit lower lately. The graph below shows September comparisons.
Note that as of day 256, 2017 has gone 250k km2 above average, 500k km2 above 2007 and 2016, and 1300k km2 greater than 2012. All regions are adding ice, with Central Arctic the only exception. That is likely due to Central Arctic sea already full of ice at 3.1M km2. The image below shows impressive refreezing in the Canadian Archipelago.
Over this decade, the Arctic ice minimum has not declined, but looks like fluctuations around a plateau since 2007. By mid-September, all the peripheral seas have turned to water, and the residual ice shows up in a few places. The table below indicates where we can expect to find ice this September. (Shows day 260 amounts with 10 year averages)
|Central Arctic Sea||2.67||3.16||2.64||2.98||2.93||2.92||2.91|
|Greenland & CAA||0.56||0.41||0.41||0.55||0.46||0.45||0.46|
BCE (Beaufort, Chukchi and East Siberian) on the Asian side are quite variable as the largest source of ice other than the Central Arctic itself. Greenland Sea and CAA (Canadian Arctic Archipelago) together hold almost 0.5M km2 of ice at minimum, fairly consistently. LKB are the European seas of Laptev, Kara and Barents, a smaller source of ice, but a difference maker some years, as Laptev was in 2016. Baffin and Hudson Bays are almost inconsequential.
For context, note that the average maximum has been 15M, so on average the extent shrinks to 30% of the March high before growing back the following winter.
Some people unhappy with the higher amounts of ice extent shown by MASIE continue to claim that Sea Ice Index is the only dataset that can be used. This is false in fact and in logic. Why should anyone accept that the highest quality picture of ice day to day has no shelf life, that one year’s charts can not be compared with another year? Researchers do this, including Walt Meier in charge of Sea Ice Index. That said, I understand his interest in directing people to use his product rather than one he does not control. As I have said before:
MASIE is rigorous, reliable, serves as calibration for satellite products, and continues the long and honorable tradition of naval ice charting using modern technologies. More on this at my post Support MASIE Arctic Ice Dataset