The graph shows the annual minimum September monthly average sea ice extent in NH from 2007 through 2019 according to two different data sets: Sea Ice Index (SII) from NOAA and Multisensor Analyzed Sea Ice Extent (MASIE) from NIC.. The chart begins with 2007 ending a decadal decline and beginning 12 years of fluctuations around a plateau. SII and MASIE give quite similar results for September, with SII slightly higher early on, and also showing more ice this year. The linear trendlines are flat for both indices with 2019 being similar to 2007.
MASIE daily results for September show 2019 early melting followed by an early stabilizing and refreezing.
Note that 2019 started the month about 800k km2 below the 12 year average (2007 through 2018 inclusive). There was little additional loss of ice, a rise then a dip below 4 M km2, and a sharp rise ending the month. Interestingly, 2019 matched the lowest year 2012 at the start, but ended the month well ahead of both 2012 and 2007.
The table for day 273 shows distribution of ice across the regions making up the Arctic ocean.
|Region||2019273||Day 273 Average||2019-Ave.||2007273||2019-2007|
Presently 2019 ice extent according to MASIE is 500k km2 (10%) below the 12 year average and 374k km2 more than 2007. Most of the deficit to average is in East Siberian and Laptev seas, along with the Pacific seas of Beaufort and Chukchi. Other places are close to normal, with Central Arctic higher than average and much greater than 2007.
The Bigger Picture
The annual Arctic ice extent minimum 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 the second week in September over the last 11 years. The Arctic heart is beating clear and strong.
These are weekly ice charts from AARI in St. Petersburg. The legend says the brown area is 7/10 to 10/10 ice concentration, while green areas are 1/10 to 6/10 ice covered. North American arctic areas are not analyzed in these images. Note how the distribution of sea ice varies from year to year, and how small was the extent after the 2012 Great Arctic cyclone.
Over this decade, the Arctic ice minimum has not declined, but since 2007 looks like fluctuations around a plateau. 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. Numbers are area units of Mkm2 (millions of square kilometers).
|Day 260||12 year|
|Central Arctic Sea||2.67||3.16||2.64||2.98||2.93||2.92||3.07||2.91||2.97||2.93|
|Greenland & CAA||0.56||0.41||0.41||0.55||0.46||0.45||0.52||0.41||0.36||0.46|
The table includes three early years of note along with the last 6 years compared to the 12 year average for five contiguous arctic regions. 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 annual 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 inconsequential as of day 260.
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.