In January, most of the Arctic ocean basins are frozen over, and so the growth of ice extent slows down. According to SII (Sea Ice Index) January on average adds 1.3M km2, and this month it was 1.4M. (background is at Arctic Ice Year-End 2020). The few basins that can grow ice this time of year tend to fluctuate and alternate waxing and waning, which appears as a see saw pattern in these images.
Two weeks into February Arctic ice extents are growing faster than the 14-year average, such that they are approaching the mean. The graph below shows the ice recovery since mid-January for 2021, the 14-year average and several recent years.
The graph shows mid January a small deficit to average, then slow 2021 growth for some days before picking up the pace in the latter weeks. Presently extents are slightly (1%) below average, close to 2019 and 2020 and higher than 2018.
February Ice Growth Despite See Saws in Atlantic and Pacific
As noted above, this time of year the Arctic adds ice on the fringes since the central basins are already frozen over. The animation above shows Barents Sea on the right (Atlantic side) grew in the last two weeks by 175k km2 and is now 9% greater than the maximum last March. Meanwhile on the left (Pacific side) Bering below and Okhotsk above wax and wane over this period. Okhotsk is seen growing 210k km2 the first week, and giving half of it back the second week. Bering waffles up and down ending sightly higher in the end.
The table below presents ice extents in the Arctic regions for day 44 (Feb. 13) compared to the 14 year average and 2018.
|Region||2021044||Day 044 Average||2021-Ave.||2018044||2021-2018|
The table shows that Bering defict to average is offset by surplus in Okhotsk. Baffin Bay show the largest deficit, mostly offset by surpluses in Barents, Kara and Greenland Sea.
The polar bears have a Valentine Day’s wish for Arctic Ice.
And Arctic Ice loves them back, returning every year so the bears can roam and hunt for seals.
Seesaw accurately describes Arctic ice in another sense: The ice we see now is not the same ice we saw previously. It is better to think of the Arctic as an ice blender than as an ice cap, explained in the post The Great Arctic Ice Exchange.
via Science Matters
February 14, 2021 at 10:53AM