Dr. Susan Crockford
Not even three weeks after the yearly minimum of sea ice extent was reached this year, new shorefast ice is already forming off the coast of Siberia, which is critical fall hunting habitat for polar bears.
Polar bears on a seal kill in new ice, 31 October 2020 in W. Hudson Bay via webcam.
So, not only was this year’s sea ice extent for September at the very lowest extreme of predicted levels for late summer, given ever-increasing CO2 concentrations in the atmosphere, new ice seems to be forming earlier in the fall as well, which bodes well for winter ice formation. It’s looking to me like the decade-long increasing trend of September ice extent since 2012 (see below) may indicate a change more biologically relevant to ice-dependent Arctic animals than the zero trend since 2007.
Shorefast ice across the Arctic
Virtually everywhere in the peripheral seas of the Arctic Ocean (Barents, Kara, Laptev, Chukchi, Beaufort, as well as Baffin Bay and Davis Strait, shorefast ice thick enough to support a polar bear forms before the mobile ice pack in the central Arctic expands to the shores of the peripheral seas (below). The Laptev Sea is often the first to experience this new shorefast ice formation because of the bitterly cold winds that blow north from Siberia.
As I’ve explained in detail previously, this new ice formation creates nutrient-rich upwelling, which attracts fish to feed on the planktonic organisms that proliferate at the surface; like clock-work, seals arrive to feed on these fish and those seals provide a predictable food source for polar bears that have spent the summer fasting onshore.
Sea ice along Laptev Sea coast
New sea ice formation at 5 October, select years since 2006 (below), courtesy NISDC MASIE, shows new ice forming in 2022, 2021, and 2017 but not in previous years (only a few shown for brevity):