Above is the nifty interactive graphic from the National Snow and Ice Data Center showing sea ice extent in the Arctic for the current year (the lower squiggle). This year’s squiggle looks like a peak, and it is possible that Arctic Sea ice extent is now on the decline. Minimum extent is typically reached in September.
The other squiggles are all the years since 1979 that seem to have had peaks later in the year than this year’s apparent peak of a couple of days ago. Those years are 1992, 1997, 1999, and 2010. In other words, for the available data set, four out of 34 years, or just over 10% of the years, had sea ice extent peaks that post date March 21st, which appears to be this year’s peak. There is still a chance that more ice will be added and this year’s squiggle will see an uptick. Well, I guess it is fair to say that there’s about a one in ten chance of that happening. But, I hear the Arctic is a bit warm and that the ice is getting all breaky-uppy so that seems like it might be a high estimate.
This is probably not too important because the relationship between what the ice does during its maximum extent and what the ice does during its minimum extent is seemingly random, and it is the minimum extent that counts.
You will recall that I’ve predicted the minimum extent of sea ice this year, here.
The degree to which sea ice extent is reduced is important. It normally melts to some degree every year, but when it melts a lot the open sea can absorb more heat from the sun, and there is less shiny ice to reflect sunlight away. This causes extra warming in the Arctic, a phenomenon known as Arctic Amplification, which may be implicated in changing large scale weather systems, resulting in the phenomenon known as Weather Whiplash.