2011 is coming to an end, which means we're halfway through the Arctic winter. The sea ice is thickening up nicely everywhere in the Arctic interior, but things aren't progressing as uniformly at the edges. Just like last year we see an above average ice cover in some regions, but a very slow freeze-up in other regions.
A good example of the former is Hudson Bay. It was extremely late in freezing over last year, and thus melted very fast in Spring. This year, however, its ice cover is almost average for the time of year according to the Cryosphere Today regional SIA graph:
The Bering Sea region is above average and will hit its maximum SIA fairly easily in the coming weeks:
But as we so often see in the Arctic, an increase in one part is countered by a decline in another part. The Siberian side of the Arctic is where we see a significant slowdown in ice formation this year. The freeze-up was slow anyhow because of relatively warm waters at the end of the melting season in the Laptev, Kara and Barents Seas. But where the Laptev Sea has frozen up alright, it seems a couple of cyclones in the past weeks have stirred things up enough for large expanses of water to stay open in the Kara and Barents Seas (white demarcations according to the CT division of regions):
This is reflected on the regional SIA graphs, showing some big anomalies:
These Seas will probably reach their maximum ice cover in the months to come, but much of it won't be very thick. We'll have to wait and see what this will mean for the ice retreat on the Siberian side of the Arctic and the Northern Sea Route when the melting season gets underway again.
Meanwhile, as Diablobanquisa reports in last week's blog post Sin hielo en el Báltico (no ice in the Baltic Sea), not too far to the south of the Barents Sea, on the other side of Finland, the Gulf of Bothnia is not showing any signs of freezing yet either:
These maps are provided by the Baltic Sea Portal and show last year's situation (left), this year's situation (middle) and average (= normaali) ice conditions (1965-1986) on the right. 'Jäätä' means ice. This year there's still no ice whatsoever (see MASIE regional map), whereas last year the ice cover was way above average.
As Diablobanquisa explains this has a lot to do with the NAO (Northern Atlantic Oscillation). When the NAO is negative a weak high west of Europe makes for weak winds, lower temperatures and thus more ice. With a positive NAO it's the other way around: stronger high, stronger winds, higher temperatures, less ice.
This image from a paper by Timo Vihmaa and Jari Haapala in Progress In Oceanography illustrates the point:
According to NOAA's Climate Prediction Center the NAO has been and currently is positive:
Three to four months left to go for the ice to stretch out as far as it can.
All the best for 2012!