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The Canadian Ice Service has a report [pdf] on the current sea ice minimum. This is an excellent summary of the mid-August state of sea ice around the Canadian Archipelago, with enough background on arctic sea ice to help beginners such as myself to understand the subject.
From the summary (note that the areas referred to are all parts of the Canadian arctic):
(there are some striking aerial photos of this "rotten" ice).
They express some gentle scepticism about the NSIDC data, based as it is on passive microwave sensors (Modis). The Canadian data and maps are based on active sensors (Radarsat), which gives higher resolution and better discrimination at low ice concentrations.
Almost all of the NSIDC ice loss is on the Russian side of the arctic. Currents (the Beaufort and Barents Gyres, combining to make the Trans-Polar Drift) drive the remaining ice up against the Canadian Archipelago and Greenland, so it's unsurprising that what ice remains is in the Canadian arctic.
It seems likely to me that the instruments and methods used by NSIDC/Cryosphere Today might be resulting in an understatement of the true sea ice area, and maybe extent. However, it is a true and unbiased measurement of something: (e.g. maybe the "sea ice extent" doesn't count areas less than 30% ice, instead of 15%). And that measured thing is something like 40% below the long-term average.
In other news, Cryosphere Today has an update, confirming that they are seeing ice area level off at 3 million square kilometres.
From the summary (note that the areas referred to are all parts of the Canadian arctic):
While less than normal, present 2007 total sea ice coverage in the Western Arctic and the Northwest Passage is not less than that observed in 1998.
Total 2007 ice coverage in the Eastern Arctic is presently less than that of 1998, but not less than that of 2006, due to greater than normal amounts of thick multi-year ice that entered the area through Nares Strait in the winter and spring.
Environment Canada is predicting a warmer than normal fall in the Arctic. Additionally, sea surface temperatures in the southern Beaufort Sea and Baffin Bay continue to be ...3–5°C above normal... freeze-up in these areas could be significantly delayed, indicating that 2007 may well set record minimum ice extents in the Canadian Arctic.
Even if 2007 does not set a new record minimum sea ice extent for the Canadian Arctic, there is no doubt that this is a year of very low sea ice coverage. The departure from normal concentration charts for early-mid August show mainly less than normal concentrations.
Additionally, ice reports from the ... central Beaufort Sea ... indicated lower than normal amounts of multi-year ice in this area this year... second-year and multi-year ice appears to be "rotten" or in an advanced state of melt.
(there are some striking aerial photos of this "rotten" ice).
They express some gentle scepticism about the NSIDC data, based as it is on passive microwave sensors (Modis). The Canadian data and maps are based on active sensors (Radarsat), which gives higher resolution and better discrimination at low ice concentrations.
Almost all of the NSIDC ice loss is on the Russian side of the arctic. Currents (the Beaufort and Barents Gyres, combining to make the Trans-Polar Drift) drive the remaining ice up against the Canadian Archipelago and Greenland, so it's unsurprising that what ice remains is in the Canadian arctic.
It seems likely to me that the instruments and methods used by NSIDC/Cryosphere Today might be resulting in an understatement of the true sea ice area, and maybe extent. However, it is a true and unbiased measurement of something: (e.g. maybe the "sea ice extent" doesn't count areas less than 30% ice, instead of 15%). And that measured thing is something like 40% below the long-term average.
In other news, Cryosphere Today has an update, confirming that they are seeing ice area level off at 3 million square kilometres.
