While I was on vacation last week, I monitored some of the comments and saw the interesting update about the Arctic ice thickness from the National Snow and Ice Data Center (NSIDC).

Earlier concerns about the Arctic sea ice was that much of the Arctic Ocean this year was covered by unusually thin, first-year ice, which is far more likely to completely melt out during the summer 2008 melt season, compared to the thicker multi-year ice.

According to the latest ICESat thickness estimates, it appears that the first-year sea ice in the Arctic Ocean so far this season is comparable in thickness to what it was in 2006 and 2007. Note the charts below. Why is that? The NSIDC says that sparse snow cover over the Arctic Ocean last winter resulted in less insulation from the bitterly cold air, resulting in faster, first-year ice growth. Snow was unable to accumulate last autumn since much of the Arctic Ocean was still ice-free, causing the snow to just melt into the open waters. Once the ice formed later in the fall, it accumulated more quickly than normal as there was very little barrier (snow) between the ice and the cold air just above the surface.

Now, correct me if I am wrong, let's assume that there is even less sea ice coverage at the end of this year's melt season compared to the last two years, based on their above explanation wouldn't that mean that there would be even less early autumn snow accumulation compared to last year and thus another slight increase in the first-year sea ice thickness for 2009?

Image courtesy of the NSIDC.

You can also see that the multi-year ice this year is clearly much thinner than the past two years. The NSIDC notes that this could be due to two factors. melting at the underside of the ice that was observed in the summer of 2007 and the greater than normal export of thick ice out of the Arctic Ocean.