Whenever I visit Cryosphere Today I have a quick look at the main graph on the front page, sometimes play the 30-day animation, and then I'm off to the next Arctic sea ice graph or map. But since a few weeks I've been wondering about something else on the CT website, the images on the comparison page to be precise.
First of all when you compare current dates with those of previous years, you notice that practically the entire ice mass looks very concentrated compared to other years (as far back as the eighties). This has reinforced the pseudo-skeptic position that the ice in the Arctic Basin is so thick it will withstand most of the summer melting and continue its recovery.
But when I compare the comparison page map with the front page map I notice some differences:
Believe it or not, but there are some things I have already found out for myself. The front page map has a much better resolution and thus shows more detail. Both maps also use a different colour scheme to depict ice concentration. And thirdly, I have read somewhere that both maps use different satellite data. The front page map uses AMSR-E data (like Uni Bremen and JAXA do), the comparison page map uses SSM/I (like Arctic ROOS does).
But does that explain the big difference I seem to be seeing in the depiction of polynyas on the map? Look at the Beaufort Sea and the Laptev Sea, or at Hudson Bay and Nares Strait. Look, I say!
I decided to check out which date of the front page map matches the one on the comparison map better:
These look more in tune, but the difference is more than 3 weeks! Isn't that weird? Especially if you consider the fact that the comparison page map doesn't show concentrations that are less than 30%. This means the comparison page map in principle should have bigger polynyas than the front page map, despite different resolutions, colour bars and satellite data. Or doesn't it?