One of the most intruiging and elusive aspects of Arctic sea ice is its overall thickness, and by implication the total volume of sea ice. The bigger the volume, the longer it will take for the Arctic Ocean to become effectively ice-free in summer. Unfortunately, despite many different kinds of data, no one can tell for sure what the current status is, except that volume has decreased significantly over the past decades.
Satellites could provide more definite answers, but we are currently in a gap between ICESat and CryoSat-2. ESA and NASA are doing a fascinating job in the Arctic gathering data which will be used to calibrate the latter as we speak. In the meantime we fill the time by speculating, and a big part of that speculation is fueled by ice thickness models.
The best known models in Arctic sea ice amateur circles are PIPS 2.0 (Polar Ice Prediction System), PIOMAS (Pan-Arctic Ice-Ocean Modeling and Assimilation System) and TOPAZ (Towards an Operational Prediction system for the North Atlantic European coastal Zones). Although model output is not as good an approximation of reality as actual data - to put it mildly - it is still interesting to look at.
Ever since Bfraser wrote his first guest blog here, TOPAZ data by Cryosphere Today regions, my hands have been itching to make an animation comparing PIPS and TOPAZ sea ice thickness maps this year so far. Now, PIPS (which is run by the US navy) has a daily updated forecast for the next day, which is great. TOPAZ however hadn't been updated ever since February 24th. It was taking so long that I decided to ask someone when the next update was due.
I promptly received an answer and it turns out the TOPAZ system - delivered as part of the MyOcean project - has been upgraded last year and transitioned to the Norwegian Met Office (met.no). Sea ice thickness maps can now be viewed with the help of this dynamic viewer and I have to say the result is stunning. You derive sea ice thickness maps by clicking on 'TOPAZ4 model results' on the left and then 'sea_ice_thickness'. Click on the little plus-sign on the right and choose 'North polar stereographic'. Then finally adjust the numbers on the colour bar, and presto, you have a sea ice thickness map. Great stuff.
What is also great is that I now am able to make an animation of sea ice thickness progress according to the models. I start off with a comparison between PIPS and TOPAZ from January 1st to February 26th 2011 (1 week intervals):
We see quite a few differences between the models. This isn't much of a surprise, as there was much ado over this last melting season when the ice thickness models received more attention for the first time, on both sides of the climate aisle. These differences won't be solved to everyone's satisfaction until CryoSat-2 data comes rolling in, and perhaps not even then.
PIOMAS and TOPAZ agree more on where all the thick ice is, mainly north of the Canadian Archipelago and Greenland, but PIPS is showing a big red blob over a much larger area north of Greenland. As for the ice that is less thick: TOPAZ shows much of the Arctic Basin to be around or below 2 metres (different shades of blue), PIOMAS indicates between 2 and 3 metres (shades of green), and PIPS seems to be slightly over that.
Which model is the best? It's hard to tell, and explaining the subtle differences between all three of them is beyond my means. What I can do, is compare this year's output of the models with previous years, which I'll do later this week.