By Steven Goddard and Anthony Watts
From Steve: In May, WUWT reported on an apparent error in the Nansen ice extent data. It appears that we were correct, as Nansen has adjusted their 2009 extent data upwards.
The (light red) line below shows their ice extent data from May 2, 2009. It had been too low since their downwards adjustment in December.
But, as of June 5th, the 2009 extent has been corrected (dark red)
Also note that the 2007/2008 lines have not changed, and that ice extent was in the normal range for most of April and May.
Interest in sea ice extent continues to run high, but there remains differences between different groups such as NSIDC and Cryosphere Today, which have both been plagued with SSMI sensor problems from the DMSP F13 satellite. NANSEN may have had the same issues with SSMI/F13, and if they did, they seem to have gotten them under control, possibly by switching to SSSMI/F17 as NSIDC did.
For example here is a page that NANSEN maintains that shows the differences between the newer AMSRE (that JAXA uses) and the SSMI. One of the images is an AMSR minus SSMI, and it looks like the two different satellites/sensors are in pretty good agreement, with areas along the ice edge (where ice/water boundaries are rapidly changing) showing noise differences where you would expect them to.
There’s another difference though between NANSEN and JAXA, and NSIDC/Cryosphere Today. The NANSEN and JAXA pages don’t have the kind of news updates that we are used to seeing from their USA counterparts. In that respect, we should probably thank NSIDC and CT for their willingness to provide timely updates and especially thanks to NSIDC’s Walt Meier for making guest posts and answering questions here.
Along the same lines, if you look at the press releases and news articles and compare them, NSIDC seems to lead in speaking to the press, followed by CT, with NANSEN/JAXA having very little press interaction.
Interestingly though, NANSEN offers forecasts of arctic sea ice extent here from their TOPAZ model with comparisons to both SSMI and AMSRE data plotted also.
What is interesting is that, at least for this year, the TOPAZ model has been underperforming both in forecasting area and extent. Perhaps this is why we don’t see much in the way of forecasts from NANSEN projected to the media. The model isn’t quite tuned yet. I applaud such caution when it comes to forecasting minimum summer sea ice extent in the spring to the media.