Saturday, March 7, 2015

Arctic Ice Update

Arctic sea ice is now close to its seasonal maximum extent, so it's a good time for an update.  The total area of ice cover has seen little growth since early February, and the extent is now running more than 2 standard deviations below the 1981-2010 normal according to the NSIDC.  The warm winter and lack of ice cover in the Bering Sea is contributing to the ice area shortfall, along with a large ice deficit in the Sea of Okhotsk and a smaller deficit in the Barents Sea.  The latest graphics from the NSIDC are shown below.

NSIDC commentary notes that if the ice extent does not advance to a new peak in the next few weeks, then this year will see the lowest maximum extent on record for the satellite era.  At first glance this would seem to bode ill for the upcoming melt season.  However, the University of Washington's ice volume analysis - last updated for the month of January - showed that ice thickness and ice volume were higher than in recent years.  First, the thickness: the PIOMAS model's estimate of average thickness at the end of January was the highest since 2006 - see below.

The estimated Arctic sea ice volume was close to that in 2009 and just over 1 standard deviation below the 1979-2014 mean (see below).  The volume was notably higher than last year in January, which reflects a persistence of the year-over-year gain that was seen during last year's melt season.  It will be most interesting to see if the volume recovery continues this year and if the ice extent and ice volume anomalies continue to show contrasting trends.

According to NOAA's CFS reanalysis, the mean air temperature has been well above normal across most of the Arctic Ocean this winter, with the highest anomalies located near Wrangel Island and the Chukchi Sea.  The extent and magnitude of the warm anomalies can be compared to the previous 10 years in the series of images below.  The previous 10 winters showed a persistent tendency for warmth over the Barents and Kara Seas and with less unusual warmth on Alaska's side of the ocean.  Last winter (2013-2014) saw warm conditions across the entire ocean, but this winter has been notably cooler between 0 and 90 °E, with the warmest conditions now prevailing on our side of the basin.


  1. I noticed that the reanalysis product is different than others that you've used. I looked around to see what made the different reanalysis products different but couldn't quite grasp it. Why did you use the CFS reanalysis over the others? Would the others make a difference in interpretation?

    Also, is that consistent extreme warmth in the northern Nordic seas real? It just seems to be so anomalous compared to everywhere else.

    1. Eric, apologies for the delay in replying. The CFS reanalysis is NOAA's modern high-resolution global product, which distinguishes it from the earlier NCEP reanalyses that had lower resolution, less (or no) satellite data and presumably inferior physics. There are other global reanalyses that may be as good as CFSR, e.g. the European or Japanese products, but I don't have access to those. But yes, they will all give different answers, and I don't know how reliable the 2m temperatures are in data-sparse regions. The assumption is that the overall anomaly patterns are reasonable, because the reanalysis should have consistent data assimilation methods over time.

      The extreme warmth on the European side reflects the lack of sea ice in that area in recent years - so yes, I believe it's real. Temperature anomalies will always be very large where sea ice is anomalously absent or abundant.