Both the models and observations exhibited a significant warming trend in 2007, followed by a cooling trend in 2009 in the top 150m layer. The models further showed an even stronger warming, beginning in 2010 and peaking in 2012. In the central part of the region, in the HYCOM model the warming was particularly manifested by the development of a warm near-surface layer, peaking at 20m depth with an excess temperature of about 0.20 deg C in 2007 and 0.60 deg C in 2011; this layer has disappeared in 2009. In the NCOM model, this layer was attached to the surface, with a peak SST in 2007 of 0.90 deg C and a low of 0.40 deg C in 2009. At the region's center at 140W, 75N, the CTDs also showed the development of both near-surface and surface- attached warm layers similar to HYCOM and NCOM, respectively. The warmest CTD temperature observed was 0.0 deg C at 50m depth in 2007, followed by an SST of -0.10 in 2008. In 2004 and 2005 only the sub-surface warm layer is observed, with its temperature excess of about 0.4 - 0.5 deg C.
Ref 1: Validation of the 1/12 deg Arctic Cap Nowcast/Forecast System (ACNFS) Pamela G. Posey et al, Tech. Report NRL/MR/732010-9287, Nov 4, 2010, Naval Research Laboratory, Stennis Space Center, MS, 39529
Ref 2: User's Manual for the Global Ocean Forecast System (GOFS) Version 2.6 Lucy F. Smedstad et al, Tech. Report NRL/MR/732010-9210, March 31, 2010, Naval Research Laboratory, Stennis Space Center, MS, 39529