The multi-year comparisons of chlorophyll and sea ice in Greenland Sea and Barents Sea and their relationships with the North Atlantic Oscillation

The Arctic Ocean (AO) has experienced very significant warming in recent decades with clear impacts on the extent and depth of sea ice cover. Sea ice serves as a primary habitat and plays an important role in the AO marine food web. The surface distributions of chlorophyll_a (CHL), sea ice concentration (ICE), sea surface temperature (SST) and North Atlantic Oscillation (NAO) are analyzed in the study region (20°W-50°E, 70°N-80°N) over the decade (2003–2014). This region spans the Barents Sea (BS), Norwegian (NS) and Greenland Sea (GS). In general, the peak of spatial averaged CHL in the BS was about 60% higher than the GS. Due to elevated SST in the southern BS, CHL was much higher especially in 2010 and 2013. In 2011, there was a strong meridional gradient in CHL decreasing from south to north of the BS, and also a strong zonal gradient from the southern GS to the southern BS. The northern GS had higher CHL than the southern GS due to the increased ice melting and nutrient-enriched runoff from east Greenland glaciers to the northern and western coastal regions of the GS. Seasonal peaks of spatially averaged CHL occurred in April or May and were about two weeks earlier in the BS than the GS. Higher ice melt in the northern BS was the main reason for CHL blooms especially in 2010 and 2011. Earlier and more extensive ice melting and a persistent negative NAO index causing atmospheric circulation patterns that favoured ice loss were the possible drivers of enhanced phytoplankton blooms in 2010. A previous negative winter NAO is thought to be linked to an increase in ICE in the following spring. NAO is mostly negative during spring in the GS. Sea ice melt was positively correlated with CHL in the northern sector of the study region.