Separating Annual, Interannual and Regional Change in Sea Surface Temperature in the Northeastern Atlantic and Nordic Seas. Issue 8 (25th August 2022)

• Record Type: Journal Article
• Authors: Saes, Mischa J. M.; Gjelstrup, Caroline V. B.; Visser, Andre W.; Stedmon, Colin A.
• Is Part Of: Journal of geophysical research. Volume 127:Issue 8(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-08-25
• Subjects: SST -- temperature -- Nordic seas -- climate -- Arctic -- North Atlantic; Oceanography -- Periodicals; 551.4605
• DOI: 10.1029/2022JC018630
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract: Sea surface temperature (SST) in the Northeastern North Atlantic and Nordic Seas exhibits pronounced variability across seasonal to decadal time scales. These changes can be expected to be driven by a combination of altered local conditions, shifts in seasonality and large‐scale regional oceanographic change. Separating the contribution from each of these offers insight into how the region is changing. Here, we present the result of an analysis of weekly satellite‐derived SST data from 1979 to 2020. An empirical orthogonal function (EOF) analysis allows us to separate observed changes in SST into independent underlying timeseries. Each timeseries explains part of the variability in SST. EOF1 can be allocated with changes in seasonality and a long‐term warming trend, with summer maxima warming with twice the rate (0.043°C year −1 ) compared to winter minima (0.023°C year −1 ). EOF2 is associated with the North Atlantic subpolar gyre and the North Atlantic Oscillation, affecting the Atlantic Water flow across the Greenland‐Scotland Ridge, imposing a dipole cooling/warming pattern. Local sea‐ice melt along the southeast Greenland shelf is represented by EOF3, and finally the influx of warmer water with the North Icelandic Irminger Current is captured by EOF4. Each of these disaggregated signals differ considerably in their contribution to driving temporal and spatial trends in SST. The isolated signals offer a high‐resolution long‐time series of valuable indicators of oceanographic change which will likely be reflected in biogeochemistry, plankton, fish, mammals, and seabirds in the region. Plain Language Summary: Sea surface temperature (SST) can be measured by sensors mounted on satellites and this provides a data set with exceptional regional and temporal coverage from 1979 to present. Here, our focus is on examining oceanographic change in the Northeastern Atlantic and Nordic Seas, bordering Greenland, Iceland, and Norway. We apply a data analysis technique that allows us to separate the variability in SST in the region into a series of underlying factors. With this we can resolve: how the seasonal winter minimum temperatures and summer maximum temperatures have been increasing; how conditions in the North Atlantic are driving changes in the region; how increased sea‐ice melt is influencing SST; and finally trace the occurrence and impact of an abrupt inflow of warmer water northwards along the west coast of Iceland. Combined these disaggregated factors may help explain changes in the distribution and structure of the marine ecosystem in the region. Key Points: Seasonal fluctuations in Nordic Seas and Northeastern Atlantic sea surface temperatures explains 90% of the variability Both summer maxima and winter minima are warming, with summer temperatures warming twice as fast (0.4 and 0.2°C per decade) Other sources of variability include sea‐ice melt and switches in large‐scale oceanographic conditions in the Northeastern Atlantic