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Freshwater from the Arctic participates in the globally important Atlantic Meridional Overturning Circulation (AMOC). We use high‐resolution, in situ observations of dissolved organic matter (DOM) fluorescence to trace the origins of freshwater and organic carbon in the densest component of the AMOC, namely Denmark Strait Overflow Water (DSOW). We find a distinct terrestrial DOM signal in DSOW and trace it upstream to the Siberian shelves in the Arctic Ocean. This implies a riverine origin of freshwater in DSOW. We estimate that the Siberian Shelf water contribution constitutes approximately 1% of DSOW. Ocean circulation modeling confirms the inferred pathway and highlights Denmark Strait as an important location for the entrainment of the riverine signal into DSOW. Our proposed method can be deployed on a range of observing systems to elucidate freshwater dispersion across the Arctic and subarctic, thereby contributing to the broader discussion on freshwater impacts and organic carbon sequestration in the AMOC. [ABSTRACT FROM AUTHOR]

Two major oceanographic changes have recently propagated through several trophic levels in coastal areas of Southeast Greenland (SEG). Firstly, the amount of drift‐ice exported from the Fram Strait and transported with the East Greenland Current (EGC) has decreased significantly over the past two decades, and a main tipping element (summer sea ice) has virtually disappeared since 2003 leading to a regime shift in oceanographic and ecological conditions in the region. The following 20‐year period with low or no coastal sea ice is unique in the 200‐year history of ice observations in the region, and the regime shift is also obvious in the volume of ice export through the Fram Strait after 2013. In the same period, the temperature of the EGC south of 73.5 N has increased significantly (>2°C) since 1980. Secondly, the warm Irminger Current, which advects warm, saline Atlantic Water into the region, has become warmer since 1990. The lack of pack ice in summer together with a warming ocean generated cascading effects on the ecosystem in SEG that are manifested in a changed fish fauna with an influx of boreal species in the south and the subarctic capelin further north. At higher trophic levels there has been an increase in the abundance of several boreal cetaceans (humpback, fin, killer, and pilot whales and dolphins) that are either new to this area or occur in historically large numbers. It is estimated that the new cetacean species in SEG are responsible for an annual predation level of 700,000 tons of fish. In addition, predation on krill species is estimated at >1,500,000 tons mainly consumed by fin whales. Simultaneously, there has been a reduction in the abundance and catches of narwhals and walruses in SEG and it is suggested that these species have been impacted by the habitat changes. [ABSTRACT FROM AUTHOR]

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 variabilityBoth 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 [ABSTRACT FROM AUTHOR]