The ICES Working Group on Ocean Hydrography met via video conference on April 13, 2021 to review oceanographic conditions in the North Atlantic in 2020. The joint analysis of the existing hydrographic timeseries provided the following highlights.
Highlights for the North Atlantic 2020
The fresh anomaly in the eastern North Atlantic persisted with a slow-down or partial reversal of freshening evident in some areas. Strong freshening trend is evident downstream either towards the Arctic and the subtropics.
While Subpolar Gyre surface waters were moderately cooler than the 2006-2015 climatology, a warming tendency is confirmed since 2016.
Arctic waters continue to freshen and warm, with salinity significantly lower than average in the Nordic Seas and Fram Strait as well as upper waters (200-400) of the Irminger Sea. A large drop in salinity was detected in the Denmark Strait Overflow Water along the Greenland slopes below 2800 m.
Lowest salinities within the upper 400 m in the last three decades were recorded in the Bay of Biscay. Notable freshening persists off the Iberian coast.
Regarding deep waters, temperature and salinity remains stable and high in the Irminger Sea (above 2000 m), presents little change in Iceland and Iberian basins, and shows warming and salinification in Rockall Through. 2020 was the second consecutive year when moderately-deep winter convection in the Labrador Sea did not exceed 1700 m.
NW Atlantic shelf waters remained warm. Warming was evident in surface and deep waters with a > 100-year record high in the Gulf of St. Lawrence.
North Sea surface water temperature remained high while in the Baltic Sea, high temperatures were observed throughout the whole water column. North Sea salinity increased and central Baltic Sea surface salinity was at a record high since the late 1980s.
Sea ice coverage was low in most regions, with record low sea-ice extent recorded in the Baltic Sea since the early 18th century.
Highlights for the North Atlantic atmosphere in winter 2019/2020
The winter 2019/2020 was the second consecutive winter with a strong positive NAO; it was the seventh positive winter NAO in a row. Air temperatures were relatively warm across Europe, north-east America, the Nordic Seas, Baltic and Labrador Sea. There were colder-than-average air temperatures over the central North Atlantic. Wind speeds across the region in winter 2019/20 were generally higher than average, and areas from the west of Ireland across the UK, North Sea and Baltic experienced particularly strong south westerly winds through much of the winter.
Initial outlook for 2021
The NAO index for December 2020--March 2021 is likely to be a strong negative, the first since 2013. The storm track from the USA east coast across the Flemish Cap through to Norway and the Nordic Seas will experience particularly weak winds throughout the season.
Experimental seasonal forecasts predict that in autumn 2021, surface temperatures are likely to be warmer than average across the region, but, waters to the northwest of Ireland and south of Cape Farewell are more likely to be near average values than other areas.
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