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Ocean climate and atmosphere highlights for the North Atlantic in 2020

ICES Working Group on Ocean ​​Hydrography (WGOH) analyses and reviews oceanographic conditions in the North Atlantic annually and has just released the 2020 highlights for the North Atlantic.
Published: 17 July 2021

​​​​​Long time-series of ocean properties are rare for the surface ocean and even more uncommon in the deep ocean. The North Atlantic region is unique, having a relatively large number of locations where oceanographic data have been collected repeatedly for multiple years or decades. The longest records extend back more than a century.

Since the early 1990s, ICES Working Group on Ocean Hydrography has published an annual review of atmospheric and oceanographic conditions in the North Atlantic as a special issue in ICES Cooperative Research Report (CRR) series, ICES Report on Ocean Climate

While the latest IROC is being prepared, WGOH have consolidated their 2021 joint analysis of the ex​​isting data​ into highlights regarding the ocean climate and atmosphere.​​​​

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. A 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 m) of the Irminger Sea. A large drop in salinity was detected in the Denmark Strait Overflow Water along the Greenland slopes below 2800 m.

The 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 Trough. 2020 was the second consecutive year when moderately-deep winter convection in the Labrador Sea did not exceed 1700 m.

The Northwest Atlantic shelf waters remained warm. Warming was evident in both surface and deep waters with the Gulf of St. Lawrence registering a >100-years record high. 

The surface water temperature of the North Sea 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 the Baltic Sea recording the lowest sea-ice extent since the early 18th century.

Highlights for the North Atlantic atmosphere in winter 2019/2020

The 2019/2020 winter was the second consecutive winter with a strong positive North Atlantic Oscillation (NAO)​, the seventh consecutive winter with a positive NAO. Air temperatures were relatively warm across Europe, northeastern North 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 2019/2020 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 east coast of the United States 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.


WGOH's findings form the basis of ICES ​​Report on Ocean Climate (IROC​), published annually. The data are available to visualize and download.​

ICES Working Group on Oceanic Hydrography (WGOH) closely monitors the ocean conditions in the ICES area by updating and reviewing results from standard hydrographic sections and stations. WGOH's work addresses Ecosystem science, Ecosystem science, Observation and exploration, and Conservation and management science, three of ICES scientific priorities. 

Discover all seven interrelated scientific priorities and how our network will address them in our Science Plan: “Marine ecosystem and sustainability science for the 2020s and beyond"

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​Station 27 Viking Buoy leaving St.John's, Newfoundland on the Canadian Coast Guard fisheries research vessel CCGS Teleost. Station 27 is a standard monitoring site off eastern Newfoundland​. Image: S.Snook.

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Ocean climate and atmosphere highlights for the North Atlantic in 2020

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