Prevailing oceanographic conditions across ICES region provide context for species, habitats, and resources in the marine ecosystem. These conditions are closely interlinked with the prevailing weather patterns in the overlying atmosphere. Long time-series of ocean properties are rare for the surface ocean and even more uncommon in the deep ocean. This makes the North Atlantic region unique as there are 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.
Highlights for the North Atlantic 2023
Sea surface temperatures were generally high across the entire North Atlantic region. This was consistent with warmer-than-average surface air temperatures across much of the region. Air temperatures were especially high in the eastern North Atlantic - off Britain and Ireland, the Bay of Biscay, and the Iberian Peninsula - in all seasons.
Several surface water marine heatwaves (i.e. prolonged periods of anomalously warm conditions) developed throughout early summer and autumn, increasing the seasonal heating. These events were particularly prevalent over larger parts of the Northwest European Shelf and the eastern Subpolar North Atlantic in June, and on the eastern North American Shelf from July until September.
Low salinity levels
The record low salinities of the mid-2010s observed in the North Atlantic Subpolar Gyre region remain evident along the ocean current pathways northward towards the Nordic Seas and southward towards the Subtropical Gyre. Most surface and intermediate layers in the eastern North Atlantic are still fresher in 2023 than the long-term mean conditions (e.g. northeastern region of the Subpolar Gyre, Barents Sea, Norwegian and Greenland seas, Bay of Biscay). The freshening signal continues along the eastern limb of the Subtropical Gyre (Gulf of Cadiz, Canary Basin).
In autumn 2022, a newly developed freshening event led to the lowest salinities in the Labrador Sea upper water column in more than three decades. This subsequently caused a significant reduction of the local convection in winter 2022/23 (to shallower than 700 m). Convection in the Irminger and Greenland seas was also limited to relatively shallow depths. This coincided with a weakening of the Subpolar Gyre and an increase in the transport by the Labrador Current south of the Grand Banks of Newfoundland for the first time in a decade. The latter led to a freshening across the Scotian and Northeast U.S. Shelf regions and the first decrease in temperature in this period in the deep channels of the Gulf of St. Lawrence and Scotian Shelf.
Baltic Sea inflow
In December 2023, the Baltic Sea saw an inflow of dense, oxygenated water from the North Sea. This was the second largest such event since the major inflow of December 2014. Qualified as a “moderate" bottom inflow, this intrusion led to an increase of dissolved oxygen concentration in these anoxic/hypoxic bottom waters, especially in the southern Baltic. The impact across the Baltic Sea still remains uncertain.
ICES Working Group on Oceanic Hydrography (WGOH) closely monitors the ocean conditions in 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.
