Summary of the ocean climate in 2023 across the ICES region
Prevailing oceanographic conditions across the 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. Below we summarise the oceanographic and atmospheric conditions in 2023 across the ICES regions in the North Atlantic Ocean. These comprise the shelf regions, the subpolar gyre and the Nordic and Barents Seas.
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 the British Isles, Bay of Biscay and the Iberian Peninsula, in all seasons.
Several surface water marine heat waves (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 North West European Shelf and the Eastern subpolar North Atlantic in June, and on the North American Shelf from July through September.
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. North East 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 the winter of 2023 (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.
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.