Long-term records of ocean conditions are rare for the surface and even more uncommon in the deep sea. 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, providing a vital, long-term perspective on the changing climate of one of the world's most studied ocean basins.
A key contributor to this work is the Working Group on Oceanic Hydrography (WGOH), which maintains some of the longest ocean observation records in the North Atlantic. Each year, experts review the latest data on temperature, salinity, and ocean conditions, publishing their findings in ICES Report on Ocean Climate.
Highlights for the North Atlantic Ocean 2025
WGOH held its annual meeting from 3–5 June 2026, bringing together experts in person at the Scottish Government's Marine Laboratory in Aberdeen, UK, and online to assess oceanographic conditions across the North Atlantic during 2025.
By combining observations and expertise from across the region, the group developed a comprehensive picture of the North Atlantic ocean climate and identified the key findings highlighted below.
Members also discussed the potential consequences of reductions in ocean observing systems, which are critical for monitoring climate change and informing science-based decision-making.
Salinity imprints in the North Atlantic suggest recent circulation change
Since the mid-2010s, freshwater anomalies originating in the western Subpolar North Atlantic have propagated at shallow and intermediate depths toward the eastern North Atlantic and adjacent marginal seas. This lower-salinity signal originated partly from changes in the Labrador Current pathway. The signal of this freshening has weakened in recent years.
2025 marked a broadscale return to average or above-average salinity conditions across most time series, except for a few regions at the limits of the propagation pathways (e.g., mode waters in the Canary Basin and the West Greenland Current). At the same time, deeper waters of the Northeast American Shelf have shown cooling and freshening, indicating an increased contribution of Labrador Current waters relative to Gulf Stream source waters since about 2023.
High temperatures in the upper layers
Sea surface and near-surface temperatures remained warm across large parts of the North Atlantic in 2025, although not as warm as those observed in 2023 and 2024. Extremely warm sea surface temperatures (including several marine heat waves) were observed in spring (in particular April, May, and June) over parts of the Northwest European shelf and the eastern North Atlantic, and in autumn in the eastern Nordic and Barents seas (October and November).
Record shallow convection in the Labrador Sea
In early 2025, winter convection in the Labrador Sea reached its shallowest depth since measurements began in the 1930s. This is due to persistently warm conditions in the subpolar North Atlantic since 2021, combined with freshening triggered by increased Arctic sea ice loss.
Changing signature of the Mediterranean Sea at depth
Observations indicate sustained warming and salinification of the Mediterranean Outflow Water affecting intermediate Atlantic waters near the Strait of Gibraltar. This signal can be traced across the eastern margin of the Atlantic Ocean from the Bay of Biscay and the Cantabrian Sea to the Canary Basin.
Early signs of a strong El Niño event
As a preview for 2026, measurements and ocean model forecasts indicate that a strong El Niño event is developing in the tropical Pacific. Previous strong El Niño events have been associated with changes in the North Atlantic Ocean, such as extended marine heatwaves in the region and a reduction in hurricanes. The 2026/27 event is therefore likely to have a strong impact on conditions in the North Atlantic.
ICES Working Group on Oceanic Hydrography (WGOH) closely monitors ocean conditions in ICES area by updating and reviewing results from standard hydrographic sections and stations. The group publishes summary information on climatic conditions in the North Atlantic in ICES Report on Ocean Climate (IROC).
