Atlantic Water

Atlantic Water
Name	Atlantic Water
Type	water mass
Location	Atlantic Ocean
Parent	North Atlantic Ocean
Source	Gulf Stream, North Atlantic Drift
Properties	salinity, temperature, density

Atlantic Water is a major warm, saline water mass originating in the Atlantic Ocean that influences circulation, climate, and ecosystems across the North Atlantic Ocean, Arctic Ocean, and adjacent seas. It interacts with prominent currents such as the Gulf Stream, North Atlantic Current, and Norwegian Current and plays a central role in exchanges between the Atlantic Meridional Overturning Circulation and regional systems including the Barents Sea and the Labrador Sea. Atlantic Water has been the focus of observational programs by institutions like the Woods Hole Oceanographic Institution, the Scripps Institution of Oceanography, and the Norwegian Polar Institute.

Definition and Characteristics

Atlantic Water denotes the warm, saline upper-layer water advected from the Subtropical Atlantic poleward by western boundary currents such as the Gulf Stream and eastern branches like the North Atlantic Current. Characteristic attributes include elevated potential temperature and higher practical salinity relative to neighboring water masses like Arctic Intermediate Water and Polar Surface Water. It is identified in hydrographic sections using temperature-salinity (T-S) relationships established in campaigns led by the International Council for the Exploration of the Sea and programs such as the Global Ocean Observing System. The water mass underpins surface exchange with the atmosphere over regions including the Norwegian Sea, the Irminger Sea, and the Greenland Sea.

Distribution and Pathways

Atlantic Water is supplied from the Gulf Stream and its continuation, the North Atlantic Current, flowing northeast toward the European continental margin and into the Norwegian Sea and Barents Sea. Branches enter the Arctic Ocean via the Fram Strait and along the Svalbard archipelago boundary currents, while western branches influence the Labrador Sea and Gulf of Maine. Seasonal and interannual variability in pathway geometry tie to modes such as the North Atlantic Oscillation and Atlantic Multidecadal Variability, and to mesoscale features like meanders and eddy fields that redistribute heat toward the Iberian Peninsula and the Biscay Abyssal Plain.

Formation and Water Masses

Atlantic Water forms by advection and modification of subtropical source waters within boundary currents and by mixing with regional waters across features including the Mid-Atlantic Ridge and continental slope regions. Along its transit it transforms into distinct varieties—e.g., Subpolar Atlantic Water and Norwegian Atlantic Current water—through processes such as air-sea heat flux, winter convective overturning in the Irminger Sea, and entrainment at frontal zones near the Rockall Trough. Interaction with polar inflows produces mixing layers that generate intermediate products like Atlantic-Origin Intermediate Water and contribute to formation of dense water feeding the Deep Western Boundary Current.

Physical and Chemical Properties

Physically, Atlantic Water is defined by higher temperatures (typically >5–10 °C in northern branches) and salinities often exceeding 35 practical salinity units, producing distinct density surfaces that separate it from Arctic Surface Water and deeper waters like North Atlantic Deep Water. Chemical signatures include conservative tracers such as potential temperature, salinity, and oxygen, complemented by transient tracers measured by the GEOTRACES and World Ocean Circulation Experiment programs: CFCs, SF6, radiocarbon (14C), and nutrients like nitrate and phosphate. Biogeochemical fingerprints—carbonate chemistry, alkalinity, and dissolved inorganic carbon—reflect air-sea gas exchange at midlatitudes and biological uptake across productive zones like the Irminger Current front and the Norwegian Shelf.

Ecological and Climatic Role

As a principal conveyor of heat and salt, Atlantic Water modulates climate over Western Europe, influences sea-ice extent in the Barents Sea and Svalbard region, and affects stratification that controls primary production in productive basins such as the North Sea and Labrador Sea. Its warmth sustains temperate habitats for species including Atlantic cod, capelin, and migratory herring, and shapes the biogeography of plankton assemblages studied by the Plymouth Marine Laboratory and the Institute of Marine Research (Norway). Variations in Atlantic Water inflow are linked to extreme events recorded in proxy archives like ice cores, marine sediments, and coral growth records, and they influence atmospheric circulation patterns associated with the European winter storm track.

Human Impacts and Research Methods

Human-driven climate change and anthropogenic emissions from nations such as the United States, United Kingdom, and Norway alter Atlantic Water properties via warming and freshening, with consequences for regional fisheries managed under agreements like the North East Atlantic Fisheries Commission and coastal infrastructure in ports such as Reykjavik and Bergen. Research employs autonomous platforms—Argo floats, gliders, and moorings deployed by the National Oceanic and Atmospheric Administration and the Laying of submarine cables for sensor arrays—together with remote sensing from satellites like ERS-1 and Sentinel-3. Numerical modeling using frameworks developed at centers such as the Met Office Hadley Centre and the European Centre for Medium-Range Weather Forecasts integrates observations to forecast changes in Atlantic Water pathways and impacts on systems including the Atlantic Meridional Overturning Circulation and the Arctic climate system.

Category:Oceanography