What is it about?
The physical state of the ocean is continually affected by atmospheric forcing involving surface winds and exchanges of heat and moisture. The ocean response to any individual atmospheric event is often hard to decipher due to the continual changes in atmospheric forcing. In this study, we identify a large number of atmospheric events in the North Atlantic (defined by a North Atlantic Oscillation index) and align all of these events together, and then examine the ocean thermal, carbon and nutrient response to that characteristic event. We find that there are fast ocean responses to that event involving the effect of local winds and air-sea heat fluxes altering convection and mixing, as well as slow ocean responses involving the ocean circulation transporting heat, carbon and nutrient anomalies over the basin.
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Why is it important?
The ocean response to atmospheric events is often explained in terms of the immediate response to forcing. However, there are slower responses involving the circulation transporting heat, carbon and nutrient anomalies over the basin. These different fast and slow responses can lead to opposing signed-ocean temperature, carbon and nutrient responses. For example, stronger westerly winds can lead to a cooling over the subpolar North Atlantic, which is followed after 3 or 4 years by a surface warming due to the transport of warmer, subtropical waters into the subpolar gyre. Hence, the evolution of the ocean temperature anomalies can only be fully explained by accounting for the fast and slow responses to atmospheric forcing. In a similar manner, there can be reversing signed carbon and nutrient anomalies over different parts of the North Atlantic basin.
Perspectives
We conducted earlier studies of how surface temperature anomalies responded to atmospheric events (https://link.growkudos.com/1e47d3rbzls). We then extended that work to understand the biogeochemical responses involving changes in nutrients and carbon. We found that there were differences in the thermal and biogeochemical responses due to the stronger vertical gradients for the biogeochemistry (leading to vertical mixing and vertical advection being important).
Professor Richard G Williams
University of Liverpool Department of Earth Ocean and Ecological Sciences
Read the Original
This page is a summary of: Contrasting Fast and Slow Ocean Thermal, Carbon and Nutrient Responses to the North Atlantic Oscillation, Global Biogeochemical Cycles, December 2025, American Geophysical Union (AGU),
DOI: 10.1029/2025gb008519.
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