Ocean Heat Convergence and North Atlantic Multidecadal Heat Content Variability

We construct an upper ocean (0–1000 m) North Atlantic heat budget (26°–67°N) for the period 1950–2020 using multiple observational datasets and an eddy-permitting global ocean model. On multidecadal time scales, ocean heat transport convergence controls ocean heat content (OHC) tendency in most regi...

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Bibliographic Details
Published in:Journal of Climate
Main Authors: Moat, B. I., Sinha, B., Berry, D. I., Drijfhout, S. S., Fraser, N., Hermanson, L., Jones, D. C., Josey, S. A., King, B., Macintosh, C., Megann, A., Oltmanns, M., Sanders, R., Williams, S.
Format: Article in Journal/Newspaper
Language:English
Published: 2024
Subjects:
North Atlantic Ocean
meridional overturning circulation
ocean circulation
ocean dynamics
Rossby waves
North Atlantic
Online Access:https://pure.uhi.ac.uk/en/publications/bad07914-e0a0-412c-85ff-db78744b1eaf
https://doi.org/10.1175/JCLI-D-23-0370.1
https://pureadmin.uhi.ac.uk/ws/files/55889656/Ocean_Heat_Convergence_and_North_Atlantic_Multidecadal_Heat_Content_Variability.pdf
https://journals.ametsoc.org/view/journals/clim/37/18/JCLI-D-23-0370.1.xml
Description
Summary:We construct an upper ocean (0–1000 m) North Atlantic heat budget (26°–67°N) for the period 1950–2020 using multiple observational datasets and an eddy-permitting global ocean model. On multidecadal time scales, ocean heat transport convergence controls ocean heat content (OHC) tendency in most regions of the North Atlantic with little role for diffusive processes. In the subpolar North Atlantic (45°–67°N), heat transport convergence is explained by geostrophic currents, whereas ageostrophic currents make a significant contribution in the subtropics (26°–45°N). The geostrophic contribution in all regions is dominated by anomalous advection across the time-mean temperature gradient although other processes make a significant contribution, particularly in the subtropics. The time scale and spatial distribution of the anomalous geostrophic currents are consistent with a simple model of basin-scale thermal Rossby waves propagating westward/northwestward in the subpolar gyre, and multidecadal variations in regional OHC are explained by geostrophic currents periodically coming into alignment with the mean temperature gradient as the Rossby wave passes through. The global ocean model simulation shows that multidecadal variations in the Atlantic meridional overturning circulation are synchronized with the ocean heat transport convergence consistent with modulation of the west–east pressure gradient by the propagating Rossby wave.

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