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Insights into decadal North Atlantic sea surface temperature and ocean heat content variability from an eddy-permitting coupled climate model

Moat, B. I., Sinha, B., Josey, S. A., Robson, J., Ortega, P., Sévellec, F., Holliday, N. P., McCarthy, G. D., New, A. L. and Hirschi, J. J.-M. (2019) Insights into decadal North Atlantic sea surface temperature and ocean heat content variability from an eddy-permitting coupled climate model. Journal of Climate, 32 (18). pp. 6137-6161. ISSN 1520-0442

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To link to this item DOI: 10.1175/JCLI-D-18-0709.1

Abstract/Summary

An ocean mixed layer heat budget methodology is used to investigate the physical processes determining subpolar North Atlantic (SPNA) sea surface temperature (SST) and ocean heat content (OHC) variability on decadal-multidecadal timescales using the state-of-the-art climate model HadGEM3-GC2. New elements include development of an equation for evolution of anomalous SST for interannual and longer timescales in a form analogous to that for OHC, parameterization of the diffusive heat flux at the base of the mixed layer and analysis of a composite AMOC event. Contributions to OHC and SST variability from two sources are evaluated i) net ocean-atmosphere heat flux and ii) all other processes, including advection, diffusion and entrainment for SST. Anomalies in OHC tendency propagate anticlockwise around the SPNA on multidecadal timescales with a clear relationship to the phase of the Atlantic meridional overturning circulation (AMOC). AMOC anomalies lead SST tendencies which in turn lead OHC tendencies in both the eastern and western SPNA. OHC and SST variations in the SPNA on decadal timescales are dominated by AMOC variability because it controls variability of advection which is shown to be the dominant term in the OHC budget. Lags between OHC and SST is traced to differences between the advection term for OHC and the advection-entrainment term for SST. The new results have implications for interpretation of variations in Atlantic heat uptake in the CMIP6 climate model assessment.

Item Type:Article
Refereed:Yes
Divisions:Faculty of Science > School of Mathematical, Physical and Computational Sciences > NCAS
Faculty of Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
ID Code:84302
Publisher:American Meteorological Society

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