Mechanisms of ocean heat uptake along and across isopycnals

Clemént, L., McDonagh, E. L., Gregory, J. M. ORCID: https://orcid.org/0000-0003-1296-8644, Wu, Q., Marzocchi, A., Zika, J. D. and Nurser, A. J. G. (2022) Mechanisms of ocean heat uptake along and across isopycnals. Journal of Climate, 35 (15). pp. 4885-4904. ISSN 1520-0442 doi: 10.1175/JCLI-D-21-0793.1

Abstract/Summary

Warming of the climate system accumulates mostly in the ocean and discrepancies in how this is modeled contribute to uncertainties in predicting sea level rise. In this study, regional temperature changes in an atmosphere–ocean general circulation model (HadCM3) are partitioned between excess (due to perturbed surface heat fluxes) and redistributed (arising from changing circulation and perturbations to mixing) components. In simulations with historical forcing, we first compare this excess–redistribution partitioning with the spice and heave decomposition, in which temperature anomalies enter the ocean interior either along isopycnals (spice) or across isopycnals (heave, without affecting the temperature–salinity curve). Second, heat and salinity budgets projected into thermohaline space naturally reveal the mechanisms behind temperature change by spice and heave linked with water mass generation or destruction. Excess warming enters the ocean as warming by heave in subtropical gyres whereas it mainly projects onto warming by spice in the Southern Ocean and the tropical Atlantic. In subtropical gyres, Ekman pumping generates excess warming as confirmed by Eulerian heat budgets. In contrast, isopycnal mixing partly drives warming and salinification by spice, as confirmed by budgets in thermohaline space, underlying the key role of salinity changes for the ocean warming signature. Our study suggests a method to detect excess warming using spice and heave calculated from observed repeat profiles of temperature and salinity.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/104447
Item Type	Article
Refereed	Yes
Divisions	Science > School of Mathematical, Physical and Computational Sciences > NCAS
Publisher	American Meteorological Society
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