Global and full-depth ocean temperature trends during the early twenty-first century from Argo and repeat hydrography

Desbruyeres, Damien; McDonagh, Elaine L.; King, Brian A. ORCID: https://orcid.org/0000-0003-1338-3234; Thierry, Virginie. 2017 Global and full-depth ocean temperature trends during the early twenty-first century from Argo and repeat hydrography. Journal of Climate, 30 (6). 1985-1997. 10.1175/JCLI-D-16-0396.1

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Text © Copyright 2017 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act September 2010 Page 2 or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17 USC §108, as revised by P.L. 94-553) does not require the AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a web site or in a searchable database, or other uses of this material, except as exempted by the above statement, requires written permission or a license from the AMS. Additional details are provided in the AMS Copyright Policy, available on the AMS Web site located at (http://www.ametsoc.org/) or from the AMS at 617-227-2425 or copyrights@ametsoc.org. JCLI-D-16-0396.1.pdf - Published Version Download (2MB) | Preview

Abstract/Summary

The early 21st century’s warming trend of the full-depth global ocean is calculated by combining the analysis of Argo (top 2000m) and repeat hydrography into a blended full-depth observing system. The surface-to-bottom temperature change over the last decade of sustained observation is equivalent to a heat uptake of 0.72 ± 0.09 W m?2 applied over the surface of the earth, 90% of it being found above 2000m depth. We decompose the temperature trend point-wise into changes in isopycnal depth (heave) and temperature changes along an isopycnal (spiciness) to describe the mechanisms controlling the variability. The heave component dominates the global heat content increase, with the largest trends found in the southern hemisphere’s extratropics (0 - 2000m) highlighting a volumetric increase of subtropical mode waters. Significant heave-related warming is also found in the deep North Atlantic and Southern Ocean (2000m - 4000m), reflecting a potential decrease in deep water mass renewal rates. The spiciness component shows its strongest contribution at intermediate levels (700m - 2000m), with striking localised warming signals in regions of intense vertical mixing (North Atlantic and Southern oceans). Finally, the agreement between the independent Argo and repeat hydrography temperature changes at 2000m provides an overall good confidence in the blended heat content evaluation on global and ocean scales, but also highlights basin scale discrepancies between the two independent estimates. Those mismatches are largest in those basins with the largest heave signature (Southern Ocean) and reflect both the temporal and spatial sparseness of the hydrography sampling.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1175/JCLI-D-16-0396.1
ISSN:	0894-8755
Date made live:	11 Jan 2017 12:01 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/515799

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