The subduction and export of Subantarctic Mode Water (SAMW) supplies the upper limb of the overturning circulation and makes an important contribution to global heat, freshwater, carbon and nutrient budgets. Upper ocean heat content has increased since 2006, helping to explain the so-called global warming hiatus between 1998 and 2014, with much of the ocean warming concentrated in extratropical latitudes of the Southern Hemisphere in close association with SAMW and Antarctic Intermediate Water (AAIW)6,7. Here we use Argo observations to assess changes in the thickness, depth and heat content of the SAMW layer. Between 2005 and 2015, SAMW has thickened (3.6 ± 0.3 m yr⁻¹), deepened (2.4 ± 0.2 m yr⁻¹) and warmed (3.9 ± 0.3 W m⁻²). Wind forcing, rather than buoyancy forcing, is largely responsible for the observed trends in SAMW. Most (84%) of the increase in SAMW heat content is the result of changes in thickness; warming by buoyancy forcing (increased heat flux to the ocean) accounts for the remaining 16%. Projected increases in wind stress curl would drive further deepening of SAMW and increase in heat storage in the Southern Hemisphere oceans.

Item Type:	Refereed Article
Keywords:	Subantarctic Mode Water, ocean heat content, Southern Hemisphere, global warming
Research Division:	Earth Sciences
Research Group:	Oceanography
Research Field:	Physical oceanography
Objective Division:	Environmental Policy, Climate Change and Natural Hazards
Objective Group:	Understanding climate change
Objective Field:	Effects of climate change on Antarctic and sub-Antarctic environments (excl. social impacts)
UTAS Author:	Rintoul, SR (Dr Steve Rintoul)
ID Code:	131757
Year Published:	2018
Web of Science® Times Cited:	45
Deposited By:	Oceans and Cryosphere
Deposited On:	2019-04-04
Last Modified:	2019-05-31
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