Decade‐long deep‐ocean warming detected in the subtropical South Pacific

Abstract

The persistent energy imbalance at the top of the atmosphere, inferred from satellite measurements, indicates that the Earth's climate system continues to accumulate excess heat. As only sparse and irregular measurements of ocean heat below 2000 m depth exist, one of the most challenging questions in global climate change studies is whether the excess heat has already penetrated into the deep ocean. Here we perform a comprehensive analysis of satellite and in situ measurements to report that a significant deep‐ocean warming occurred in the subtropical South Pacific Ocean over the past decade (2005–2014). The local accumulation of heat accounted for up to a quarter of the global ocean heat increase, with directly and indirectly inferred deep ocean (below 2000 m) contribution of 2.4 ± 1.4 and 6.1–10.1 ± 4.4%, respectively. We further demonstrate that this heat accumulation is consistent with a decade‐long intensification of the subtropical convergence, possibly linked to the persistent La Niña‐like state.

Halosteric Sea Level Changes during the Argo Era

“…This is consistent with the observational findings that the Southern Hemisphere experienced its strongest warming in the recent decade, and dominated the global ocean heat content change [48]. Recent publications highlight the intensification of Ekman pumping (associated with changes in wind stress curl), which deepens the isopycnal surface and results in more heat sequestration under the upper ocean layer [49,50]. In the North tropics/subtropics (Equator to 20 • N), SSLA is dominated by HSLA, since the mean TSLA changes in this region are around zero over 2005-2015.…”

The post‐2002 global surface warming slowdown caused by the subtropical Southern Ocean heating acceleration

“…Using Argo profile data from 2004 to 2015, Roemmich et al [2016] discussed the multidecadal trend in OHC and sea surface height around 35°S, 160°W (around the positive OHC anomaly focused here) and proposed that this is caused by the intensified wind-driven convergence and associated Ekman pumping. Volkov et al [2016] reported the local deep-ocean warming signal around this subtropical region and supported the same mechanism. Our model results are consistent with these recent observational analyses and clearly demonstrate that OHC anomaly in this subtropical gyre is explained by increasing trend of trade winds.…”

“…Volkov et al . [] reported the local deep‐ocean warming signal around this subtropical region and supported the same mechanism. Our model results are consistent with these recent observational analyses and clearly demonstrate that OHC anomaly in this subtropical gyre is explained by increasing trend of trade winds.…”

Contributions of Atmospheric Forcing and Chaotic Ocean Variability to Regional Sea Level Trends Over 1993–2015

“…Forced sea level trends display large‐scale spatially coherent patterns in the tropical Pacific and Indian oceans, in line with the literature. The wind stress was indeed shown to drive a substantial sea level rise seen here in the western tropical Pacific ocean (England et al, ; Merrifield, ), the equatorial and north Indian ocean (Thompson et al, ) over 1993–2015, and in the south subtropical gyres of the Pacific and Indian oceans (Llovel & Terray, ; Volkov et al, ) over 2005–2015.…”