Is Southern Ocean sea surface warming linked with changes in the westerlies?

Abstract

We aim to investigate the contribution of the wind changes to SST trends by analyzing an AVHRR-based sea surface temperature dataset during the last three decades. A distinct difference in SST trends is observed between Subtropic and ACC regions. On a long-term timescale, a negligible trend with year-to-year perturbations in the ACC contrasts with a persistent warming trend by 0.15±0.08°C per decade throughout subtropics. The intensified winds, as an instantaneous influence, contribute to a broad warming over the subtropics, while the winds lead to a slight cooling trend in the ACC. Collectively, at most 8% of the SST trend is accountable as a direct response of the wind system changes. Localized warming over the Southeast Indian and Atlantic sectors of the ACC offsets the wind-driven broad cooling trend in the ACC region, indicating that this warming is determined largely by a localized oceanic mechanism. It is hypothesized that the poleward expansion of the Indo-Atlantic supergyre might lead to the localized warming.gions. On a long-term timescale, a negligible trend with year-to-year perturbations in the ACC contrasts with a persistent warming trend by 0.15±0.08°C per decade throughout subtropics. The intensified winds, as an instantaneous influence, contribute to a broad warming over the subtropics, while the winds lead to a slight cooling trend in the ACC. Collectively, at most 8% of the SST trend is accountable as a direct response of the wind system changes. Localized warming over the Southeast Indian and Atlantic sectors of the ACC offsets the wind-driven broad cooling trend in the ACC region, indicating that this warming is determined largely by a localized oceanic mechanism. It is hypothesized that the poleward expansion of the Indo-Atlantic supergyre might lead to the localized warming.