Recent Changes in Southern Ocean Circulation and Climate

Abstract

The Southern Ocean (SO) is essential to global ocean circulation and climate variability. The strength and position of the Southern Hemisphere (SH) westerlies are largely thought to be driving recent trends in the SO. We find increasing SH wind speeds between 45° S and 60° S by $0.0075\pm 0.00013\,\,\text{m}\cdot \text{s}^{-1}\cdot $ year−1 and decreasing in the mid-latitude region of $-0.0054\pm 0.00011\,\,\text{m}\cdot \text{s}^{-1}\cdot $ year−1. Mean surface temperatures (depth-integrated ocean heat content) are significantly increasing at $0.0066\pm 0.0057~^{\circ }\text{C}\cdot $ year−1 ( $3.8 \pm 2.4\,\,\text{W}\cdot \text{m}^{-2}$ ), although significantly decreasing within the high-latitude Pacific and Atlantic basins. Sea level change indicates that the median trend in the SH is 3.1 ± 0.69 mm $\cdot $ year−1, although there is a negative trend in the central South Pacific. Our analysis concludes that changes in surface wind speeds are significantly driving regional changes in sea level, heat content, and surface temperatures in the SH high latitudes, contributing to negative trends in the South Pacific.