Enhanced warming over the global subtropical western boundary currents

Abstract

Subtropical western boundary currents are warm, fast-flowing currents that form on the western side of ocean basins. They carry warm tropical water to the mid-latitudes and vent large amounts of heat and moisture to the atmosphere along their paths, affecting atmospheric jet streams and mid-latitude storms, as well as ocean carbon uptake 1-4 . The possibility that these highly energetic currents might change under greenhouse-gas forcing has raised significant concerns 5-7 , but detecting such changes is challenging owing to limited observations. Here, using reconstructed sea surface temperature datasets and century-long ocean and atmosphere reanalysis products, we find that the post-1900 surface ocean warming rate over the path of these currents is two to three times faster than the global mean surface ocean warming rate. The accelerated warming is associated with a synchronous poleward shift and/or intensification of global subtropical western boundary currents in conjunction with a systematic change in winds over both hemispheres. This enhanced warming may reduce the ability of the oceans to absorb anthropogenic carbon dioxide over these regions. However, uncertainties in detection and attribution of these warming trends remain, pointing to a need for a long-term monitoring network of the global western boundary currents and their extensions.

Drift in ocean currents impacts intergenerational microbial exposure to temperature

“…Studies on macroscopic marine biota indicate that organisms with broad temperature tolerance are more likely to establish in new habitats (43), suggesting that temperature generalists may become more prevalent in regions influenced by strong ocean currents. A good example of this is in western boundary currents, which are intensifying and increasing their poleward extension with global warming (44). A corollary of this is that thermal specialists with narrower thermal histories are more vulnerable to temperature change.…”

Marine projections of warming and ocean acidification in the Australasian region

“…In the Australian region a warming of about +0.5 °C has occurred since 1880 (HadiSST; Rayner et al, 2003) but the changes have not been homogenous. Some of the largest changes have been seen in the boundary currents along the east coast of Australia (Holbrook and Bindoff, 1997) where the warming has been 2 to 3 times faster than the global mean (Wu et al, 2012). The Leeuwin Current along the Western Australian Coast has also warmed, especially post-1980 (Zinke et al, 2014).…”

“Hot Spots” in the climate system—new developments in the extratropical ocean–atmosphere interaction research: a short review and an introduction

“…Although most of the findings are concerning the KOE region and the East Asian marginal seas, they, overall, must be commonly applicable to other climatic "hot spots". Over the last century, all the five "hot spots" have undergone warming trends much faster than the the global oceanic average (Wu et al 2012), suggesting increasing climatic significance of the "hot spots". We hope that this special section, as a highlight of the "Hotspot Project", makes an important contribution to the advancement of our understanding of climatic "hot spots" and, thereby, the broadening of our knowledge of extratropical airsea interaction, a rapidly developing area of climate science that has been drawing increased attention of the international community.…”