Abstract
AbstractRecent evidence shows that wind‐driven ocean currents, like the western boundary currents, are strongly affected by global warming. However, due to insufficient observations both on temporal and spatial scales, the impact of climate change on large‐scale ocean gyres is still not clear. Here, based on satellite observations of sea surface height and sea surface temperature, we find a consistent poleward shift of the major ocean gyres. Due to strong natural variability, most of the observed ocean gyre shifts are not statistically significant, implying that natural variations may contribute to the observed trends. However, climate model simulations forced with increasing greenhouse gases suggest that the observed shift is most likely to be a response of global warming. The displacement of ocean gyres, which is coupled with the poleward shift of extratropical atmospheric circulation, has broad impacts on ocean heat transport, regional sea level rise, and coastal ocean circulation.
Highlights
Ocean gyres represent large systems of ocean currents, which are driven by the wind (Munk, 1950)
Model simulations suggest that poleward shift of ocean gyres are most likely to be a consequence of global warming, driven by a systematic poleward displacement of the extratropical atmospheric circulation
Model simulations imply that increasing greenhouse gases (Cai et al, 2003; Fyfe et al, 1999; Kushner et al, 2001), ozone depletion over the South Pole (Thompson & Solomon, 2002; Thompson et al, 2011) and increasing aerosols (Allen et al, 2012) over the Northern Hemisphere all contribute to the observed shift in atmospheric circulation, suggesting that human activity is reshaping the climate
Summary
Ocean gyres represent large systems of ocean currents, which are driven by the wind (Munk, 1950). At the western edge of subtropical gyres are the western boundary currents, which carry warm water from the tropics poleward, contributing to a warm and wet climate on the adjacent mainland. The eastern margins of the subtropical gyres are manifested by upwelling and cold eastern boundary currents. These provide abundant nutrients for marine ecosystems and contribute to maintaining a relatively cold and dry climate on the nearby continents. Oceanic productivity is low over the central parts of the subtropical gyres (commonly called ocean deserts), whereas the subpolar gyres are relatively nutrient rich, sustaining an abundance of marine life. Given the broad impacts of ocean gyres on the climate and ecosystems, it is crucial to understand how they respond to climate change
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