Global Warming May Increase Ocean Upwelling and Impact Global Fisheries

Global warming may just increase upwelling in several ocean current systems around the world by the end of this century. The findings could mean some major shifts in marine biodiversity as temperatures climb.

Upwelling of colder, nutrient-rich water is a driving force behind marine productivity. This means that increased upwelling could cause a surge in growth, and may enhance some of the world's fisheries.

In this latest study, the researchers examined the effect of warmer temperatures on upwelling. Solar heating, in theory, could increase the persistence of "stratification," which is the horizontal layer of ocean water of different temperatures. The result would be a warm, near-surface layer and a deep, cold layer.

"Our modeling indicates that normally weaker upwelling toward the polar ends of upwelling-dominated regions will strengthen," said Bruce Menge, one of the researchers, in a news release. "Ordinarily, you would expect that an increase in upwelling would mean an increase in marine coastal productivity, and that might happen. However, a think and warmer top layer, and more stratified ocean waters may put the cold, nutrient-rich waters too deep for upwelling to bring them up, and reduce the availability of upwelling to energize the coastal ocean food web. This could have a very negative impact on marine production and fisheries."

There's also another possibility, though. It's possible that there may be changes in the frequency or severity of low-oxygen events, such as those that have plagued the Pacific Northwest in the last decade. Depending on where the layers of warm and cold water end up, the hypoxic events could become either less common or more severe.

This isn't all that the researchers found out. It turns out that the change in upwelling will likely be more severe in the Southern Hemisphere, and major current systems will be affected off the western coasts of North America, South America, Africa and parts of Europe. These findings reveal how warming temperatures may influence the oceanic system and this, in turn, may influence climate. By understanding climate-mediated hotspots in upwelling, researchers can better manage productive fisheries and coastal ecosystems in the future.

The findings are published in the journal Nature.

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