Climate Change Impacts Ocean Upwelling Ecosystems: Food Chain Modified

The world's oceans are full of deep sea currents that circulate around the globe. As our climate changes, though, understanding these currents and the upwelling that occurs at certain points are crucial for learning how conditions will impact marine resources. Now, scientists have discovered a little bit more about upwelling ecosystems, which could reveal how our world's oceans will be impacted in the future.

Since the 1990s, scientists believed that upwelling of cold, deep water was intensifying. This phenomenon actually provides up to 20 percent of global production of fish since the water itself is very rich in nutrients. Researchers believed that the rising temperatures of the air masses above continents would quicken the trade winds which would, in turn, increase upwellings. Now, it turns out this isn't the case.

The scientists examined wind measurements taken over the past 40 years and data of meteorological models along the Spanish and West African coastline. They found that, surprisingly, the data did not show an acceleration of the wind on a regional scale. In fact, it seems that the opposite is true. There seems to be a distinct upward trend in ocean temperatures for the entire zone, which contradicts the idea that upwelling is intensifying.

In fact, past evidence actually supports this finding. Scientists discovered that planktonic organisms have evolved in an increasingly cold environment over the last few decades. Although researchers first thought that this was because the temperature at the surface was dropping, it's now likely that these creatures were actually migrating toward the depths.

What the current findings might mean for the future is still unknown. The reaction of coastal ecosystems to climate change is complex since it depends greatly on local specificities. For example, other upwelling ecosystems, such as that of the California Current, clearly show a trend of intensification and cooling of the water in recent decades. The effects of warming surface waters can be antagonistic; it can encourage the growth of fish larvae, but also increase the temperature gradient between surface waters and deeper water and thus modify the food chain. Currently, researchers are planning on looking how this change in upwelling might impact fish species.

The findings are published in the journal Progress in Oceanography.