Scientists predict ocean temperatures will rise in the equatorial Pacific by the end of the century, wreaking havoc on coral reef ecosystems.
But a new study shows that climate change could cause ocean currents to operate in a way that mitigates warming near a handful of islands right on the equator.
Those islands include some of the 33 coral atolls that form the nation of Kiribati. This low-lying country is at risk from sea-level rise caused by global warming.
Surprisingly, these Pacific islands within two degrees north and south of the equator may become isolated climate change refuges for corals and fish.
"The finding that there may be refuges in the tropics where local circulation features buffer the trend of rising sea surface temperature has important implications for the survival of coral reef systems," said David Garrison, program director in the National Science Foundation's (NSF) Division of Ocean Sciences, which funded the research.
Here's how it could happen, according to the study by Woods Hole Oceanographic Institution (WHOI) scientists Kristopher Karnauskas and Anne Cohen, published today in the journal Nature Climate Change.
At the equator, trade winds push a surface current from east to west.
About 100 to 200 meters below, a swift countercurrent develops, flowing in the opposite direction.
This, the Equatorial Undercurrent (EUC), is cooler and rich in nutrients. When it hits an island, like a rock in a river, water is deflected upward on an island's western flank.
This upwelling process brings cooler water and nutrients to the sunlit surface, creating localized areas where tiny marine plants and corals flourish.
On color-enhanced satellite maps showing measurements of global ocean chlorophyll levels, these productive patches of ocean stand out as bright green or red spots--for example, around the Galapagos Islands in the Eastern Pacific.
|Contact: Cheryl Dybas|
National Science Foundation