Coral sanctuaries in a warming world ?

Oceanus -

Climate scientists have predicted that ocean temperatures in the equatorial Pacific will rise significantly 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 surprising way that mitigates the warming near some islands right on the equator.

As a result these Pacific islands may become isolated refuges for corals and fish, according to the study by Woods Hole Oceanographic Institution scientists Kristopher Karnauskas and Anne Cohen, published April 29 in the journal Nature Climate Change.

Here's how it would happen: At the equator, trade winds push a surface current from east to west. About 100 to 200 meters below, a swift countercurrent flows in the opposite direction.

This Equatorial Undercurrent (EUC) is cooler and rich in nutrients. When it hits an island, like current hitting a rock in a river, water is deflected upward on the island's western flank and around the islands.

This well-known 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.

One of the most prominent occurs around the Galapagos Islands in the eastern Pacific.

But heading westward from the Galapagos, chlorophyll levels fade like a comet tail, giving scientists little reason to look closely at scattered low-lying coral atolls farther west.

The islands are easy to overlook because they are tiny, remote, and lie at the far left edge of standard global satellite maps that place continents in the center.

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