太平洋海岛可能成为珊瑚礁的避难所

Scientists have predicted that ocean temperatures will rise in the equatorial（赤道的） Pacific by the end of the century, wreaking¹ havoc²（肆虐） on coral reef ecosystems³. But a new study shows that climate change could cause ocean currents to operate in a surprising way and mitigate⁴ the warming near a handful of islands right on the equator. As a result these Pacific islands may become isolated⁵ refuges for corals and fish. Here's how it would happen, according to the study by Woods Hole Oceanographic Institution scientists Kristopher Karnauskas and Anne Cohen, published April 29 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 nutrients⁶. When it hits an island, like a rock in a river, water is deflected⁷ upward on the island's western flank（侧面） and around the islands. This well-known upwelling（上涌） process brings cooler water and nutrients to the sunlit surface, creating localized areas where tiny marine⁸ plants and corals flourish.

On color-enhanced satellite maps showing measurements of global ocean chlorophyll（叶绿素） levels, these productive patches of ocean stand out as bright green or red spots, for example around the Galapagos Islands in the eastern Pacific.

But as you look west, chlorophyll levels fade like a comet tail, giving scientists little reason to look closely at scattered⁹ 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.

Karnauskas, a climate scientist, was working with WHOI coral scientist Anne Cohen to explore how climate change would affect central equatorial Pacific reefs.

#