This article was originally published by The same review.
Due to climate change, almost all parts of the ocean are warming up. But off the west coast of the Galápagos Islands lies a cold, nutrient-rich body of water. This thriving patch feeds phytoplankton and breathes life into the archipelago.
“Cool water supports populations of penguins, marine iguanas, sea lions, fur seals and cetaceans that could not stay on the equator all year round,” says Judith Denkinger, marine ecologist at Universidad San Francisco in Quito, Ecuador.
Over the past four decades, this cold zone has cooled by about half a degree. Its persistence has scientists wondering how long it will last. The Galápagos Islands are already renowned for their biodiversity. Could the open waters become a refuge for marine animals seeking a cold environment in a warming world? The answer, it seems, is yes, at least for a while.
There are other cold pools on the planet. One, in the North Atlantic just south of Greenland, is caused by the weakening of a global current that carries heat north. But according to a new study led by Kris Karnauskas and Donata Giglio, climatologists at the University of Colorado at Boulder, the Galápagos Cold Pool is a product of the island’s topography, something that is unlikely to change due to climate change. increase in greenhouse gases.
And the Galápagos are not the only islands feeling this effect. Along the equator, several islands have exceptionally cold water located immediately to their west. According to the work of Karnauskas and Giglio, this cooling is the product of an upwelling caused by the collision of a deep ocean current against the islands in its path.
By analyzing 22 years of ocean temperature data collected by Argo floats, as well as observations from satellites and cruises, scientists constructed temperature profiles around several equatorial islands and identified the location of the sub -equatorial current, a cold, fast current that moves eastward about 100 meters below the surface of the Pacific Ocean. The EUC is held in place along the equator by the Coriolis effect, an inertial force caused by the Earth’s rotation. This same effect twists hurricanes counter-clockwise north of the equator and clockwise south of it.
Work from Karnauskas and Giglio shows that when the EUC comes within 100 kilometers west of the Galápagos Islands, it suddenly intensifies as it is deflected upward by the islands. This makes the water in this cold pool typically more than 1 degree Celsius colder than the water outside. The researchers found a similar but weaker effect west of the Gilbert Islands in the western Pacific Ocean.
In a separate study, Karnauskas found that over the past few decades, EUC has grown stronger and deeper. It also moved about 10 kilometers south, aligning its track more with the Galápagos Islands. All of these changes contribute to the observed cooling, Karnauskas says.
For the Galápagos marine ecosystem, this cooling is “a bit mixed,” says Jon Witman, a marine ecologist at Brown University who was not involved in the studies. “The fresh upwelling water from EUC certainly has significant positive impacts,” he says. But when combined with other ocean processes that also cause temperatures to drop, such as La Niña, the cooling can harm some wildlife, including causing cold shocks to corals, causing them to bleach and sometimes die. .
In the near future, this cold shield will likely benefit life around the Galápagos and other equatorial islands. But it’s a losing battle with a warming atmosphere, says Karnauskas: “This cooling trend probably won’t last the whole century; it will eventually be overwhelmed.
If certain species are protected for at least a while, however, the Galapagos could become a gene bank that could be used to reseed devastated marine ecosystems elsewhere, suggests Karnauskas: “And it’s just beautiful that it’s the iconic Galapagos. we’re talking about. here.”
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