Ocean currents have protected the Galápagos from global warming. Now is the time to protect them | CU Boulder today

Banner image: An endangered Galapagos fur seal. (Credit: Andrew Turner)

As most of the world’s oceans are warming due to climate change, a new study by CU Boulder explains how the waters around the Galápagos Islands are staying cool and cooling.

Posted in PLOS Climate, the study shows that not only does a cold, eastward equatorial ocean current provide the Galápagos Islands with a buffer against an otherwise warming Pacific Ocean, but that this current has been building for decades. In fact, the waters off the west coast of the Galápagos have cooled by 0.9 degrees Fahrenheit (0.5 degrees Celsius) since the early 1990s.

“There is a tug of war between our greenhouse effect which causes upward warming and the cold ocean current. Right now, the ocean current is winning – it’s not just about staying cool, it’s getting colder every year,” said study lead author Kris Karnauskas, an associate professor in the Department of Atmospheric and Atmospheric Sciences. and member of the Cooperative Institute for Research in Environmental Sciences (CIRES).

This phenomenon is cause for cautious optimism for the world’s second largest marine reserve and a biodiverse island ecosystem that is home to several endangered species and designated as a UNESCO World Heritage Site.

The Galápagos Islands are a volcanic archipelago located west of the Equator in the Pacific Ocean. (Credit: European Space Agency)

If corals don’t bleach and die in these waters off the west coast of Ecuador, and the marine food web doesn’t struggle as it will in nearby warming waters, the flora and Galápagos wildlife could help reseed struggling ecosystems and keep the region’s fisheries functioning.

“As the Galápagos have so far been relatively untouched by climate change, it is worth considering the Galápagos as a potential site to really try to put climate change mitigation efforts there,” Karnauskas said.

But as one of the few remaining places in the world’s oceans that isn’t currently warming, the waters off the west coast of the Galápagos also likely need additional protections from overfishing as well as pressures from increased ecotourism. .

“Human pressures on this area and this mechanism that keeps it alive are at odds,” Karnauskas said. “It’s a major resource that needs to be protected.”

A geological accident

The Galápagos Archipelago may seem insignificant from space, like several small dots in the eastern Pacific Ocean. But it’s their location – right on the equator – that makes them quite important.

Because Earth rotates on an axis, this equatorial undercurrent in the Pacific Ocean is also stuck at the equator, blocked by the planet’s rotational force. This current below the surface of the ocean runs rapidly from west to east, its cold water rich in nutrients. When it hits the Galápagos Islands, some of this water is forced to the surface and the chemical reaction of photosynthesis causes an explosion of food for all kinds of creatures.

So while the islands are located in the tropics, this cold ocean current hitting them creates a cooler, more stable environment for the coral reefs, as well as the sea animals and birds that normally live much closer to the poles. The endangered Galápagos penguin, Galápagos fur seal and Galápagos sea lion all thrive on these islands, touted as a “living museum and showcase of evolution” by the World Heritage Convention of the United States. ‘UNESCO.

Published in August in Geophysical Research Lettersanother paper from Karnauskas, and Donata Giglio, an assistant professor of atmospheric and oceanic sciences at CU Boulder, used data from thousands of floating ocean sensors, in place since 2000, to observe and confirm that this Pacific equatorial undercurrent is responsible for the cold water that rises from below to surround and support the islands’ thriving ecosystem.

Crab
penguin

Top: a sally lightfoot crab (Grapsus (grapsus) of the Galapagos Islands. (Credit: NOAA Photo Library) Bottom: Galapagos Penguin. (Credit: Derek Keats)

A cold current that strengthens

Karnauskas used different data, when ten years ago at the Woods Hole Oceanographic Institution, to show how cold ocean currents could protect certain islands or coastlines from the adverse effects of climate change on global warming. This new study shows that not only does this hold true for the Galápagos, but that the cold current is getting stronger.

“There is clear evidence that shows since 1982 that this current has strengthened and the cold water on the western shores of the islands has cooled,” Karnauskas said.

But why is this cold ocean current getting stronger?

This current, which originates near Australia, is already among the strongest in the world. Using a recently developed high-resolution ocean model, Karnauskas concluded that its continued cooling results from changes in the winds across the equator.

Although this acceleration of the equatorial undercurrent is consistent with model simulations of future climate change, according to Karnauskas, it is not yet clear if this trend can be directly attributed to human-induced climate change or if it is the result of natural cycles.

Are the Galápagos Islands safe forever? Not quite, says Karnauskas.

El Niño (the warm phase of a recurring climate pattern in the tropical Pacific) poses a temporary threat – stopping the cold current every two years causing penguin populations to crash. Although El Niño occurs independently of the cold current, it offers a glimpse of what might happen without it.

“The concern is that if in the future there were changes to this current, it could be really devastating to the ecosystem,” Karnauskas said.

And if the oceans keep warming the way they have been, says Karnauskas, this refuge from climate change might not stay that way.

“What the data shows very clearly is that he’s hanging on so far,” Karnauskas said. “That doesn’t mean it’s going to last forever.”

Teresa H. Sadler