Persistent nutrient-rich cold pool may help buffer Galápagos Islands from climate change impacts
CU Boulder scientists show strong cold undercurrent, vertical ocean mixing sustain Galàpagos Cold Pool
While most of the world’s oceans are warming, a “cold pool” just west of the Galápagos Islands is getting colder. The cool, nutrient-rich water fuels the islands’ famed biodiverse ecosystems — and new CIRES research shows the Galápagos Cold Pool will persist even if the level of carbon dioxide in the atmosphere rises to 550 parts per million, which the Intergovernmental Panel on Climate Change (IPCC) predicts could happen by 2050 if emissions do not change.
The work suggests the western edge of the Galápagos Islands could become a climate refugia, shielding plants and animals from severe climate change impacts felt elsewhere in the Pacific Ocean basin.
“The Galápagos is this amazing sanctuary. It’s a natural laboratory for biologists and a large source of tourist revenue for Ecuador,” said Mikell Warms, a PhD candidate at CIRES and CU Boulder who presented this work today at the 2024 AGU conference in Washington, D.C. “We want to be able to let policymakers know what may be coming in terms of environmental changes to this region.”
Peeking into the islands’ future, Warms and CIRES Fellow Kris Karnauskas used a high-resolution global climate model to investigate the impacts of atmospheric carbon dioxide on the ocean at the western edge of the Galápagos islands. This area is where the Equatorial Undercurrent, which flows eastward under the ocean’s surface, collides with the islands, forcing cold, nutrient-rich water to the surface.
(Right) The Equatorial Undercurrent flows from west to east across the Pacific Ocean before running into the Galápagos Islands on the eastern side of the basin. (Left) Ocean surface temperatures in degrees Celsius and the direction of currents around the Galápagos Islands. The Galápagos Cold Pool is visible to the west of the islands. Credit: Kris Karnauskas/CIRES
“There are only a handful of places in the world’s oceans where surface temperatures are actually getting colder right now–the Galápagos Cold Pool is one of them,” Warms said. “We’re trying to understand how increased atmospheric carbon dioxide might impact the oceanic processes sustaining the cold pool and whether there is a tipping point in the future.”
The scientists analyzed three model simulations with varying levels of atmospheric carbon dioxide: present-day levels for the year 2000 (367 parts per million), double present-day levels (734 parts per million), and four times present-day levels (1,468 parts per million). They then compared how ocean mixing and upwelling changed between each simulation. They focused on these processes because when the surface layer of the ocean warms, it becomes harder for the deeper and cooler upwelling waters to penetrate and mix upwards.
The team found that when carbon dioxide levels are double the present-day values, the cold pool significantly warms, but upwelling and mixing still maintain a cold pool relative to the rest of the Tropical Pacific Ocean basin. Their analysis showed that when carbon dioxide levels exceed 1,000 parts per million, significant ocean surface warming inhibits ocean mixing, leading to a loss of the cold pool.
“Our results suggest that the Galápagos may luckily be in just the right place to get a boost from mother nature in its battle against climate change,” said Karnauskas, who’s also an associate professor of Atmospheric and Oceanic Sciences at CU Boulder. “Upwelling is such a vital lifeline for this tropical marine ecosystem.”
Warms and Karnauskas’ efforts highlight the importance of using high-resolution models to accurately capture upwelling processes and provide reliable projections about climate change.
