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Our oceans have been changing color over the past 20 years, a new study suggests.
More than 56% of the world’s oceans have changed color to an extent that cannot be explained by natural variability, according to a team of researchers led by scientists from the National Oceanographic Center in the UK and the Massachusetts Institute of Technology in the US. A statement.
Tropical oceans, particularly near the equator, have greened over the past two decades, reflecting changes in their ecosystems, according to a study published Wednesday in the journal Nature.
The color of the ocean is derived from the substances found in its upper layers. For example, a deep blue ocean has very little life, whereas a green one has ecosystems based on phytoplankton, which are plant-like microbes that contain chlorophyll. Phytoplankton form the base of the food web, supporting larger organisms such as krill, fish, seabirds and marine mammals.
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Greener oceans mean more phytoplankton in the water.
It’s unclear how these ecosystems are changing, said study co-author Stephanie Dutkiewicz, a senior research scientist in MIT’s Department of Earth, Atmospheric and Planetary Sciences and Center for Global Change Science. While some areas are likely to have fewer phytoplankton, others may have more—and all areas of the ocean are likely to see changes in phytoplankton species at present.
Ocean ecosystems are finely balanced and any change in phytoplankton can send ripples throughout the food chain. “All change creates an imbalance in the natural makeup of ecosystems. If our oceans continue to warm, this imbalance will worsen over time,” he told CNN.
Because different plankton absorb different amounts of carbon, it also affects the ocean’s ability to act as a store of carbon, Dutkiewicz said.
While researchers are still working to sort out what the changes mean, it’s clear that the changes are being driven by human-induced climate change.
researchers It monitored changes in ocean color from space by monitoring how much green or blue light was reflected from the ocean’s surface.
It used data from the Aqua satellite, which has been tracking ocean color changes for more than two decades and is able to pick up differences that are invisible to the human eye.
They analyzed color variation data from 2002 to 2022, then used climate change models to simulate what would happen to the oceans with and without additional planet-warming pollution.
The color changes match Dutkiewicz’s prediction that about 50% of our oceans would change color if greenhouse gases were added to the atmosphere.
Dutkiewicz, who has been running simulations showing that the oceans are changing color for years, said he was not surprised by the finding.
“But still I found the results very sobering; Another wake-up call is human-induced climate change [has] had a significant impact on the Earth’s structure,” he told CNN via email.
Dutkiewicz told CNN that if the process continues, it’s hard to say if the color changes will be visible to humans.
“If you’ve reached a big tip in some places: maybe. You have to study the colors for a while to see the changes,” Dutkiewicz said.
Next, Dutkiewicz will try to better understand the color changes in different ocean regions and investigate what might be causing them, he said.