This trend is global and one of the consequences of human-induced climate change on our planet. According to scientists from the United Kingdom’s National Oceanographic Center and the Massachusetts Institute of Technology (MIT), An article Recently published in the magazine Nature, The color of Earth’s oceans has changed significantly over the past 20 years.
In it, a team led by researchers from MIT’s Department of Earth, Atmospheric and Planetary Sciences and the Center for Global Change Science, Stephanie DutkiewiczThey found changes in ocean color over the past two decades that usually cannot be explained by natural variability alone from one year to the next.
These color changes, though subtle to the human eye, have occurred in them 56% of the world’s oceansAn area larger than the total land area of the Earth. In particular, the researchers found that areas of the tropical oceans near the equator have become increasingly green, which they note The surface ecosystem of the ocean must be changing The color of the ocean is a reflection of its water creatures and elements.
The color of the ocean is a reflection of its water creatures and elements.
At this point, researchers cannot explain what exactly is happening in marine ecosystems to reflect this color change. However, they are convinced that a possible driver of this process is human-induced climate change. “It’s not surprising to see how this happens, but horrifying,” he declares. Dutkiewicz argues that These changes are consistent with human-induced changes in climate. “
“This is further evidence of how human activities affect life on Earth on a large scale,” says the study’s co-author, Get the BB, a researcher at the National Oceanographic Center in Southampton, United Kingdom. “It’s another way humans affect the biosphere“ .
Why are the oceans (at least so far) blue?
The color of the ocean is a product of everything in its upper layers. Generally, Deep blue water reflects very small life, while green water indicates the presence of mainly phytoplankton, A group of unicellular plant organisms that are abundant in the surface of the ocean and contain the green pigment responsible for photosynthesis: chlorophyll.
This Plankton help collect sunlight that these organisms capture carbon dioxide from the atmosphere and convert it into sugar. Phytoplankton is the base of the marine food chain, supporting an increasingly complex array of organisms, from krill through many fish to hundreds of birds and dozens of marine mammals.
Curupi Delta, Marakume Triacu Rivers, Brazil.
But phytoplankton play an important role in the ocean’s ability to capture and store carbon dioxide. Therefore, scientists are interested in monitoring phytoplankton on the surface of the oceans and seeing how these essential communities may respond to climate change. To do so, they monitored spatial changes in chlorophyll as a function of the ratio of the amount of blue and green light reflected from the ocean surface.
7 colors for 7 seas
Therefore, the researchers studied the variation in ocean color using data acquired over 21 years by the Moderate Resolution Imaging Spectroradiometer.Modis) in the satellite Aqua From NASA. MODIS takes measurements at seven visible wavelengths, including two colors that researchers traditionally use to assess chlorophyll.
The color differences captured by the satellite are too subtle to be seen by the human eye.. Much of the ocean appears blue to our eyes, while its true color may be a mixture of subtle wavelengths ranging from blue to green to red.
To correctly discriminate these color changes, Gale’s group LA statistical analysis was carried out using seven colors of the ocean measured by satellite between 2002 and 2022. They first looked at how much the seven colors changed from one region to another in a given year, giving the researchers an idea of their natural annual variation.
However, when they adjusted their observations over a longer period of two decades, they found a shift above normal interannual variability, demonstrating that More than 50% of the world’s oceans were changing color. “This suggests that the trends we’re seeing are not random variation in the Earth system,” Gale explains. “This is consistent with anthropogenic climate change.”
“The color of the seas has changed,” Dutkiewicz adds for his part. “We cannot explain the reasons at this time.”But let’s say thatColor changes reflect changes in plankton communitiesThis will affect the entire food chain,” he continues. “This TIt can also change the amount of carbon absorbed by the ocean because different types of plankton have different capacities to assimilate carbon.”
The team’s results show that monitoring ocean colors beyond chlorophyll could provide scientists with a clearer and faster way to detect changes in marine ecosystems caused by climate change. “We hope the community will understand the magnitude of this problem; nOr it’s about models that predict changes, but we check in real time how these changes are happening in the ocean, and it’s impossible to predict their long-term consequences,” Dutkiewicz concludes.