Shifts in Ocean Color Signal a Warming Ocean Across Global Seas

No time to read?
Get a summary

The color of the seas is shifting as oceans warm, signaling ecological changes that may not be obvious at first glance. Over the past two decades, ocean color has altered in meaningful ways, a change linked to human-caused climate trends according to a recent Nature study.

The research, led by investigators from the Massachusetts Institute of Technology and the United Kingdom’s National Oceanography Centre, notes that the shift was detected in 56% of the world’s oceans, an expanse larger than the combined land area of the planet.

Experts describe tropical ocean regions near the equator turning greener, reflecting shifts in surface ecosystems. Ocean color acts as a direct indicator of the organisms and materials in surface waters, making color a true mirror of the ocean’s biological state.

While scientists cannot yet detail every facet of these ecological changes, they are confident that climate change is the primary driver.

Changing the tone of the seas

For years, simulations warned that shifts in ocean color were likely. It is no longer surprising, but it remains alarming, according to comments compiled by news agencies from MIT scientist Stephanie Dutkiewicz, a co-author of the study.

changes in plankton

Ocean color reflects the makeup of the upper layers. Azure hues suggest limited life, while greener tones indicate thriving surface ecosystems, especially phytoplankton, the plant-like microbes abundant near the surface.

Phytoplankton forms the base of the marine food web, supporting a chain that leads from krill and fish to seabirds and marine mammals. They also play a pivotal role in the ocean’s capacity to capture and store carbon dioxide.

Scientists have spent decades monitoring phytoplankton from the surface and using satellite observations to track how these crucial communities respond to climate shifts.

The ocean’s color shifts because plankton communities change. That will influence every organism that feeds on plankton.

These changes will also influence how much carbon the ocean absorbs because different plankton species have different capacities for carbon uptake. People should take this seriously. Models alone cannot predict these changes. Now we can observe them, and the ocean is changing, according to Dutkiewicz.

The prediction has come true

Researchers analyzed ocean color data from the Moderate Resolution Imaging Spectroradiometer on the Aqua satellite, tracking color for 21 years across seven visible wavelengths.

Even though much of the ocean appears blue to the naked eye, the true color may be a blend of lighter wavelengths, spanning from blue through green to red.

Cael and colleagues conducted a statistical analysis using seven ocean colors measured by satellite between 2002 and 2022. They first examined year-to-year regional changes across each color, then extended the analysis to a twenty-year horizon.

The results show a clear trend exceeding typical annual variability.

To test the climate-change link, the team revisited Dutkiewicz’s 2019 model, which simulates Earth’s oceans under two scenarios: with added greenhouse gases and without. In the greenhouse-gas scenario, the model forecast a pronounced trend emerging within two decades, altering the color of about half of the world’s surface oceans—precisely the pattern revealed in the satellite data analysis.

Reference work: Nature study on ocean color and climate influences.

Notes on data availability and interpretation appear in the Nature article, which documents the satellite-derived color changes and the ecological implications. Further information is documented through the broader environmental research community and related data archives.

No time to read?
Get a summary
Previous Article

Russia Paralympic Committee Faces Key IPC Proceedings and Paralympic Paris 2024 Eligibility

Next Article

Crimean Senator Calls Crimea Status a Historical Matter; Warns Against Ukrainian Territorial Reclamation