Climate change will turn the oceans bluer. And that’s bad

As a new global climate slowly becomes our reality, the world is starting to look a bit different. Take the surface of our oceans. According to a new study in Nature Communications, it might just take a few decades for the ocean’s color to completely change its current look.

Too small for us to see, bacteria that makeup phytoplankton are at the base of all processes occurring in our oceans, playing a key role in the global carbon cycle and the global food web. Thus, if something happens to phytoplankton it means it happens to the planet as a whole.

Using satellite data collected since 1990s, researchers have modeled the impact of changes in ocean temperatures on the growth and spread of the phytoplankton around the globe. Developed by a team at MIT, this is the first model ever to explore ocean biodiversity through satellite imaging.

Findings suggest that as the Earth keeps warming, shifts in phytoplankton populations globally are likely to occur. What’s stunning is that in the case of the 3°C warming we are currently heading by the end of the century around half of the global ocean surface is going to look quite different: beautiful but lifeless. And with the rising severity of ocean heatwaves and growing pollution, things might get really bad.

The subtropics, which are home to warm waters, are likely to go through a large-scale extinction of phytoplankton, along with overall decreases in ocean biodiversity. And with little phytoplankton in them the waters will turn blue. Meanwhile, in colder regions we are likely to see greener water as warmer temperatures will lead to rising phytoplankton populations and their diversity, at least until it gets too warm there too.

The changes in ocean color are no coincidence but an outcome of how light is reflected from different surfaces, based on the length of waves that they absorb or reflect back. Since water absorbs red, yellow and green light better than blue, it is the color of the pristine ocean that has little life in it. Meanwhile, the more phytoplankton inhabits the ocean, the more diverse hues of green we are likely to see.

While the new approach might not look like a breakthrough on the surface, it will actually allow scientists to greatly improve their current ocean biodiversity datasets as well as the accuracy of future projections of phytoplankton populations depending on changes in ocean temperature. The lead author of the study, Stephanie Dutkiewicz, considers the model a unique source of information for people who work with marine environments, climate change, and biodiversity. It will allow them to tap into complex changes in ocean resilience and food webs.

With this study, the team hopes to inspire experts and laypeople alike to start paying wider attention to the vulnerability of oceans to climate change and the complex interconnectedness of life on earth.