Study Shows Warming Ocean, Vicious Carbon Cycle

Graphic: Annabel Driussi for Our Daily Planet

By Amy Lupica, ODP Contributing Writer

A new study found that the ocean is showing signs of intensifying stratification, a phenomenon in which the layers of water in the ocean become more distinct and mix less. As mixing between layers slows, so does the transfer of nutrients and oxygen to other layers, endangering ocean ecosystems and wildlife. As the surface layer of the ocean warms, it empowers storm systems like typhoons and hurricanes, increasing their destructiveness. The warming of the ocean due to climate change also impairs its ability to remove carbon from the atmosphere, accelerating climate change further in a vicious cycle of temperature increases.

Why This Matters: The mixing of ocean layers is crucial to sea life and human life. When ocean layers interact enough, they transfer nutrients and oxygen from upper layers to lower layers, supporting life in both the depths and the shallows. When they don’t, it prevents animals at lower depths from getting enough oxygen to breathe, and it prevents salt from deeper waters from migrating upwards, harming ecosystems and wildlife that humans rely on for food and trade. In addition, currents rely on movement between layers of ocean water; as those layers stabilize, it may threaten shipping routes and travel. The warmer layers are also losing their ability to hold CO2, which experts predict could cause atmospheric CO2 to triple by 2100 and raise the global average temperature by eight degrees Fahrenheit.

A Vicious Cycle

That’s a double whammy. In the first case, that means that the ocean is less able to take up CO2 from the atmosphere, and so atmospheric CO2 builds up even faster. The ocean becomes less effective as a “carbon sink,” said Michael Mann, a climate scientist at Penn State and co-author of the study. “In the second case, it means that the oceans hold less oxygen. That’s problematic for sea life that, like us, needs oxygen. It’s a threat to the food web, including fish,” Mann added.  There is evidence it is already impacting the food chain.  For example, in 2017 dramatic ocean warming led to a drought in East Africa, leaving 6 million Somalian people facing food shortages. As water-scarcity increases, so does conflict in affected regions.

Experts have found a direct connection between the warming of the ocean and the increased number and power of hurricanes and storms. Ryan Truchelut, the chief meteorologist at WeatherTiger, said of the onslaught of Atlantic hurricanes in 2020, “The culprit is much warmer than average waters in the western Atlantic, coupled with generally lower than average wind shear in the same area driven by the tilt into La Niña.” Strong storm systems once churned ocean water, bringing cooler water to the surface, weakening storm development. But as historically cool layers grow warmer, that churning could actually empower storms further.

The warming of the ocean and subsequent loss of them as a carbon sink would prove catastrophic to the planet, and it’s only one of the many carbon sinks that could be lost in the near future. Paul Durack, a research scientist at Lawrence Livermore National Laboratory in California, thinks experts may still not know the full scope of ocean warming, saying “I would not be surprised if this study underestimates the observed change.”

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