Impacts of COVID-19 emissions reductions remain murky in the oceans

Off the coast of Hawaii, a Woods Hole Oceanographic Institution (WHOI) Hawaii Ocean Time-series Station buoy makes measurements of air-sea carbon dioxide, seawater pH, and other oceanographic parameters.
Off the coast of Hawaii, a Woods Hole Oceanographic Institution (WHOI) Hawaii Ocean Time-series Station buoy makes measurements of air-sea carbon dioxide, seawater pH, and other oceanographic parameters. Credit: Al Plueddemann, WHOI.

As the COVID-19 pandemic took hold in the first half of 2020, humans around the world stopped moving and making, resulting in a 9% drop in the greenhouse gas emissions at the root of climate change.

Almost overnight, the Himalayas became visible from a distance for the first time in years. Rivers flowed free of toxic pollutants and the air sparkled with blue skies in major cities like New Delhi and Los Angeles. While internet rumors of swans and dolphins returning to Venetian canals were debunked, the idea that “nature is healing” in 2020 quickly took root. 

Unfortunately, any silver lining from the pandemic remains murky in the oceans. 

At the American Geophysical Union 2020 Fall Meeting last week, a team of scientists, including Christopher Sabine, SOEST oceanography professor, shared the results of their research that showed no detectable slowing of ocean acidification due to COVID-19 emissions reductions. Even at emissions reductions four times the rate of those in the first half of 2020, the change would be barely noticeable. 

“It’s almost impossible to see it in pH,” said Nicole Lovenduski, University of Colorado associate professor and lead author of the study. “So has this solved ocean acidification? No, it has not.” 

On the bright side, the researchers now have a better idea of where to look for the signs if emissions reductions are having an impact on the Earth system, what they will look like and the resources they will need to gather that data. 

Lovenduski analyzed data shared by a group of Canadian modelers, who ran a suite of experiments to see how the climate has been impacted by the reduction in emissions in 2020. Using a fingerprinting technique on the data often used to differentiate humans’ impacts on the climate from non-human impacts like volcanic eruptions, the team separated COVID-19 emissions reductions from non-human influences on the oceans. 

While they found no perceptible change in ocean acidity, their analysis showed that by 2021, the oceans will be absorbing slightly less carbon from the atmosphere due to COVID-19 emissions reductions. 

“What this suggests is that pretty much immediately, the exchange of carbon between the ocean and atmosphere responds to the change in the loading of carbon in the atmosphere because we’ve decreased our emissions,” said Lovenduski. 

The ocean is a major climate change buffer, absorbing a large fraction of the carbon dioxide that human activity emits into the atmosphere and a significant portion of resulting heat. This mitigates the immediate impacts of climate change but as the ocean heats up the water expands and contributes to rising sea levels. Additionally, increased carbon in the ocean causes ocean acidification, which is detrimental to coral reefs and a significant swath of ocean life. 

However, if emissions are mitigated year after year to avoid the worst global warming scenarios, there is a chance to slow the rate of ocean acidification in the long term.

While it is too soon to measure ocean changes from the COVID-19 related carbon emissions reductions, there is a network of ocean observatories regularly making the measurements necessary to detect the signal when it does show up.

“We are constantly monitoring the carbon concentrations in the ocean and the atmosphere around Hawai‘i,” said Sabine. “If emissions continue to drop, we are well positioned to document the positive impact that will have on our ocean chemistry and the health of our coral reefs.”  

Studying the COVID-19 signal in the ocean provides a unique opportunity to understand how implementing the emissions reductions called for in the Paris Agreement will benefit our state and the world.

Marcie Grabowski, University of Hawai’i at Manoa, 14 December 2020. Article.

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