Mon. Jan 17th, 2022

New research uses airborne measurements of carbon dioxide to estimate ocean uptake

Research published in recent years has suggested that the Southern Ocean may be absorbing less carbon dioxide (CO2) from the atmosphere than previously thought. But a new study published this week in the journal Science confirms the role of the Southern Ocean as a significant carbon drain.

Using observations from research aircraft flown under three field projects over nearly a decade, as well as a collection of atmospheric models, the researchers found that the South Seas absorb 550 million tons of carbon from the atmosphere each year, or about 18 percent of the amount absorbed. by all the world’s oceans. The study highlighted the value of airborne observations when examining the global carbon cycle.

“You can not fool the atmosphere,” said NCAR researcher Matthew Long, the paper’s lead author. “While measurements taken from the sea surface and from land are important, they are too sparse to provide a reliable picture of air-ocean carbon flux. However, the atmosphere can integrate currents over large expanses.”


Samples trapped across the southern ocean during three airborne research missions, including the ATom, helped confirm that the southern ocean is a large carbon drain. Credit: Sam Hall / NCAR.

NOAA’s Global Monitoring Laboratory measured CO2 from the samples collected during the airborne projects and gave atmospheric CO2 records from the surface monitoring stations of its Global Greenhouse Gas Reference Network.

“Airborne measurements have the advantage of a very large footprint over thousands of kilometers,” said Colm Sweeney, a scientist at NOAA’s Global Monitoring Laboratory and a co-author. “These measurements allow us to see the strong summer uptake and almost neutral winter degassing over the southern ocean.”

Uncertainty about the role of the Southern Ocean

Once CO2 emissions enter the atmosphere, some are absorbed by plants, and some are absorbed into the ocean. These land and ocean “sinks” slow down the rises in atmospheric CO2 levels.

As society continues to emit more CO2, understanding the location, scale and variation of carbon sinks is crucial to understanding the future trajectory of climate change and evaluating the impact of future emission reduction measures and CO2 removal technologies.

By pooling airborne measurements from three different field projects (HIPPO, ORCAS, ATom) with deployments spanning nearly a decade, the researchers showed that the Southern Ocean absorbs significantly more CO22 in summer than it loses in winter. In summer, flowering of photosynthetic algae or phytoplankton plays a key role in driving CO2 recording in the sea.

“It is crucial that we have a finger on the pulse of the carbon cycle as we enter a period in which the global community is taking steps to reduce CO2 in the atmosphere, ‚ÄĚLong said. “These observations can help us do just that.”

The research was funded by the National Science Foundation, which is the sponsor of NCAR, as well as by NOAA and NASA.

This story was adapted from an NCAR press release.

For more information, contact Theo Stein, NOAA Communications, at


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