Researchers at Scripps’ Institute of Oceanography will participate in a series of airborne expeditions over the Southern Ocean to better gauge the region’s ability to absorb atmospheric carbon dioxide this month. The O2/N2 Ratio and CO2 Airborne Southern Ocean study, funded by the National Center for Atmospheric Research, will be led by SIO alumnus Britton Stephens.
Over the course of several flights, researchers will collect atmospheric samples from the remote Antarctic region. Upon the study’s completion, ORCAS team member and SIO Professor Ralph Keeling will perform an analysis of the samples with an emphasis on measuring carbon dioxide levels.
According to ORCAS team member and SIO post-doctoral candidate Eric Morgan, carbon dioxide is regularly exchanged between the atmosphere and the ocean; the group hopes to gain insight into this exchange process.
“The point is to better understand the carbon-cycle processes that affect CO2 levels in the atmosphere,” Morgan told the UCSD Guardian. “Aircraft measurements afford the opportunity to characterize a larger region [of water] … we can use this to estimate how much CO2 is being released or taken up by the ocean.”
The Southern Ocean is of particular interest to Keeling and his team because it absorbs carbon at a much faster rate than it is released due to the mixing of deep and shallow water in that region.
“The Southern Ocean is a major conduit between the atmosphere and the [deep] ocean,” Keeling told the Guardian. “[Elsewhere] the ocean is capped with water that isolates the deep from the surface. It just sits there. In the Southern Ocean the waters mix freely.”
Because of the interaction between the deep and shallow water in the Southern Ocean, carbon captured in shallower parts can be pushed downward to open up space on the surface for further CO2 uptake.
The deep ocean — depths greater than 1000 meters — serves as a “huge reservoir of carbon” and is capable of storing excess CO2 to slow down the accumulation of greenhouse gases.
According to a 2015 paper released by the National Oceanic and Atmospheric Administration, the Southern Ocean has absorbed approximately 40 percent of all man-made CO2, despite only making up 29 percent of the planet’s total ocean area.
But as the amount of CO2 in the atmosphere increases, researchers are unsure if the process of CO2 uptake will maintain its current speed or slow down due to oversaturation.
“As levels of CO2 rise in the atmosphere, the Southern Ocean should absorb increasing amounts, although this hasn’t always been true in the last couple of decades,” Morgan said. “The extent to which this region will continue to absorb CO2 from the atmosphere in a warming climate is an important question.”
However, predicting just how the Southern Ocean will react to rising CO2 levels may be a challenging task.
“[Our understanding of] the Southern Ocean comes from existing observations — which are sparse, both in space and time — and computational numerical models,” Keeling explained. “But those models have a lot of flaws … they show different things.”
Because there is not a lot of existing data on the Southern Ocean, Keeling believes analysts tend to extrapolate on whatever small patterns they can find to build their predictive models.
With the data gathered from ORCAS, researchers may be able to at least reach a consensus on how to model the short-term carbon cycle more accurately.
“We’ll be in a position to take these models apart and say which models are better and which models are worse,” Keeling said. “We won’t know what’s going to happen in 100 years, but we should at least be able to get the seasonal changes right.”
Keeling disclosed that the first flight in the ORCAS study takes off next week.
