A specialized atmospheric instrument is flying on board routine transportation missions to and from McMurdo Station during this Antarctic summer, providing rare measurements of how carbon dioxide is exchanged between the atmosphere and the Southern Ocean.
The Southern Ocean Carbon Gas Observatory (SCARGO) project, led by the US National Science Foundation National Center for Atmospheric Research (NSF NCAR), runs from November through February and aims to fill one of the largest remaining gaps in global carbon cycle observations.
Because of the region’s extreme remoteness and harsh weather, existing carbon measurements rely mostly on sparse shipborne sensors and robotic floats. To address this, NSF NCAR researchers are using regularly scheduled LC-130 flights operated by the New York Air National Guard, which transport staff and supplies between McMurdo Station, Christchurch in New Zealand and the NSF Amundsen-Scott South Pole Station.
“The Southern Ocean is one of the only places where the deep ocean interacts directly with the atmosphere,” said Britton Stephens, NSF NCAR senior scientist and SCARGO’s lead investigator. “It will play an outsized role in determining the future behavior of the Earth system. We’re trying to figure out exactly what is going on in the region and use that information to make our models better.”
SCARGO is funded by the NSF Office of Polar Programs and includes collaboration with NOAA, the Cooperative Institute for Research In Environmental Sciences (CIRES), non-profit [C]Worthy and Earth Sciences New Zealand. Flight scheduling is supported by the Antarctic WRF Mesoscale Prediction System (AMPS), another NSF NCAR project.
To minimize its footprint on crowded Antarctic flights, NSF NCAR spent three years designing a compact, wheeled instrument box that can be rolled onto the aircraft without displacing critical cargo. Inside the enclosure are a laser-based analyzer, a GPS receiver and a laptop. A pump draws outside air through a custom-built hatch replacing the aircraft’s standard escape hatch, enabling the system to capture vertical profiles of carbon dioxide and other gases throughout each flight.
NSF NCAR personnel will support operations from McMurdo, occasionally accompanying flights to the South Pole. Because seats between Christchurch and Antarctica are limited, the McMurdo team will often load and configure the instrument before departure and rely on Christchurch-based crews to prepare it for return flights.
The Southern Ocean’s deep-water circulation enables surface waters to absorb atmospheric carbon dioxide before returning it to the deep ocean for centuries or longer. However, how much carbon is being absorbed, and whether that uptake is changing, remains uncertain.
By the end of the season, the SCARGO team expects to have collected one of the most detailed atmospheric carbon datasets ever obtained for the region.
“The Southern Ocean is providing a great service to society by taking up a large amount of the carbon dioxide that we’re emitting every year,” said Stephens. “But we need to better understand the processes involved to be able to predict whether this uptake is going to stay steady, slow down or speed up in the future.”
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