麻豆影院

Since 2002, the Southern Ocean has been removing more of the greenhouse gas carbon dioxide from the atmosphere, according to two new studies. These studies, out today in the journals Geophysical Research Letters () and , make use of millions of ship-based observations and a variety of data analysis techniques to conclude that that the Southern Ocean has increasingly taken up CO2 during the last 13 years. That follows a decade from the early 1990s to 2000s, where evidence suggested the Southern Ocean carbon dioxide (CO2) sink was weakening.

The global oceans are an important sink for human-released CO₂, absorbing nearly a quarter of the total CO₂ emissions every year. Of all ocean regions, the Southern Ocean below the 35th parallel south plays a particularly vital role. 鈥淎lthough it comprises only 26 percent of the total ocean area, it has absorbed nearly 40 percent of all anthropogenic CO₂ taken up by the global oceans up to the present,鈥� says David Munro, a scientist at the Institute of Arctic and Alpine Research () at the 麻豆影院 () and an author on the GRL paper, which also includes researchers from the Cooperative Institute for Research in Environmental Sciences () at CU-麻豆影院, the at Columbia University, and the National Center for Atmospheric Research (). 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听 听

The GRL paper听focuses on one region of the Southern Ocean extending from the tip of South America to the tip of the Antarctic Peninsula. 鈥淭he Drake Passage is the windiest, roughest part of the Southern Ocean,鈥� says Colm Sweeney, lead investigator on the Drake Passage study, co-author on both the GRL and Science papers, and a CIRES scientist working in the NOAA Earth System Research Laboratory (). 鈥淭he critical element to this study is that we were听 able to sustain measurements in this harsh environment as long as we have鈥攂oth in the summer and the winter, in every year over the last 13 years. This data set of ocean carbon measurements is the densest ongoing time series in the Southern Ocean.鈥�

The team was able to take these long-term measurements by piggybacking instruments on the Antarctic Research Supply Vessel Laurence M. Gould. The Gould, operated by the National Science Foundation (), makes nearly 20 crossings of the Drake Passage each year, transporting people and supplies to and from Antarctic research stations. For over 13 years, it鈥檚 taken chemical measurements of the atmosphere and surface ocean along the way.

By analyzing more than one million surface ocean observations, the researchers could tease out subtle differences between the CO2 trends in the surface ocean and the atmosphere that suggest a strengthening of the carbon sink. This change is most pronounced in the southern half of the Drake Passage during winter. Although the researchers aren鈥檛 sure of the exact mechanism driving these changes, 鈥渋t鈥檚 likely that winter mixing with deep waters that have not had contact with the atmosphere for several hundred years plays an important role,鈥� says Munro.

The Science paper, led by Peter Landsch眉tzer at the ETH Zurich, takes a more expansive view of the Southern Ocean. This study uses two different methods to analyze a dataset of surface water CO₂ spanning almost three decades and covering all of the waters below the 35th parallel south. These data鈥攊ncluding Sweeney and Munro鈥檚 data from the Drake Passage鈥攁lso show that the surface water CO₂ is increasing slower than atmospheric CO₂, a sign that the Southern Ocean as a whole is more efficiently removing carbon from the atmosphere.

Despite the high density of sampling by Sweeney鈥檚 group in the Drake Passage and other researchers around the globe, the Southern Ocean remains highly under-sampled, in particular during wintertime when weather conditions make ocean research in the region very difficult. 鈥淕iven the importance of the Southern Ocean to the global oceans鈥� role in absorbing atmospheric CO₂, these studies suggest that we must continue to expand our measurements in this part of the world despite the challenging environment,鈥� says Sweeney.

This study was funded primarily by the NSF and NOAA鈥檚 .

The paper's co-authors include David Munro (CU 麻豆影院, INSTAAR and the Department of Atmospheric and Oceanic Sciences ()); Nicole Lovenduski (CU 麻豆影院, INSTAAR and ATOC); Taro Takahashi (Lamont-Doherty Earth Observatory); Britton Stephens (National Center for Atmospheric Research); Timothy Newberger (CIRES and NOAA); and Colm Sweeney (CIRES and NOAA ESRL Global Monitoring Division).

CIRES is a partnership of and . This is a joint release of the Cooperative Institute for Research in Environmental Sciences () and the American Geophysical Union ().

Contact:
Colm Sweeney, CIRES/NOAA, 303-497-4771
Colm.Sweeney@noaa.gov
David Munro, CU 麻豆影院/INSTAAR, 303-735-6582
david.munro@colorado.edu
Karin Vergoth, CIRES communications, 303-497-5125
karin.vergoth@noaa.gov
Nanci Bompey, AGU communications, 202-777-7524
nbompey@agu.org