Recent evidence for a strengthening CO₂ sink in the Southern Ocean from carbonate system measurements in the Drake Passage (2002-2015)

• Published in: Geophysical Research Letters
• Other Authors: Munro, David (author), Lovenduski, Nicole (author), Takahashi, Taro (author), Stephens, Britton (author), Newberger, Timothy (author), Sweeney, Colm (author)
• Format: Article in Journal/Newspaper
• Language: English
• Published: John Wiley & Sons 2015
• Subjects: Antarctic; Drake Passage; Southern Ocean; The Antarctic; Antarc*
• Online Access: http://nldr.library.ucar.edu/repository/collections/OSGC-000-000-022-324; https://doi.org/10.1002/2015GL065194

We present a 13 year (2002-2015) semimonthly time series of the partial pressure of CO₂ in surface water (pCO₂surf) and other carbonate system parameters from the Drake Passage. This record shows a clear increase in the magnitude of the sea-air pCO₂ gradient, indicating strengthening of the CO₂ sink in agreement with recent large-scale analyses of the world oceans. The rate of increase in pCO₂surf north of the Antarctic Polar Front (APF) is similar to the atmospheric pCO₂ (pCO₂atm) trend, whereas the pCO₂surf increase south of the APF is slower than the pCO₂atm trend. The high-frequency surface observations indicate that an absence of a winter increase in total CO₂ (TCO₂) and cooling summer sea surface temperatures are largely responsible for increasing CO₂ uptake south of the APF. Muted winter trends in surface TCO₂ also provide temporary stability to the carbonate system that is already close to undersaturation with respect to aragonite.