The Variable Southern Ocean Carbon Sink

• Published in: Annual review of marine science Vol. 11; no. 1; pp. 159 - 186
• Main Authors: Gruber, Nicolas, Landschützer, Peter, Lovenduski, Nicole S
• Format: Journal Article
• Language: English
• Published: United States Annual Reviews 03.01.2019; Annual Reviews, Inc
• Subjects: anthropogenic carbon; Anthropogenic factors; Carbon; Carbon dioxide; Carbon Dioxide - chemistry; Carbon Dioxide - metabolism; Carbon Sequestration; Carbon sinks; decadal variability; Models, Theoretical; natural carbon; ocean carbon sink; Ocean circulation; Ocean models; Oceans and Seas; Outgassing; Seawater - chemistry; Southern Ocean; Storage; Stratification; Uptake; Upwelling; Water Movements; Westerlies; Southern Ocean; anthropogenic carbon; decadal variability; ocean carbon sink; Southern Ocean; natural carbon
• ISSN: 1941-1405; 1941-0611
• DOI: 10.1146/annurev-marine-121916-063407

The CO 2 uptake by the Southern Ocean (<35°S) varies substantially on all timescales and is a major determinant of the variations of the global ocean carbon sink. Particularly strong are the decadal changes characterized by a weakening period of the Southern Ocean carbon sink in the 1990s and a rebound after 2000. The weakening in the 1990s resulted primarily from a southward shift of the westerlies that enhanced the upwelling and outgassing of respired (i.e., natural) CO 2 . The concurrent reduction in the storage rate of anthropogenic CO 2 in the mode and intermediate waters south of 35°S suggests that this shift also decreased the uptake of anthropogenic CO 2 . The rebound and the subsequent strong, decade-long reinvigoration of the carbon sink appear to have been driven by cooling in the Pacific Ocean, enhanced stratification in the Atlantic and Indian Ocean sectors, and a reduced overturning. Current-generation ocean models generally do not reproduce these variations and are poorly skilled at making decadal predictions in this region.