Science 11 September 2015:
Vol. 349 no. 6253 pp. 1221-1224
Full article available: Table of Contents:
The reinvigoration of the Southern Ocean carbon sink
Peter Landschützer1,*, Nicolas Gruber1,2, F. Alexander Haumann1,2, Christian Rödenbeck3, Dorothee C. E. Bakker4, Steven van Heuven5,†, Mario Hoppema5, Nicolas Metzl6, Colm Sweeney7,8, Taro Takahashi9, Bronte Tilbrook10, Rik Wanninkhof11
Several studies have suggested that the carbon sink in the Southern Ocean—the ocean’s strongest region for the uptake of anthropogenic CO2 —has weakened in recent decades. We demonstrated, on the basis of multidecadal analyses of surface ocean CO2 observations, that this weakening trend stopped around 2002, and by 2012, the Southern Ocean had regained its expected strength based on the growth of atmospheric CO2. All three Southern Ocean sectors have contributed to this reinvigoration of the carbon sink, yet differences in the processes between sectors exist, related to a tendency toward a zonally more asymmetric atmospheric circulation. The large decadal variations in the Southern Ocean carbon sink suggest a rather dynamic ocean carbon cycle that varies more in time than previously recognized.
An increasing carbon sink?
Since 1870, Earth’s oceans have absorbed more than one-quarter of the carbon dioxide emitted to the atmosphere from fossil fuel burning and other human activities, thereby dramatically slowing climate change (1). The Southern Ocean is responsible for ~40% of this global ocean carbon sink (2). Recent studies have suggested that the rate of carbon uptake by the Southern Ocean may be slowing (3, 4). Such a positive climate feedback effect would reduce the Southern Ocean’s capacity to slow climate change. On page 1221 of this issue, Landschützer et al. show that although the rate of carbon uptake by the Southern Ocean slowed between the 1980s and early 2000s, it began to strengthen again in 2002 and continued to do so until at least 2012 (5).