Water Mass Analysis of Effect of Climate Change on Air–Sea CO 2 Fluxes: The Southern Ocean
International audience Impacts of climate change on air–sea CO 2 exchange are strongly region dependent, particularly in the Southern Ocean. Yet, in the Southern Ocean the role of water masses in the uptake of anthropogenic carbon is still debated. Here, a methodology is applied that tracks the carb...
Published in: | Journal of Climate |
---|---|
Main Authors: | , , , , |
Other Authors: | , , , , , , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
HAL CCSD
2012
|
Subjects: | |
Online Access: | https://hal.science/hal-01414759 https://hal.science/hal-01414759/document https://hal.science/hal-01414759/file/%5B15200442%20-%20Journal%20of%20Climate%5D%20Water%20Mass%20Analysis%20of%20Effect%20of%20Climate%20Change%20on%20Air%E2%80%93Sea%20CO2%20Fluxes%20The%20Southern%20Ocean.pdf https://doi.org/10.1175/JCLI-D-11-00291.1 |
Summary: | International audience Impacts of climate change on air–sea CO 2 exchange are strongly region dependent, particularly in the Southern Ocean. Yet, in the Southern Ocean the role of water masses in the uptake of anthropogenic carbon is still debated. Here, a methodology is applied that tracks the carbon flux of each Southern Ocean water mass in response to climate change. A global marine biogeochemical model was coupled to a climate model, making 140-yr Coupled Model Intercomparison Project phase 5 (CMIP5)-type simulations, where atmospheric CO 2 increased by 1% yr−1 to 4 times the preindustrial concentration (4 × CO 2 ). Impacts of atmospheric CO 2 (carbon-induced sensitivity) and climate change (climate-induced sensitivity) on the water mass carbon fluxes have been isolated performing two sensitivity simulations. In the first simulation, the atmospheric CO 2 influences solely the marine carbon cycle, while in the second simulation, it influences both the marine carbon cycle and earth’s climate. At 4 × CO 2 , the cumulative carbon uptake by the Southern Ocean reaches 278 PgC, 53% of which is taken up by modal and intermediate water masses. The carbon-induced and climate-induced sensitivities vary significantly between the water masses. The carbon-induced sensitivities enhance the carbon uptake of the water masses, particularly for the denser classes. But, enhancement strongly depends on the water mass structure. The climate-induced sensitivities either strengthen or weaken the carbon uptake and are influenced by local processes through changes in CO 2 solubility and stratification, and by large-scale changes in outcrop surface (OS) areas. Changes in OS areas account for 45% of the climate-induced reduction in the Southern Ocean carbon uptake and are a key factor in understanding the future carbon uptake of the Southern Ocean. |
---|