Open AccessDrivers of Air‐Sea CO 2 Flux Seasonality and its Long‐Term Changes in the NASA‐GISS Model CMIP6 Submission
Author(s) -
Lerner Paul,
Romanou Anastasia,
Kelley Maxwell,
Romanski Joy,
Ruedy Reto,
Russell Gary
Publication year - 2021
Publication title -
journal of advances in modeling earth systems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.03
H-Index - 58
ISSN - 1942-2466
DOI - 10.1029/2019ms002028
Subject(s) - seasonality , environmental science , alkalinity , ocean gyre , climatology , atmospheric sciences , flux (metallurgy) , biogeochemical cycle , biogeochemistry , coupled model intercomparison project , sink (geography) , climate model , oceanography , subtropics , climate change , geology , chemistry , geography , environmental chemistry , statistics , mathematics , organic chemistry , cartography , fishery , biology
Climate change will affect both the mean state and seasonality of marine physical and biogeochemical properties, with important implications for the oceanic sink of atmospheric CO 2 . Here, we investigate the seasonal cycle of the air‐sea exchange of CO 2 and pCO 2, sw (surface seawater pCO 2 ) and their long term changes using the CMIP6 submission of the NASA‐GISS modelE (GISS‐E2.1‐G). In comparison to the CMIP5 submission (GISS‐E2‐R), we find that on the global scale, the seasonal cycles of the CO 2 flux and NPP have improved, while the seasonal cycles of dissolved inorganic carbon (DIC), alkalinity, and macronutrients have deteriorated. Moreover, for all ocean biogeochemistry fields, changes in skill between E2.1‐G and E2‐R display large regional variability. For E2.1‐G, we find similar modeled and observed CO 2 flux seasonal cycles in the subtropical gyres, where seasonal anomalies of pCO 2, sw and the flux are temperature‐driven, and the Southern Ocean, where anomalies are DIC‐driven. Biases in these seasonal cycles are largest in the subpolar and equatorial regions, driven by a combination of biases in temperature, DIC, alkalinity, and wind speed. When comparing the historical simulation to a simulation with an idealized increase in atmospheric pCO 2 , we find that the seasonal amplitudes of the CO 2 flux and pCO 2, sw generally increase. These changes are produced by increases in the sensitivity of pCO 2, sw to its respective drivers. These findings are consistent with the notion that the seasonality of pCO 2, sw is expected to increase due to the increase of atmospheric pCO 2 , with changes in the seasonality of temperature, DIC, and alkalinity having secondary influences.