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Seasonal Asymmetry in the Evolution of Surface Ocean p CO 2 and pH Thermodynamic Drivers and the Influence on Sea‐Air CO 2 Flux
Author(s) -
Fassbender Andrea J.,
Rodgers Keith B.,
Palevsky Hilary I.,
Sabine Christopher L.
Publication year - 2018
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2017gb005855
Subject(s) - alkalinity , carbon dioxide , carbon cycle , environmental science , flux (metallurgy) , dissolved organic carbon , total inorganic carbon , sea surface temperature , atmospheric sciences , salinity , seasonality , oceanography , climatology , biological pump , environmental chemistry , chemistry , ecology , geology , ecosystem , biology , organic chemistry
It has become clear that anthropogenic carbon invasion into the surface ocean drives changes in the seasonal cycles of carbon dioxide partial pressure ( p CO 2 ) and pH. However, it is not yet known whether the resulting sea‐air CO 2 fluxes are symmetric in their seasonal expression. Here we consider a novel application of observational constraints and modeling inferences to test the hypothesis that changes in the ocean's Revelle factor facilitate a seasonally asymmetric response in p CO 2 and the sea‐air CO 2 flux. We use an analytical framework that builds on observed sea surface p CO 2 variability for the modern era and incorporates transient dissolved inorganic carbon concentrations from an Earth system model. Our findings reveal asymmetric amplification of p CO 2 and pH seasonal cycles by a factor of two (or more) above preindustrial levels under Representative Concentration Pathway 8.5. These changes are significantly larger than observed modes of interannual variability and are relevant to climate feedbacks associated with Revelle factor perturbations. Notably, this response occurs in the absence of changes to the seasonal cycle amplitudes of dissolved inorganic carbon, total alkalinity, salinity, and temperature, indicating that significant alteration of surface p CO 2 can occur without modifying the physical or biological ocean state. This result challenges the historical paradigm that if the same amount of carbon and nutrients is entrained and subsequently exported, there is no impact on anthropogenic carbon uptake. Anticipation of seasonal asymmetries in the sea surface p CO 2 and CO 2 flux response to ocean carbon uptake over the 21st century may have important implications for carbon cycle feedbacks.