Abstract
High-frequency wind speed and wave variability influence the air-sea CO2
flux by modulating the gas transfer velocity. Traditional gas transfer
velocity formulations scale solely with wind speed and ignore wave
activity, including wave breaking and bubble-mediated transfers. In this
study, we quantify the effects of wave-induced spatiotemporal
variability on the CO2 flux and the ocean carbon storage using a
wind-wave-dependent gas transfer velocity formulation in an ocean
general circulation model (MOM6-COBALTv2). We find that wave activity
introduces a hemispheric asymmetry in ocean carbon storage, with gain in
the southern hemisphere where wave activity is robust year-round and
loss in the northern hemisphere where continental sheltering reduces
carbon uptake. Compared to a traditional wind-dependent formulation, the
wind-wave-dependent formulation yields a modest global increase in ocean
carbon storage of 4.3 PgC over 1959-2018 (~4%), but on
average, enhances the CO2 gas transfer velocity and flux variability by
5-30% on high-frequency and seasonal timescales in the extratropics and
up to 200-300% during storms (>15 m s-1 wind speed). This
wave-induced spatiotemporal variability in CO2 flux is comparable to the
flux expected from marine carbon dioxide removal (mCDR) techniques, such
that neglecting wind-wave variability in modeled CO2 fluxes could hinder
distinguishing between natural variability and human-induced changes,
undermining mCDR verification and monitoring efforts.