부산대학교 도서관

Despite the impact of the ocean's biological pump on future atmospheric CO2 and deep ocean O2 concentrations, organic matter export rates are poorly known because observations are scarce and mostly short term. Thus, we rely on satellite data and models to yield export rates, yet neither approach is sufficiently validated. We present multiyear export estimates based mainly on observed O2 and CO2 surface layer budgets across the Pacific and North Atlantic Oceans and compare to satellite‐ and model‐based estimates. We find that regional variability in observed export is modest (threefold) and lower than model‐ and satellite‐based estimates (threefold to sevenfold). Neither model‐ nor satellite‐based export reproduces the regional export trends in the Pacific. We find that winter mixed layer depth is critical in determining annual export rates in the subpolar N. Atlantic. Plain Language Summary: A small fraction of the organic matter photosynthetically produced by phytoplankton in the surface ocean is transferred (exported) to deeper layers of the ocean. The rate of export has an important impact on atmospheric carbon dioxide (CO2) concentrations. Yet, measurements of the organic matter export rate are too scarce to yield a useful picture of how this export rate varies between different ocean regions. Here we present 85 multiyear estimates of export rate spread across the Pacific and North Atlantic oceans and find only modest variations (threefold). When we compare these observations to satellite‐ and model‐based estimates of export, we find the latter approaches overestimate regional variations by up to twofold and fail to yield observed north‐south trends in export. Our findings indicate that more field measurements of export are needed to better test the model‐ and satellite‐based estimates. We expect the number of field measurements of export rate to increase markedly during the next decade as sensors that measure oxygen, CO2, and nitrate are increasingly deployed on floats, gliders, moorings, and ships. As a result, our ability to predict the impact of climate change on ocean export and, in turn, its impact on future levels of CO2 in the atmosphere should improve significantly. Key Points: Observed annual export varies regionally by three times in Pacific and Atlantic Oceans compared to three to seven times for satellite‐ and model‐based estimatesSatellite‐ and model‐based export do not produce latitudinal trends in observed export in the Pacific OceanObserved export estimates yield global export rate of ~9 Pg C/yr which is similar to many model‐ and satellite‐based estimates [ABSTRACT FROM AUTHOR]