Enhanced Winter Carbon Export Observed by BGC-Argo in the Northwest Pacific Ocean

The winter- and spring-time mixed-layer pump (MLP) significantly augments the global carbon transport from the surface mixed layer to deeper waters when ephemeral surface phytoplankton blooms are repeatedly mixed to depth. Exploiting unusual 190 + daily BGC-Argo profiling measurements within a recirculation gyre, we show repetitive MLP episodes generating a January-March averaged particulate organic carbon (POC) export of similar to 110 mg C m(-2) day(-1) in the midlatitude (31 degrees N) Northwest Pacific. Subsampling this dataset on a 5- or 10-day cycle yielded an order of magnitude less export, or even totally missed all the MLP events. The evidence here supports the need for new strategies if the BGC-Argo program is to adequately quantify ocean carbon cycling and its effects on biological systems. We propose that a handful of floats be tasked with daily profiling, and machine learning strategies be used to link these data with satellite derived measurements to estimate the synoptic-scale MLP export. Plain Language Summary The Biogeochemical-Argo program (BGC-Argo) is an essential tool for quantifying carbon export from surface waters to the ocean interior, which is critical for understanding and forecasting changes in atmospheric CO2. Using novel, high-frequency (1-day cycle during 9- month period) BGC-Argo data, we estimated the carbon export in the midlatitude Northwest Pacific Ocean stemming from unexpectedly continuous mixed-layer pump (MLP) events. Such events occur when wintertime phytoplankton blooms developed during calm wind periods then are injected to depth by storms. This process generated remarkably high carbon export over winter, with values ranging from 18% to 30% of that from the massive North Atlantic spring bloom. These events, however, are largely (80%) or entirely missed using the longer standard float cycling intervals (5-10 days) accepted by the BGC-Argo program. The findings here suggest that some high-frequency BGC-Argo observations are necessary for more accurately estimating the global carbon export.