From seasonal cruises in the NE Pacific Ocean during 2017, we (1) determined dissolved organic carbon concentrations; (2) calculated net community production (NCP) from nitrate drawdown; and (3) established relationships between NCP and seasonal dissolved organic carbon (DOC) accumulation in the upper 75 m. The fraction of NCP that accumulated as DOC, hereafter referred to as the net dissolved production ratio, was calculated for several stations during spring and summer. The net dissolved production ratio was about 0.26 at the oceanic station Ocean Station Papa during different seasons and years. Using nitrate concentration profiles obtained from Bio‐Argo floats during 2009–2018 operating near Ocean Station Papa, we calculated NCP at high temporal resolution and then applied the 0.26 constant in order to (4) estimate DOC variability for the 9‐year period. We found strong seasonality near Ocean Station Papa, with NCP maxima during summers ranging from 0.3 to 2.9 mol C/m2 and surface DOC concentrations estimated from 56 μmol/kg in winters to 73 μmol/kg in summers. There was a 10‐fold interannual variability in the seasonally accumulated inventory of DOC, ranging from 0.078 to 0.75 mol C/m2. This study reinforces the value of deploying floats equipped with chemical sensors in order to better understand marine biogeochemical cycles, especially when high resolution data cannot be obtained otherwise. Given that ~26% of NCP accumulates as DOC in the central Gulf of Alaska, the remaining balance of ~74% is available for export as sinking biogenic particles.
Between 2013 and 2016, a series of warm events induced by ocean atmosphere oscillations negatively impacted productivity in the northeast Pacific Ocean. For two consecutive winters (2013–2014 and 2014–2015), suppressed wind stress and warm near‐surface ocean temperature anomalies restricted vertical mixing between the surface and underlying nutrient‐enriched waters. Here we assess historical data of sea surface temperature and sea level pressure, along with nearly a decade of biogeochemical float data to evaluate the impact of these warm events on organic carbon production. The first stratified winter experienced little apparent impact on the magnitude of net organic carbon production in the growing season relative to prior years, suggesting an immediate resilience from reduced new nutrients, apparently depending on recycled iron. However, the subsequent winter experienced virtually zero net production; a loss of resilience, perhaps due to net iron removal with export, was evident. We find that consistently enhanced winter stratification decreased carbon production much more so than a single warm winter. This study highlights the sensitivity of marine productivity to ocean atmosphere oscillations, reducing deep ocean carbon sequestration with prolonged ocean warming and stratification.
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