Mooring Measurements of Anadyr Current Nitrate, Phosphate, and Silicate Enable Updated Bering Strait Nutrient Flux Estimates

Abstract

In situ nutrient concentration data and salinity-nutrient parameterizations established at Anadyr Strait from June 2017 to June 2018 are used to estimate monthly Pacific-to-Arctic fluxes of nitrate, phosphate, and silicate through Bering Strait over 1997–2019. In most months our estimates rely on measurements made from mooring-based sensors and whole water samples, while over May–August the basis is shipboard hydrography. We find annually averaged Bering Strait fluxes of 16 ± 6, 1.5 ± 0.5, and 30 ± 11 kmol/s for nitrate, phosphate, and silicate, respectively, with inter-annual variability ±30% of the mean. Maximum fluxes occur in April, exceeding the annual average by ∼50%, while minimum fluxes occur in December. Annually averaged fluxes estimated here are ∼50% higher than previous estimates. Significant (p < 0.05) increasing trends in phosphate and silicate fluxes are found over 1998–2018, but not nitrate. However, it is unclear if these trend results are due to differences in draw-down or limitations of the salinity-nutrient parameterizations.