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

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 similar to 50%, while minimum fluxes occur in December. Annually averaged fluxes estimated here are similar to 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.

Automated summary

Using data collected from June 2017 to June 2018 at Anadyr Strait, this study estimates the monthly fluxes of nitrate, phosphate, and silicate from the Pacific Ocean to the Arctic Ocean through Bering Strait over the period 1997-2019. The study finds significant inter-annual variability in the fluxes, with the estimated values being about 50% higher than previous estimates. Increasing trends in phosphate and silicate fluxes are observed from 1998 to 2018, but the trend for nitrate is unclear.