Assessing Net Community Production in the Sargasso Sea Using Autonomous Underwater Glider Observations

Net community production is a key measure of the biological carbon pump, through which inorganic carbon is photosynthetically fixed and exported to the interior ocean, where it is sequestered from the atmosphere. This study demonstrates the potential for glider observations to provide accurate estimates of O₂-based net community production (NCP) through greatly improved temporal resolution over ship-based methods. High-resolution glider-based observations are used to estimate NCP near the Bermuda Atlantic Time-series Study (BATS) site through an oxygen mass balance. Glider time-series spanning from January 2017 to August 2018 demonstrate sharp seasonal contrasts and the existence of vertical biogeochemical zones that require separate, as well as collective consideration, to properly understand the biological carbon cycle at this site. NCP is then evaluated within a dynamically-based vertical framework in which the euphotic zone is divided into layers based on both stratification index and characteristic optical properties (ChlF and Bp700) during the stratified periods. Seasonal variations in NCP are explored, and an annual NCP (ANCP) estimate is compared to previous mass-balance based estimates of ANCP in the Sargasso Sea.