Autonomous Wintertime Observations of Air‐Sea Exchange in the Gulf Stream Reveal a Perfect Storm for Ocean CO<sub>2</sub> Uptake
Sarah Nickford, Jaime B. Palter, Kathleen Donohue, Andrea J. Fassbender, Alison R. Gray, Jacqueline S. Long, Adrienne J. Sutton, Nicholas R. Bates, Yuichiro Takeshita
Abstract
Abstract A scarcity of wintertime observations of surface ocean carbon dioxide partial pressure ( p CO 2 ) in and near the Gulf Stream creates uncertainty in the magnitude of the regional carbon sink and its controlling mechanisms. Recent observations from an Uncrewed Surface Vehicle (USV), outfitted with a payload to measure surface ocean and lower atmosphere p CO 2 , revealed sharp gradients in ocean p CO 2 across the Gulf Stream. Surface ocean p CO 2 was lower by ∼50 μatm relative to the atmosphere in the subtropical mode water (STMW) formation region. This undersaturation combined with strong wintertime winds allowed for rapid ocean uptake of CO 2 , averaging −11.5 mmol m −2 day −1 during the February 2019 USV mission. The unique timing of this mission revealed active STMW formation. The USV proved to be a useful tool for CO 2 flux quantification in the poorly observed, dynamic western boundary current environment.