Collaborative Research: Investigating Bubble-Mediated Gas Exchange in a Strongly Convective Ocean during the Bubble Exchange in the Labrador Sea (BELS) Experiment

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The Labrador Sea, part of the North Atlantic Ocean between Canada and Greenland, is one of the few places in the world where the deep ocean is ventilated. It is where salts and dissolved gases enter the deep ocean, thereby setting the chemical and physical environments of the deep ocean. An earlier study using data collected during a field campaign in the Labrador Sea from fall 2016 to spring 2017 showed that the traditional mathematical formulas used to calculate air-sea gas fluxes, i.e., how fast gases go in and out of the ocean, are inaccurate for the Labrador Sea. The reason may have to do with the unique environment there: strong wind, big waves, and chilling air. The earlier study indicated that it is not possible to make accurate estimates of how much gases, such as oxygen and carbon dioxide, are supplied to the deep ocean. Since oxygen is crucial to marine animals and carbon dioxide is one of the greenhouse gases contributing to global warming, there is an urgent need to develop more accurate formulas for air-sea gas fluxes that could be used in the Labrador Sea and elsewhere. In this project, scientists will go to the Labrador Sea in fall 2023 to make detailed measurements of oceanic and atmospheric conditions near the air-sea interface using recently developed techniques such as autonomous vehicles. In addition, high-fidelity computer simulations, only possible using supercomputers, will be conducted for the physical and chemical environments of the upper ocean. By synthesizing the new data and computer solutions, more accurate mathematical formulas for air-sea gas fluxes suitable for the world’s oceans including the Labrador Sea will be developed. The overarching objectives of the proposed study are to better understand bubble processes and bubble-mediated gas transfer and to propose a revised parameterization suitable for the world’s ocean, including strongly convective environments typical of the high-latitude ocean. An associated objective is to quantify the effect of solubility on bubble-mediated gas transfer. The proposed research includes an observational program and a modeling program. The observational component is part of the Bubble Exchange in the Labrador Sea (BELS) experiment – an international program during the Fall of 2023 in the Labrador Sea. The researchers will measure bubble-mediated air-sea invasion rates of CO2/O2/N2 and evasion rates of 3He/SF6 and make detailed measurements of gas flux forcing including bubbles and turbulent currents in the mixed layer. They will employ various approaches including 1D- and 3D-budgets, shipboard direct eddy covariance fluxes, as well as autonomous vehicles. These observations will be synthesized using state-of-the-art numerical models that concurrently simulate turbulent ocean currents, bubbles, and dissolved gases. The project aims to improve parameterizations of air-sea gas fluxes and reduce uncertainty in future predictions of gas uptake during ocean ventilation that may result from global warming.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.