Collaborative Research: Interannual variability and connectivity of the oxygen supply to the deep ocean from the Labrador and Irminger Seas

About This Grant

The primary goal of this project is to recover, calibrate, and analyze oxygen data from an array of moorings in the Labrador and Irminger Seas in the North Atlantic Ocean. The subpolar North Atlantic Ocean is important to global oxygen and carbon dioxide cycling as it has the largest water column inventories of anthropogenic, meaning human-produced, carbon in the world oceans. To date, observations have been too sparse to fully understand what controls dissolved gas pathways into the ocean interior in this region. The new oxygen observations will help characterize these pathways, will allow extrapolation from oxygen to carbon cycling, and will help examine the mechanisms that make surface waters sink and mix as they move into the deep ocean This project will advance our knowledge of how the uptake of oxygen and carbon by the ocean might be changing and how these changes are related to circulation changes in the North Atlantic Ocean that are key to regulating climatic conditions on the adjacent continents as well as globally. The subpolar North Atlantic is known to be a globally significant gateway for carbon dioxide and oxygen into the deep ocean. At the same time, climate models are unable to reproduce the observed global patterns of oxygen change, hindered largely by a dearth of year-round oxygen observations that target pathways into the interior North Atlantic and their dynamics. This project seeks a better understanding of these ventilation pathways through the analysis of an unprecedented six-year moored oxygen time series that has been added to the Overturning in the Subpolar North Atlantic Program (OSNAP) mooring array deployed across the Labrador and Irminger Seas. Part of the project is to recover the oxygen sensors from this array on an OSNAP cruise that is planned for 2026 and to calibrate the oxygen data using water sample data from the cruise. The scientific analysis of the data is then organized into three main areas: 1) an investigation into the coupling between ventilation and overturning for dissolved oxygen and inorganic carbon, 2) quantification of the contribution of direct air-sea exchange within boundary currents to overall ventilation and examination of its sensitivity to freshwater anomalies along the boundary, and 3) characterization of overflow water transformation from the Irminger to the Labrador Sea and identification of sources of Denmark Straight Overflow Water oxygen variability. It is hypothesized that the convection in the Labrador Sea contributes significantly to ventilation though it does not contribute to overturning strength and variability. The data analysis focuses on interannual variability of the ventilation processes in the North Atlantic Ocean during a time of emerging impact of freshwater on deep convection. 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.