Evaluating the potential of SMART subsea cable pressure sensors to constrain Subpolar North Atlantic circulation variability through Observing System Simulation Experiments

Matthew Goldberg , An Nguyen, Helen Pillar, Bruce M Howe, Patrick Heimbach

Bolstering global ocean observing infrastructure is critical for understanding, quantifying, and predicting Earth's climate variability and change. The emerging SMART (Science Monitoring And Reliable Telecommunications) Subsea Cables present an opportunity to acquire high-frequency, seafloor-based observations of ocean variables, encouraging assessment of their value prior to deployment. We conduct Observing System Simulation Experiments (OSSEs) to quantify potential for constraining ocean circulation using simulated SMART sensor data from a proposed cable in the Subpolar North Atlantic. Synthetic daily SMART ocean bottom pressure anomaly observations from a high-resolution global “nature run” are assimilated into a regional ocean model. Model-data misfit is reduced via gradient-based adjustments to atmospheric control variables. Synthetic data value is then quantified via the error reduction and improved skill between the regional model and the nature run. Assimilation of synthetic SMART data improves regional estimates of ocean bottom pressure as well as unobserved quantities such as barotropic (depth-integrated) transport and Arctic freshwater exports, demonstrating the SMART system’s potential to constrain basin-scale ocean circulation. On annual time scales SMART cables are shown to complement satellite altimetry data by providing unique constraints on sub-monthly and coastal oceanic mass transport,  leading to larger localized reductions in ocean bottom pressure uncertainty. Atmospheric pressure, followed by zonal and meridional surface winds, are identified as the primary control variables driving daily bottom pressure anomaly correction, which is understood through the inverse barometer effect. Our results underscore the value of high-frequency seafloor pressure data for improving estimates of climate-relevant ocean transports and highlight their promise for enhancing the spatiotemporal resolution of ocean mass distribution and circulation estimates.