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. While new observing technologies are in development, their deployment and calibration often span years before becoming fully operational. This study evaluates one such system: SMART (Science Monitoring And Reliable Telecommunications) Subsea Cables, which provide high-frequency, seafloor-based observations. We conduct Observing System Simulation Experiments (OSSEs) to quantify the potential of constraining the ocean circulation using simulated SMART sensor data. Within the Estimating the Circulation and Climate of the Ocean (ECCO) framework, we apply adjoint-based state and parameter estimation to constrain a Subpolar North Atlantic regional ocean model using synthetic ocean bottom pressure anomaly observations from a high-resolution global “nature run.” Model skill is quantified using a score reflecting error reduction between the regional model trajectory and the nature run. Model gradients capture sensitivity information, revealing the significant role of atmospheric surface forcing uncertainty in bottom pressure variations. The forcing adjustments obtained through gradient-based optimization are validated for their dynamical relevance. Atmospheric pressure, followed by zonal and meridional surface winds, are identified as the primary control variables driving bottom pressure anomaly correction—consistent with physical oceanography theory. Assimilation of bottom pressure anomaly also improves estimates of barotropic (depth-integrated) transport and Arctic freshwater export, demonstrating the SMART system’s
potential to constrain basin-scale ocean circulation. These results underscore the value of highfrequency seafloor pressure data in reducing uncertainty in dynamically important ocean processes that lack constraint from sufficient observational infrastructure. SMART cables complement satellite altimetry and promise to enhance the spatiotemporal resolution of the global ocean observing system.