Monitoring Labrador Current Transport Variability With Satellite Gravity

Abstract The Labrador Current is a major pathway for export of North Atlantic Deep Water across 53°N. While direct measurements of the integrated transport of the current were made from 1997 to 2014 at the 53°N Moored Observatory and since 2014 as part of the Overturning in the Subpolar North Atlantic Program (OSNAP), the calculations of integrated transport are typically delayed by years due to the time to recover and process moored instrumentation. Here, we examine a method to compute variations in the transport from ocean bottom pressure gradients determined from the GRACE and GRACE‐FO satellite missions since 2002, which will allow near‐real‐time monitoring. After verifying the method using an ocean state estimate that captures the mean and variable transport similar to the observations, we calculate the variability using the satellite observations. While there is a notable degradation at the end of the GRACE mission after 2012, results from 2002 to 2011 are consistent with interannual variations seen in the 53°N Moored Observatory and results from the GRACE Follow‐on mission (starting in 2018) are consistent with observations made by the OSNAP array. Monthly differences are of the order of 3–4 Sv compared to overall variability of ±6 Sv (one standard deviation). No statistically significant trend since 2002 was found.