Meridional Transport Variability from GRACE Follow-On Derived Ocean Bottom Pressure Anomalies

Abstract:

The Atlantic Meridional Overturning Circulation (AMOC) is a key driver of northward heat transport for a warm climate in Northern Europe. Despite its crucial role, the AMOC is only scarcely observed, as observations covering all of the Atlantic Ocean for an extended time are difficult to obtain. Compared to in-situ data, the global coverage of ocean bottom pressure anomalies derived from satellite gravimetry potentially enables the monitoring of meridional flow throughout the Atlantic Ocean basin. However, the increase in coverage comes with a steep trade-off in spatial resolution. As a consequence, both the accuracy of meridional transport estimates and the vertical resolution of the streamfunction, from which the MOC strength is computed, suffer. The novel laser ranging interferometer (LRI) aboard GRACE Follow-On, with its increased precision compared to the established microwave ranging instrument, promises a better determination of small spatial scales and consequently a better separation of depth layers.

In this contribution we investigate the impact of the novel observations on derived ocean bottom pressure anomalies and meridional transport estimates. The basis of our evaluation are time series of deep ocean transport from GRACE and GRACE Follow-On microwave ranging data and GRACE Follow-On LRI data. We evaluate our findings by comparison of LRI and microwave ranging derived solutions with transport estimates from in-situ instrument arrays.