Measuring ocean bottom pressure for geostrophic reference velocities

Montag 06.07.2026, 11:00 → 12:00 Europe/Berlin

5-1.214 - PAZIFIK / PACIFIC- Rechte Seite - Großer, unterteilbarer Konferenzraum (GEOMAR - Standort Ostufer / GEOMAR - East Shore)

Speaker: Dr. Simon Wett, Experimental Oceanography Unit, Institute of Oceanography, Hamburg

Hybrid  -  online via 

https://geomar.webex.com/geomar-en/j.php?MTID=m6f187b689fccd196c05d249d28f6d0d8

Abstract:
Large scale estimates of ocean transport are routinely made from moored hydrographic measurements. This is done using the thermal wind relation, which relates zonal density gradients to vertical gradients of meridional velocities. To estimate meridional transport, a constant of integration – the geostrophic reference level velocity – is required, typically a level-of-no-motion or a level-of-known-motion. If ocean pressure at the seafloor is known to high accuracy, then the velocity can be computed directly from zonal pressure gradients. However, oceanographic pressure sensors suffer from intrinsic drift, which results in a drift in the calculated velocity. For a 1-year deployment, this drift can be several centimeters of liquid water equivalent, corresponding to a meridional transport of several Sverdrups. Novel drift-correcting bottom pressure recorders are capable of determining the sensor drift by using multiple pressure sensors. We evaluate pressure measurements obtained from a pair of drift-correcting bottom pressure sensors deployed at the tail of the Grand Banks (2023-2025). We compare the drift-corrected pressure estimates with GLORYS reanalysis data. The required residual accuracy is roughly O(1 cm); if this accuracy can be achieved in situ, drift-correcting bottom pressure sensors would provide a valuable additional constraint on the time-varying, zonally-averaged barotropic circulation estimated from mooring arrays spanning the Atlantic.