Towards consistent Regional Sea Level Budgets

Author:

Jürgen Kusche - (University of Bonn)

Co-Investigator(s):

Luciana Fenoglio-Marc (University of Bonn)
Sophie Stolzenberger (University of Bonn)
Bernd Uebbing (University of Bonn)

Abstract:

The project “Small Scale Detection and COnsistent Regional sea level Budgets” is (OSTST_TOSCALE) makes optimal use of the new altimetry observations of high spatial resolution to study (1) globally small scale phenomena in water not resolved previously from space and (2) regional and global sea level budget.

The primary satellite-based observation is the water surface height from satellite altimetry. The spatio-temporal coverage of altimetry observations is limited to 300 km/10 days and 80 km/35 days depending on the satellite mission. A higher space/time resolution (e.g. 50 km/5 days) could be achieved through a satellite constellation combining swath altimetry and nadir Synthetic Aperture Radar (SAR) altimetry. SWOT will be the first swath mission launched during the Sentinel-3 and Sentinel-6 SAR altimetric mission life-time.

The central hypothesis of TOSCALE is that the novelty of these new instruments opens a large variety of new possible applications on climate related topics which have to be investigated timely.

TOSCALE will focus on four themes. The first theme (A) is the understanding of system and of the new measurements to maximize their usefulness for applications. The second scientific theme (B) is the analysis of small-scale processes in ocean (mesoscale and sub-mesoscale processes, coast and estuaries (coastal and estuary dynamics due to tides and flow velocity) and on rivers (water level, width and discharge of rivers). The third theme (C) is the closure of sea level budget at regional and global scales. The fourth theme (D) is the sea level change in polar regions.

Target regions for goal B are the coastal regions of the North Eastern Atlantic and inland waters in Germany and for goal C the global ocean and selected regional sub-regions and for goal D the northeast coast of Greenland.

TOSCALE is a follow-up of the projects STREMP-OSTST (2009-2012), FICOSELA (2013-2016) and OSTST_CORSEB (2017-2020) which were part of previous OSTSTs. Achievements of OSTST_CORSEB concern improved processing of altimetry data in SAR mode in open sea and coastal regions (Fenoglio 2020, Buchhaupt 2018, 2020; Dinardo 2018, 2020). This proposal includes further developments in altimeter processing and their validation, and the use of the 2D-wide-swath data SWOT to study small scale oceanic and hydrodynamic processes.

For the global sea level budget, during OSTST_CORSEB we have shown an agreement within 0.1 mm/yr between ocean mass change estimated from the “direct” and “inverse” methodologies (Uebbing et al. 2019). Furthermore, we have simulated the influence of Greenland freshwater on the North Atlantic. Although the Greenland freshwater is intruded at the model surface, the freshwater effects on salinity and temperature fields are visible in the upper 100 m due to vertical mixing processes (Stolzenberger et al., in prep).