Consistent Ocean Mass Time Series from LEO Potential Field Missions (CONTIM-2)

• Applicants: Dr. Sergey Danilov; Professor Dr.-Ing. Jürgen Kusche, since 8/2020
• Subject Area: Geodesy, Photogrammetry, Remote Sensing, Geoinformatics, Cartography ; Oceanography
• Term: from 2015 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 273514821

Besides global temperature, sea level is an essential indicator which reflects the state of the Earth’s climate and its change. Sea level rise has multiple impacts with direct societal consequences. In this light, we plead that a data-constrained separation of the different drivers for sea level change is crucial for supporting both science and political decision making. We will concentrate on ocean mass variations which are directly linked to ocean bottom pressure. Spatial variations of ocean bottom pressure, as induced by wind and baroclinic processes, take place over months to years. However, their behavior is up to now not entirely understood. Many deep ocean processes can only be explained when, besides the sea surface height changes from radar altimetry and volumetric changes from temperature and salinity variations (e.g. from Argo floats in the upper ocean), ocean bottom pressure is also taken into account. In that light, the uptake of heat by the deep ocean, slowing down the Earth‘s surface warming according to numerous studies, can only be properly explained when all of the above processes are accounted for in a consistent manner. To this end we will continue with our approach developed in CONTIM-1.The spaceborne Gravity Recovery and Climate Experiment (GRACE) has provided unprecedented estimates of the mass fluctuations of the ocean, but is about to be decommisioned and suffers from degraded measurements due to aging batteries. Building upon the achievements of the previous funding period, CONTIM-2 will provide time series of consistent ocean mass variations which extend outside the GRACE-era and allow a transition to the upcoming GRACE-FO mission. This is achieved by combining expertise in orbit determination of Low Earth Orbiters (LEO‘s) such as SWARM the computation of time variable gravity, joint inversion techniques of multiple datasets, and physical modelling of the ocean. The precise orbit determination of the LEO‘s, with the use of GNSS receivers on SWARM, under heavily fluctuating ionospheric situations, will play an important role in this project. We anticipate that CONTIM-2 will significantly contribute to our understanding of ocean variability, sea level change and the heat uptake of the ocean.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1788: Study of Earth system dynamics with a constellation of potential field missions
• Co-Investigator: Dr. Jens Schröter
• Ehemaliger Antragsteller: Dr.-Ing. Roelof Rietbroek, until 7/2020