Consistent Ocean Mass Time Series from LEO Potential Field Missions (CONTIM) Team: Jürgen Kusche + Roelof Rietbroek + Christina Lück, Bonn Jens Schröter + Sergey Danilov + Alexey Androsov, Bremerhaven Steffen Schön + Le Ren, Hannover Current sea level rise ~3mm/a, how much of this is mass (Rietbroek et al., 2016, PNAS)?

Project CONTIM – Outlook to the 2nd phase of SPP We combine expertise on precise satellite orbit determination, gravity field/mass modeling, and physical oceanography Retrieve, analyze and verify consistent time series of ocean mass variations from LEOs extending the GRACE time series. Where are we now? POD works well (equivalent or improved compared to others) TVG comparable to other Swarm solutions  compare to OBP modeling  start work on inversion (with altimetry) for ocean mass and steric contribution Observation weighting  separation of ionospheric effects/fluctuations (SPP) and  elimination of high frequency noise in orbit) Modelling: small scale variations (eddies) do not average out over the GRACE/Swarm scale? Relevant developments GRACE lifetime + gap, GRACE-FO launch Improvements in thermosphere modeling through SPP GNSS Doppler Observations for test purposes available

Project CONTIM – Outlook to the 2nd phase of SPP IfE: Kinematic Orbits Jan-2016 (500km Gauss) IGG solution computed with IfE orbits IGG: TVG and mass change ITSG-Grace2016 Time series of EWH (500km Gauss) Orbits from ESA IGG Swarm ITSG-Swarm2016 Carrier phase + kinematic orbits of Swarm severely degraded under influence of ionospheric scintillation, could also degrade TVG Will investigate impact of ionospheric scintillation on GPS phase observations and eliminate impact on orbit by adequate observation weighting AWI: OBP Modeling with data assimilation Next: Fingerprint Inversion Use all results (NEQs) in a fingerprint inversion to split ocean mass changes into individual components

Project CONTIM – Outlook to the 2nd phase of SPP Address in the second phase Jointly extend ocean mass time series further in the past using SLR (and possibly DORIS) Swarm for linking GRACE and GRACE-FO Bonn use kinematic baselines ( IfE) as observations, Swarm drag modelling Parameterization  Kalman filter to make trend of SHCs /ocean mass time-variable AND resolve fast ocean signals Hannover use Doppler frequency shift to improve the orbits  independent velocity obs? investigate the impact of ionospheric scintillation on GPS observations and orbits Bremerhaven effect of small scale eddies, refining ocean models apply data assimilation to (1) locate eddies correctly, (2) incorporate GRACE/Swarm results for analysis of deep ocean circulation and warming