Sea surface topography and mass transport of the Antarctic Circumpolar Current (GEO-TOP)

The study aims at the determination of the absolute, but temporally changing ocean circulation flow field and of associated mass and heat transports. It is based on a state-of-the-art circulation model assimilating geodetic data of the dynamic sea surface topography (SST) and oceanographic in-situ data. The ocean model is focused on the Atlantic sector of the Antarctic Circumpolar Current and the Weddell Sea. This is one of the most dynamic ocean areas and one of the most critical regions for global climate, due to the impact of circumpolar bottom water production on global deep sea circulation. The high resolution regional model is embedded into a coarser global model to avoid systematic distortions.

The geodetic SST (a small up to 2 m deviation between sea surface and geoid) is determined with an accuracy of a few cm from the new geoid models from the GRACE and later GOCE satellite missions combined with a long-term time series of sea surface height from multi-mission satellite altimetry. The accuracy level of the satellite data enables for the first time of the proposed approach to be practical implemented. The geodetic focus is on a maximum spatial resolution and accuracy in SST, including thorough error estimation, rigorous error propagation and adaptation to the finite element grid of the ocean model. The dynamically consistent ocean model assimilation is based on a combined geodeticoceanographic cost function. The model input and output are iteratively compared to assess the consistency of each of the data sets and the parameterization of the ocean model.

GEO-TOP results

: Comparison of the mean dynamic topography from profile approach with Maximenko, 2009 (upper panel) and Rio, 2009 (lower panel).

Project information

Funding: DFG

Period: 01/2007-02/2013

Project partners: Institut für Astronomische und Physikalische Geodäsie (IAPG) / TUM, Alfred-Wegener-Institut für Polar- und Meeresforschung (AWI) and Institut für Planetare Geodäsie (IPG) / TUD

Responsible persons at DGFI: Wolfgang Bosch, Roman Savcenko

Selected publications

Bosch W., Savcenko R., Dettmering D., Schwatke C.: A two decade time series of eddy-resolving dynamic ocean topography (iDOT). Proceedings of 20 years of Progress in Radar Altimetry Symposium, Venice, Italy, ESA SP-710, ESA/ESTEC (accepted), 2012

Janjic T., Schröter J., Albertelle A., Bosch W., Rummel R., Savcenko R., Schwabe J., Scheinert M.: Assimilation of geodetic dynamic ocean topography using ensemble based Kalman filter. J. Geodynamics, early online release, DOI:10.1016/j.jog.2011.07.001, 2011

Bosch W.: Instantaneous ocean dynamic topography profiles - assessment through smoothed GRACE geoids and altimetric sea surface height profiles. EGU general Assembly, Vienna, Austria, 2008-04-16

Bosch W., Savcenko R.: On the recovery of the mean dynamic topography - a profile approach. IAG International Symposium on Gravity, Geoid and Earth Observations (GGEO2008) , Chania, Greece, 2008-07-27 (Poster)

Albertella A., Savcenko R., Bosch W., Rummel R.: Dynamic ocean topography - the geodetic approach. . DGFI/IAPG Report 82, Deutsches Geodätisches Forschungsinstitut (DGFI), München , 2008

Bosch W., Savcenko R.: A profile approach for the recovery of the mean dynamic topography. Joint International GSTM and DFG SPP Symposium, Potsdam, Germany, 2007-10-15/17 (Poster)

Bosch W., Savcenko R.: Estimating the sea surface topography - profile approach with error examination. IUGG General Assembly 2007, Perugia, Italy, 2007-07-02/09