New CNES‐CLS09 global mean dynamic topography computed from the combination of GRACE data, altimetry, and in situ measurements

[1] An accurate knowledge of the ocean mean dynamic topography (MDT) is mandatory for the optimal use of altimetric data, including their assimilation into operational ocean forecasting systems. A new global 1/4° resolution MDT was computed for the 1993–1999 time period with improved data and methodology compared to the previous RIO05 MDT field. First, a large-scale MDT is obtained from the CLS01 altimetric Mean Sea Surface and a recent geoid model computed from 4.5 years of GRACE (Gravity Recovery and Climate Experiment) data. Altimetric sea level anomalies and in situ measurements are then combined to compute synthetic estimates of the MDT and the corresponding mean currents. While the RIO05 MDT was based on 10 years of in situ dynamic heights and drifting buoy velocities, the new field benefits from an enlarged data set of in situ measurements ranging from 1993 to 2008 and includes all hydrological profiles from the Argo array. Moreover, the processing of the in situ data has been updated. A new Ekman model was developed to extract the geostrophic velocity component from the drifting buoy measurements. The handling of hydrologic measurements has also been revisited. Compared to the previous RIO05 solution, the new global MDT resolves much stronger gradients in western boundary currents, with mean velocities being doubled in some places. Moreover, in comparison to several other recent MDT estimates, we find that the new CNES-CLS09 MDT is in better agreement with independent in situ observations.

[1]  G. Mitchum,et al.  Tropical Pacific near‐surface currents estimated from altimeter, wind, and drifter data , 1999 .

[2]  A high resolution satellite‐only GRACE‐based mean dynamic topography of the South Atlantic Ocean , 2007 .

[3]  P. Poulain,et al.  Quality Control and Interpolations of WOCE-TOGA Drifter Data , 1996 .

[4]  Gilles Larnicol,et al.  On the Use of Satellite Altimeter Data in Argo Quality Control , 2009 .

[5]  Ole Baltazar Andersen,et al.  DNSC08 mean sea surface and mean dynamic topography models , 2009 .

[6]  Nicolas Ferry,et al.  Mercator Global Eddy Permitting Ocean Reanalysis GLORYS1V1: Description and Results , 2010 .

[7]  Gilles Larnicol,et al.  What can we learn from Global Altimetry/Hydrography comparisons? , 2006 .

[8]  Gregory C. Johnson,et al.  In Situ Data Biases and Recent Ocean Heat Content Variability , 2009 .

[9]  S. Jayne,et al.  Circulation of the North Atlantic Ocean from altimetry and the Gravity Recovery and Climate Experiment geoid , 2006 .

[10]  K. Haines,et al.  Interpretation of Water Mass Transformations Diagnosed from Data Assimilation , 2003 .

[11]  F. Hernandez,et al.  A mean dynamic topography computed over the world ocean from altimetry, in situ measurements, and a geoid model , 2004 .

[12]  N. G. Val’es,et al.  CNES/GRGS 10-day gravity field models (release 2) and their evaluation , 2010 .

[13]  Nonlinear anisotropic diffusive filtering applied to the ocean's mean dynamic topography , 2009 .

[14]  Gary S. E. Lagerloef,et al.  Diagnostic Model and Analysis of the Surface Currents in the Tropical Pacific Ocean , 2002 .

[15]  Keith Haines,et al.  Calculating the Ocean’s Mean Dynamic Topography from a Mean Sea Surface and a Geoid , 2008 .

[16]  V. Menezes,et al.  Mean mesoscale global ocean currents from geodetic pre-GOCE MDTs with a synthesis of the North Pacific circulation , 2010 .

[17]  Brian D. Beckley,et al.  Global mesoscale variability from collinear tracks of SEASAT altimeter data , 1983 .

[18]  Rosemary Morrow,et al.  Global surface currents: a high-resolution product for investigating ocean dynamics , 2008 .

[19]  M. Arhan,et al.  Dynamics of Eddy Motions in the Eastern North Atlantic , 1985 .

[20]  F. Bretherton,et al.  A technique for objective analysis and design of oceanographic experiments applied to MODE-73 , 1976 .

[21]  L. Fu.  Pathways of eddies in the South Atlantic Ocean revealed from satellite altimeter observations , 2006 .

[22]  Nikolai Maximenko,et al.  Stationary mesoscale jet‐like features in the ocean , 2008 .

[23]  D. Chambers,et al.  Mean Dynamic Topography of the Ocean Derived from Satellite and Drifting Buoy Data Using Three Different Techniques , 2009 .

[24]  John C. Ries,et al.  Large scale ocean circulation from the GRACE GGM01 Geoid , 2003 .

[25]  D. Wright,et al.  Mean surface topography of the northwest Atlantic: Comparison of estimates based on satellite, terrestrial gravity, and oceanographic observations , 2009 .

[26]  F. Hernandez,et al.  High‐frequency response of wind‐driven currents measured by drifting buoys and altimetry over the world ocean , 2003 .

[27]  A. Pascual,et al.  A Mean Dynamic Topography of the Mediterranean Sea computed from altimetric data, in-situ measurements and a general circulation model , 2007 .

[28]  C. Provost,et al.  Long-term variation in the anticyclonic ocean circulation over the Zapiola Rise as observed by satellite altimetry: Evidence of possible collapses , 2009 .

[29]  An Oceanographer's Guide to GOCE and the Geoid , 2006 .

[30]  K. A. Mork,et al.  Absolute flow field estimation for the Nordic seas from combined gravimetric, altimetric, and in situ data , 2009 .

[31]  Gilles Reverdin,et al.  Global high-resolution mapping of ocean circulation from TOPEX/Poseidon and ERS-1 and -2 , 2000 .

[32]  Bo Qiu,et al.  Eddy-mean flow interaction in the decadally modulating Kuroshio Extension system , 2010 .

[33]  Absolute Dynamic Topography from Altimetry: Status and Prospects in the Upcoming GOCE Era , 2010 .