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Keywords:

  • GRACE;
  • altimetry;
  • barotropic;
  • ocean bottom pressure;
  • sea level

[1] Previous theoretical and model-based studies of the relationship between ocean bottom pressure (pb) and sea level (ζ) suggest primarily barotropic variability at mid to high latitudes for scales greater than a few hundred kilometers and periods less than a few months. We use 7-day GRACE solutions and equivalent satellite altimetry maps, spatially smoothed over 750 km, to investigate the relation between pb and ζ. The observed fields are significantly coherent at high latitudes for periods of ∼14–180 days and mid latitudes for periods of ∼30–100 days. The admittance amplitude between observed pb and ζ is close to 1 for higher frequencies and drops off for lower frequencies. The results provide, for the first time, global observational evidence for the barotropic nature of large-scale ocean variability at mid and high latitudes. We also demonstrate that GRACE data contain significant information over the oceans at periods <60 days, i.e., shorter than the nominal monthly time resolution.