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Barotropic Ocean Tides Models

A Barotropic Ocean Tides Model of the
Southern Ocean and Antarctic Seas


The Circum-Antarctic Tidal Simulation (CATS) is a high-resolution 2-D model of depth-integrated tides of the Southern Ocean and Antarctic Seas. The model domain extends to 58oS, and explicitly includes the ocean cavities under the Amery, Filchner-Ronne, George VI, and Ross Ice Shelves. The resolution is 1/4o E/W and 1/12o N/S, for a typical grid spacing of ~10 km at 70oS. The present version (2002), CATS02.01, is forced by height fields along 58o S obtained from the Oregon State University TPXO6.2 global tidal solution and by astronomical forcing. Topography is obtained from ETOPO-5, updated in the Weddell and Ross Seas (Þ more details on the bathymetry grid). Ten constituents are modeled, four diurnal (O1, K1, P1, Q1), four semidiurnal (M2, S2, N2, K2), and two long-period (fortnightly) (Mm, Mf). All constituents are evaluated concurrently in this time-stepping model. Output fields include sea surface height amplitude and phase, and depth-averaged velocity components amplitude and phase. Details of this model can be found in Padman et al., 2002.

At this time, the model is available in Matlab™ and Fortran format. Further details of the model, including download instructions, can be found on our Polar Tides Model page.

We also solicit interest in comparing the model solution to new data sets, including traditional current meter, bottom pressure, and coastal tide height data, and also less traditional measurements such as ice shelf motion from differential 3-D GPS or SAR interferometry, and ice-mounted buoy drift velocities. Note that the tidal current predictions, specifically in the diurnal band, may be subject to significant error because of the sensitivity of tidal currents to the details of bathymetry, which is very poorly sampled in many regions around Antarctica.





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A Barotropic Ocean Tides Model of the Weddell and Scotia Seas


Robin Robertson (now at Lamont-Doherty Earth Observatory) was the primary investigator on this project. Collaborators are Laurie Padman and Susan Howard (ESR), and Lana Erofeeva and Gary Egbert (Oregon State U.).

Tides in the Weddell and Scotia Seas can provide a major fraction of the total oceanic energy. Tides affect:
  • mixing in the ocean, both at the seabed and in the stratified ocean interior;
  • sea-ice concentration via modified upper ocean mixing and through the dynamical effect of tide-induced ocean stress on the ice base; and
  • the dynamics and thermodynamics of the massive floating glacial ice shelves. 


A paper on the topic, "Tides in the Weddell Sea", has been published in: Ocean, Ice, and Atmosphere: Interactions at the Antarctic Continental Margin, Antarctic Research Series, Volume 75, pp. 341-369, 1998. You may view an html version of the Abstract or download an Acrobat PDF version (2.93 MB file) of the entire paper (please note: this manuscript contains figures that are best printed in color). Using output from this model, we have also investigated the generation of baroclinic tides in the southern Weddell Sea (see Baroclinic tides section for summary).

A second paper was prepared for the 13th Filchner-Ronne Ice Shelf Program (FRISP) meeting held in Bremerhaven, Germany, in June 1998. This paper, entitled "Modelling tides in the southern Weddell Sea: updated model with new bathymetry from ROPEX", is available for download in Acrobat PDF form (2.6 MB file). (Please note: this manuscript contains figures that are best printed in color.) As the title states, the recent acquisition of new depth data from the Ronne Polynya Experiment (ROPEX) changes the modelled tidal currents along the southern outer shelf and slope, especially in the area of the General Belgrano Bank (GBB). In particular, the currents for the diurnal tidal constituents are reduced by about a factor of four over the GBB. Currents elsewhere in the model domain are also affected by modifications to model bathymetry in the southwestern Weddell Sea, because of changes in dissipation by bottom stress as well as topographic steering of the tidal energy fluxes.



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