| Gary Egbert, OSU | 
Map of M2 load tide height amplitude (m) from TPXO6.2_load. Click on image for clearer figure. |
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| Lana Erofeeva, OSU | ||||
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| Laurence Padman, ESR (TMD issues) | ||||
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TPXO6.2 is a medium-resolution, 1/4o x 1/4o global model developed by Gary Egbert and coworkers at Oregon State University. The model domain includes ocean cavities under the floating ice shelves. The principal assimilated data set is TOPEX/Poseidon (T/P) satellite radar altimetry, between +/-66o latitude. However, the model also includes patches for various "coastal" oceans, including the Antarctic (assimilating tide gauge data used in circum-Antarctic inverse model CADA00.10 and the Ross Sea height-based inverse model Ross_Inv_2002, and the Arctic (cf. the Arctic inverse model AOTIM-5). TPXO6.2 is one of the most accurate global tidal solutions, particularly for high latitudes since it utilizes recent Antarctic grounding line information and Antarctic and Arctic tide height data.
The load tide associated with TPXO6.2 (denoted "TPXO62_load") is a correction to TPXO6.2 to account for the deformation of the solid earth due to the added weight of water above it. The correction is usually a few percent of the local tidal amplitude. The load tide is used to correct the ocean tide to a geocentric tide height (e.g., the displacement of the ocean's free surface as measured by a satellite altimeter. The load tide is roughly out-of-phase with the ocean tide. Thus, adding the predicted load tide to the ocean tide leads to smaller tide heights. For altimetry, this means that the altimetrically-observed tide-forced variation of, say, an ice shelf surface, is typically less than the ocean tide. The load tide (or, more precisely, the "ocean self attraction and loading" term), is also required to correct the barotropic pressure gradient (i.e., sea surface slope) in the shallow water wave equations used to run dynamically based tide models.
The load tide is not the same as the earth's own body-tide response to lunar and solar gravitation: the body tide must be estimated separately from solid-earth models if required. However, the load tide is defined under continents as well as under the ocean: ocean tides force deformation of the earth's crust well inland of the coastal boundary (see the above figure).
TPXO62_load is distributed with a Matlab Graphical User Interface ("GUI") called "TMD" (the Tide Model Driver). TMD can be used to quickly access and browse the model, and to make load tide height predictions. The TMD package also contains scripted functions for use in batch-mode Matlab processing. For an overview of the GUI and scripts, view or download the README PDF file. For FORTRAN access, please go to the Oregon State "OTIS" web page.
Please reference Egbert and Erofeeva (2002) for the use of TPXO62_load.
Contact Laurie Padman for advice on which model to use for a particular application, to be added to an update notification list, or for further information on the tide models.
The Matlab-based version of TPXO62_load, plus the TMD Toolbox, can be downloaded by clicking on the links below. The TPXO6.2 file size is ~169 MB. If you prefer to receive the model by CD, please contact us. TPXO tide models will continue to be developed by OSU. We will also occasionally make updates to TMD.
If you prefer, the model and TMD toolbox can be downloaded from our FTP site, as follows:
