Arctic and Antarctic Barotropic Tide Models

Laurence Padman, ESR
Phone: +1 (541) 753-6695 Fax: +1 (541) 753-1999
Susan Howard, ESR
Phone: +1 (206) 726-0501 Fax: +1 (206) 726-0524
Lana Erofeeva, OSU
Phone: +1 (541) 737-3964 Fax: +1 (541) 737-2064
Funded by NSF Polar Programs

Overview

Scientists at ESR, in collaboration with Oregon State University (OSU), run and update barotropic tide models for the Arctic Ocean and the seas surrounding Antarctica. There are two types of model: "forward" models based on numerical solution of the astronomically forced shallow-water wave equation; and "inverse" models which assimilate tide data to constrain the solution to match data within some prescribed error. While our long-term goal is to create accurate forward models, there is an immediate need for accurate tide models that are best achieved through data inversion.

Several models (listed below) are available to interested researchers. The model grid files are formatted to match the Oregon State Tidal Inversion Software (OTIS) format, and so can be accessed using FORTRAN-based OTIS code available from OSU. ESR provides Matlab software, the Tide Model Driver (TMD) package, to access all the listed models and to make tidal predictions. TMD includes both a Graphical User Interface (GUI) and lower-level scripts. The TMD package is available following the links for model grids. See README_TMD.pdf for a detailed description of the software.

Follow the links below for further information on each model, and download instructions.

Model Comparisons to Altimetric and GPS-derived Elevation

The models all report ocean tide, i.e., the height of the ocean surface relative to the seabed. For tide model use in correction of satellite-derived altimetric heights (e.g., detiding of satellite-derived ice shelf elevation), ocean tide model predictions must be corrected by the "load tide", i.e., the deformation of the solid earth by the water above it. At this time the only load tide model we provide is based on TPXO6.2. This model, TPXO6.2_load, can be used to calculate load tides (generally, roughly out of phase with the ocean tide) which must be added to the ocean tide prediction to provide altimetric elevation.

The Models

Compatible Models from Oregon State University

The structure of the bathymetry and tidal harmonic coefficient grid files for the models available here are consistent with the Oregon State University suite of global and regional tide model solutions (see http://www.coas.oregonstate.edu/research/po/research/tide/index.html and http://www.coas.oregonstate.edu/research/po/research/tide/region.html). Thus, these models can also be run in Matlab with the TMD toolbox. Download the required model(s) from the OSU sites, then create a 'Model' file that names each of the necessary binary grid files. For example, the file, Model_tpxo6.2, is an ASCII file containing the following 3 lines:

These lines refer to the binary (OTIS format) files containing complex harmonic coefficient grids for height (h_tpxo6.2) and velocity (u_tpxo6.2), and the bathymetry grid file grid_tpxo6.2. For further information, see the README_TMD.pdf file.

Baroclinic Models

ESR also carries out studies of baroclinic (depth-dependent) tides for specific high-latitude regions including the Scotia Sea and northern Weddell Sea along the South Scotia Ridge, which is the site of the Deep Ocean Ventilation through Antarctic Intermediate Layers (DOVETAIL) program.