TOPAZ Ice Drift Forecast - Fram Strait

Forecast

Validation

Click here to view recent validation maps. It consists of forecast maps on which are superposed the true ice edge retrieved from AMSR-E satellite data (the 15% concentration contour).

Archive

Click here to view archived maps.

System description

The Fram Strait model is based on the NERSC version 2.1.03 of HYCOM (HYbrid Coordinate Ocean Model). Until January 2011, the model was based on HYCOM 2.1.03. From February 2011, the model is upgraded to HYCOM 2.2.12. The grid is a conformal mapping with the poles located far from the domain so that the grid resolution is as uniform and isotroppic as possible. The horizontal resolution is approximately 3.5 km partially resolving the scale of baroclinic motion. Boundary conditions are obtained from the 10-days TOPAZ3 forecast runs with data assimilation. The Fram Strait model is forced with ECMWF forecasts and the free runs are launched every day at 21:30:00 CET and go from 00:00:00 GMT day+1 to 24:00:00 GMT day+3. Plotted variables are a daily average from midnight to midnight.

The sea ice model uses the EVP formulation and a rheology specific to the marginal ice zone (MIZ). Because waves are not yet explicitly included in the system, the boundary between the two dynamical regimes is set at a concentration cutoff value (c=0.89). This is represented in the colorbar for ice concentration. The green zone represents compact ice in the viscous-plastic regime while the yellow-orange-red zone represents the collisional regime. The ice edge, usually diagnosed by the 0.15 contour is in the white zone while very low concentration ice is coloured in blue. This strategy of setting the boundary between the two regimes is based on the fact that in Fram Strait, areas of lower ice concentration are likely to be affected by ocean waves which break the ice cover into multiple floes interacting with each other, drastically affecting its dynamical nature.

NOTE: TOPAZ3 forecast runs are launched on Wednesday each week and because they require a significant amount of time, the nesting files for the Fram Strait model are usually not available when the run is launched. Consequently, the forecast for Friday is only available on Thursday.

Updates

• 14.10.2011 :: Operational webpage is not running anymore
• • 14.02.2011 :: Due to a bug in the salinity on the Operational Topaz run, the nesting is operated by Topaz free run for the moment.
  • 11.02.2011 :: The Framstrait model is spun-up with Hycom 2.2.12. In addition the tides are included (barotropic forcing at the open boundaries).
  • 01.02.2011 :: Dany Dumont does not maintain this page anymore. See new contact below.
  • 09.08.2010 :: The criterion differentiating MIZ and VP regimes was updated based on results obtained with a waves-in-ice model. The MIZ regime is now allowed for concentration higher than c=0.89, but for ice thinner than a concentration-dependent value prescribed by a linear function. For e.g., 0.5m-thick ice will be in the MIZ regime even for c=1.
  • 20.04.2010 :: A change in the server configuration at NERSC corrupted some of the operational scripts for a certain period. These scripts have been updated and the system is now operational and up-to-date again.
  • 25.02.2010 :: Change of colorbar for ice thickness and concentration. The new colormaps better match the WMO color code for ice type and concentration. They also have been applied in TOPAZ ice forecasts for the Beaufort Sea. The MIZ boundary is no more highlighted since the definition of the MIZ dynamical regime will soon be updated with a wave parameterization.
  • 12.11.2009 :: Change of colorbar for ice thickness and speed.
  • 09.11.2009 :: Page set-up improvements.
  • 02.11.2009 :: The map domain has been modified to better focus on the model domain. Time stepping of the EVP model has been tuned to damp out an instability observed north of Greenland. In order to minimize the consequences of past instabilities, the model has been rerun with a clean restart from 28 October 2009. To avoid further instabilities, the MIZ criterion has been updated to limit the MIZ regime for thickness below 2.0m. Finally, the strength parameter (Pstar) has been changed from 35e3 to 27.5e3 Pa m.
  • 21.10.2009 :: Archived images consist now of forecast maps with the stellite derived ice edge superposed (from 15 September until 3 days before the present day).
  • 20.10.2009 :: Change of colorbar for the ice concentration maps to better highlight the two different dynamical regimes, namely the viscous-plastic regime, characterized by the green zone, and the collisional regime of the MIZ, characterized by the yellow-orange-red zone. The ice edge (=0.15) is in the white zone while low concentration ice (<0.15) is coloured in blue. Vectors are plotted each 10 instead of each 8.
  • 15.10.2009 :: Addition of the System description section where current versions of model and forecast systems in operation are desribed. If you want more details about the system, please send an email to the contact person.
  • 22.09.2009 :: Addition of a Validation section with archived forecast maps on which is superposed the ice edge position retrieved from AMSR-E satellite data.
  • 17.09.2009 :: Addition of two new sections to this page: Archive and Updates.
  • 09.09.2009 :: Bug in ice drift velocity display. Speeds were divided by the ice concentration while it was not required. Speed values are now smaller than before, especially in areas of low ice concentration.
  • 27.08.2009 :: Change of colorbar to match those used in other areas.
  • 11.08.2009 :: Launch of the operational Fram Strait model providing 3-day forecasts of sea ice variables and updated every day.

Contact

Intissar Keghouche (intissar.keghouche@nersc.no)