modeling circulation and ice in the chukchi and beaufort seas seth danielson, uaf enrique...
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Modeling circulation and ice in the Chukchi and Beaufort Seas
Seth Danielson, UAFEnrique Curchitser, RutgersKate Hedstrom, UAFTom Weingartner, UAF
Colors: Sea Surface TemperatureSpeckles: Ice
Outline
• Description of model• Some model-data comparisons• Ongoing development & future improvements
Model setup
• Pan-arctic domain• 50 vertical levels• 20-year hindcast
(1985-2004)• Telescoping grid
3.5-7 km resolution in Chukchi-Beaufort Seas
Seafloor Topography
Model setup
• Pan-arctic domain• 50 vertical levels• 20-year hindcast
(1985-2004)• Telescoping grid
3.5-7 km resolution in Chukchi-Beaufort Seas
Grid size (km)
Arctic ice-ocean model• Built on the Regional Ocean Modeling System (ROMS)• Oceanic boundary and initial conditions from the Simple Ocean
Data Assimilation (SODA) reanalysis• Surface forcing from Common Ocean Reference Experiment
(CORE-2)• Air-sea fluxes computed via bulk formulae• Monthly and inter-annually varying river discharge from Dai and
Trenberth (2002)• Dynamic-thermodynamic sea ice model following Budgell (2005)
Sea ice component• Dynamic-thermodynamic sea ice model implementation of Budgell
(2005)• Elastic-Viscous-Plastic (EVP) following Hunke and Dukowicz (1997)
and Hunke (2001)• Thermodynamics following Mellor and Kantha (1989) and Hakkinen
and Mellor (1992)• Frazil ice production following Steele et al., (1989)
• Imposition of landfast ice extent in the Beaufort Sea following monthly climatology of Mahoney et al. (2006; http://mms.gina.alaska.edu/)
Model-data comparisons
• SSM/I passive microwave ice concentration• ICESat sea ice thickness• Moored temperature, salinity, velocity• CTD hydrography• Satellite-tracked drifters
No data assimilation: we can use a wide variety of historical data to independently assess performance.
Sea ice concentration observed:modeled cross-correlation
1.00.80.60.40.2
-0.2-0.4-0.6-0.8-1.0
Sea ice concentration Averaged over Chukchi-Beaufort region
Modeled Observed
Timing of ice setup in fall
RMSD = 15.5 days RMSD = 6.5 days
Mid-winter ice thicknessModel – ICESat Observed (m)
• Model ice too thin in NE Chukchi • Model Ice too thick along Siberian coast
Model ice thickness (m)
Northeast Chukchi near Barrow Canyon (site MK1, 71.1°N, 159.5°W)
Northeast Chukchi Offshore (site C2, 71.3°N, 164.5°W)
Landfast Ice Open water
Nearshore Beaufort Sea (McClure site, 70.3°N, 147.5°W)
Landfast Ice
Northeast Chukchi near Barrow Canyon (site MK1, 71.1°N, 159.5°W)
Nearshore Beaufort Sea (Dinkum site, 70.4°N, 147.95°W)
ObservedRun #5 Run #7 (NEP6)
• Surface forcing from Modern-Era Retrospective Analysis for Research and Applications (MERRA)
• Northeast Pacific (NEP6) regional hindcast used for oceanic boundary conditions in Bering Strait
• Improved bathymetric Digital Elevation Models
Next Steps: model improvements underway
Alaska Region Digital Elevation Model
(ARDEM)
Help improve your region of interest!ARDEM update coming in 2012-2013 through
funding from the North Pacific Research Board.
All bathymetric sounding data [email protected]
Alaska Region Digital Elevation Model
(ARDEM)
http://mather.sfos.uaf.edu/~seth/bathy/
Next steps: toward ice/ocean model improvements and operational applications
Success in many future model advances depends on field observations
• Algorithm development and testing:• Growth and breakup of landfast ice• Melt pond dynamics… ice algae?• Wind-ice-ocean-oil interactions• Merge ice/ocean components… ice shelf approach?• Surface heat flux algorithms for ice-infested waters
• Model validation through community-based ocean monitoring. • Real-time nowcast/forecast ice-ocean models could inform industry,
regulators, scientific research programs and emergency response efforts.
Summary• Model strengths include:
– Capturing seasonal changes in nearshore Beaufort Sea – Wind-driven flows– Reproduction of sea ice concentration anomalies
• Model weaknesses include:– Mid-winter ice thickness: too thin in the northeast Chukchi,
too thick along the Siberian Coast– Insufficient summer ice melt or too much winter ice growth
• The data-model comparisons continue to guide model development efforts by identifying features and sub-grid scale processes that require better parameterizations.