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A High Resolution Coupled Sea-Ice/Ocean Model for the Antarctic Peninsula Region

A High Resolution Coupled Sea-Ice/Ocean Model for the Antarctic Peninsula Region. Michael S. Dinniman John M. Klinck Andrea Piñones Center for Coastal Physical Oceanography Old Dominion University. Outline of Presentation. Introduction and Model Description Ice Shelf Modeling

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A High Resolution Coupled Sea-Ice/Ocean Model for the Antarctic Peninsula Region

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  1. A High Resolution Coupled Sea-Ice/Ocean Model for the Antarctic Peninsula Region Michael S. Dinniman John M. Klinck Andrea Piñones Center for Coastal Physical Oceanography Old Dominion University

  2. Outline of Presentation • Introduction and Model Description • Ice Shelf Modeling • Sea Ice Modeling • Cross-shelf Transport • Future plans • Conclusions

  3. Research Questions • What is the magnitude and extent of cross-shelf exchange? • What is the structure of the circulation on the WAP shelf? • What are the circulation dynamics that drive the coastal current? • Which physical processes are responsible for exchanges across the permanent pycnocline? • What processes control sea ice in the region? What do we need in a circ. model to help answer?

  4. Antarctic Peninsula Model • ROMS: 4 km horizontal resolution, 24 levels • Ice shelves (mechanical and thermodynamic) • Dynamic sea ice • Bathymetry: ETOPO2v2 + WHOI SOGLOBEC region + Padman grid+ BEDMAP + Maslanyj • Open boundaries: T + S set to SODA, barotropic V relaxed to SODA, baroclinic V pure radiation • Daily wind forcing from a blend of QSCAT data and NCEP reanalyses or Antarctic Mesoscale Prediction System (AMPS) winds • Other atmospheric parameters from several sources (including AMPS)

  5. Ice Shelf Modeling • Ice Shelf basal melt can add large amounts of freshwater to the system (e.g. George VI estimated basal melt: 2-5 m/yr) which can affect circulation (AP coastal current?) • Ice Shelf does not change in time in model • Three equation viscous sub-layer model for heat and salt fluxes (Holland and Jenkins 1999) • PGF calculation assumes the ice shelf has no flexural rigidity and pressure at the base comes from the floating ice

  6. Warm CDW entering the ice shelf cavity => Large basal melt: 2.1 m/yr (Potter and Paren, 1985) 2.8 m/yr (Corr et al., 2002) 3.1-4.8 m/yr (Jenkins and Jacobs,2008) Model average basal melt under GVI: 6.0 m/yr Jenkins and Jacobs, 2008

  7. Model average velocity (net through flow: 0.13 Sv.) Potter and Paren (top,1985) and Jenkins and Jacobs (bottom, 2008, net S to N through flow 0.17-0.27 Sv.)

  8. Sea Ice Modeling • Budgell (2005) model (built into ROMS) • - Thermodynamics based on Mellor and Kantha (1989) with two ice layers, a snow layer, surface melt ponds and a molecular sub layer at the ice/ocean interface • - Dynamics based on an elastic-viscous-plastic rheology after Hunke and Dukowicz (1997) and Hunke (2001) • Los Alamos CICE available, but not using yet due to time constraints

  9. Model daily ice concentration (12/24/03 – 5/23/04)

  10. January 2001 January 2002 model ice concentration SSM/I ice concentration

  11. QSCAT/NCEP winds AMPS winds

  12. AMPS winds QSCAT/NCEP winds Model ice concentration: November 2004 SSM/I: November 2004

  13. Maximum temperature below 200 m from observations. Klinck et al., 2004 Maximum temperature below 200m from model (average).

  14. Trajectories of model floats released along the shelf break to show cross- shelf exchange. Average model velocity at 400m

  15. Future Plans • Validation of this model • 1 km nested model in MB • CICE sea ice model? • Bathymetry: new Smith and Sandwell, other updates? • Different atmospheric forcing experiments • Lower trophic level ecosystem model • Any suggestions?

  16. Conclusions • Model is still a work in progress • Winds are important and good bathymetry is critical • Several model features appear to be working well - George VI Ice Shelf and supply of fresh water to Marguerite Bay - Sea ice model and interannual variability of ice concentration - CDW intrusion location • Lower trophic level ecosystem processes are now being added to the model

  17. Acknowledgements • AMPS winds courtesy of John Cassano (U. Colorado) • Computer facilities and support provided by the Center for Coastal Physical Oceanography • Financial support from the U.S. National Science Foundation (ANT-0523172)

  18. July 2001 July 2002 model ice concentration SSM/I ice concentration

  19. AMPS Forcing • Antarctic Mesoscale Prediction System: Quasi-Operational atmospheric forecast system in use for the Antarctic • Currently based on PMM5, but transitioning to WRF • We have an archive of analyses and forecasts from 30km grid for 2001-2005 (but much of our model domain not covered before 11/02)

  20. AMPS winds QSCAT/NCEP winds Model ice concentration: August 2004 SSM/I: August 2004

  21. AMPS winds QSCAT/NCEP winds Model ice concentration: October 2004 SSM/I: October 2004

  22. Feb-Apr 2004 surface velocity QSCAT/NCEP winds Feb-Apr 2004 surface velocity AMPS winds

  23. AMPS Precipitation (9/03-9/05, m/yr) Xie and Arkin Precipitation (m/yr)

  24. Feb-Apr 2004 surface velocity AMPS winds Feb-Apr 2004 surface velocity AMPS winds + runoff

  25. Trajectories of model floats released along the shelf break to show cross- shelf exchange. Average model velocity at 400m

  26. Based on Smith and Sandwell (v8.2, only north of 72S) Smith and Sandwell (v 10.1)

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