a high resolution coupled sea-ice/ocean model for the antarctic peninsula region

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

Michael S. DinnimanMichael S. DinnimanJohn M. KlinckJohn M. Klinck

Center for Coastal Physical Center for Coastal Physical OceanographyOceanography

Old Dominion UniversityOld Dominion University

See also (poster this evening): West Antarctic See also (poster this evening): West Antarctic Peninsula Circulation and Implications for Peninsula Circulation and Implications for Biological Production: Andrea Piñones et al.Biological Production: Andrea Piñones et al.

Outline of PresentationOutline of Presentation

• Introduction and Model Description

• Ice Shelf Modeling

• Sea Ice Modeling

• Cross-shelf Transport

• Future plans

• Conclusions

Research QuestionsResearch 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?

Antarctic Peninsula ModelAntarctic Peninsula Model• ROMS: 4 km horizontal resolution, 24 levelsROMS: 4 km horizontal resolution, 24 levels• Ice shelves (mechanical and Ice shelves (mechanical and

thermodynamic)thermodynamic)• Imposed sea ice or dynamic sea ice modelImposed sea ice or dynamic sea ice model• Bathymetry: ETOPO2v2 + WHOI SOGLOBEC Bathymetry: ETOPO2v2 + WHOI SOGLOBEC

region + region + Padman gridPadman grid + BEDMAP + Maslanyj+ BEDMAP + Maslanyj• Open boundaries: T + S set to SODA, Open boundaries: T + S set to SODA,

barotropic V relaxed to SODA, baroclinic V barotropic V relaxed to SODA, baroclinic V pure radiationpure radiation

• Daily wind forcing from a blend of QSCAT Daily wind forcing from a blend of QSCAT data and NCEP reanalyses or Antarctic data and NCEP reanalyses or Antarctic Mesoscale Prediction System (AMPS) windsMesoscale Prediction System (AMPS) winds

• Other atmospheric parameters from several Other atmospheric parameters from several sources (including AMPS)sources (including AMPS)

Ice Shelf ModelingIce Shelf Modeling

• Ice Shelf basal melt can add large Ice Shelf basal melt can add large amounts of freshwater to the system amounts of freshwater to the system (George VI estimated basal melt: 2-5 m/yr)(George VI estimated basal melt: 2-5 m/yr)

• Ice Shelf does not change in time in modelIce Shelf does not change in time in model

• Three equation viscous sub-layer model Three equation viscous sub-layer model for heat and salt fluxes (Holland and for heat and salt fluxes (Holland and Jenkins 1999)Jenkins 1999)

• PGF calculation assumes the ice shelf has PGF calculation assumes the ice shelf has no flexural rigidity and pressure at the no flexural rigidity and pressure at the base comes from the floating icebase comes from the floating ice

Model average velocity(net through flow: 0.09 Sv.)

Potter and Paren (top,1985) andJenkins and Jacobs (bottom, 2008, netS to N through flow 0.17-0.27 Sv.)

Sea Ice ModelingSea 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

Model daily ice

concentration

(12/24/03 – 5/23/04)

January 2001

January 2002

model ice concentration

SSM/I ice concentration

Figure 4. Trajectories of floats released along the shelf break, at several depths below 250 m. Bottom bathymetry (grey contours) is given in meters. The simulation was run for 1 year. Figure 4. Trajectories of floats released along the shelf break, at several depths below 250 m. Bottom bathymetry (grey contours) is given in meters. The simulation was run for 1 year.

Trajectories of model floats releasedalong the shelf break to show cross-shelf exchange.

Piñones et al., poster this evening

Maximum temperature below 200 mfrom observations.

Klinck et al., 2004

Future PlansFuture Plans

• Validation of this modelValidation of this model• 1 km nested model in MB1 km nested model in MB• CICE sea ice model?CICE sea ice model?• Bathymetry: new Smith and Sandwell, Bathymetry: new Smith and Sandwell,

other updates?other updates?• Different atmospheric forcing experimentsDifferent atmospheric forcing experiments• Lower trophic level ecosystem modelLower trophic level ecosystem model

ConclusionsConclusions

• Model is still a work in progressModel is still a work in progress

• Several model features appear to be Several model features appear to be working wellworking well

- George VI Ice Shelf and supply of fresh - George VI Ice Shelf and supply of fresh water to Marguerite Baywater to Marguerite Bay

- Sea ice model and interannual variability - Sea ice model and interannual variability of ice concentrationof ice concentration

• Model should be a useful tool for Model should be a useful tool for studying effects of circulation on studying effects of circulation on ecosystems in the regionecosystems in the region

AcknowledgementsAcknowledgements

• AMPS winds courtesy of John Cassano AMPS winds courtesy of John Cassano (U. Colorado)(U. Colorado)

• Computer facilities and support Computer facilities and support provided by the Center for Coastal provided by the Center for Coastal Physical OceanographyPhysical Oceanography

• Financial support from the U.S. Financial support from the U.S. National Science Foundation (ANT-National Science Foundation (ANT-0523172)0523172)

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

Smith andSandwell(v 9.2)

Much warmer water entering the ice shelf cavity than Ross => Much greater melting: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: 6.2 m/yrJenkins and Jacobs, 2008

Model average velocity 50mbelow surface (free surface or ice shelf)

Model average velocity 400mbelow surface (free surface or ice shelf)

AMPS ForcingAMPS 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)

Model ice concentrati

on:October

2004

SSM/I:October

2004

QSCAT/NCEP windsAMPS winds

QSCAT/NCEP winds

AMPS winds

Xie and Arkin Precipitation(m/yr)

AMPS Precipitation(9/03-9/05, m/yr)

Summer surface velocityOriginal forcing

Summer surface velocityAMPS forcing

Model ice concentrati

on:November

2004

SSM/I:November

2004

AMPS winds QSCAT/NCEP winds

Model ice concentrati

on:February

2005

SSM/I:February

2005

AMPS winds QSCAT/NCEP winds