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Numerical Modeling of ocean circulation
over the continental shelf and
beneath the ice shelves
in the Amundsen Sea, Antarctica
WAISSeptember 28, 2006
Courant Institute of Mathematical
Sciences New York University
New York, U.S.A.
David Holland Adrian Jenkins British Antarctic SurveyNatural Environment Research CouncilCambridge, U.K.
Stan Jacobs Lamont-Doherty Earth
Observatory,Columbia UniversityNew York, U.S.A.
Continental Shelf, Amundsen Sea
Ice Shelves, Amundsen Sea
Outline
1. Ice Pump
2. POLAIR
3. Model Domain
4. Sea-Ice Simulation
5. CDW Pathways
6. Melt Rates
7. Tides
8. Heat Budget
9. Sensitivity CDW
1 Ice Pump Pressure-Dependent Freezing-Point
Polar Ocean Land Atmosphere Ice Regional (POLAIR)
Model(l)ing System
2 POLAIR Schematic
2 POLAIR Components
• Isopycnic-ocean
• modification/combination of MICOM/Higdon
• Thermodynamic-dynamic sea-ice
• icepycnic & cavitating fluid
• Thermodynamic ice-shelf
• viscous-sublayer
• Forced by daily wind & air temperature (NCEP)
• Applied to Amundsen Sea and Ice Shelves
2 POLAIR Hardware/Software columbia@nasa
3 Model Domain Geographic Orientation
Red box - full model domain
Yellow Box- sub model domain (for most of analysis)
3 Model Domain BEDMAP Bathymetry
3 Model Domain Updated Bathymetry
Nitsche & Jacobs LDEO (in prep.)
3 Model Domain Bathymetry
3 Model Domain Ice Shelf Thickness
4 Sea-Ice - Concentration (& Velocity)
Black-Hatched is Land (i.e., Grounded Ice)
Lite-Blue-Hatched is Ice Shelf (i.e., Floating Ice)
Vector Arrows are sea-ice motion
Color is Sea-Ice Concentration (red is lots; blue is little)
Grey-Hatched is open-ocean surface (i.e., no sea ice)
5 CDW Pathways Depth 0000 m
Lite-Blue-Hatched is Ice Shelf (i.e., Floating Ice)
Black-Hatched is Land (i.e., Grounded Ice)
Color is Ocean Temperature (red is warm; blue is cold)
Vector Arrows are ocean motion
5 CDW Pathways Depth 0100 m
5 CDW Pathways Depth 0200 m
5 CDW Pathways Depth 0300 m
5 CDW Pathways Depth 0400 m
5 CDW Pathways Depth 0500 m
6 Melt Rate Year 5; Big Domain
6 Melt Rate Model Equilibration Y0 to Y10
Large Interseasonal Variability
7 Tides Variation of Sea-Surface Height
Cyclonic Coastal Kelvin Wave
7 Tides Basal Melt Rate (Tidal Forcing OFF)
Annual Mean Basal Melt Rate is 66 cm/a
7 Tides Basal Melt Rate (Tidal Forcing
ON)
Annual Mean Basal Melt Rate is 83 cm/a
25% Increase
8 Heat Budget Continental Shelf Area Mask
8 Heat Budget Ice Shelf Cavity Mask
Land
Continental Shelf
CDW
8 Heat Budget Tally
62 TW
60 TW
1 TW
1 TW 41 TW
40 TW
9 Sensitivity CDW CDW Amount
9 Sensitivity CDW CDW Temperature
• Small fraction (~5%) available ocean heat used for melting
Conclusions
• Linear increase in melt rate with increase in CDW amount
• Non-linear increase in melt rate with increase in CDW temperature