Circulation and Biogeochemical Processes in a Numerical Model
of the West Antarctic Peninsula

Introduction and purpose
Model details
Model results and comparison with observations
Proposed mechanism for cross shelf flow
Future plans

Model Configuration
Rutgers/UCLA Regional Ocean Model System (ROMS)
Primitive equation model with free surface
Terrain following vertical coordinate
General surface fluxes
Open boundary conditions
Parallel computer implementation using openmp
Initial fields from World Ocean Data Atlas (1998)
Nitrate and Silicate are included as freely evolving concentrations
Bottom topography based on Sandwell and Smith (ETOPO2)

Slide 4

Model results
Circulation averaged over winter
Circulation at 200 m compared to ADCP
SST comparison to AVHRR climatology
Vertical section of temperature compared to hydrographic measurements (Jan-Feb, April)
Vertical sections of Nitrate
Temperature at Tmax below 200 m
Analysis of transport across the shelf break

Slide 6

Flow Comparison at 200m

Surface Temperature Comparison

Slide 9

Temperature Section North of
Marguerite Bay

Temperature Section North of
Marguerite Bay

Nitrate Section off Adelaide Island

Nitrate Comparison in Early September

Comparison of Tmax below 200m

Calculation of Across-shelf-break Flux
Define the shelf-break section along the 1000 m isobath in the model. Include across-shelf sections at either end to close the box.
At every point, calculate the gradient of bathymetry. Get the component of vertically integrated flow in that direction.
Calculate the curvature, and the change of curvature, along the shelf-break section.
Calculate the lagged correlation of onshelf transport and shelf-break curvature.

Integrated Cross-shelf Fluxes
of Volume, Heat and Salt

Persistent Across-shelf-break Transport

Cross Shelf Transport Mechanism
Flow crosses shelf break if topography turns in front of the flow.
Water penetrates onshore if shelf circulation is towards the coast

Circulation shows some comparison with present understanding of circulation
Surface temperature compares well to observations
Mixed layer follows realistic seasonal patterns, although is too deep in winter
Onshore flux of CDW occurs at observed locations
Onshore flux due to combination of bathymetric curvature and shelf circulation

Future Plans
Expand comparison of model solutions to observations
Use recent observations to construct more realistic initial conditions for T, S and nutrients
Add forcing for coastal current (ice melt or Gerlache exchange)
Add a dynamic sea-ice model (working on CISE by E. Hunkins)
Add coastal fast ice and ice shelves including George VI sound
Include tidal variability driven at the boundaries by a global model
Add a bio-optical primary production model
Better large scale Southern Ocean model for boundary forcing

Slide 21

Model Temperature Sections
north of Marguerite Bay

Slide 23

Slide 24

Nitrate Comparison in Early March