Arctic Modelling at the Proudman Oceanographic Laboratory Clare

Arctic Modelling at the Proudman Oceanographic Laboratory Clare Postlethwaite 1) Work to date: regional modelling study 2) Next step: Global model with high resolution Arctic model 3) Ideas for future AOMIP experiment

Bathymetry of the Arctic Ocean Shelf < 400 m Deep From GEBCO

Tides and ice Tides are omitted from Global Climate Models

Modelled Tides (POLCOMS-CICE) IHO Tidal constituent Bank, Gjevik and Straume (1989), Kowalik and Proshutinsky (1994, 1995)

Tides – no tides 4 cm 1 cm Total ice volume

Bottom salinity difference in March tides – no tides)

20% 30% Tides give thicker ice (6 cm) 5 -10% 25% Tides make less ice 3 cm

Total freezing

Bottom salinity difference in March (tides – no tides) Salinity difference Extra sea ice adds < 0. 05 PSU / year Extra frazil ice production adds < 0. 4 PSU for March

Sea surface salinity difference in summer (tides – no tides) Tides export fresh water more efficiently out of the Kara Sea Tides maintain a front here

Summary Tides cause significant changes to Arctic shelf sea models The changes are regional and complicated Requires a pan-Arctic model

Next Step Technical issues • Process studies of whole Arctic Ocean – Tides – Eddies – Dense water formation – Polynyas – Cascading – Mixing • NEMO-LIM 3 -CICE GMU Poseidon Model Tripole Grid, Murray (1996) • High resolution Arctic/North Atlantic Model (3 -9 km) as part of a coarser resolution Global Model (1 -2°)

How do tides affect Arctic Models? Add tidal forcing to 50 year control run. What tidal forcing? How many constituents? Outputs standard + fluxes Data for comparison