Monday 22 August 2005

P5
1000-1230 hours

039
Simulation of sea ice and ocean variability in the Arctic during 1955-2002 with an intermediate complexity model
Mysak, Lawrence¹, Wright, Kate M¹, Sedlacek, Jan¹, Eby, Mike²
1 McGill University, Montreal, Quebec, Canada
2 University of Victoria, Victoria, British Columbia, Canada
Author email: lawrence.mysak@mcgill.ca
A number of recent sea ice and ocean changes in the Arctic and subarctic regions are investigated using the global UVic Earth System Climate Model version 2.6. This is an intermediate complexity model which includes a 3-dimensional ocean model (MOM 2.2), an energy-moisture balance model for the atmosphere with heat and moisture transport, and a thermodynamic sea ice model with elastic-viscous-plastic rheology. After two appropriate spin-up periods, the model is run with interannually varying wind stresses for the period 1948-2002 with an average forcing interval of 2.5 days and an exponentially increasing atmospheric CO2 concentration varying from 315 to 365 ppm. However, the analysis of the model output is done only for the year 1955-2002. The simulated maximum and minimum sea ice areas for the Arctic are within 6% of the observed climatologies over the years 1978-2001. In addition, the model simulates a decrease of sea ice thickness in the SCICEX measurement area in the central Arctic that is consistent with but smaller than that observed from submarine sonar profiling data. The observed export of sea ice through Fram Strait is quite well captured in the simulation. The change in correlation between the NAO index and the sea ice export at around 1977 is also reproduced. Within the Arctic basin the model simulates well the patterns and the timing of the two major regimes of wind-forced sea ice drift circulation (cyclonic and anticyclonic). The relatively recent temperature and salinity increases at depths of 200-300 m as observed in the eastern Arctic are just visible in the model simulation. The increases are more noticeable, however, when the ocean model data are averaged over the pentade 1995-2000 and compared with model data averaged over the pentade 1955-1960.

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