Opening and closing of the Storfjorden polynya

Coastal Polynya Skogseth (2003), PhD thesis Storfjorden is estimated to supply 5-10% of the newly formed dense waters of the Arctic Ocean

The Barents Sea and Storfjorden

Storfjorden Skogseth et al. (2005), CSR Is approximately 190 km long and 190 m deep at its maximum depth. A 120 m deep sill at about 77°N in the south. The basin covers an area of about 13·10 3 km 2 with a volume of 8.5·10 11 m 3.

Storfjorden Polynya Skogseth (2003), PhD thesis

Maximum Salinity observed in the deepest part of Storfjorden Skogseth & Fer (2005), AGUAnderson et al. (2004), JGR

Polynya Area and SAR We utilize the polynya width model formulated by Haarpaintner et al. (2001) and Skogseth et al. (2004). The model calculates the area of open water and thin ice defined as the polynya area, and the area of fast and pack ice. The model consist of two algorithms: polynya width algorithm and an open water width algorithm. The polynya width algorithm needs two empirical factors as input: the opening (OF) and closing (CF) factors.

Empirical Tuning

Wind Stress Curl field (DJFM, ) From the Hindcast data base (met.no) with a 75 km resolution

Sea Ice Drift

DJFMA wind stress

OF and CF correlated with the winter mean wind stress curl

DJFMA wind stress

Mechanical and thermodynamical sea ice growth 1- O(1) + O(10) = CF1+ O(1) + O(0) = OF

Result Summary

Winters with low I w More positive curl  Divergence

Winters with high I w More negative curl  Convergence

Reproduced OF as a function of the curl at 75.4°N, 25.1°E

Total ice production (normalized)

Conclusions Physical explanations for the empirical OF and CF are found. CF is dominated by thermodynamical ice growth through consolidation of frazil ice, but mechanical ice growth determine the interannual variations. OF’s deviations from the free drift solution is determined by divergence and convergence in the compact ice cover outside Storfjorden. Annual variations in OF and CF are directly linked to the wind stress curl field and an empirical relations is found from the hindcast data base (met.no) time series. The polynya model gives a more realistic sea ice production when the model is run with time varying OF and CF.

The Barents Sea Ice Index I w Ådlandsvik & Loeng (1990), Polar Res. The integrated winter ice covered area south of 76ºN in a zone between 25ºE and 45ºE.

Correlation between the curl (DJFM) and I w ( )