On the tidal forcing of an Arctic coastal polynya—Storfjorden polynya

Storfjorden in eastern Svalbard is known to be an “ice factory” during winter and a key dense water formation site due to its recurring coastal polynya. Additional sea ice formation and salt release due to semi-diurnal tidal current forcing in the Storfjorden polynya near the critical latitude has been estimated with a one-dimensional polynya model. This model showed that during a half-tidal period, the tidal current was powerful enough to open an additional area between 1.60 and 1.95 km when the ice thickness varied between 50 and 10 cm, respectively. Inclusion of tides for the winters 1997/1998–2001/2002 caused the average open water area, total ice production, frazil ice production, and salt release to increase by 0.3%, (0.54 km 3 ), 2.7% (0.66 km 3 ), and 1.2% (12.9 Mt), respectively. Strong tidal currents close to inertial resonance weaken the ice cover and break off the land-fast ice, allowing out-fjord wind to carry it away, which explains the location of the recurrent polynya in Storfjorden. Our findings suggest that the tidal influence on Arctic coastal polynyas will intensify in tandem with the ongoing thinning of sea ice, attributable to the ongoing Atlantification and Pacification affecting the continental shelf seas surrounding the Arctic Ocean.