Brines, which appear as salty and cold bottom water layers on Arctic shelves, form by salt rejection during sea ice formation. High ice production occurs in latent heat polynyas such as the one that appears in Storfjorden under northerly winds. Using ERS-2 synthetic aperture radar imagery, we observed the ice cover in Storfjorden over the winter 1997/1998, revealing an area of over 6000 km2 of the open water and thin ice that are characteristic of a polynya. Changes in the polynya extent correlated well with a simple wind-driven polynya size algorithm. Furthermore, using a frazil ice formation algorithm and the hypothesis of ice accumulation at the lee side of the polynya, we distinguished between open water, thin ice, and fast/pack ice. The average polynya width during the 6 winter months was about 30 km, with a maximum of 130 km in March; thus Storfjorden was composed of 5/6 fast and pack ice and 1/6 polynya. Open water occupied about half of the polynya; the other half was composed of brash ice and thin ice involved in ridging and rafting. A total ice volume of 40 km3 was produced in Storfjorden between November 15, 1997, and May 15, 1998. About 57% of it was formed in the open water area; 9%, in the thin ice area; and 34%, in the fast/pack ice area. This ice production released more than 1 Gt (gigaton) of salt, able to increase the salinity of the Storfjorden waters by 1.4 practical salinity units (psu). Assuming that brine-enriched waters are 0.3 psu more saline than the parent waters, the above salt release is able to ventilate Storfjorden 4--5 times during the course of the productive season. ¿ 2001 American Geophysical Union