Winter Gale Day Frequency in Shetland and Faeroes, AD 1866-1905: Links to Sea Ice History and the North Atlantic Oscillation

The paper describes changes in winter gale day frequency that took place in the Shetland and Faeroe Isles between ca. AD 1866-1905. During the early part of this period, winter gale day frequencies reached values that have never been exceeded since. During the later part of this time interval, culminating in the winters of 1903-04 and 1904-05, scarcely any gales occurred. The majority of the time interval between 1866 -1895 was characterized by high-amplitude fluctuations in the sign of the North Atlantic Oscillation (NAO) index (extreme positive to extreme negative) and by extreme changes in annual sea ice extent across the Greenland Sea. Between 1866-1894, however, winter gale day frequencies remained consistently high. It is suggested that this unusual relationship may be explained through the important role of sea ice extent across the Greenland Sea affecting the extent of the polar anticyclone and hence the position of the North Atlantic storm track. By contrast, the later part of this time interval (AD 1894-1905) was characterized by very few winter gales and no extremes in the monthly NAO Index.