Secular variations in cyclone frequencies near the Drake Passage, southwest Atlantic

Abstract

Analysis of a 22‐year sequence of summer and winter cyclone frequencies for the Drake Passage‐Weddell Sea area produces important differences from previous short term studies. Two principal cyclone tracks are shown to occur in both seasons at around 55° and 65°S. Principal components analysis suggests that the minor cyclone track was more variable than the major track in both seasons. Variations in cyclone frequency at high latitudes appear to be directly linked to the strength of the westerly circulation actively enhancing lee cyclogenesis near the Antarctic Peninsula. Investigation of the relationship between the predominant cyclone track and the inferred movement of the Weddell Sea pack ice does not support the hypothesis that cyclonic activity is determined by the position of the pack ice boundary. Furthermore, there is an observed, but not statistically proven, link between cyclone movement and the mean annual position of the Oceanic Polar Front.