Climatology and Interannual Variability of Arctic Cyclone Activity: 1948–2002

TLDR

The study investigates Arctic cyclone activity from 1948–2002, extending previous work by applying a modified automated cyclone identification algorithm that counts each cyclone once, and by documenting seasonality, dominant temporal modes, and regional activity through a cyclone activity index. The authors use the modified algorithm to generate a cyclone activity index that integrates cyclone intensity, frequency, and duration, providing a comprehensive measure of activity over the 55‑year period. Results show that Arctic cyclone activity rose in the second half of the twentieth century while midlatitude activity fell from 1960 to the early 1990s, with increased midlatitude cyclone influx, stronger storm‑track shifts into the Arctic, synchronized phase and amplitude variations across the Arctic Ocean and marginal zone, and significant low‑frequency variability marked by 7.8‑ and 4.1‑year oscillations linked to sea‑ice and ocean regimes.

Abstract

Arctic cyclone activity is investigated in the context of climate change and variability by using a modified automated cyclone identification and tracking algorithm, which differs from previously used algorithms by single counting each cyclone. The investigation extends earlier studies by lengthening the time period to 55 yr (1948– 2002) with a 6-hourly time resolution, by documenting the seasonality and the dominant temporal modes of variability of cyclone activity, and by diagnosing regional activity as quantified by the cyclone activity index (CAI). The CAI integrates information on cyclone intensity, frequency, and duration into a comprehensive index of cyclone activity. Arctic cyclone activity has increased during the second half of the twentieth century, while midlatitude activity generally decreased from 1960 to the early 1990s, in agreement with previous studies. New findings include the following. 1) The number and intensity of cyclones entering the Arctic from the midlatitudes has increased, suggesting a shift of storm tracks into the Arctic, particularly in summer. 2) Positive tendencies of midlatitude cyclone activity before and after the 1960–93 period of decreasing activity correlate most strongly with variations of cyclone activity in the North Atlantic and Eurasian sectors. 3) Synchronized phase and amplitude variations in cyclone activity over the Arctic Ocean (70°–90°N) and the Arctic marginal zone (60°– 70°N) play a critical role in determining the variations of cyclone activity in the Arctic as a whole. 4) Arctic cyclone activity displays significant low-frequency variability, with a negative phase in the 1960s and a positive phase in the 1990s, upon which 7.8- and 4.1-yr oscillations are superimposed. The 7.8-yr signal generally corresponds to the alternation of the cyclonic and anticyclonic regimes of the Arctic sea ice and ocean motions.