Trends of Cyclone Characteristics in the Arctic and Their Patterns From Different Reanalysis Data

Abstract

Cyclones in the Arctic are detected and tracked in four different reanalysis data sets from 1981 to 2010. In great detail the spatial and seasonal patterns of changes are scrutinized with regards to their frequencies, depths, and sizes. We find common spatial patterns for their occurrences, with centers of main activity over the seas in winter, and more activity over land and over the North Pole in summer. The deep cyclones are more frequent in winter, and the number of weak cyclones peaks in summer. Overall, we find a good agreement of our tracking results across the different reanalyses. Regarding the frequency changes, we find strong decreases in the Barents Sea and along the Russian coast toward the North Pole and increases over most of the central Arctic Ocean and toward the Pacific in winter. Areas of increasing and decreasing frequencies are of similar size in winter. In summer there is a longish region of increase from the Laptev Sea toward Greenland, over the Canadian archipelago, and over some smaller regions west of Novaya Zemlya and over the Russia. The larger part of the Arctic experiences a frequency decrease. All the summer changes are found statistically unrelated to the winter patterns. In addition, the frequency changes are found unrelated to changes in cyclone depth and size. There is generally good agreement across the different reanalyses in the spatial patterns of the trend sign. However, the magnitudes of changes in a particular region may strongly differ across the data.

Trends in cyclones in the high‐latitude North Atlantic during 1979–2016

“…Considering trends in cyclone densities over the period 1979 to 2016, we see the strongest ones in DJF (Figure b), which is in line with previous studies (Rudeva and Simmonds, ; Zahn et al ., ). In the Fram Strait, Greenland Sea and Barents Sea regions, we find the strongest positive trends around Svalbard.…”

“…Further, as Shepherd () writes, “we have much less confidence in the atmospheric circulation aspects of climate change [compared to the thermodynamic aspect], which are primarily controlled by dynamics and exert a strong control on regional climate”. Regarding cyclones being an important component of atmospheric dynamics, several studies have addressed the question of how cyclone activity has changed and will change in the future Arctic (Rinke et al ., ; Zhang et al ., ; Sepp and Jaagus, ; Li et al ., ; Koyama et al ., ; Zahn et al ., )…”

“…Both Rudeva and Simmonds () addressing the period 1979–2013, and Zahn et al . () addressing the period 1981–2010, found statistically significant increases (at the 90% level, hereafter “significant”) in the cyclone frequency north of the Canadian Arctic, over the Arctic Ocean and around Svalbard during these respective periods. Furthermore, they found a significant decrease in the cyclone frequency over the southern Barents Sea in the winter season.…”

“…Zahn et al . () based their results on four different reanalyses, including the Climate Forecast System Reanalysis (CFSR: Saha et al ., ) from the National Centers for Environmental Prediction (NCEP), the Japanese 55‐year reanalysis (JRA‐55: Ebita et al ., ; Kobayashi et al ., ) from the Japan Meteorological Agency (JMA), and the Modern Era Retrospective analysis for Research and Applications version 2 (MERRA‐2) reanalysis (Gelaro et al ., ), and ERAI. Zahn et al .…”

“…Zahn et al . () report that the different reanalysis products are in good agreement in catching the overall atmospheric circulation patterns, differing, however, to some degree in the magnitude of the trends on a regional level. These differences probably result from the combined effects of differences in model resolution and model physics.…”