Fig. 4

Evolution of geopotential height and wind speed anomalies during the spring season associated with low and high sea ice years in the upper (200 hPa) and lower (850 hPa) troposphere (a) Composite anomalies of geopotential height (shaded) and wind speed (vectors) at 200 hPa during low sea ice years (b) Same as (a) but for high sea ice years (c) Wind speed anomalies (shaded and vectors) at 200 hPa during low sea ice years (d) Composite anomalies of geopotential height (shaded) and wind speed (vectors) at 850 hPa during low sea ice years (e) Same as (d) but for high sea ice years (f) Wind speed anomalies (shaded and vectors) at 850 hPa during low sea ice years. The geopotential height anomalies reveal a ridge–trough–ridge–trough wave train structure in the 50°N–65°N latitudinal band, indicative of enhanced Rossby wave activity during low sea ice years. Note that ridges and troughs represent the high- and low-pressure systems, respectively.