Mar 17, 2012

Evidence linking Arctic amplification to extreme weather in mid-latitudes

Francis, Jennifer A., Vavrus, Stephen J.
Geophysical Research Letters
  • States that arctic amplification (AA) – the observed enhanced warming in high northern latitudes relative to the northern hemisphere – is evident in lower-tropospheric temperatures and in 1000-to-500 hPa thicknesses
  • Analyzes daily fields of 500 hPa heights from the National Centers for Environmental Prediction Reanalysis over N. America and the N. Atlantic to assess changes in north-south (Rossby) wave characteristics associated with AA and the relaxation of poleward thickness gradients
  • Identifies two effects that each contribute to a slower eastward progression of Rossby waves in the upper-level flow: 1) weakened zonal winds, and 2) increased wave amplitude
  • Finds that these effects are particularly evident in autumn and winter consistent with sea-ice loss, but are also apparent in summer, possibly related to earlier snow melt on high-latitude land
  • Suggests that slower progression of upper-level waves would cause associated weather patterns in mid-latitudes to be more persistent, which may lead to an increased probability of extreme weather events that result from prolonged conditions, such as drought, flooding, cold spells, and heat waves