May 2, 2016

Greenland Blocking Index 1851-2015: a regional climate change signal

by
Hanna, E., Cropper, T.E., Hall, R.J. and Cappelen, J.
,
International Journal of Climatology
  • Presents an extended monthly and seasonal Greenland Blocking Index (GBI) from January 1851- December 2015, which more than doubles the length of the existing published GBI series
  • Finds there are significant decreases for the whole time period in GBI in autumn, October and November, and no significant monthly, seasonal or annual increases
  • Finds there are significant GBI increases since 1981 in all seasons and annually, with the strongest monthly increases in July and August
  • Finds evidence of a recent clustering of high GBI values in summer, when seven out of the top eleven values in the last 165 years – including the two latest years 2014 and 2015 - occurred since 2007
  • Finds there have been significant increases in GBI variability since 1851 in May and especially December—December has also shown a significant clustering of extreme high and low GBI values since 2001, mirroring a similar, recently identified phenomenon in the December North Atlantic Oscillation index, suggesting a related driving mechanism
  • Discusses changes in hemispheric circulation that are associated with high compared with low GBI conditions