Extreme Atmospheric Blocking Events and the NAO: Seasonality, Predictability and Implications for Pituffik Space Base

Atmospheric blocking events occur when an upper level ridge in the atmosphere persists, in some cases for 5-7 days, resulting in surface conditions that can include increased southerly flow and moisture advection. Recent trends from observations indicate an increase in frequency of extreme blocking events in recent decades; however future climate scenarios from global climate models vary when it comes to projections of future blocking in a warming world. Extreme blocking events impact both the North Atlantic Arctic region, and the Greenland ice sheet and ice mass balance. Specifically, Pituffik Space Base in northwest Greenland is increasingly affected by such events, via episodes of extreme flooding that hinder the operational mission and security of the Base.

In this study, we seek to explore potential predictability of extreme blocking, by investigating the relationship between extreme blocking over Greenland with other modes of atmospheric variability, such as the NAO. Leveraging previous work which connects an increase in atmospheric blocking to the negative phase of the NAO, this study further explores this relationship by analyzing the seasonality of this relationship, and potential impacts on ice sheet growth versus melt. Any insights to predictors of surface runoff that impacts military operations at Pituffik is critical. Preliminary findings suggest the seasonality of NAO and extreme blocking are stronger in the summer, resulting in elevated surface runoff that impacts base operations at Pituffik.