Extreme Blocking in the North Atlantic Arctic in Future Climates

Blocked atmospheric flows over Greenland and the North Atlantic Arctic (NAA) have been studied for decades and are an integral part of the climatology of that region. An atmospheric blocking event is defined as the breaking of the synoptic-scale Rossby waves, resulting in a quasi-stationary high pressure system that further disrupts the synoptic-scale circulation. Blocking events typically result in a reversal of the geopotential height gradient and can lead to amplified wind patterns that impact both moisture transport and climate. One way to quantify the intensity of blocking in the NAA is the Greenland Blocking Index (GBI). The GBI is defined as the mean 500-hPa geopotential height for the 60° -80°N, 20°-80° W region. A positive (negative) GBI is typically associated with an increase (decrease) in the 500-hPa heights to the north and a decrease (increase) in heights to the south. While the GBI has been used in the current climate regime, it has not been used much to examine blocking in future climates, particularly as it connects to moisture transport in the NAA. The goal of the Climate Model Intercomparison Project Phase 6 is to better understand past, present, and future climates resulting from both unforced and forced modeled climate scenarios. In this study, model data from CMIP6 will be used to model extreme blocking scenarios, more specifically the upper 90^th percentile and lower 10^th percentile, for the years 1850-2015. Additionally, daily surface pressure, wind, and specific humidity anomalies will be analyzed to better understand the impact of extreme blocking events in this region. These modeled atmospheric conditions and modeled variability of integrated moisture transport will be compared to data collected and analyzed from ERA-Interim and MERRA2 reanalyses in order to assess the tendency of extreme blocking and moisture transport in model simulation of future climate over Greenland and the NAA.