The goal of this work was to understand and quantify the role of large-scale, low-frequency atmospheric circulation anomalies and moisture transport on the climate system of the North Atlantic sector of the Arctic (North Atlantic Arctic, NAA). This work was motivated by recent changes in atmospheric circulation in the NAA, and their influence on sensible heat and moisture advection from the mid-latitudes into the Arctic, the surface energy budget over the Greenland Ice Sheet (GrIS) and adjacent sea ice, resulting in unprecedented melt and freshwater runoff events. Impacts of such extreme events have significant implications on Department of Defense (DoD) infrastructure and operations in the NAA, and have the potential to disrupt mission training at DoD installations across the region.

To anticipate and reduce the negative consequences of these extreme events, and to assess their impacts, this project’s research objectives were to; 1) quantify the contributions from large-scale atmospheric circulation and moisture transport to ice melt events across multiple time scales, 2) understand how atmospheric blocking and Rossby wave breaking impact, and are impacted by, the transport of moisture from mid-latitudes into the NAA, and 3) investigate the role of this moisture advection in altering radiative and turbulent fluxes, winds, precipitation, surface melting, and snow accumulation in the NAA.

To accomplish the overarching research goal and the three objectives stated above, the research tasks included creation of a moisture transport and blocking climatology in the NAA region using a variety of blocking metrics, assessment of the impact of Rossby Wave Breaking on moisture transport into the NAA region, and finally quantification of such relationships and mechanisms in future climate scenarios via the use of climate model ensemble output.

Results of this project have shown that it is critical to understand patterns of atmospheric circulation in the high latitudes, including when those patterns are disrupted, which happens during atmospheric blocking events. The project team found that blocking has the potential to significantly impact the GrIS via rapid melting and runoff, depending on the location where the blocking pattern sets up. The project team also found trends toward more periods of extreme blocking in the most recent 20 years, and continue to analyze whether that trend appears in sophisticated climate model predictions of the coming decades. In terms of types of blocking episodes, summer ridge patterns produced more melt over the southern GrIS, with Omega blocks producing more melt across the northern ice sheet, and cyclonic wave breaking patterns producing more melt in northeast Greenland. While occurrences of the Omega blocking pattern have increased more than other blocking types, the number of days in the North Atlantic exhibiting cyclonic wave breaking characteristics in June, July and August have significantly increased, which corresponds to observed increased Greenland blocking conditions and increased moisture transport.

More work is needed on blocking's impacts on specific sensitive DoD infrastructure and operations in Greenland, including and specifically at Thule Air Base, which is now home to critical operations of USSF Delta 2 (space situational awareness) and Delta 4 (spaceborne missile detection) groups.