Detecting the effects of atmospheric rivers on glacier mass balance: a case study in Denali National Park, Alaska

English Abstract:

An atmospheric river made landfall over Alaska on January 23, 2014. This system advected moisture and heat from the Pacific Ocean east of Hawaii to Alaska over the course of two days causing anomalously high temperatures, heavy rainfall, avalanching, and disruption of human infrastructure. There likely was also rainfall at higher elevations, which would cause a significant change in the mid-winter energy and mass balance of regional glaciers. To investigate whether there is a detectable physical and chemical signature of the atmospheric river event in Central Alaska glaciers, we collected geophysical and geochemical data on the Ruth, Kahiltna, and Mt, Hunter Plateau Glaciers during May-June 2014. High-frequency (400 MHz) ground penetrating radar (GPR) transects over a total of 10 Km were collected on the Ruth Glacier to determine the spatial continuity of an ice layer potentially created by the event. Two snowpits on the Ruth Glacier (1.2 and 3.5 meter depths), one on the Kahiltna Glacier (3 m depth), and one on the Mt. Hunter Plateau (4.05 m depth) were sampled for δ¹⁸O and δD analysis. Based on simple isotope fractionation modeling, we hypothesize that moisture from the atmospheric river event would be isotopically heavy relative to typical mid-winter precipitation in the area. We observe a positive δ¹⁸O deviation in the Mt. Hunter and eastern Ruth Amphitheater snowpits at 3-3.5 meter depth, which given estimated snow accumulation rates may be consistent with the river event. We will discuss ongoing statistical comparison of snowpit physical and isotope data, processing and interpretation of the GPR data, and detailed time-series analysis of the river event using climate reanalysis and station data.