Modeling the impacts of climate change on mass balance and discharge of Eklutna Glacier, Alaska, 1985–2019

Abstract

Alaska's largest city, Anchorage, depends on Eklutna Glacier meltwater for drinking water and hydropower generation; however, the 29 km2 glacier is rapidly retreating. We used a temperature-index model forced with local weather station data to reconstruct the glacier's mass balance for the period 1985–2019 and quantify the impacts of glacier change on discharge. Model calibration involved a novel combination of in situ, geodetic mass-balance measurements and observed snowlines from satellite imagery. A resulting ensemble of 250 best-fitting model parameters was used to model mass balance and discharge. Eklutna Glacier experienced a significant negative trend (−0.31 m w.e. decade−1) in annual mean surface mass balance (mean: −0.62 ± 0.06 m w.e.). The day of the year when 95% of annual melt occurs was five days later in 2011–19 than in 1985–93, demonstrating a prolongation of melt season (May–September). Modeled mean specific discharge increased at 0.14 m decade−1, indicating peak water, the year when annual discharge reaches a maximum due to glacier retreat, has not been reached. Four of the five highest discharge years occurred since 2000. Increases in discharge quantity and melt season length require water resource managers consider future decreased discharge as the glacier continues to shrink.

Fluvial suspended sediment transfer and lacustrine sedimentation of recent flood turbidites in proglacial Eklutna Lake, western Chugach Mountains, Alaska

“…An improved understanding of sediment transfer dynamics could come from physically‐based system assessments (Hodder et al, 2007). Aiding steps in that direction, ongoing efforts for the watershed system include distributed hydrologic simulation (Ostman, in progress), glaciological studies (Geck et al, 2021), and publication of our original, high‐quality datasets (Ostman et al, in progress). Eklutna Lake is situated near major population and economic centers of south‐central Alaska, including the city of Anchorage and lower Matanuska‐Susitna basin.…”