Year Established: 2014 Start Date: 2014-03-01 End Date: 2015-02-28
Total Federal Funds: $19,730 Total Non-Federal Funds: $39,605
Principal Investigators: Michael Loso
Abstract: Glaciers store large quantities of fresh water in both liquid and solid form. Storage varies on several time-scales, ranging from englacial and subglacial storage that damps the diurnal cycle of early season runoff (Bartholomaus et al. 2008) to changes in overall ice volume that occur over decades to millennia (Larsen et al. 2005). Glaciers, and in particular their changing rates of water storage, are thus an important part of the fresh water cycle (Radic and Hock 2013). Changing rates of glacier water storage have several direct societal impacts. Of widespread modern interest is the role of glacier mass loss (reduced long-term storage) on sea level rise (Pfeffer et al. 2008). From 2003-2009, for example, Alaska’s glaciers lost approximately 50 Gt/yr of ice, a greater contribution to global sea level rise than any other glaciated region on Earth, excluding the icesheets of Antarctica and Greenland (Gardner et al. 2013). At the regional level, glacier water storage impacts water supplies for downstream irrigation and urban usage (Fountain and Tangborn 1985). Even in the comparatively wet climate of southcentral Alaska, the state’s largest city (Anchorage) provides an example: it is dependent on glacier melt for over 80% of its water supply (Larquier 2010). Glacier runoff changes also impact farms, cities, and infrastructure through altered flood regimes. These changes can occur suddenly, as in the case of glacier outburst floods (Loso et al. 2006) or through more subtle impacts on seasonal runoff (Anderson et al. 1999). Glacier water storage is important for operators of hydropower developments in Alaska and throughout the Pacific Northwest (Burger et al. 2011). In particular, glacier volume changes buffer the impacts of melt-season climatic variability through the “deglaciation discharge dividend”, a temporary increase in glacier runoff during hot, dry summers (Collins 2008). Glacier water storage also impacts geomorphic stability (Moore et al. 2009) and biological productivity (Jacobsen et al. 2012) in downstream ecosystems. For all these reasons, glaciologists and other scientists have invested much effort in quantifying the changing rates of glacier storage. In a simple glacial hydrologic budget, storage (S) is quantified as a rate dictated by the difference between rates of inputs and outputs: dS/dt = inputs – outputs. Outputs from the glacier system include snow and ice lost to sublimation, surface water lost to evaporation, and meltwater runoff. In Alaska, the latter term dominates, and is relatively easy to measure with some combination of on-glacier ablation stakes and a downstream river gage. The inputs to the glacier system—rain and snow—are not so easily quantified. Snowfall, in particular, is notoriously difficult to measure directly (McKay 1968). Furthermore, precipitation has tremendous spatial variability in comparison with the main drivers of melt (temperature and solar radiation). Winds accentuate this variability, eroding and redepositing snow over the course of even a single storm. For these reasons, the biggest challenge in the measurement, understanding, and prediction of temporal changes in glacier water storage is accurately assessing the rate of snow accumulation. We propose a modest expansion of efforts, already underway on two well-studied glaciers (Taku and Eklutna), to use ground-penetrating radar as a rapid, accurate measurement tool for the measurement of seasonal snow thickness. The specific tasks identified in this proposal contribute to ongoing assessments of mass balance and related glaciological phenomena on these two Alaskan glaciers, so we begin by briefly summarizing existing work on those two glaciers, noting particularly the preliminary efforts of two Alaska Pacific University students identified in this proposal. We follow with a summary of the broader benefits of this project.