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Glacial mass loss due to climate change has been well documented for decades and is projected to continue as air temperatures rise. Baseflow, known as a proxy for groundwater discharge to streams, can be derived from subglacial melt recharge. The groundwater regime thus acts as a hydrologic buffer and connector between glacial melt recharge and streamflow, particularly during periods of low precipitation or overland flow. Understanding the temporal and spatial relationship between glacial melt, baseflow, and subsequent streamflow is necessary to assess the sustainability of current and future streamflow conditions. To evaluate how groundwater flow connects glacial meltwater to downstream hydrology both temporally and spatially, a 2D coupled heat transfer and groundwater flow model with seasonal freeze-thaw was developed using USGS Saturated-Unsaturated Transport modeling software (SUTRA).Ìý
Arikaree glacier is an alpine glacier located in Green Lakes Valley in the upper Boulder Creek watershed in Boulder, Colorado. Melting of Arikaree has potentially notable impacts on streamflow. Because of Arikaree’s small size, changes in mass balance occur on human timescales, which can be feasibly observed and underscore the importance of understanding flow dynamics in this region. Using 3 different air temperature warming scenarios, based on the Intergovernmental Panel on Climate Change (IPCC) projections or observed warming trends within the Green Lakes Valley watershed, the subsurface temperature and groundwater flow field underneath Arikaree glacier is simulated. Groundwater flow and heat transport in alpine regions is defined by phase transitions between solid ice and liquid water as subsurface temperature fluctuates seasonally. With future warming the spatial extent of seasonal freeze-thaw may expand, impacting glacial melt-groundwater-surface water dynamics. We elucidate groundwater discharge rates, and how these rates vary seasonally and throughout decades into the future. Furthermore, we aim to quantify how the addition of a frozen soil routine, in which changes to subsurface permeability due to the presence of ice are considered, impacts the magnitude and location of groundwater discharge under projected air temperature warming scenarios.Ìý
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