Subglacial Drainage

Abstract

Subglacial drainage can occur wherever ice at a glacier bed reaches the pressure melting point. The subglacial drainage system is fed from a mixture of surface, englacial, subglacial, and groundwater sources that differ in terms of their spatial distribution and characteristic patterns of temporal variability. Subglacial drainage systems are not readily accessible, and knowledge of their characteristics is derived from a range of indirect methods including radio-echo sounding, the use of artificial tracers, monitoring, and manipulation of subglacial conditions via boreholes, and monitoring of glacial runoff properties. Subglacial water flow is driven by gradients in hydraulic potential, and occurs through either fast/channelized or slow/distributed systems located at the icebed interface, or through subglacial aquifers. Water can be stored subglacially in cavities, in the pore space of subglacial sediments, or in subglacial lakes. Drainage system structure evolves continually on various timescales in response to changing water inputs, evolving glacier geometry, and changes in glacier flow dynamics. Major hydrological events in such systems include the spring and fall transitions, outburst floods, and structural changes related to glacier advances and glacier surging. In the absence of variable water inputs from the glacier surface, subglacial drainage systems may be sensitive to forcing by earth, ocean, and atmospheric tides.Encyclopedia of Hydrological Sciences. Edited by M G Anderson.

After the peak water: the increasing influence of rock glaciers on alpine river systems

“…Multiple energy fluxes (e.g., net radiation and sensible heat) influence the ablation process on glaciers (Hannah, Gurnell, & McGregor, ), and ice ablation is reduced or absent during autumn and winter (Cuffey & Paterson, ). Accordingly, autumn discharge from glaciers is typically dominated by the baseflow (see Table ), which is mostly driven by the subglacial/englacial contribution associated with waters enriched in solutes (Sharp, ) and metals/metalloids (Mitchell, Brown, & Fuge, ). Accordingly, highest concentrations of major ions (Ca 2+ , Mg 2+ , SO 4 2− , and NO 3 − ) and trace elements were recorded in this period in both glacier‐fed streams.…”

Nutrient and Carbon Export From a Tidewater Glacier to the Coastal Ocean in the Canadian Arctic Archipelago

“…Over the course of the melt season, basal flow evolves from a slow and distributed system, dominated by snowmelt and basal ice‐melt, to a fast and channelized one, dominated by ice‐melt originating from the surface (Flowers, 2015; Gray, 2005; Hubbard et al., 1995). This evolution leads to shorter retention and rock‐water interaction times at the bed, and consequently lower entrained nutrient and carbon concentrations/fluxes during peak melt (Brown, 2002; Sharp, 2005).…”

Role of sediment in solute acquisition in the Himalayan glacier meltwater stream, Gangotri glacier, Uttarakhand, India

“…p (CO 2 ) signature of meltwater may be used to interpret different glacial hydrological weathering environments (Sharp, 1991; Wadham, Hodson, et al, 1998). The system characteristics of Gangotri glacier headwater stream has already been discussed in details and inferred the continuum of closed system conditions along the Bhagirathi stream reach from Gomukh to Gangotri (Sharma et al, 2019).…”