Effect of Snow and Firn Hydrology on the Physical and Chemical Characteristics of Glacial Runoff

Fountain, Andrew G.

doi:10.1002/(sici)1099-1085(199604)10:4<509::aid-hyp389>3.0.co;2-3

Cited by 68 publications

(54 citation statements)

References 49 publications

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“…The differences in ice content, and therefore densities, between mountain glaciers and the southeast Greenland firn aquifer are in part due to the long-term (decades), perennial nature of the aquifer in southeast Greenland. Aquifers in mountain glaciers are generally smaller, thinner, and steeper, allowing for annual drainage and more refreeze when air temperatures dip below 0 • C in the winter (Vallon et al, 1976;Oerter et al, 1983;Fountain, 1989Fountain, , 1996Jansson et al, 2003). The perennial aquifer in southeast Greenland is in general deeper (10's of m) and thicker (10's of m), which limits refreezing in the saturated zone ( Table 2).…”

Section: Discussionmentioning

confidence: 99%

Hydraulic Conductivity of a Firn Aquifer in Southeast Greenland

et al. 2017

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Some regions of the Greenland ice sheet, where snow accumulation and melt rates are high, currently retain substantial volumes of liquid water within the firn pore space throughout the year. These firn aquifers, found between ∼10 and 30 m below the snow surface, may significantly affect sea level rise by storing or draining surface meltwater. The hydraulic gradient and the hydraulic conductivity control flow of meltwater through the firn. Here we describe the hydraulic conductivity of the firn aquifer estimated from slug tests and aquifer tests at six sites located upstream of Helheim Glacier in southeastern Greenland. We conducted slug tests using a novel instrument, a piezometer with a heated tip that melts itself into the ice sheet. Hydraulic conductivity ranges between 2.5 × 10 −5 and 1.1 × 10 −3 m/s. The geometric mean of hydraulic conductivity of the aquifer is 2.7 × 10 −4 m/s with a geometric standard deviation of 1.4 from both depth specific slug tests (analyzed using the Hvorslev method) and aquifer tests during the recovery period. Hydraulic conductivity is relatively consistent between boreholes and only decreases slightly with depth. The hydraulic conductivity of the firn aquifer is crucial for determining flow rates and patterns within the aquifer, which inform hydrologic models of the aquifer, its relation to the broader glacial hydrologic system, and its effect on sea level rise.

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Section: Discussionmentioning

confidence: 99%

Hydraulic Conductivity of a Firn Aquifer in Southeast Greenland

et al. 2017

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“…At the beginning of the melt season, saturated snow may transition into channelized meltwater flow through the formation of rills [1,5,53,54], overflow from slush swamps, lakes or hollows [9,23,55,56], or slush avalanches [57,58]. Although these processes have been empirically described, there has been only one numerical description of the hydrodynamic controls on rill-like supraglacial channel initiation [59].…”

Section: Channel Initiation Thresholdmentioning

confidence: 99%

Flow Routing for Delineating Supraglacial Meltwater Channel Networks

et al. 2016

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Abstract:Growing interest in supraglacial channels, coupled with the increasing availability of high-resolution remotely sensed imagery of glacier surfaces, motivates the development and testing of new approaches to delineating surface meltwater channels. We utilized a high-resolution (2 m) digital elevation model of parts of the western margin of the Greenland Ice Sheet (GrIS) and retention of visually identified sinks (i.e., moulins) to investigate the ability of a standard D8 flow routing algorithm to delineate supraglacial channels. We compared these delineated channels to manually digitized channels and to channels extracted from multispectral imagery. We delineated GrIS supraglacial channel networks in six high-elevation (above 1000 m) and one low-elevation (below 1000 m) catchments during and shortly after peak melt (July and August 2012), and investigated the effect of contributing area threshold on flow routing performance. We found that, although flow routing is sensitive to data quality and moulin identification, it can identify 75% to 99% of channels observed with multispectral analysis, as well as low-order, high-density channels (up to 15.7 km/km 2 with a 0.01 km 2 contributing area threshold) in greater detail than multispectral methods. Additionally, we found that flow routing can delineate supraglacial channel networks on rough ice surfaces with widespread crevassing. Our results suggest that supraglacial channel density is sufficiently high during peak melt that low contributing area thresholds can be employed with little risk of overestimating the channel network extent.

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“…This may lead to some underestimation of melt, by overestimating albedo in extreme years where the annual ELA greatly increases, exposing snow that is greater than one year old and has not yet transferred to the ice layer. Additionally, while melt water storage is represented in the snowpack, the explicit representation of storage and routing in a porous firn layer (Fountain, 1996;Jansson et al, 2003) is neglected. This simple configuration may limit the simulation of streamflow at fine timescales at locations close to glacier termini, but may have a smaller influence at the watershed scale.…”

Section: Model Integrationmentioning

confidence: 99%

Modeling the effect of glacier recession on streamflow response using a coupled glacio-hydrological model

Naz

Frans

Clarke

et al. 2014

Hydrol. Earth Syst. Sci.

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Abstract. We describe an integrated spatially distributed hydrologic and glacier dynamic model, and use it to investigate the effect of glacier recession on streamflow variations for the upper Bow River basin, a tributary of the South Saskatchewan River, Alberta, Canada. Several recent studies have suggested that observed decreases in summer flows in the South Saskatchewan River are partly due to the retreat of glaciers in the river's headwaters. Modeling the effect of glacier changes on streamflow response in river basins such as the South Saskatchewan is complicated due to the inability of most existing physically based distributed hydrologic models to represent glacier dynamics. We compare predicted variations in glacier extent, snow water equivalent (SWE), and streamflow discharge with satellite estimates of glacier area and terminus position, observed glacier mass balance, observed streamflow and snow water-equivalent measurements, respectively over the period of 1980-2007. Observations of multiple hydroclimatic variables compare well with those simulated with the coupled hydrology-glacier model. Our results suggest that, on average, the glacier melt contribution to the Bow River flow upstream of Lake Louise is approximately 22 % in summer. For warm and dry years, however, the glacier melt contribution can be as large as 47 % in August, whereas for cold years, it can be as small as 15 % and the timing of the glacier melt signature can be delayed by a month. The development of this modeling approach sets the stage for future predictions of the influence of warming climate on streamflow in partially glacierized watersheds.

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Effect of Snow and Firn Hydrology on the Physical and Chemical Characteristics of Glacial Runoff

Cited by 68 publications

References 49 publications

Hydraulic Conductivity of a Firn Aquifer in Southeast Greenland

Hydraulic Conductivity of a Firn Aquifer in Southeast Greenland

Flow Routing for Delineating Supraglacial Meltwater Channel Networks

Modeling the effect of glacier recession on streamflow response using a coupled glacio-hydrological model

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