Role of discrete water recharge from supraglacial drainage systems in modeling patterns of subglacial conduits in Svalbard glaciers

Abstract

Abstract. As the behavior of subglacial water plays a determining role in glacier dynamics, it requires particular attention, especially in the context of climate warming, which is increasing ablation and generating greater amounts of meltwater. On many glaciers, water flowing from the glacier's surface is the main source of supply to the subglacial drainage system. This system is largely influenced by the supraglacial drainage system, which collects meltwater and precipitation and rapidly delivers it to discrete points in the glacier bed via moulins and crevassed areas, called water input areas (WIAs). Models of patterns of subglacial conduits mainly based on the hydrological potential gradient are still regularly performed without taking into account the supraglacial drainage system. We modeled the pattern of subglacial channels in two glaciers located in Svalbard, the land-terminating Werenskioldbreen and the tidewater Hansbreen during the 2015 melt season. We modeled a spatial and a discrete water recharge in order to compare them. First, supraglacial catchments were determined for each WIA on a high-resolution digital elevation model using the standard watershed modeling tool in ArcGIS. Then, interpolated water runoff was calculated for all the main WIAs. Our model also accounts for several water pressure conditions. For our two studied glaciers, during the ablation season 2015, 72.5 % of total runoff was provided by meltwater and 27.5 % by precipitation. Changes in supraglacial drainage on a decadal timescale are observed in contrast to its nearly stable state on an annual timescale. Nevertheless, due to the specific nature of those changes, it seems to have a low impact on the subglacial system. Therefore, our models of subglacial channel are assumed to be valid for a minimum period of two decades and depend on changes in the supraglacial drainage system. Results showed that, for Svalbard tidewater glaciers with large crevassed areas, models of subglacial channels that assume spatial water recharge may be somewhat imprecise but are far from being completely incorrect, especially for the ablation zone. On the other hand, it is important to take discrete water recharge into account in the case of land-terminating Svalbard glaciers with limited crevassed areas. In all cases, considering a discrete water recharge when modeling patterns of theoretical subglacial channels seems to produce more realistic results according to current knowledge.

Changes of glacier facies on Hornsund glaciers (Svalbard) during the decade 2007–2017

“…SAR SI of Hansbreen covered at least 7 km 2 in 2007 and 2010, and since 2012 has not been distinguished as a vast area. This is probably a consequence of negative mass balance, changes in the glacier topography (Błaszczyk et al 2019a) and the effective drainage system of Hansbreen (Decaux et al 2019). Dunse et al (2009) observed an increase in firn area extent of Austfonna between the 2003 and summer surface.…”

“…Müller 1962;Dyurgerov et al 2009), water drainage (e.g. Jansson et al 2003;Decaux et al 2019), surface energy balance (e.g. Braun and Hock 2004;Hoffman et al 2008) or microbiology of glacier habitats (e.g.…”

Reconciling Svalbard Glacier Mass Balance

“…Furthermore, these aquifers may promote microbial production (e.g., Anesio et al, 2017), and are the focus of ongoing research on glacier ecology (Hodson et al, 2015). In general, more sophisticated drainage system models have to be developed, to account for differences in spatially distributed or localized recharge (Gulley et al, 2012;Decaux et al, 2019). However, our understanding of processes that control the vertical percolation of surface meltwater and associated firn warming needs to be refined, and studies of horizontal water motion are largely absent.…”

Pressure and inertia sensing drifters for glacial hydrology flow path measurements

“…Depending on sensor payload, drifters can be used for a wide range of applications, including coastal and ocean surface current monitoring (Boydstun et al, 2015;Jaffe et al, 2017) to estimate river bathymetry and surface velocities (Landon et al, 2014;Almeida et al, 2017) and to collect imagery for underwater photogrammetry (Boydstun et al, 2015). Recent payloads in river studies included sensors for temperature (e.g., Tinka et al, 2013;Oroza et al, 2013;Allegretti, 2014), dissolved oxygen (e.g., D'Este et al, 2012;Tinka et al, 2013), pH (e.g., Tinka et al, 2013;Arai et al, 2014), turbidity (e.g., Marchant et al, 2015), GPS receivers (e.g., Stockdale et al, 2008;Tinka et al, 2013), acoustic Doppler current profilers (e.g., Tinka et al, 2009;Postacchini et al, 2016) and inertial measurement units (e.g., Arai et al, 2014). Additionally, sensor payloads in oceanographic applications included devices for the measurement of conductivity (e.g., Reverdin et al, 2010;Jaffe et al, 2017), chlorophyll (e.g., Jaffe et al, 2017) and underwater imagery (e.g., Boydstun et al, 2015;Xanthidis et al, 2016).…”