Acceleration and flotation of a glacier terminus during formation of a proglacial lake in Rhonegletscher, Switzerland

Abstract

In 2005 the ongoing retreat of Rhonegletscher, Switzerland, led to the formation of a proglacial lake. To investigate the influence of proglacial lake formation on the dynamics and evolution of glaciers, we measured horizontal flow velocity, vertical ice motion and water levels in boreholes with high spatial resolutions during the summer seasons of 2007-09. Annual flow speeds near the terminus increased by a factor of 2.7 from 2005/06 to 2007/08, and exceeded 20 m a -1 in 2009. The velocity increased towards the glacier front, indicating that the ice was thinning under a longitudinally stretching flow regime. Our observations show that the increase in flow speed near the terminus was due to increases in basal motion as a result of ice thinning. During summer 2009, the ice surface at the terminus moved vertically upwards by up to 4.69 m as the ice began to float on the lake. The observed ice motion can be explained by the upward bending of marginal ice and the formation of faults that cut through the entire ice thickness.We predict that if the current ice thinning continues, the basal water pressure will exceed the pressure exerted by the ice overburden, and the glacier will progressively disintegrate over an expanding area.

Detecting and characterising an englacial conduit network within a temperate Swiss glacier using active seismic, ground penetrating radar and borehole analysis

“…The glacier flows southwards from 3556 to 2208 m above mean sea level (AMSL) with a total ice volume of 2.11 ± 0.38 km 3 (Farinotti and others, 2009) and a surface area of 16 km 2 (Bauder and others, 2017). A proglacial lake formed in 2005 as a result of the retreating glacier (Tsutaki and others, 2013), which will continue to increase in size (Church and others, 2018) with the continued retreat of the glacier. The proglacial lake's elevation is held constant at ~2208 m AMSL as a result of a granite riegel damming the lake and there is likely a hydrological interaction between the lake and the glacier's hydrological system.…”

“…The proglacial lake's elevation is held constant at ~2208 m AMSL as a result of a granite riegel damming the lake and there is likely a hydrological interaction between the lake and the glacier's hydrological system. The Rhone Glacier's proglacial lake is a potential candidate for hydropower generation as a result of the expanding lake (Tsutaki and others, 2013; Church and others, 2018).…”

Irish Ice Sheet dynamics during deglaciation of the central Irish Midlands: Evidence of ice streaming and surging from airborne LiDAR

“…An external control on ice marginal dynamics during recession may have been the presence of a large proglacial lake (Paleolake Riada), as modern and Quaternary proglacial lakes have been linked to enhanced ice flow velocity, changing flow direction and enhancing retreat rates through iceberg calving (e.g., Kirkbride and Warren, 1999;Stokes and Clark, 2003;Walder et al, 2006;Tsutaki et al, 2013). The proglacial lake had not yet formed during MSGL and CSR formation in area 1, as the ice margin extended across the watershed.…”

Seasonal Variations in Ice-Front Position Controlled by Frontal Ablation at Glaciar Perito Moreno, the Southern Patagonia Icefield

“…A limited number of studies on processes near the front of freshwater calving glaciers indicate some similarities and some differences with tidewater glaciers (e.g., Carrivick and Tweed, 2013). Both lake and ocean water influences subglacial hydraulic conditions, which favors fast ice flow of calving glaciers near the front (e.g., Meier and Post, 1987;Tsutaki et al, 2013). The fast flow causes formation of crevasses at the glacier surface, which causes calving.…”