Evidence for subglacial ponding across Taylor Glacier, Dry Valleys, Antarctica

Abstract

Ice-penetrating radar and modelling data are presented suggesting the presence of a zone of temperate ice, water ponding or saturated sediment beneath the tongue of Taylor Glacier, Dry Valleys, Antarctica. The proposed subglacial zone lies 3-6 km up-glacier of the terminus and is 400-1000 m across. The zone coincides with an extensive topographic overdeepening to 80 m below sea level. High values of residual bed reflective power across this zone compared to other regions and the margins of the glacier require a high dielectric contrast between the ice and the bed and are strongly indicative of the presence of basal water or saturated sediment. Analysis of the hydraulic equipotential surface also indicates strong convergence into this zone of subglacial water flow paths. However, thermodynamic modelling reveals that basal temperatures in this region could not exceed -78C relative to the pressure-melting point. Such a result is at odds with the radar observations unless the subglacial water is a hypersaline brine.

Helicopter-borne transient electromagnetics in high-latitude environments: An application in the McMurdo Dry Valleys, Antarctica

“…An AEM sounding at the same location shows a sharp drop in resistivity between depths of 200 and 275 m coincident with sharp increases in salinity within marine sediments (Figure 7). This occurs over a range of temperatures (approximately −10°C to −5°C) consistent with temperatures at which MDV brines could exist: The saline bottom waters of Lake Bonney are −5.3°C (Spigel and Priscu, 1996); water exits Blood Falls, a hypersaline discharge at the terminus of TG, at −5.6°C (Mikucki et al, 2009);and Hubbard et al (2004) . AEM data compared with DVDP 11 borehole temperatures (Decker and Bucher, 1982) and salinity (McGinnis et al, 1982).…”

“…Low-frequency radar (10-100 MHz) is commonly used to measure the basal topography of glaciers (e.g., Berthling et al, 2000;Isaksen et al, 2000;Degenhardt and Giardino, 2003;Hubbard et al, 2004;Engel et al, 2012), whereas a shorter wavelength (100-400 MHz) is used when high resolution is required (e.g., Fukui et al, 2008;Sold et al, 2014). Because the speed of EM waves in ice is in the range of 0.167-0.169 m:ns −1 , (which adds some uncertainties depending on the value chosen), the vertical resolution (about a quarter of the radar wavelength) ranges from approximately 4 m at 10 MHz to 0.1 m at 400 MHz.…”

“…Because the speed of EM waves in ice is in the range of 0.167-0.169 m:ns −1 , (which adds some uncertainties depending on the value chosen), the vertical resolution (about a quarter of the radar wavelength) ranges from approximately 4 m at 10 MHz to 0.1 m at 400 MHz. Hubbard et al (2004) used 10-MHz radar to image the lower part of TG, which terminates in Lake Bonney at the western end of TV. Based on strong basal reflectivity, they inferred the presence of a liquid water reservoir stored in an overdeepening located 3-6 km from the glacier terminus.…”

Greenland subglacial lakes detected by radar

“…In the first case, the lakes might resemble that found beneath 450 m of ice, 4 km from the terminus of Taylor Glacier in the McMurdo Dry Valleys, East Antarctica [Hubbard et al, 2004], a region where mean annual surface temperatures (À17°C) and basal temperatures (À8°C) are similar to those in our study area. The Taylor Glacier subglacial lake consists of brine that may have been cryoconcentrated to~1375 mM prior to isolation from direct contact with the atmosphere, about 1.5 Ma ago [Mickuchi et al, 2009].…”

Bacterial Diversity Associated with Blood Falls, a Subglacial Outflow from the Taylor Glacier, Antarctica

“…The Taylor Glacier is unique among the Dry Valley glaciers in that the presence of subglacial brine near its terminus results in geomorphic behavior more like that of a temperate or polythermal glacier (54). Ice-penetrating-radar data indicate water or slush below the glacier corresponding to an 80-m depression in the bedrock topology at ϳ4 km up-glacier from the terminus (28). This depression is below sea level and forms what is believed to have been a third lobe of Lake Bonney (43).…”