Thermodynamics of a fast-moving Greenlandic outlet glacier revealed by fiber-optic distributed temperature sensing

Abstract

Measurements of ice temperature provide crucial constraints on ice viscosity and the thermodynamic processes occurring within a glacier. However, such measurements are presently limited by a small number of relatively coarse-spatial-resolution borehole records, especially for ice sheets. Here, we advance our understanding of glacier thermodynamics with an exceptionally high-vertical-resolution (~0.65 m), distributed-fiber-optic temperature-sensing profile from a 1043-m borehole drilled to the base of Sermeq Kujalleq (Store Glacier), Greenland. We report substantial but isolated strain heating within interglacial-phase ice at 208 to 242 m depth together with strongly heterogeneous ice deformation in glacial-phase ice below 889 m. We also observe a high-strain interface between glacial- and interglacial-phase ice and a 73-m-thick temperate basal layer, interpreted as locally formed and important for the glacier’s fast motion. These findings demonstrate notable spatial heterogeneity, both vertically and at the catchment scale, in the conditions facilitating the fast motion of marine-terminating glaciers in Greenland.

Controls on Water Storage and Drainage in Crevasses on the Greenland Ice Sheet

“…where n is the flow law exponent with value 3 and B is a viscosity parameter, which we assign a value of 324 kPa a 1/3 (Cuffey & Paterson, 2010) based on an assumed 10 m ice temperature of −5°C. This uniform temperature assumption follows that made in other regional studies examining similar spatial scales (Clason et al, 2015;Koziol et al, 2017;Williamson, Willis, et al, 2018), and matches observations made using distributed temperature sensing measurements at Store Glacier (Law et al, 2021). The effective strain rate, ε e , was then calculated following Cuffey and Paterson (2010) as…”

Controls on water storage and drainage in crevasses on the Greenland Ice Sheet

“…where n is the flow law exponent with value 3 and B is a viscosity parameter, which we assign a value of 324 kPa a 1/3 (Cuffey & Paterson, 2010) based on an assumed 10 m ice temperature of −5°C. This uniform temperature assumption follows that made in other regional studies examining similar spatial scales (Clason et al, 2015;Koziol et al, 2017;Williamson, Willis, et al, 2018), and matches observations made using distributed temperature sensing measurements at Store Glacier (Law et al, 2021). The effective strain rate, ε e , was then calculated following Cuffey and Paterson (2010) as…”

Water flow through sediments and at the ice-sediment interface beneath Sermeq Kujalleq (Store Glacier), Greenland

“…Temperature was measured using high-accuracy (± 0.05°C) thermistors (Littelfuse: PR502J2) at ∼0, 1, 3, 5 and 10 m above the bed in BH19c and BH19e and also throughout the full ice column in BH19c using fibre-optic DTS (Law and others, 2021). Here we present temperature measurements recorded by the lowermost thermistor in BH19c, which was mounted with the Geokon 4500SH piezometer.…”

“…where γ = 9.14 × 10 −8 K Pa −1 is the Clausius-Clapeyron gradient determined from the basal temperature gradient (Law and others, 2021), and T tr = 273.16 K and p tr = 611.73 Pa are the triple point temperature and pressure of water, respectively.…”