Hurd Peninsula glaciers, Livingston Island, Antarctica, as indicators of regional warming: ice-volume changes during the period 1956–2000

Abstract

Johnsons and Hurd Glaciers are the two main glacier units of Hurd Peninsula ice cap, Livingston Island, South Shetland Islands, Antarctica. They presently cover an area of about 10 km 2 . Johnsons is a tidewater glacier, while Hurd Glacier ends on emerged land. In this paper, we estimate the changes in ice volume during the period 1956-2000, and compare them with the regional meteorological records. The volume-change estimates are based on the comparison of digital terrain models for the glacier surface, constructed from aerial photographs taken by the British Antarctic Survey in 1956 and from our geodetic measurements in 1999/2000. The total volume estimates are based on an ice-thickness map constructed from radio-echo sounding profiles (18-25 MHz) done in 1999-2001, showing maximum ice thickness of about 200 m. We estimate the changes in ice volume during the period 1956-2000 to be -0.108 AE AE 0.048 km 3 , which represents a 10.0 AE 4.5% % decrease from the 1956 total volume of 1.076 AE 0.055 km 3 and is equivalent to an average annual mass balance of -0.23 AE 0.10 m w.e. during 1956-2000. Ice-thickness changes range from -40 to þ20 m, averaging -5.5 AE 4.4 m. Most areas show ice thinning; the thickening is limited to a small area within Johnsons Glacier. All glacier fronts, except Johnsons' calving front, show retreat. These changes are consistent with the regional meteorological records for mean summer temperature, which show a trend of þ0.023 AE 0.0058C a -1 during the period 1956-2000.

Geomatic methods applied to the study of the front position changes of Johnsons and Hurd Glaciers, Livingston Island, Antarctica, between 1957 and 2013

“…Johnsons and Hurd glaciers are polythermal, though Johnsons, as compared with Hurd, has a higher proportion of temperate ice . Typical velocities near the calving front of Johnsons Glacier are about 50 m yr −1 (Rodríguez, 2014), whereas maximum velocities in Hurd Glacier are reached in its central zone, and are typically around 5 m yr −1 (Molina, 2014), decreasing towards the terminal zones, which have been suggested to be frozen to bed on the basis of ground-penetrating radar studies, glacier velocities and geomorphological evidences Molina et al, 2007). The annual average temperature at Juan Carlos I Station (12 m a.s.l., in Hurd Peninsula) between 1988 and 2011 was −0.9 • C, with average summer (DJF) and winter (JJA) temperatures of 2.4 and −4.4 • C, respectively (Osmanoglu et al, 2014).…”

“…The annual average temperature at Juan Carlos I Station (12 m a.s.l., in Hurd Peninsula) between 1988 and 2011 was −0.9 • C, with average summer (DJF) and winter (JJA) temperatures of 2.4 and −4.4 • C, respectively (Osmanoglu et al, 2014). The main glaciological studies in Hurd Peninsula include cartography of volcanic ash layers (Palà et al, 1999;Ximenis, 2001;Molina, 2014), shallow ice coring , numerical modeling of glaciers dynamics (Martín et al, 2004;Otero et al, 2010), analysis of glacier volume changes 1957-2000 (Molina et al, 2007), seismic and ground-penetrating radar surveys (Benjumea et al, 1999(Benjumea et al, , 2001(Benjumea et al, , 2003Navarro et al, 2005Navarro et al, , 2009, modeling of melting (Jonsell et al, 2012), massbalance observations Ximenis, 2001;Navarro et al, 2013) and geomorphological and glacier dynamics studies (Ximenis et al, 2000;Molina, 2014). Glaciological studies covering the whole Livingston Island include the analysis of Livingston ice cap front position changes 1956-1996, ground-penetrating radar surveys ) and estimates of ice discharge to the ocean (Osmanoglu et al, 2014).…”

“…More recently, Osmanoglu et al (2014), using unpublished outlines for 2004 from Jaume Calvet and David García-Sellés, estimated the glacierized area to be 697 km 2 . Molina et al (2007) analyzed the volume changes 1957-2000 of Hurd Peninsula glaciers comparing digital elevation models (DEMs) for 1957, obtained by photogrammetric restitution from the British Antarctic Survey (BAS) aerial photographs of 1957 and theodolite and GNSS surface-based measurements in 1999-2001. We note, however, that their photogrammetric restitution was done from paper-printed photos (the only available at that time), while our work is based on a digitization from the original films performed later by the BAS.…”

A 14-year dataset of in situ glacier surface velocities for a tidewater and a land-terminating glacier in Livingston Island, Antarctica

“…This is sup- ported by both geomorphological observations, in particular the presence of compressional structures such as thrust faults close to the glacier termini (Molina et al, 2007;Molina, 2014) and to ground-penetrating radar studies that show that the cold ice layer reaches the bedrock in these zones (Navarro et al, 2009;Molina, 2014).…”

“…In the snouts of Hurd Glacier (in Sally Rocks area) and its side lobes Argentina and Las Palmas, where the glacier thickness tapers to zero, the cold ice layer extends down to bedrock, so the glacier is frozen to the bed, implying a compressional stress regime. In contrast, the area close to the Johnsons calving front shows the extensional stress regime characteristic of the terminus of tidewater glaciers (Molina et al, 2007;Navarro et al, 2009;Otero et al, 2010).…”