Recovery giant subglacial lakes: new assessments using IceGRAV airborne radar data
Friday, 19 December 2014
Recovery Glacier penetrates deep into the interior of East Antarctica. The subglacial hydraulic system beneath this glacier includes active lakes aligned along the glacier trunk and four giant lakes near the onset of the fast flow. The characteristics of this subglacial system and its impacts on ice flow are therefore central questions for the dynamics of the East Antarctic Ice Sheet. The existence of these lakes is hypothesized to explain satellite-measured ice-surface motion and smoothness. However, direct evidence of the existence of the giant Recovery lakes has until recently been limited to ground-based radar measurements during IPY, showing that the lakes A and B were not distinct lakes at the time of the measurement (January, 2009) and may have drained recently. In order to fill the significant data gap over the Recovery catchment identified by the BEDMAP2 project, over 29,000 line km of new radio-echo sounding, laser altimetry, gravity and magnetic data were acquired using a British Antarctic Survey Twin Otter during the IceGRAV 2012-13 field season. Here, we present a subset of this Recovery Frontier dataset in the vicinity of the giant Recovery lakes A and B to assess their current conditions. Bed reflectivity derived for a range of englacial attenuation rates indicates that the lake surface has larger reflectivity than the adjacent grounded areas, by more than 10 dB. Bed reflectivity varies little over short distances (< 1 km), both around the lakes and adjacent areas. Hydraulic potential varies little over the lakes as well as their downstream sides but increases in the upstream directions. These recent characteristics are clearly distinct from the previous ground-based measurements taken in 2009. We hypothesize that these differences indicate that lakes A and B may be filling. The existence of a major active hydrological system in the interior of the East Antarctic Ice Sheet could influence ice streaming also further downstream, where smaller-scale active lake systems have been inferred.