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Abstract Lemon Creek Glacier, a temperate valley glacier in the Juneau Icefield of Southeast Alaska, is the site of long running (>60 years) glaciological studies. However, the most recent published estimates of its thickness and subglacial topography come from two ~50 years old sources that are not in agreement and do not account for the effects of years of negative mass balance. We collected a 1-km long active-source seismic line on the upper section of the glacier parallel and near to the centerline of the glacier, roughly straddling the equilibrium-line altitude. We used these data to perform joint reflection-refraction velocity modeling and reflection imaging of the glacier bed. We find that this upper section of Lemon Creek Glacier is as much as 150 m (~65%) thicker than previously suggested with a large overdeepening in an area previously believed to have a uniform thickness. Our results lead us to reinterpret the impact of basal motion on ice flow and have a significant impact on expectations of subglacial hydrology. We suggest that further efforts to develop a whole-glacier model of subglacial topography are necessary to support studies that require accurate models of ice thickness and subglacial topography.
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Basal conditions of Malaspina Glacier
In this active seismic experiment we will collect AVO data at two glacier sites. One is located over a glacier bed high and the other one over a depression. The goals is to use Amplitude vs Offset methods to determine the nature of the subglacial material. A line of 24 geophones will be buried in snow to protect them from wind noise and the line will be accurately surveyed with GPS. A set of 100 shot holes will be drilled into the underlying ice to obtain a large range of offsets, so that amplitudes can be compared over large offset angles. If possible, the data will also be used to find the thickness of a subglacial till layer. The seismic experiment is part of a large geophysical and remote sensing observational program with the goal to provide input data for an ice flow model that will explore possible future scenarios for this large glacier that is very vulnerable to future climate change. In a second experiment we will do attempt to measure the extent of buried ice in the glacier foreland. For this experiment we propose to use 4.5 Hz geophones and we will use a hammer for the active source. This is part of the same NSF funded work.
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- Award ID(s):
- 1929566
- PAR ID:
- 10657043
- Publisher / Repository:
- International Federation of Digital Seismograph Networks
- Date Published:
- Format(s):
- Medium: X Size: 390 MB Other: SEED data
- Size(s):
- 390 MB
- Sponsoring Org:
- National Science Foundation
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