Abstract
The geoPebble system is a network of wirelessly interconnected seismic and GPS sensor nodes with geophysical sensing capabilities for the study of ice sheets in Antarctica and Greenland, as well as mountain glaciers. We describe our design methodology, which has enabled us to develop these state-of-the art units using commercial-off-the-shelf hardware combined with custom-designed hardware and software. Each geoPebble node is a self-contained, wirelessly connected sensor for collecting seismic activity and position information. Each node is built around a three-component seismic recorder, which includes an amplifier, filter, and 24-bit analog-to-digital converter that can sample incoming seismic signals up to 10 kHz. The timing for each node is available from GPS measurements and a local precision oscillator that is conditioned by the GPS timing pulses. In addition, we record the carrier-phase measurement of the L1 GPS signal in order to determine location at sub-decimeter accuracy (relative to other geoPebble nodes within a radius of a few kilometers). Each geoPebble includes 32 GB of solid-state storage, wireless communications capability to a central supervisory unit, and auxiliary measurements capability (including tilt from accelerometers, absolute orientation from magnetometers, and temperature). The geoPebble system has been successfully validated in the field in Antarctica and Greenland.
Highlights
Introduction published maps and institutional affilThe ice sheets of Antarctica and Greenland contain nearly 33-million cubic kilometers of ice
The Greenland Ice Sheet is the largest contributor to sea level rise [16], mainly from increases in surface melting and iceberg calving [10,17,18,19], both of which are expected to increase with continued warming
The geoPebble system’s network of wirelessly interconnected seismic and GPS sensor nodes with geophysical sensing capabilities is well positioned to support the new paradigm necessary for the study of ice sheets in Antarctica and Greenland, as well as mountain glaciers
Summary
Climate change poses a significant threat to coastal and inland communities, ocean and land biomes, Polar environments, and water resources with large uncertainties that arise from the response of the natural system to CO2 emissions. The Greenland Ice Sheet is the largest contributor to sea level rise [16], mainly from increases in surface melting and iceberg calving [10,17,18,19], both of which are expected to increase with continued warming. Iceberg calving is a poorly understood process, but likely initiates with fracture propagation at the surface and the base of the glacier. Monitoring this process through seismic detection and recording can lead to a better understanding of the mechanisms and to better models mass loss [20,21]. The GPS L1 carrier-phase measurements can be recorded and post-processed to determine sub-centimeter relative position between the nodes. The single-frequency GPS receiver is appropriate for the scale of the deployment (i.e., all nodes view the same GPS satellites) and, as the geoPebbles are inexpensive compared to dual-frequency receivers, the network can be much denser
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