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| Titel |
Ross Ice Shelf Seismic Survey and Future Drilling Recommendation |
| VerfasserIn |
Laurine van Haastrecht, Christian Ohneiser, Andrew Gorman, Christina Hulbe |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250132108
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| Publikation (Nr.) |
 EGU/EGU2016-12584.pdf |
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| Zusammenfassung |
| The Ross Ice Shelf (RIS) is one of three gateways through which change in the ocean can be
propagated into the interior of West Antarctica. Both the geologic record and ice
sheet models indicate that it has experienced widespread retreat under past warm
climates. But inland of the continental shelf, there are limited data available to
validate the models. Understanding what controls the rate at which the ice shelf will
respond to future climate change is central to making useful climate projections.
Determining the retreat rate at the end of the last glacial maximum is one part of this
challenge.
In November 2015, four lines of multi-channel seismic data, totalling over 45 km, were
collected on the Ross Ice Shelf, approximately 300 km south of Ross Island using a thumper
seismic source and a 96 channel snow streamer. The seismic survey was undertaken under the
New Zealand Antarctic Research Institute (NZARI) funded Aotearoa New Zealand
Ross Ice Shelf Programme to resolve bathymetric details and to image sea floor
sediments under a proposed drilling site on the ice shelf, at about 80.7 S and 174
E.
The thumper, a purpose-built, trailer mounted, weight-drop seismic source was
towed behind a Hägglund tracked vehicle to image the bathymetry and sediments
underneath the RIS. Seismic data collection on an ice shelf has unique challenges, in
particular strong attenuation of the seismic energy by snow and firn, and complex
multiple ray paths. The thumper, which consists of a heavy weight (250kg) that is
dropped on a large, ski mounted steel plate, produced a consistent, repeatable higher
energy signal when compared to sledge hammer source and allowed for a greater
geographic coverage and lower environmental impact than an explosive source
survey.
Our survey revealed that the seafloor is smooth and that there may be up to 100 m of
layered sediments beneath the seafloor and possibly deeper, more complex structures.
A multiple generated by internally reflected seismic energy within the ice shelf
may indicate that the underside of the ice is smooth in sector of the Ross Ice Shelf. |
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