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| Titel |
Ice sheet sensitivity experiments as part of an assessment of long-term safety for a planned repository for spent nuclear fuel in Sweden |
| VerfasserIn |
Claudia Wekerle, Florence Colleoni, Simona Masina, Jens-Ove Näslund, Jenny Brandefelt |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250086791
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| Publikation (Nr.) |
 EGU/EGU2014-717.pdf |
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| Zusammenfassung |
| An application to build a deep geological repository for spent nuclear fuel in Forsmark
in south-central Sweden is currently under consideration by Swedish authorities.
As part of the safety assessment, the response of the repository to an extensive
glaciation over time scales of several hundred thousand years, in terms of ice thickness,
bedrock depression and hydrostatic pressure, has to be evaluated. The most extensive
glaciation over Eurasia recorded in geological proxies occurred during the MIS
6, at around 140 kyrs BP (Late Saalian glaciation). At this time, the few existing
numerical ice-sheet reconstructions suggest that the Eurasian ice volume reached more
than 70 m SLE, which is at least three times larger than during the Last Glacial
Maximum (21 kyrs BP). The reconstruction of this ice sheet is complicated by the fact
that the timing of the maximum ice volume may not have been coeval with the
maximum eastern and southern extent of the Saalian ice sheet. In the present study,
the maximum geographical extension of the Late Saalian glaciation serves as an
extreme test case to assess the impact of ice thickness over the Forsmark repository
site.
We use the 3D-thermodynamical ice sheet-ice shelves and ice stream model GRISLI (Ritz
et al. 2001) to simulate the Northern Hemisphere ice sheet topography of the Late Saalian
glaciation. The model is forced by steady-state climatic fields (surface air temperature and
precipitation) computed using the coupled atmosphere-ocean Community Earth System
Model (CESM, NCAR) at ~1°x1° resolution, with boundary and forcing conditions
representative for the MIS6 glacial maximum. Ice sheet simulations are run on a 20
km regular rectangular grid over the northern high latitudes and allow for floating
ice.
First, as part of the model validation, we show a numerical reconstruction of the MIS 6
Eurasian ice sheet using standard parameters for lapse rate, PDD coefficients and basal
hydrology. Second, sensitivity experiments are presented, studying the impact of model
parameters such as surface mass balance parameters and schemes of calving and basal
hydrology on the ice thickness. With this approach we are able to provide reasonable upper
and lower bounds of ice thickness for a possible extreme glaciation over the Forsmark
area. |
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