Zobrazeno 1 - 10
of 30
pro vyhledávání: '"Nicholas M. Rathmann"'
Autor:
Nicholas M. Rathmann, David A. Lilien
Publikováno v:
Journal of Glaciology, Vol 68, Pp 1243-1248 (2022)
We compare different ways the bulk flow nonlinearity of glacier ice can be captured in an orthotropic rheology. Specifically, we compare the unapproximated orthotropic rheology, derived from plastic potential theory, to existing approximations that a
Externí odkaz:
https://doaj.org/article/83ccacc3b5614adb8cb8d60bc9861d7c
Autor:
Aslak Grinsted, Christine S. Hvidberg, David A. Lilien, Nicholas M. Rathmann, Nanna B. Karlsson, Tamara Gerber, Helle Astrid Kjær, Paul Vallelonga, Dorthe Dahl-Jensen
Publikováno v:
Nature Communications, Vol 13, Iss 1, Pp 1-4 (2022)
A new study finds that the North East Greenland ice stream is not as stable as previously thought and that this will affect its future evolution.
Externí odkaz:
https://doaj.org/article/2ead4269b9444a59ae8f9b93754e57e5
Autor:
Nicholas M. Rathmann, David A. Lilien
Publikováno v:
Journal of Glaciology, Vol 68, Pp 236-252 (2022)
We investigate the errors caused by neglecting the crystal-orientation fabric when inferring the basal friction coefficient field, and whether such errors can be alleviated by inferring an isotropic enhancement factor field to compensate for missing
Externí odkaz:
https://doaj.org/article/9cc26a5085d142e29434bbc4b84fe851
Effect of an orientation-dependent non-linear grain fluidity on bulk directional enhancement factors
Autor:
Nicholas M. Rathmann, Christine S. Hvidberg, Aslak Grinsted, David A. Lilien, Dorthe Dahl-Jensen
Publikováno v:
Journal of Glaciology, Vol 67, Pp 569-575 (2021)
Bulk directional enhancement factors are determined for axisymmetric (girdle and single-maximum) orientation fabrics using a transversely isotropic grain rheology with an orientation-dependent non-linear grain fluidity. Compared to grain fluidities t
Externí odkaz:
https://doaj.org/article/b4fe359c86e147459c8960807867537a
Autor:
Christine S. Hvidberg, Mikkel Lauritzen, Nicholas M. Rathmann, Anne M. Solgaard, Dorthe Dahl-Jensen
Publikováno v:
XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
The stability of the Greenland ice sheet through past glacial-interglacial cycles provides knowledge that can contribute to understanding the future mass loss from the Greenland ice sheet in a warmer climate. Paleo-climatic records from ice cores pro
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::d321deed2c93e276f4f7e98f3ac51165
https://gfzpublic.gfz-potsdam.de/pubman/item/item_5021082
https://gfzpublic.gfz-potsdam.de/pubman/item/item_5021082
Autor:
Nicholas M. Rathmann, Aslak Grinsted, Klaus Mosegaard, David A. Lilien, Julien Westhoff, Christine S. Hvidberg, David J. Prior, Franz Lutz, Rilee E. Thomas, Dorthe Dahl-Jensen
Publikováno v:
Rathmann, N M M, Grinsted, A, Mosegaard, K, Lilien, D A A, Westhoff, J, Hvidberg, C S S, Prior, D J J, Lutz, F, Thomas, R E E & Dahl-Jensen, D 2022, ' Elastic wave propagation in anisotropic polycrystals : inferring physical properties of glacier ice ', Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, vol. 478, no. 2268, 20220574 . https://doi.org/10.1098/rspa.2022.0574
An optimization problem is proposed for inferring physical properties of polycrystals given ultrasonic (elastic) wave velocity measurements, made across multiple sample orientations. The feasibility of the method is demonstrated by inferring both the
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::4e3c66f4d39be305ea2adafc4ce98de7
https://doi.org/10.1098/rspa.2022.0574
https://doi.org/10.1098/rspa.2022.0574
Autor:
David A. Lilien, Nicholas M. Rathmann
Publikováno v:
Rathmann, N M & Lilien, D A 2022, ' Inferred basal friction and mass flux affected by crystal-orientation fabrics ', Journal of Glaciology, vol. 68, no. 268, pp. 236-252 . https://doi.org/10.1017/jog.2021.88
We investigate the errors caused by neglecting the crystal-orientation fabric when inferring the basal friction coefficient field, and whether such errors can be alleviated by inferring an isotropic enhancement factor field to compensate for missing
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::4fdb8335c4ef6cdf8a0d2ffee7867f54
https://doi.org/10.1017/jog.2021.88
https://doi.org/10.1017/jog.2021.88
Effect of an orientation-dependent non-linear grain fluidity on bulk directional enhancement factors
Autor:
David A. Lilien, Nicholas M. Rathmann, Aslak Grinsted, Dorthe Dahl-Jensen, Christine S. Hvidberg
Publikováno v:
Rathmann, N M, Hvidberg, C S, Grinsted, A, Lilien, D A & Dahl-Jensen, D 2021, ' Effect of an orientation-dependent non-linear grain fluidity on bulk directional enhancement factors ', Journal of Glaciology, vol. 67, no. 263, pp. 569-575 . https://doi.org/10.1017/jog.2020.117
Bulk directional enhancement factors are determined for axisymmetric (girdle and single-maximum) orientation fabrics using a transversely isotropic grain rheology with an orientation-dependent non-linear grain fluidity. Compared to grain fluidities t
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::e2dd38d285bfa4a0eb5ce73ef7b24ec9
https://doi.org/10.1017/jog.2020.117
https://doi.org/10.1017/jog.2020.117
Autor:
Nicholas M. Rathmann, David A. Lilien, Aslak Grinsted, Tamara A. Gerber, Tun Jan Young, Dorthe Dahl‐Jensen
Publikováno v:
Rathmann, N M, Lilien, D A, Grinsted, A, Gerber, T A, Young, T J & Dahl-Jensen, D 2022, ' On the Limitations of Using Polarimetric Radar Sounding to Infer the Crystal Orientation Fabric of Ice Masses ', Geophysical Research Letters, vol. 49, no. 1, ARTN e2021GL096244 . https://doi.org/10.1029/2021GL096244
Funding: The research leading to these results has received funding from the Villum Investigator grant no. 16572 as part of the IceFlow project. We introduce a transfer matrix model for radio-wave propagation through layered anisotropic ice that perm
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::1899cf98ac7aab16712058ddf9ff47d7
https://hdl.handle.net/10023/27406
https://hdl.handle.net/10023/27406
Publikováno v:
Lilien, D A, Rathmann, N M, Hvidberg, C S & Dahl-Jensen, D 2021, ' Modeling Ice-Crystal Fabric as a Proxy for Ice-Stream Stability ', Journal of Geophysical Research: Biogeosciences, vol. 126, no. 9, e2021JF006306 . https://doi.org/10.1029/2021JF006306
The crystal structure within an ice sheet evolves in response to deformation; hence ice-crystal fabric records ice-flow history. However, the complexity of crystal-fabric evolution, and the lack of model results with which to compare data, limit the
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::b19b877a8da4cfbf8f2a9df2a12d776a
https://curis.ku.dk/portal/da/publications/modeling-icecrystal-fabric-as-a-proxy-for-icestream-stability(f4ea2d49-b792-445b-b12e-7eac4bc3225c).html
https://curis.ku.dk/portal/da/publications/modeling-icecrystal-fabric-as-a-proxy-for-icestream-stability(f4ea2d49-b792-445b-b12e-7eac4bc3225c).html