Assimilation of surface observations in a transient marine ice sheet model using an ensemble Kalman filter

Marine-based sectors of the Antarctic Ice Sheet are increasingly contributing to sea level rise. The basal conditions exert an important control on the ice dynamics and can be propitious to instabilities in the grounding line position. Because the force balance is non-inertial, most ice flow models...

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Published in:The Cryosphere
Main Author: Gillet-Chaulet, Fabien
Format: Article in Journal/Newspaper
Language:English
Published: Copernicus Publications 2020
Subjects:
Online Access:https://doi.org/10.5194/tc-14-811-2020
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spelling ftnonlinearchiv:oai:noa.gwlb.de:cop_mods_00050863 2023-05-15T13:54:46+02:00 Assimilation of surface observations in a transient marine ice sheet model using an ensemble Kalman filter Gillet-Chaulet, Fabien 2020-03 electronic https://doi.org/10.5194/tc-14-811-2020 https://noa.gwlb.de/receive/cop_mods_00050863 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00050520/tc-14-811-2020.pdf https://tc.copernicus.org/articles/14/811/2020/tc-14-811-2020.pdf eng eng Copernicus Publications The Cryosphere -- ˜Theœ Cryosphere -- http://www.bibliothek.uni-regensburg.de/ezeit/?2393169 -- http://www.the-cryosphere.net/ -- 1994-0424 https://doi.org/10.5194/tc-14-811-2020 https://noa.gwlb.de/receive/cop_mods_00050863 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00050520/tc-14-811-2020.pdf https://tc.copernicus.org/articles/14/811/2020/tc-14-811-2020.pdf https://creativecommons.org/licenses/by/4.0/ uneingeschränkt info:eu-repo/semantics/openAccess CC-BY article Verlagsveröffentlichung article Text doc-type:article 2020 ftnonlinearchiv https://doi.org/10.5194/tc-14-811-2020 2022-02-08T22:36:40Z Marine-based sectors of the Antarctic Ice Sheet are increasingly contributing to sea level rise. The basal conditions exert an important control on the ice dynamics and can be propitious to instabilities in the grounding line position. Because the force balance is non-inertial, most ice flow models are now equipped with time-independent inverse methods to constrain the basal conditions from observed surface velocities. However, transient simulations starting from this initial state usually suffer from inconsistencies and are not able to reproduce observed trends. Here, using a synthetic flow line experiment, we assess the performance of an ensemble Kalman filter for the assimilation of transient observations of surface elevation and velocities in a marine ice sheet model. The model solves the shallow shelf equation for the force balance and the continuity equation for ice thickness evolution. The position of the grounding line is determined by the floatation criterion. The filter analysis estimates both the state of the model, represented by the surface elevation, and the basal conditions, with the simultaneous inversion of the basal friction and topography. The idealised experiment reproduces a marine ice sheet that is in the early stage of an unstable retreat. Using observation frequencies and uncertainties consistent with current observing systems, we find that the filter allows the accurate recovery of both the basal friction and topography after few assimilation cycles with relatively small ensemble sizes. In addition it is found that assimilating the surface observations has a positive impact on constraining the evolution of the grounding line during the assimilation window. Using the initialised state to perform century-scale forecast simulations, we show that grounding line retreat rates are in agreement with the reference; however remaining uncertainties in the basal conditions may lead to significant delays in the initiation of the unstable retreat. These results are encouraging for the application to real glacial systems. Article in Journal/Newspaper Antarc* Antarctic Ice Sheet The Cryosphere Niedersächsisches Online-Archiv NOA Antarctic The Antarctic The Cryosphere 14 3 811 832
institution Open Polar
collection Niedersächsisches Online-Archiv NOA
op_collection_id ftnonlinearchiv
language English
topic article
Verlagsveröffentlichung
spellingShingle article
Verlagsveröffentlichung
Gillet-Chaulet, Fabien
Assimilation of surface observations in a transient marine ice sheet model using an ensemble Kalman filter
topic_facet article
Verlagsveröffentlichung
description Marine-based sectors of the Antarctic Ice Sheet are increasingly contributing to sea level rise. The basal conditions exert an important control on the ice dynamics and can be propitious to instabilities in the grounding line position. Because the force balance is non-inertial, most ice flow models are now equipped with time-independent inverse methods to constrain the basal conditions from observed surface velocities. However, transient simulations starting from this initial state usually suffer from inconsistencies and are not able to reproduce observed trends. Here, using a synthetic flow line experiment, we assess the performance of an ensemble Kalman filter for the assimilation of transient observations of surface elevation and velocities in a marine ice sheet model. The model solves the shallow shelf equation for the force balance and the continuity equation for ice thickness evolution. The position of the grounding line is determined by the floatation criterion. The filter analysis estimates both the state of the model, represented by the surface elevation, and the basal conditions, with the simultaneous inversion of the basal friction and topography. The idealised experiment reproduces a marine ice sheet that is in the early stage of an unstable retreat. Using observation frequencies and uncertainties consistent with current observing systems, we find that the filter allows the accurate recovery of both the basal friction and topography after few assimilation cycles with relatively small ensemble sizes. In addition it is found that assimilating the surface observations has a positive impact on constraining the evolution of the grounding line during the assimilation window. Using the initialised state to perform century-scale forecast simulations, we show that grounding line retreat rates are in agreement with the reference; however remaining uncertainties in the basal conditions may lead to significant delays in the initiation of the unstable retreat. These results are encouraging for the application to real glacial systems.
format Article in Journal/Newspaper
author Gillet-Chaulet, Fabien
author_facet Gillet-Chaulet, Fabien
author_sort Gillet-Chaulet, Fabien
title Assimilation of surface observations in a transient marine ice sheet model using an ensemble Kalman filter
title_short Assimilation of surface observations in a transient marine ice sheet model using an ensemble Kalman filter
title_full Assimilation of surface observations in a transient marine ice sheet model using an ensemble Kalman filter
title_fullStr Assimilation of surface observations in a transient marine ice sheet model using an ensemble Kalman filter
title_full_unstemmed Assimilation of surface observations in a transient marine ice sheet model using an ensemble Kalman filter
title_sort assimilation of surface observations in a transient marine ice sheet model using an ensemble kalman filter
publisher Copernicus Publications
publishDate 2020
url https://doi.org/10.5194/tc-14-811-2020
https://noa.gwlb.de/receive/cop_mods_00050863
https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00050520/tc-14-811-2020.pdf
https://tc.copernicus.org/articles/14/811/2020/tc-14-811-2020.pdf
geographic Antarctic
The Antarctic
geographic_facet Antarctic
The Antarctic
genre Antarc*
Antarctic
Ice Sheet
The Cryosphere
genre_facet Antarc*
Antarctic
Ice Sheet
The Cryosphere
op_relation The Cryosphere -- ˜Theœ Cryosphere -- http://www.bibliothek.uni-regensburg.de/ezeit/?2393169 -- http://www.the-cryosphere.net/ -- 1994-0424
https://doi.org/10.5194/tc-14-811-2020
https://noa.gwlb.de/receive/cop_mods_00050863
https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00050520/tc-14-811-2020.pdf
https://tc.copernicus.org/articles/14/811/2020/tc-14-811-2020.pdf
op_rights https://creativecommons.org/licenses/by/4.0/
uneingeschränkt
info:eu-repo/semantics/openAccess
op_rightsnorm CC-BY
op_doi https://doi.org/10.5194/tc-14-811-2020
container_title The Cryosphere
container_volume 14
container_issue 3
container_start_page 811
op_container_end_page 832
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