Initialization of a global glacier model based on present-day glacier geometry and past climate information: an ensemble approach

To provide estimates of past glacier mass changes over the course of the 20th century, an adequate initial state is required. However, empirical evidence about past glacier states at regional or global scales is largely incomplete, both spatially and temporally, calling for the use of automated nume...

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Published in:The Cryosphere
Main Authors: J. Eis, F. Maussion, B. Marzeion
Format: Article in Journal/Newspaper
Language:English
Published: Copernicus Publications 2019
Subjects:
geo
Online Access:https://doi.org/10.5194/tc-13-3317-2019
https://www.the-cryosphere.net/13/3317/2019/tc-13-3317-2019.pdf
https://doaj.org/article/ee901aaf71b14d4d8736065ab901796b
id fttriple:oai:gotriple.eu:oai:doaj.org/article:ee901aaf71b14d4d8736065ab901796b
record_format openpolar
spelling fttriple:oai:gotriple.eu:oai:doaj.org/article:ee901aaf71b14d4d8736065ab901796b 2023-05-15T18:32:20+02:00 Initialization of a global glacier model based on present-day glacier geometry and past climate information: an ensemble approach J. Eis F. Maussion B. Marzeion 2019-12-01 https://doi.org/10.5194/tc-13-3317-2019 https://www.the-cryosphere.net/13/3317/2019/tc-13-3317-2019.pdf https://doaj.org/article/ee901aaf71b14d4d8736065ab901796b en eng Copernicus Publications doi:10.5194/tc-13-3317-2019 1994-0416 1994-0424 https://www.the-cryosphere.net/13/3317/2019/tc-13-3317-2019.pdf https://doaj.org/article/ee901aaf71b14d4d8736065ab901796b undefined The Cryosphere, Vol 13, Pp 3317-3337 (2019) geo envir Journal Article https://vocabularies.coar-repositories.org/resource_types/c_6501/ 2019 fttriple https://doi.org/10.5194/tc-13-3317-2019 2023-01-22T17:53:11Z To provide estimates of past glacier mass changes over the course of the 20th century, an adequate initial state is required. However, empirical evidence about past glacier states at regional or global scales is largely incomplete, both spatially and temporally, calling for the use of automated numerical methods. This study presents a new way to initialize the Open Global Glacier Model from past climate information and present-day glacier states. We use synthetic experiments to show that even with these perfectly known but incomplete boundary conditions, the problem of model initialization is an ill-posed inverse problem leading to nonunique solutions, and we propose an ensemble approach as a way forward. The method works as follows: we generate a large set of physically plausible glacier candidates for a given year in the past (e.g., 1850 in the Alps), all of which are then modeled forward to the date of the observed glacier outline and evaluated by comparing the results of the forward runs to the present-day states. We test the approach on 2660 Alpine glaciers and determine error estimates of the method from the synthetic experiments. The results show that the solution is often nonunique, as many of the reconstructed initial states converge towards the observed state in the year of observation. We find that the median state of the best 5 % of all acceptable states is a reasonable best estimate. The accuracy of the method depends on the type of the considered observation for the evaluation (glacier length, area, or geometry). Trying to find past states from only present-day length instead of the full geometry leads to a sharp increase in uncertainty. Our study thus also provides quantitative information on how well the reconstructed initial glacier states are constrained through the limited information available to us. We analyze which glacier characteristics influence the reconstructability of a glacier, and we discuss ways to develop the method further for real-world applications. Article in Journal/Newspaper The Cryosphere Unknown The Cryosphere 13 12 3317 3335
institution Open Polar
collection Unknown
op_collection_id fttriple
language English
topic geo
envir
spellingShingle geo
envir
J. Eis
F. Maussion
B. Marzeion
Initialization of a global glacier model based on present-day glacier geometry and past climate information: an ensemble approach
topic_facet geo
envir
description To provide estimates of past glacier mass changes over the course of the 20th century, an adequate initial state is required. However, empirical evidence about past glacier states at regional or global scales is largely incomplete, both spatially and temporally, calling for the use of automated numerical methods. This study presents a new way to initialize the Open Global Glacier Model from past climate information and present-day glacier states. We use synthetic experiments to show that even with these perfectly known but incomplete boundary conditions, the problem of model initialization is an ill-posed inverse problem leading to nonunique solutions, and we propose an ensemble approach as a way forward. The method works as follows: we generate a large set of physically plausible glacier candidates for a given year in the past (e.g., 1850 in the Alps), all of which are then modeled forward to the date of the observed glacier outline and evaluated by comparing the results of the forward runs to the present-day states. We test the approach on 2660 Alpine glaciers and determine error estimates of the method from the synthetic experiments. The results show that the solution is often nonunique, as many of the reconstructed initial states converge towards the observed state in the year of observation. We find that the median state of the best 5 % of all acceptable states is a reasonable best estimate. The accuracy of the method depends on the type of the considered observation for the evaluation (glacier length, area, or geometry). Trying to find past states from only present-day length instead of the full geometry leads to a sharp increase in uncertainty. Our study thus also provides quantitative information on how well the reconstructed initial glacier states are constrained through the limited information available to us. We analyze which glacier characteristics influence the reconstructability of a glacier, and we discuss ways to develop the method further for real-world applications.
format Article in Journal/Newspaper
author J. Eis
F. Maussion
B. Marzeion
author_facet J. Eis
F. Maussion
B. Marzeion
author_sort J. Eis
title Initialization of a global glacier model based on present-day glacier geometry and past climate information: an ensemble approach
title_short Initialization of a global glacier model based on present-day glacier geometry and past climate information: an ensemble approach
title_full Initialization of a global glacier model based on present-day glacier geometry and past climate information: an ensemble approach
title_fullStr Initialization of a global glacier model based on present-day glacier geometry and past climate information: an ensemble approach
title_full_unstemmed Initialization of a global glacier model based on present-day glacier geometry and past climate information: an ensemble approach
title_sort initialization of a global glacier model based on present-day glacier geometry and past climate information: an ensemble approach
publisher Copernicus Publications
publishDate 2019
url https://doi.org/10.5194/tc-13-3317-2019
https://www.the-cryosphere.net/13/3317/2019/tc-13-3317-2019.pdf
https://doaj.org/article/ee901aaf71b14d4d8736065ab901796b
genre The Cryosphere
genre_facet The Cryosphere
op_source The Cryosphere, Vol 13, Pp 3317-3337 (2019)
op_relation doi:10.5194/tc-13-3317-2019
1994-0416
1994-0424
https://www.the-cryosphere.net/13/3317/2019/tc-13-3317-2019.pdf
https://doaj.org/article/ee901aaf71b14d4d8736065ab901796b
op_rights undefined
op_doi https://doi.org/10.5194/tc-13-3317-2019
container_title The Cryosphere
container_volume 13
container_issue 12
container_start_page 3317
op_container_end_page 3335
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