scholarly journals Recent progress on combining geomorphological and geochronological data with ice sheet modelling, demonstrated using the last British–Irish Ice Sheet

2019 ◽  
Author(s):  
Jeremy C. Ely ◽  
Chris D. Clark ◽  
Richard C. A. Hindmarsh ◽  
Anna L. C. Hughes ◽  
Sarah L. Greenwood ◽  
...  
Keyword(s):  
Recent Progress ◽  
Ice Sheet ◽  
Geochronological Data ◽  
Ice Sheet Modelling

scholarly journals ATAT 1.1, the Automated Timing Accordance Tool for comparing ice-sheet model output with geochronological data

2019 ◽  
Vol 12 (3) ◽  
pp. 933-953 ◽  
Author(s):  
Jeremy C. Ely ◽  
Chris D. Clark ◽  
David Small ◽  
Richard C. A. Hindmarsh
Keyword(s):  
Goodness Of Fit ◽  
Expert Knowledge ◽  
Numerical Models ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Model Performance ◽  
Geochronological Data ◽  
Improve Model ◽  
Geochronological Evidence ◽  
Ice Sheet Modelling

Abstract. Earth's extant ice sheets are of great societal importance given their ongoing and potential future contributions to sea-level rise. Numerical models of ice sheets are designed to simulate ice-sheet behaviour in response to climate changes but to be improved require validation against observations. The direct observational record of extant ice sheets is limited to a few recent decades, but there is a large and growing body of geochronological evidence spanning millennia constraining the behaviour of palaeo-ice sheets. Hindcasts can be used to improve model formulations and study interactions between ice sheets, the climate system and landscape. However, ice-sheet modelling results have inherent quantitative errors stemming from parameter uncertainty and their internal dynamics, leading many modellers to perform ensemble simulations, while uncertainty in geochronological evidence necessitates expert interpretation. Quantitative tools are essential to examine which members of an ice-sheet model ensemble best fit the constraints provided by geochronological data. We present the Automated Timing Accordance Tool (ATAT version 1.1) used to quantify differences between model results and geochronological data on the timing of ice-sheet advance and/or retreat. To demonstrate its utility, we perform three simplified ice-sheet modelling experiments of the former British–Irish ice sheet. These illustrate how ATAT can be used to quantify model performance, either by using the discrete locations where the data originated together with dating constraints or by comparing model outputs with empirically derived reconstructions that have used these data along with wider expert knowledge. The ATAT code is made available and can be used by ice-sheet modellers to quantify the goodness of fit of hindcasts. ATAT may also be useful for highlighting data inconsistent with glaciological principles or reconstructions that cannot be replicated by an ice-sheet model.

scholarly journals ATAT 1.0, an Automated Timing Accordance Tool for comparing ice-sheet model output with geochronological data

2018 ◽  
Author(s):  
Jeremy C. Ely ◽  
Chris D. Clark ◽  
David Small ◽  
Richard C. A. Hindmarsh
Keyword(s):  
Goodness Of Fit ◽  
Expert Knowledge ◽  
Numerical Models ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Model Performance ◽  
Geochronological Data ◽  
Improve Model ◽  
Geochronological Evidence ◽  
Ice Sheet Modelling

Abstract. Earth's extant ice sheets are of great societal importance given their ongoing and potential future contributions to sea-level rise. Numerical models of ice sheets are designed to simulate ice sheet behaviour in response to climate changes, but to be improved require validation against observations. The direct observational record of extant ice sheets is limited to a few recent decades, but there is a large and growing body of geochronological evidence spanning millennia constraining the behaviour of palaeo-ice sheets. Hindcasts can be used to improve model formulations and study interactions between ice sheets, the climate system and landscape. However, ice-sheet modelling results have inherent quantitative errors stemming from parameter uncertainty and their internal dynamics, leading many modellers to perform ensemble simulations, while uncertainty in geochronological evidence necessitates expert interpretation. Quantitative tools are essential to examine which members of an ice-sheet model ensemble best fit the constraints provided by geochronological data. We present an Automated Timing Accordance Tool (ATAT version 1.0) used to quantify differences between model results and geo-data on the timing of ice sheet advance and/or retreat. To demonstrate its utility, we perform three simplified ice-sheet modelling experiments of the former British-Irish Ice Sheet. These illustrate how ATAT can be used to quantify model performance, either by using the discrete locations where the data originated together with dating constraints or by comparing model outputs with empirically-derived reconstructions that have used these data along with wider expert knowledge. The ATAT code is made available and can be used by ice-sheet modellers to quantify the goodness of fit of hindcasts. ATAT may also be useful for highlighting data inconsistent with glaciological principles or reconstructions that cannot be replicated by an ice sheet model.

scholarly journals Recent Progress in Greenland Ice Sheet Modelling

2017 ◽  
Vol 3 (4) ◽  
pp. 291-302 ◽  
Author(s):  
Heiko Goelzer ◽  
Alexander Robinson ◽  
Helene Seroussi ◽  
Roderik S.W. van de Wal
Keyword(s):  
Recent Progress ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Sheet Modelling

scholarly journals Drivers of abrupt Holocene shifts in West Antarctic ice stream direction determined from combined ice sheet modelling and geologic signatures

2014 ◽  
Vol 26 (6) ◽  
pp. 674-686 ◽  
Author(s):  
C.J. Fogwill ◽  
C.S.M. Turney ◽  
N.R. Golledge ◽  
D.H. Rood ◽  
K. Hippe ◽  
...  
Keyword(s):  
Flow Direction ◽  
Ice Sheet ◽  
Weddell Sea ◽  
Last Deglaciation ◽  
Ice Streams ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
Ice Stream ◽  
Ice Sheet Modelling

AbstractDetermining the millennial-scale behaviour of marine-based sectors of the West Antarctic Ice Sheet (WAIS) is critical to improve predictions of the future contribution of Antarctica to sea level rise. Here high-resolution ice sheet modelling was combined with new terrestrial geological constraints (in situ14C and 10Be analysis) to reconstruct the evolution of two major ice streams entering the Weddell Sea over 20 000 years. The results demonstrate how marked differences in ice flux at the marine margin of the expanded Antarctic ice sheet led to a major reorganization of ice streams in the Weddell Sea during the last deglaciation, resulting in the eastward migration of the Institute Ice Stream, triggering a significant regional change in ice sheet mass balance during the early to mid Holocene. The findings highlight how spatial variability in ice flow can cause marked changes in the pattern, flux and flow direction of ice streams on millennial timescales in this marine ice sheet setting. Given that this sector of the WAIS is assumed to be sensitive to ocean-forced instability and may be influenced by predicted twenty-first century ocean warming, our ability to model and predict abrupt and extensive ice stream diversions is key to a realistic assessment of future ice sheet sensitivity.

scholarly journals Pliocene Ice Sheet Modelling Intercomparison Project (PLISMIP) – experimental design

2012 ◽  
Vol 5 (4) ◽  
pp. 963-974 ◽  
Author(s):  
A. M. Dolan ◽  
S. J. Koenig ◽  
D. J. Hill ◽  
A. M. Haywood ◽  
R. M. DeConto
Keyword(s):  
Experimental Design ◽  
Sea Level ◽  
Atmospheric Carbon Dioxide ◽  
Climate Models ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Warm Period ◽  
Modern World ◽  
Intercomparison Project ◽  
Ice Sheet Modelling

Abstract. During the mid-Pliocene warm period (3.264 to 3.025 million years ago), global mean temperature was similar to that predicted for the next century and atmospheric carbon dioxide concentrations were slightly higher than today. Sea level was also higher than today, implying a reduction in the extent of the ice sheets. Thus, the mid-Pliocene warm period (mPWP) provides a unique testing ground to investigate the stability of the Earth's ice sheets and their contribution to sea level in a warmer-than-modern world. Climate models and ice sheet models can be used to enhance our understanding of ice sheet stability; however, uncertainties associated with different ice-sheet modelling frameworks mean that a rigorous comparison of numerical ice sheet model simulations for the Pliocene is essential. As an extension to the Pliocene Model Intercomparison Project (PlioMIP; Haywood et al., 2010, 2011a), the Pliocene Ice Sheet Modelling Intercomparison Project (PLISMIP) will provide the first assessment as to the ice sheet model dependency of ice sheet predictions for the mPWP. Here we outline the PLISMIP experimental design and initialisation conditions that have been adopted to simulate the Greenland and Antarctic ice sheets under present-day and warm mid-Pliocene conditions. Not only will this project provide a new benchmark in the simulation of ice sheets in a past warm period, but the analysis of model sensitivity to various uncertainties could directly inform future predictions of ice sheet and sea level change.

European Ice Sheet Modelling Initiative (EISMINT) model intercomparison experiments with first-order mechanics

2006 ◽  
Vol 111 (F2) ◽  
Author(s):  
Fuyuki Saito ◽  
Ayako Abe-Ouchi ◽  
Heinz Blatter
Keyword(s):  
Ice Sheet ◽  
Model Intercomparison ◽  
First Order ◽  
Ice Sheet Modelling

Shallow ice approximation, second order shallow ice approximation, and full Stokes models: A discussion of their roles in palaeo-ice sheet modelling and development

2016 ◽  
Vol 147 ◽  
pp. 136-147 ◽  
Author(s):  
N. Kirchner ◽  
J. Ahlkrona ◽  
E.J. Gowan ◽  
P. Lötstedt ◽  
J.M. Lea ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Second Order ◽  
Ice Sheet Modelling

scholarly journals Devising quality assurance procedures for assessment of legacy geochronological data relating to deglaciation of the last British-Irish Ice Sheet

2017 ◽  
Vol 164 ◽  
pp. 232-250 ◽  
Author(s):  
David Small ◽  
Chris D. Clark ◽  
Richard C. Chiverrell ◽  
Rachel K. Smedley ◽  
Mark D. Bateman ◽  
...  
Keyword(s):  
Quality Assurance ◽  
Ice Sheet ◽  
Geochronological Data

scholarly journals An ETKF approach for initial state and parameter estimation in ice sheet modelling

2014 ◽  
Vol 21 (2) ◽  
pp. 569-582 ◽  
Author(s):  
B. Bonan ◽  
M. Nodet ◽  
C. Ritz ◽  
V. Peyaud
Keyword(s):  
Parameter Estimation ◽  
Ensemble Kalman Filter ◽  
State Of The Art ◽  
Ice Sheet ◽  
Initial State ◽  
Ice Dynamics ◽  
State Data ◽  
Good Convergence ◽  
Model Equations ◽  
Ice Sheet Modelling

Abstract. Estimating the contribution of Antarctica and Greenland to sea-level rise is a hot topic in glaciology. Good estimates rely on our ability to run a precisely calibrated ice sheet evolution model starting from a reliable initial state. Data assimilation aims to provide an answer to this problem by combining the model equations with observations. In this paper we aim to study a state-of-the-art ensemble Kalman filter (ETKF) to address this problem. This method is implemented and validated in the twin experiments framework for a shallow ice flowline model of ice dynamics. The results are very encouraging, as they show a good convergence of the ETKF (with localisation and inflation), even for small-sized ensembles.

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