scholarly journals Deep learning speeds up ice flow modelling by several orders of magnitude

2021 ◽  
pp. 1-14
Author(s):  
Guillaume Jouvet ◽  
Guillaume Cordonnier ◽  
Byungsoo Kim ◽  
Martin Lüthi ◽  
Andreas Vieli ◽  
...  
Keyword(s):  
High Spatial Resolution ◽  
State Of The Art ◽  
Ice Sheets ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Flow Models ◽  
Mountain Glaciers ◽  
Central Processing ◽  
Model Component ◽  
User Friendly

Abstract This paper introduces the Instructed Glacier Model (IGM) – a model that simulates ice dynamics, mass balance and its coupling to predict the evolution of glaciers, icefields or ice sheets. The novelty of IGM is that it models the ice flow by a Convolutional Neural Network, which is trained from data generated with hybrid SIA + SSA or Stokes ice flow models. By doing so, the most computationally demanding model component is substituted by a cheap emulator. Once trained with representative data, we demonstrate that IGM permits to model mountain glaciers up to 1000 × faster than Stokes ones on Central Processing Units (CPU) with fidelity levels above 90% in terms of ice flow solutions leading to nearly identical transient thickness evolution. Switching to the GPU often permits additional significant speed-ups, especially when emulating Stokes dynamics or/and modelling at high spatial resolution. IGM is an open-source Python code which deals with two-dimensional (2-D) gridded input and output data. Together with a companion library of trained ice flow emulators, IGM permits user-friendly, highly efficient and mechanically state-of-the-art glacier and icefields simulations.

Self-consistency of the regolith hypothesis for the mid-Pleistocene Transition

2021 ◽  
Author(s):  
Matthew Drew ◽  
Lev Tarasov
Keyword(s):  
Sediment Transport ◽  
State Of The Art ◽  
Flow Line ◽  
Ice Sheets ◽  
Balance Model ◽  
Clear Understanding ◽  
Ice Dynamics ◽  
Ice Volume ◽  
Systems Model ◽  
Fully Coupled

<p>Is the regolith hypothesis consistent with the physics of glacial removal of mechanically weak surface material? </p><p> </p><p>The  mid-Pleistocene transition (MPT) from small 40 kyr glacial cycles to large, abruptly terminating 100 kyr ones represents a major climate system reorganization for which a clear understanding is lacking. A leading mechanism for this transition is a stabilization of ice sheets due to a shift to higher friction substrate. The Pleistocene saw the removal of deformable regolith -- laying bare hard higher-friction bedrock that would help preserve regional ice during warm interstadials. This is the regolith hypothesis. </p><p> </p><p>The removal of regolith by Pleistocene ice sheets remains poorly constrained. To date, only models with a forced change in area of regolith cover or 1D flow line models with simplistic sediment transport have been used to probe the role of regolith in the MPT. It is therefore unclear if the appropriate amount of regolith removal can occur within the time-frame of the MPT.</p><p> </p><p>To properly test the hypothesis, at least three components are required: capable model, observational constraint, and a probe of uncertainties. A capable model must explicitly represent relevant processes in a fully coupled self-consistent manner. We have therefore configured a state of the art 3D glacial systems model (GSM). The GSM incorporates a state-of-the-art fully coupled sediment production/transport model, subglacial hydrology, visco-elastic glacial isostatic adjustment, 3D thermomechanically coupled hybrid shallow ice/shallow shelf ice dynamics, and internal climate solution from an energy balance model. The model generates sediment by quarrying and abrasion, and both subglacial and englacial sediment transport. The subglacial hydrology model employs a linked-cavity system with a flux based switch to tunnel drainage, giving dynamic effective pressure needed for realistic sediment and sliding processes. The coupled model is driven only by prescribed atmospheric CO2 and orbitally derived insolation.</p><p> </p><p>The required observational constraints include present-day regolith distribution and inferred Pleistocene ice volume from proxy records.</p><p> </p><p>The final component is  a large ensemble of full Pleistocene simulations that probe both initial regolith distribution uncertainties and model parametric uncertainties. We present the results of such an ensemble, examining both rates of computed regolith removal and changes in ice volume cycling across the MPT interval.</p>

Antarctic blue ice areas - towards extracting palaeoclimate information

2010 ◽  
Vol 22 (2) ◽  
pp. 99-115 ◽  
Author(s):  
Anna Sinisalo ◽  
John C. Moore
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Thermal Transition ◽  
Gas Composition ◽  
Accumulation Rates ◽  
Ice Flow ◽  
Flow Models ◽  
Flow Modelling ◽  
Substantial Progress ◽  
The Last Glacial

AbstractWe review the current scientific knowledge about Antarctic Blue Ice Areas (BIAs) with emphasis on their application for palaeoclimate studies. Substantial progress has been made since the review by Bintanja (1999), in particular dating the archive of ancient ice found on the surface of BIAs has progressed with advances in 14C measurements, tephrachronology, and geomorphological evidence giving better constraints to more sophisticated ice flow models. Flow modelling also provides information about past changes in ice flow velocities, accumulation rates and ice sheet elevation. The availability of gas composition in vertical cores from BIAs allows matching to well-dated global records of greenhouse gas variability over the last glacial-interglacial cycle and longer. It is clear from the limited number of studies to date that BIAs from different regions have quite different histories of formation and preservation, and that they are intimately linked to the response of their surrounding ice sheets to climate variability on glacial-interglacial time-scales. Looking to the future, climate records from BIAs are expected to provide information on variations in Southern Ocean processes as well as ice sheet evolution within the East Antarctic ice sheet at the thermal transition from cold based to warm based ice.

scholarly journals Glaciological advances made with interferometric synthetic aperture radar

2010 ◽  
Vol 56 (200) ◽  
pp. 1026-1042 ◽  
Author(s):  
Ian Joughin ◽  
Ben E. Smith ◽  
Waleed Abdalati
Keyword(s):  
Synthetic Aperture Radar ◽  
Flow Velocity ◽  
Synthetic Aperture ◽  
Interferometric Synthetic Aperture Radar ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Outlet Glacier ◽  
Mountain Glaciers ◽  
Ice Stream ◽  
Aperture Radar

AbstractSpaceborne interferometric synthetic aperture radar (InSAR) techniques for measuring ice flow velocity and topography have developed rapidly over the last decade and a half, revolutionizing the study of ice dynamics. Spaceborne interferometry has contributed to major progress in many areas of glaciological study by: providing the first comprehensive measurements of ice-stream flow velocity over the major outlets of Greenland and Antarctica; revealing that ice-stream and outlet-glacier flow can change rapidly (months to years); improving understanding of several ice-sheet and ice-shelf processes; providing velocity for flux-gate based mass-balance assessment; mapping flow of mountain glaciers; and capturing the geomorphic traces of past ice flow. We review the basic technique development, the measurement characteristics, and the extensive set of results yielded by these measurements.

scholarly journals Modelling water flow under glaciers and ice sheets

2015 ◽  
Vol 471 (2176) ◽  
pp. 20140907 ◽  
Author(s):  
Gwenn E. Flowers
Keyword(s):  
Rapid Development ◽  
Ice Sheets ◽  
Coupled System ◽  
Ice Streams ◽  
Widespread Application ◽  
Ice Flow ◽  
Strict Adherence ◽  
Mountain Glaciers ◽  
Subglacial Environment ◽  
Subglacial Drainage

Recent observations of dynamic water systems beneath the Greenland and Antarctic ice sheets have sparked renewed interest in modelling subglacial drainage. The foundations of today's models were laid decades ago, inspired by measurements from mountain glaciers, discovery of the modern ice streams and the study of landscapes evacuated by former ice sheets. Models have progressed from strict adherence to the principles of groundwater flow, to the incorporation of flow ‘elements’ specific to the subglacial environment, to sophisticated two-dimensional representations of interacting distributed and channelized drainage. Although presently in a state of rapid development, subglacial drainage models, when coupled to models of ice flow, are now able to reproduce many of the canonical phenomena that characterize this coupled system. Model calibration remains generally out of reach, whereas widespread application of these models to large problems and real geometries awaits the next level of development.

scholarly journals Comparison of adjoint and nudging methods to initialise ice sheet model basal conditions

2016 ◽  
Vol 9 (7) ◽  
pp. 2549-2562 ◽  
Author(s):  
Cyrille Mosbeux ◽  
Fabien Gillet-Chaulet ◽  
Olivier Gagliardini
Keyword(s):  
Sea Level ◽  
21St Century ◽  
Initial Conditions ◽  
Ice Sheets ◽  
Transient Effects ◽  
Flux Divergence ◽  
Short Term ◽  
Ice Flow ◽  
Flow Models ◽  
Model Response

Abstract. Ice flow models are now routinely used to forecast the ice sheets' contribution to 21st century sea-level rise. For such short term simulations, the model response is greatly affected by the initial conditions. Data assimilation algorithms have been developed to invert for the friction of the ice on its bedrock using observed surface velocities. A drawback of these methods is that remaining uncertainties, especially in the bedrock elevation, lead to non-physical ice flux divergence anomalies resulting in undesirable transient effects. In this study, we compare two different assimilation algorithms based on adjoints and nudging to constrain both bedrock friction and elevation. Using synthetic twin experiments with realistic observation errors, we show that the two algorithms lead to similar performances in reconstructing both variables and allow the flux divergence anomalies to be significantly reduced.

scholarly journals Towards a better ice sheet model initialisation and basal knowledge using data assimilation

2016 ◽  
Author(s):  
Cyrille Mosbeux ◽  
Fabien Gillet-Chaulet ◽  
Olivier Gagliardini
Keyword(s):  
Data Assimilation ◽  
Initial Conditions ◽  
Ice Sheets ◽  
Transient Effects ◽  
Flux Divergence ◽  
Short Term ◽  
Ice Flow ◽  
Flow Models ◽  
Model Response ◽  
Using Data

Abstract. Ice flow models are now routinely used to forecast the ice-sheets contribution to 21st century sea-level rise. For such short term simulations, the model response is greatly affected by the initial conditions. Data assimilation algorithms have been developed to invert for the friction of the ice on its bedrock using observed surface velocities. A drawback of these methods is that remaining uncertainties, especially in the bedrock elevation, lead to non-physical ice flux divergence anomalies resulting in undesirable transient effects. In this study, we compare two different assimilation algorithms based on adjoints and nudging to constrain both bedrock friction and elevation. Using synthetic twin experiments with realistic observation errors, we show that the two algorithms lead to similar performances in reconstructing both variables and allow the flux divergence anomalies to be significantly reduced.

scholarly journals Sampo-UI: A full stack JavaScript framework for developing semantic portal user interfaces

Semantic Web ◽  
2021 ◽  
pp. 1-16
Author(s):  
Esko Ikkala ◽  
Eero Hyvönen ◽  
Heikki Rantala ◽  
Mikko Koho
Keyword(s):  
User Interfaces ◽  
Linked Data ◽  
State Of The Art ◽  
Software Framework ◽  
End User ◽  
Faceted Search ◽  
Software Developer ◽  
Current State ◽  
Knowledge Graphs ◽  
User Friendly

This paper presents a new software framework, Sampo-UI, for developing user interfaces for semantic portals. The goal is to provide the end-user with multiple application perspectives to Linked Data knowledge graphs, and a two-step usage cycle based on faceted search combined with ready-to-use tooling for data analysis. For the software developer, the Sampo-UI framework makes it possible to create highly customizable, user-friendly, and responsive user interfaces using current state-of-the-art JavaScript libraries and data from SPARQL endpoints, while saving substantial coding effort. Sampo-UI is published on GitHub under the open MIT License and has been utilized in several internal and external projects. The framework has been used thus far in creating six published and five forth-coming portals, mostly related to the Cultural Heritage domain, that have had tens of thousands of end-users on the Web.

Basal processes beneath an Arctic glacier and their geomorphic imprint after a surge, Elisebreen, Svalbard

2005 ◽  
Vol 64 (2) ◽  
pp. 125-137 ◽  
Author(s):  
Poul Christoffersen ◽  
Jan A. Piotrowski ◽  
Nicolaj K. Larsen
Keyword(s):  
Flow Instability ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Water System ◽  
Water Drainage ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Glacier Ice ◽  
Water Saturated ◽  
Arctic Glacier

AbstractThe foreground of Elisebreen, a retreating valley glacier in West Svalbard, exhibits a well-preserved assemblage of subglacial landforms including ice-flow parallel ridges (flutings), ice-flow oblique ridges (crevasse-fill features), and meandering ridges (infill of basal meltwater conduits). Other landforms are thrust-block moraine, hummocky terrain, and drumlinoid hills. We argue in agreement with geomorphological models that this landform assemblage was generated by ice-flow instability, possibly a surge, which took place in the past when the ice was thicker and the bed warmer. The surge likely occurred due to elevated pore-water pressure in a thin layer of thawed and water-saturated till that separated glacier ice from a frozen substratum. Termination may have been caused by a combination of water drainage and loss of lubricating sediment. Sedimentological investigations indicate that key landforms may be formed by weak till oozing into basal cavities and crevasses, opening in response to accelerated ice flow, and into water conduits abandoned during rearrangement of the basal water system. Today, Elisebreen may no longer have surge potential due to its diminished size. The ability to identify ice-flow instability from geomorphological criteria is important in deglaciated terrain as well as in regions where ice dynamics are adapting to climate change.

scholarly journals On the effect of short-term climate variability on mountain glaciers: insights from a case study

2013 ◽  
Vol 59 (217) ◽  
pp. 992-1006 ◽  
Author(s):  
Daniel Farinotti
Keyword(s):  
Climatic Variability ◽  
Swiss Alps ◽  
Ice Dynamics ◽  
Mountain Glaciers ◽  
Temperature And Precipitation ◽  
Glacier Ice ◽  
Long Term Trends ◽  
Model Set ◽  
Set Up

AbstractStudies addressing the response of glaciers to climate change have so far analyzed the effect of long-term trends in a particular set of meteorological variables only, implicitly assuming an unaltered climatic variability. Here a framework for distinguishing between year-to-year, month-to-month and day-to-day variability is proposed. Synthetically generated temperature and precipitation time series following the same long-term trend but with altered variability are then used to force an ice-dynamics model set up for Rhonegletscher, Swiss Alps. In the case of temperature, variations in the day-to-day variability are shown to have a larger effect than changes at the yearly scale, while in the case of precipitation, variability changes are assessed as having negligible impact. A first set of scenarios is used to show that compared to reference, doubling the temperature variability can reduce glacier ice volume by up to 64% within half a decade. A second set derived from the results of the European ENSEMBLES project, however, shows that such changes are expected to remain below 8% even for extreme scenarios. Although the latter results relativize the importance of the effect in the near future, the analyses indicate that at least caution is required when assuming ‘unchanged variability’.

scholarly journals A system of conservative regridding for ice–atmosphere coupling in a General Circulation Model (GCM)

2014 ◽  
Vol 7 (3) ◽  
pp. 883-907 ◽  
Author(s):  
R. Fischer ◽  
S. Nowicki ◽  
M. Kelley ◽  
G. A. Schmidt
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Circulation Model ◽  
Grid Cell ◽  
Surface Model ◽  
Ice Flow ◽  
Surface Mass ◽  
Flow Models ◽  
Ice Surface ◽  
Ice Model

Abstract. The method of elevation classes, in which the ice surface model is run at multiple elevations within each grid cell, has proven to be a useful way for a low-resolution atmosphere inside a general circulation model (GCM) to produce high-resolution downscaled surface mass balance fields for use in one-way studies coupling atmospheres and ice flow models. Past uses of elevation classes have failed to conserve mass and energy because the transformation used to regrid to the atmosphere was inconsistent with the transformation used to downscale to the ice model. This would cause problems for two-way coupling. A strategy that resolves this conservation issue has been designed and is presented here. The approach identifies three grids between which data must be regridded and five transformations between those grids required by a typical coupled atmosphere–ice flow model. This paper develops a theoretical framework for the problem and shows how each of these transformations may be achieved in a consistent, conservative manner. These transformations are implemented in Glint2, a library used to couple atmosphere models with ice models. Source code and documentation are available for download. Confounding real-world issues are discussed, including the use of projections for ice modeling, how to handle dynamically changing ice geometry, and modifications required for finite element ice models.

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