Catherine Ritz

Centre National de la Recherche Scientifique

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Frédéric Parrenin

Institut des Géosciences de l'Environnement

G. Durand

Université Grenoble Alpes

S. Charbit

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

Christophe Dumas

Laboratoire des Sciences du Climat et de l'Environnement

Valérie Masson‐Delmotte

CEA Paris-Saclay

Robert Mulvaney

British Antarctic Survey

Olivier Gagliardini

Centre National de la Recherche Scientifique

V. Lipenkov

Arctic and Antarctic Research Institute

Dominique Raynaud

Université Grenoble Alpes

Masa Kageyama

Centre National de la Recherche Scientifique

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Centre National de la Recherche Scientifique

201

Laboratoire des Sciences du Climat et de l'Environnement

University of Copenhagen

Laboratoire de Glaciologie et Géophysique de l’Environnement

Université Grenoble Alpes

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung

CEA Paris-Saclay

British Antarctic Survey

Institut de Recherche pour le Développement

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Methane measured on ice core NGRIP on AICC2012 chronology

Lucie Bazin Amaëlle Landais B. Lemieux-Dudon Habib Toye Daniel Vereș

Chronology

Ice core

10.1594/pangaea.824885

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Citations (0)

Data assimilation in glaciology

Oxford University Press eBooks (2014)

Bertrand Bonan Maëlle Nodet Olivier Ozenda Catherine Ritz

Abstract This chapter addresses an inverse problem in glaciology, namely how to infer a climatic scenario (i.e. how to reconstruct past polar temperature) from ice volume records. Ice volume observations are available from oceanic records, giving information about sea level, and therefore about the amount of water stored in ice sheets, ice caps, and glaciers. The link between the climatic scenario and the ice sheet volume is complex. The temperature affects the ice mass budget (accumulating minus melting ice). Then, the ice mass budget is a key factor in ice dynamics, which is quite complex in itself (non-Newtonian fluid and nonlinear rheology). The few previous studies of this subject have used fairly simple inverse methods. The idea of the approach described in this chapter is to explore, with idealized twin experiments, the ability of the adjoint method to solve the inverse problem of reconstructing past temperature given all available observations.

Glaciology

10.1093/acprof:oso/9780198723844.003.0025

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Citations (1)

Coupling an AGCM with an ISM to investigate the ice sheets mass balance at the Last Glacial Maximum

Geophysical Research Letters (1998)

Adeline Fabre Gilles Ramstein Catherine Ritz Sophie Pinot Nicolas Fournier

The aim of this paper is to investigate the consistency between the ice sheets reconstruction at the LGM and the climate simulated by AGCM. In particular, to investigate whether the laurentian and the fennoscandian ice sheets have an equilibrated mass balance, we use two complementary approaches. First we analyze the changes of snow and water budgets over the ice sheets, only using the model results of LGM runs. Second, we use a thermomechanical ice sheet model [ Ritz et al. , 1997] forced with the AGCM simulated climate, to perform long term runs at finer spatial resolution. Analyzing the results obtained with both approaches, we show that the ice sheet mass balance computed directly from AGCM results may be biaised. Moreover we show, using two versions of the LMD AGCM, that the ice sheet mass balance computed by the ISM is drastically sensitive to the summer surface temperatures simulated by the AGCM.

Glacier mass balance

Ice-sheet model

Greenland ice sheet

Last Glacial Maximum

10.1029/98gl00133

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Citations (18)

Modelling of Last Glacial Maximum ice sheets using different accumulation parameterizations

Annals of Glaciology (1997)

Adeline Fabre Catherine Ritz Gilles Ramstein

We use a three-dimensional thermomechanical ice-sheet model, previously tested on the Greenland ice sheet, to reconstruct Last Glacial Maximum (LGM) ice sheets. We compare the effects on the results of the ice-sheet model of three different accumulation parameterization schemes. In the first and second schemes, LGM precipitation is computed from the present precipitation, taking and not taking into account moisture transport. In the third scheme, LGM precipitation and surface temperatures are computed using outputs of an atmospheric global circulation model (AGCM), treated in anomaly mode. Results are compared to the last reconstruction of the Northern Hemisphere ice sheets (Peltier, 1994), computed using global rebound rates in a visco-elastic model of the Earth’s crust. The first two accumulation parameterizations do not give satisfactory reconstructions of the LGM ice sheets, since they are unable to compute realistic LGM climatic conditions. The third method gives very satisfactory results, which leads us to conclude that the best way to obtain realistic LGM climatic conditions is to use AGCM outputs.

Last Glacial Maximum

Ice-sheet model

Greenland ice sheet

10.3189/s0260305500012210

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Effect of uncertainty in surface mass balance–elevation feedback on projections of the future sea level contribution of the Greenland ice sheet

The cryosphere (2014)

Tamsin Edwards Xavier Fettweis Olivier Gagliardini Fabien Gillet‐Chaulet Heiko Goelzer

Abstract. We apply a new parameterisation of the Greenland ice sheet (GrIS) feedback between surface mass balance (SMB: the sum of surface accumulation and surface ablation) and surface elevation in the MAR regional climate model (Edwards et al., 2014) to projections of future climate change using five ice sheet models (ISMs). The MAR (Modèle Atmosphérique Régional: Fettweis, 2007) climate projections are for 2000–2199, forced by the ECHAM5 and HadCM3 global climate models (GCMs) under the SRES A1B emissions scenario. The additional sea level contribution due to the SMB–elevation feedback averaged over five ISM projections for ECHAM5 and three for HadCM3 is 4.3% (best estimate; 95% credibility interval 1.8–6.9%) at 2100, and 9.6% (best estimate; 95% credibility interval 3.6–16.0%) at 2200. In all results the elevation feedback is significantly positive, amplifying the GrIS sea level contribution relative to the MAR projections in which the ice sheet topography is fixed: the lower bounds of our 95% credibility intervals (CIs) for sea level contributions are larger than the "no feedback" case for all ISMs and GCMs. Our method is novel in sea level projections because we propagate three types of modelling uncertainty – GCM and ISM structural uncertainties, and elevation feedback parameterisation uncertainty – along the causal chain, from SRES scenario to sea level, within a coherent experimental design and statistical framework. The relative contributions to uncertainty depend on the timescale of interest. At 2100, the GCM uncertainty is largest, but by 2200 both the ISM and parameterisation uncertainties are larger. We also perform a perturbed parameter ensemble with one ISM to estimate the shape of the projected sea level probability distribution; our results indicate that the probability density is slightly skewed towards higher sea level contributions.

HadCM3

Elevation (ballistics)

Greenland ice sheet

Ice-sheet model

10.5194/tc-8-195-2014

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Citations (102)

Ice-sheet mass balance and climate change

Nature (2013)

Edward Hanna Francisco Navarro Frank Pattyn Catia M. Domingues Xavier Fettweis

Future sea level

Iceberg

Greenland ice sheet

Peninsula

Antarctic ice sheet

10.1038/nature12238

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Citations (297)

Sensitivity of a Greenland ice sheet model to atmospheric forcing fields

The cryosphere (2012)

Aurélien Quiquet Heinz Jürgen Punge Catherine Ritz Xavier Fettweis Hubert Gallée

Abstract. Predicting the climate for the future and how it will impact ice sheet evolution requires coupling ice sheet models with climate models. However, before we attempt to develop a realistic coupled setup, we propose, in this study, to first analyse the impact of a model simulated climate on an ice sheet. We undertake this exercise for a set of regional and global climate models. Modelled near surface air temperature and precipitation are provided as upper boundary conditions to the GRISLI (GRenoble Ice Shelf and Land Ice model) hybrid ice sheet model (ISM) in its Greenland configuration. After 20 kyrs of simulation, the resulting ice sheets highlight the differences between the climate models. While modelled ice sheet sizes are generally comparable to the observed one, there are considerable deviations among the ice sheets on regional scales. These deviations can be explained by biases in temperature and precipitation near the coast. This is especially true in the case of global models. But the deviations between the climate models are also due to the differences in the atmospheric general circulation. To account for these differences in the context of coupling ice sheet models with climate models, we conclude that appropriate downscaling methods will be needed. In some cases, systematic corrections of the climatic variables at the interface may be required to obtain realistic results for the Greenland ice sheet (GIS).

Ice-sheet model

Greenland ice sheet

Forcing (mathematics)

Future sea level

10.5194/tc-6-999-2012

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Citations (41)

Accumulation patterns around Dome C, East Antarctica, in the last 73 kyr

The cryosphere (2018)

Marie G. P. Cavitte Frédéric Parrenin Catherine Ritz D. A. Young Brice Van Liefferinge

Abstract. We reconstruct the pattern of surface accumulation in the region around Dome C, East Antarctica, since the last glacial. We use a set of 18 isochrones spanning all observable depths of the ice column, interpreted from various ice-penetrating radar surveys and a 1-D ice flow model to invert for accumulation rates in the region. The shallowest four isochrones are then used to calculate paleoaccumulation rates between isochrone pairs using a 1-D assumption where horizontal advection is negligible in the time interval of each layer. We observe that the large-scale (100s km) surface accumulation gradient is spatially stable through the last 73 kyr, which reflects current modeled and observed precipitation gradients in the region. We also observe small-scale (10 s km) accumulation variations linked to snow redistribution at the surface, due to changes in its slope and curvature in the prevailing wind direction that remain spatially stationary since the last glacial.

Dome (geology)

10.5194/tc-12-1401-2018

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Citations (38)

Inverse Modeling of the Greenland Ice Sheet Flow Dynamics: from Local Sensitivity to Large-Scale Model Initialisation

HAL (Le Centre pour la Communication Scientifique Directe) (2013)

Fabien Gillet‐Chaulet Olivier Gagliardini Jérôme Monnier Nathan Martin Catherine Ritz

Over the last two decades, the Greenland Ice Sheet has been losing mass at an increasing rate, with an important contribution coming from acceleration and thinning of numerous outlet glaciers. Representing these changes in flow models is a challenge requiring the development of (i) grid refinement strategies to capture individually the narrow outlet glaciers, (ii) efficient numerical schemes to solve the appropriate flow equations and (iii) inverse methods to constrain poorly known parameters. Here, we will present details and applications of these recent developments from local sensitivity analysis to large-scale model initialisation

Greenland ice sheet

Future sea level

Ice-sheet model

Source

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Citations (0)

Where to find 1.5 million yr old ice for the IPICS "Oldest Ice" ice core

Hubertus Fischer Jeffrey P. Severinghaus Edward J. Brook E. W. Wolff M. R. Albert

Abstract. The recovery of a 1.5 Myr long ice core from Antarctica represents a keystone to our understanding of Quaternary climate, the progression of glaciation over this time period and the role of greenhouse gas cycles in this progression. Here we show that such old ice is most likely to exist in the plateau area of the East Antarctic Ice Sheet (EAIS) without stratigraphic disturbance and should be able to be recovered after careful pre-site selection studies. Based on a simple ice and heat flow model and glaciological observations, we conclude that positions in the vicinity of major domes and saddle positions on the East Antarctic Plateau will most likely have such old ice in store and represent the best study areas for dedicated reconnaissance studies in the near future. In contrast to previous ice core drill site selections, we strongly argue for significantly reduced ice thickness to avoid bottom melting, while at the same time maximizing the resolution and the distance of such old ice to the bedrock. For example for the geothermal heat flux and accumulation conditions at Dome C, an ice thickness lower than 2500 m would be required to find 1.5 Myr old ice. However, the final choice is strongly dependent on the local geothermal heat flux, which is largely unknown for the EAIS and has to be determined beforehand. In addition, the detailed bedrock topography and ice flow history for candidates of an Oldest Ice ice coring site has to be reconstructed. Finally, we argue strongly for rapid access drilling before any full deep ice coring activity commences to bring datable samples to the surface and to allow an age check of the oldest ice.

Ice divide

Ice-albedo feedback

Iceberg

Ice core

Ice-sheet model

Lead (geology)

Antarctic ice sheet

Dome (geology)

10.5194/cpd-9-2771-2013

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Citations (6)