S. Charbit

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

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Christophe Dumas

Laboratoire des Sciences du Climat et de l'Environnement

Masa Kageyama

Centre National de la Recherche Scientifique

Catherine Ritz

Centre National de la Recherche Scientifique

Gilles Ramstein

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

Aurélien Quiquet

Laboratoire des Sciences du Climat et de l'Environnement

Didier M. Roche

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

Th. Stolarczyk

Institut de Recherche sur les Lois Fondamentales de l'Univers

T. Kirsten

Max Planck Institute for Nuclear Physics

R.W. Stoenner

Brookhaven National Laboratory

C. Bacci

Roma Tre University

Cooperative Institutions

Centre National de la Recherche Scientifique

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

CEA Paris-Saclay

Laboratoire des Sciences du Climat et de l'Environnement

Université de Versailles Saint-Quentin-en-Yvelines

Université Paris-Saclay

FZI Research Center for Information Technology

Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Gran Sasso

Institut Pierre-Simon Laplace

Max Planck Institute for Nuclear Physics

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Improving modelled albedo over the Greenland ice sheet through parameter optimisation and MODIS retrievals

Nina Raoult S. Charbit Christophe Dumas Fabienne Maignan Catherine Ottlé

Abstract. Greenland ice sheet mass loss continues to accelerate as global temperatures increase. The surface albedo of the ice sheet determines the amount of absorbed solar energy, which is a key factor in driving surface snow and ice melting. Satellite retrieved albedo allows us to compare and optimise modelled albedo over the entirety of the ice sheet. We optimise the parameters of the albedo scheme in the ORCHIDEE land surface model for three random years taken over the 2000–2017 period and validate over the remaining years. In particular, we want to improve the albedo at the edges of the ice sheet since they correspond to ablation areas and show the greatest variations in runoff and surface mass balance. By giving a larger weight to points at the ice sheet's edge, we improve the model-data fit by reducing the RMSD by over 25 % for the whole ice sheet for the summer months. This improvement is consistent for all years, even those not used in the calibration step. We conclude by showing which additional model outputs are impacted by changes to the albedo parameters encouraging future work using multiple data streams for optimisation.

Albedo (alchemy)

Greenland ice sheet

Ice-albedo feedback

10.5194/egusphere-2022-745

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Citations (0)

Update of GALLEX solar neutrino results and implications

Nuclear Physics B - Proceedings Supplements (1995)

P. Anselmann W. Hampel G. Heusser J. Kiko T. Kirsten

Standard solar model

Solar neutrino problem

10.1016/0920-5632(94)00735-e

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Citations (16)

Solar neutrinos observed by GALLEX at Gran Sasso

CRC Press eBooks (2018)

P. Anselmann W. Hampel G. Heusser J. Kiko T. Kirsten

152We have measured the rate of production of 71Ge from 71Ga by solar neutrinos. The target consists of 30.3 t of gallium in the form of 8.13 M aqueous gallium chloride solution (101 t), shielded by ≈ 3300 m water equivalent of standard rock in the Gran Sasso Underground Laboratory (Italy). In nearly one year of operation, 14 measurements of the production rate of 71Ge were carried out to give, after corrections for side reactions and other backgrounds, an average value of 83 +19 (sut.) ± 8 (syst.) SNU (1σ) due to solar neutrinos. This conclusion constitutes the first observation of solar pp neutrinos. Our result is consistent with the presence of the full pp neutrino flux expected according to the "standard solar model" together with a reduced flux of "B+7Be neutrinos as observed in the Homestake and Kamiokande experiments. Astrophysical reasons remain as a possible explanation of the solar neutrino problem. On the other hand, if the result is to be interpreted in terms of the MSW effect, it would fix neutrino masses and mixing angles within a very restncted range.

10.1201/9780429502811-50

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Citations (4)

Initializing the Greenland ice sheet to investigate its sensitivity to climate changes: a study with the GRISLI model.

EGUGA (2016)

Sébastien Le clec’h Christophe Dumas Masa Kageyama S. Charbit Catherine Ritz

Greenland ice sheet

Ice-sheet model

Initialization

Source

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An energy budget approach to understand the Arctic warming during the Last Interglacial

Climate of the past (2022)

Marie Sicard Masa Kageyama S. Charbit Pascale Braconnot Jean‐Baptiste Madeleine

Abstract. The Last Interglacial period (129–116 ka) is characterised by a strong orbital forcing which leads to a different seasonal and latitudinal distribution of insolation compared to the pre-industrial period. In particular, these changes amplify the seasonality of the insolation in the high latitudes of the Northern Hemisphere. Here, we investigate the Arctic climate response to this forcing by comparing the CMIP6 lig127k and piControl simulations performed with the IPSL-CM6A-LR (the global climate model developed at Institut Pierre-Simon Laplace) model. Using an energy budget framework, we analyse the interactions between the atmosphere, ocean, sea ice and continents. In summer, the insolation anomaly reaches its maximum and causes a rise in near-surface air temperature of 3.1 ∘C over the Arctic region. This warming is primarily due to a strong positive anomaly of surface downwelling shortwave radiation over continental surfaces, followed by large heat transfer from the continents to the atmosphere. The surface layers of the Arctic Ocean also receive more energy but in smaller quantity than the continents due to a cloud negative feedback. Furthermore, while heat exchange from the continental surfaces towards the atmosphere is strengthened, the ocean absorbs and stores the heat excess due to a decline in sea ice cover. However, the maximum near-surface air temperature anomaly does not peak in summer like insolation but occurs in autumn with a temperature increase of 4.2 ∘C relative to the pre-industrial period. This strong warming is driven by a positive anomaly of longwave radiation over the Arctic Ocean enhanced by a positive cloud feedback. It is also favoured by the summer and autumn Arctic sea ice retreat (-1.9×106 and -3.4×106 km2, respectively), which exposes the warm oceanic surface and thus allows oceanic heat storage and release of water vapour in summer. This study highlights the crucial role of sea ice cover variations, Arctic Ocean, as well as changes in polar cloud optical properties on the Last Interglacial Arctic warming.

Arctic geoengineering

Arctic dipole anomaly

Anomaly (physics)

10.5194/cp-18-607-2022

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Citations (3)

Impact of planetary waves on ice-sheet evolution throughout the last glacial - interglacial cycle

EGUGA (2012)

Pauline Beghin S. Charbit Christophe Dumas Masa Kageyama Didier M. Roche

Ice-sheet model

Ice age

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Solar neutrinos observed by GALLEX at Gran Sasso

Nuclear Physics B - Proceedings Supplements (1993)

P. Anselmann W. Hampel G. Heusser J. Kiko T. Kirsten

Solar neutrino problem

Standard solar model

10.1016/0920-5632(93)90122-m

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Citations (20)

Modelling snowpack on ice surfaces with the ORCHIDEE land surface model: application to the Greenland ice sheet

The cryosphere (2024)

S. Charbit Christophe Dumas Fabienne Maignan Catherine Ottlé Nina Raoult

Abstract. Current climate warming is accelerating mass loss from glaciers and ice sheets. In Greenland, the rates of mass changes are now dominated by changes in surface mass balance (SMB) due to increased surface melting. To improve the future sea-level rise projections, it is therefore critical to have an accurate estimate of the SMB, which depends on the representation of the processes occurring within the snowpack. The Explicit Snow (ES) scheme implemented in the land surface model Organising Carbon and Hydrology In Dynamic Ecosystems (ORCHIDEE) has not yet been adapted to ice-covered areas. Here, we present the preliminary developments we made to apply the ES model to glaciers and ice sheets. Our analysis mainly concerns the model's ability to represent ablation-related processes. At the regional scale, our results are compared to the MAR regional atmospheric model outputs and to MODIS albedo retrievals. Using different albedo parameterizations, we performed offline ES simulations forced by the MAR model over the 2000–2019 period. Our results reveal a strong sensitivity of the modelled SMB components to the albedo parameterization. Results inferred with albedo parameters obtained using a manual tuning approach present very good agreement with the MAR outputs. Conversely, with the albedo parameterization used in the standard ORCHIDEE version, runoff and sublimation were underestimated. We also tested parameters found in a previous data assimilation experiment, calibrating the ablation processes using MODIS snow albedo. While these parameters greatly improve the modelled albedo over the entire ice sheet, they degrade the other model outputs compared to those obtained with the manually tuned approach. This is likely due to the model overfitting to the calibration albedo dataset without any constraint applied to the other processes controlling the state of the snowpack. This underlines the need to perform a “multi-objective” optimization using auxiliary observations related to internal snowpack processes. Although there is still room for further improvements, the developments reported in the present study constitute an important advance in assessing the Greenland SMB with possible extension to mountain glaciers or the Antarctic ice sheet.

Greenland ice sheet

Snowpack

Glacier mass balance

Albedo (alchemy)

Ice-albedo feedback

Ablation zone

Snowmelt

10.5194/tc-18-5067-2024

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Role of the feedbacks between ocean /ice-shelves /streams in Heinrich events: from a conceptual to a 3D model

EGUGA (2009)