Articles | Volume 15, issue 5
https://doi.org/10.5194/tc-15-2251-2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/tc-15-2251-2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
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17 May 2021
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Comment on “Exceptionally high heat flux needed to sustain the Northeast Greenland Ice Stream” by Smith-Johnsen et al. (2020)
School of Earth Science and Resources, China University of Geosciences, Beijing, China
Department of Geosciences, Eberhard Karls University Tübingen,
Tübingen, Germany
Tamara de Riese
Department of Geosciences, Eberhard Karls University Tübingen,
Tübingen, Germany
Steven Franke
Alfred Wegener Institute Helmholtz Centre for Polar and Marine
Research, Bremerhaven, Germany
Maria-Gema Llorens
Geosciences Barcelona, CSIC, Barcelona, Spain
Till Sachau
Department of Geosciences, Eberhard Karls University Tübingen,
Tübingen, Germany
Nicolas Stoll
Alfred Wegener Institute Helmholtz Centre for Polar and Marine
Research, Bremerhaven, Germany
Ilka Weikusat
Department of Geosciences, Eberhard Karls University Tübingen,
Tübingen, Germany
Alfred Wegener Institute Helmholtz Centre for Polar and Marine
Research, Bremerhaven, Germany
Julien Westhoff
Physics of Ice, Climate and Earth, University of Copenhagen,
Copenhagen, Denmark
Department of Geosciences, Eberhard Karls University Tübingen,
Tübingen, Germany
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Steven Franke, Alfons Eckstaller, Tim Heitland, Thomas Schaefer, and Jölund Asseng
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Till Sachau, Haibin Yang, Justin Lang, Paul D. Bons, and Louis Moresi
Geosci. Model Dev., 15, 8749–8764, https://doi.org/10.5194/gmd-15-8749-2022, https://doi.org/10.5194/gmd-15-8749-2022, 2022
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Knowledge of the internal structures of the major continental ice sheets is improving, thanks to new investigative techniques. These structures are an essential indication of the flow behavior and dynamics of ice transport, which in turn is important for understanding the actual impact of the vast amounts of water trapped in continental ice sheets on global sea-level rise. The software studied here is specifically designed to simulate such structures and their evolution.
Vjeran Višnjević, Reinhard Drews, Clemens Schannwell, Inka Koch, Steven Franke, Daniela Jansen, and Olaf Eisen
The Cryosphere, 16, 4763–4777, https://doi.org/10.5194/tc-16-4763-2022, https://doi.org/10.5194/tc-16-4763-2022, 2022
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Alfons Eckstaller, Jölund Asseng, Erich Lippmann, and Steven Franke
Geosci. Instrum. Method. Data Syst., 11, 235–245, https://doi.org/10.5194/gi-11-235-2022, https://doi.org/10.5194/gi-11-235-2022, 2022
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We present a mobile and self-sufficient seismometer station concept for operation in polar regions. The energy supply can be adapted as required using the modular cascading of battery boxes, wind generators, solar cells, or backup batteries, which enables optimum use of limited resources. Our system concept is not limited to the applications using seismological stations. It is a suitable system for managing the power supply of all types of self-sufficient measuring systems in polar regions.
Maria-Gema Llorens, Albert Griera, Paul D. Bons, Ilka Weikusat, David J. Prior, Enrique Gomez-Rivas, Tamara de Riese, Ivone Jimenez-Munt, Daniel García-Castellanos, and Ricardo A. Lebensohn
The Cryosphere, 16, 2009–2024, https://doi.org/10.5194/tc-16-2009-2022, https://doi.org/10.5194/tc-16-2009-2022, 2022
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Polar ice is formed by ice crystals, which form fabrics that are utilised to interpret how ice sheets flow. It is unclear whether fabrics result from the current flow regime or if they are inherited. To understand the extent to which ice crystals can be reoriented when ice flow conditions change, we simulate and evaluate multi-stage ice flow scenarios according to natural cases. We find that second deformation regimes normally overprint inherited fabrics, with a range of transitional fabrics.
Julien Westhoff, Giulia Sinnl, Anders Svensson, Johannes Freitag, Helle Astrid Kjær, Paul Vallelonga, Bo Vinther, Sepp Kipfstuhl, Dorthe Dahl-Jensen, and Ilka Weikusat
Clim. Past, 18, 1011–1034, https://doi.org/10.5194/cp-18-1011-2022, https://doi.org/10.5194/cp-18-1011-2022, 2022
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We present a melt event record from an ice core from central Greenland, which covers the past 10 000 years. Our record displays warm summer events, which can be used to enhance our understanding of the past climate. We compare our data to anomalies in tree ring width, which also represents summer temperatures, and find a good correlation. Furthermore, we investigate an outstandingly warm event in the year 986 AD or 991 AD, which has not been analyzed before.
Nicolas Stoll, Maria Hörhold, Tobias Erhardt, Jan Eichler, Camilla Jensen, and Ilka Weikusat
The Cryosphere, 16, 667–688, https://doi.org/10.5194/tc-16-667-2022, https://doi.org/10.5194/tc-16-667-2022, 2022
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We mapped and analysed solid inclusion in the upper 1340 m of the EGRIP ice core with Raman spectroscopy and microstructure mapping, based on bulk dust content derived via continuous flow analysis. We observe a large variety in mineralogy throughout the core and samples. The main minerals are sulfates, especially gypsum, and terrestrial dust minerals, such as quartz, mica, and feldspar. A change in mineralogy occurs around 900 m depth indicating a climate-related imprint.
Steven Franke, Daniela Jansen, Tobias Binder, John D. Paden, Nils Dörr, Tamara A. Gerber, Heinrich Miller, Dorthe Dahl-Jensen, Veit Helm, Daniel Steinhage, Ilka Weikusat, Frank Wilhelms, and Olaf Eisen
Earth Syst. Sci. Data, 14, 763–779, https://doi.org/10.5194/essd-14-763-2022, https://doi.org/10.5194/essd-14-763-2022, 2022
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The Northeast Greenland Ice Stream (NEGIS) is the largest ice stream in Greenland. In order to better understand the past and future dynamics of the NEGIS, we present a high-resolution airborne radar data set (EGRIP-NOR-2018) for the onset region of the NEGIS. The survey area is centered at the location of the drill site of the East Greenland Ice-Core Project (EastGRIP), and radar profiles cover both shear margins and are aligned parallel to several flow lines.
Nicolas Stoll, Jan Eichler, Maria Hörhold, Tobias Erhardt, Camilla Jensen, and Ilka Weikusat
The Cryosphere, 15, 5717–5737, https://doi.org/10.5194/tc-15-5717-2021, https://doi.org/10.5194/tc-15-5717-2021, 2021
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We did a systematic analysis of the location of inclusions in the EGRIP ice core, the first ice core from an ice stream. We combine this with crystal orientation and grain size data, enabling the first overview about the microstructure of this unique ice core. Micro-inclusions show a strong spatial variability and patterns (clusters or horizontal layers); roughly one-third is located at grain boundaries. More holistic approaches are needed to understand deformation processes in the ice better.
Tamara Annina Gerber, Christine Schøtt Hvidberg, Sune Olander Rasmussen, Steven Franke, Giulia Sinnl, Aslak Grinsted, Daniela Jansen, and Dorthe Dahl-Jensen
The Cryosphere, 15, 3655–3679, https://doi.org/10.5194/tc-15-3655-2021, https://doi.org/10.5194/tc-15-3655-2021, 2021
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We simulate the ice flow in the onset region of the Northeast Greenland Ice Stream to determine the source area and past accumulation rates of ice found in the EastGRIP ice core. This information is required to correct for bias in ice-core records introduced by the upstream flow effects. Our results reveal that the increasing accumulation rate with increasing upstream distance is predominantly responsible for the constant annual layer thicknesses observed in the upper 900 m of the ice core.
Sebastian Hellmann, Melchior Grab, Johanna Kerch, Henning Löwe, Andreas Bauder, Ilka Weikusat, and Hansruedi Maurer
The Cryosphere, 15, 3507–3521, https://doi.org/10.5194/tc-15-3507-2021, https://doi.org/10.5194/tc-15-3507-2021, 2021
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In this study, we analyse whether ultrasonic measurements on ice core samples could be employed to derive information about the particular ice crystal orientation in these samples. We discuss if such ultrasonic scans of ice core samples could provide similarly detailed results as the established methods, which usually destroy the ice samples. Our geophysical approach is minimally invasive and could support the existing methods with additional and (semi-)continuous data points along the ice core.
Sebastian Hellmann, Johanna Kerch, Ilka Weikusat, Andreas Bauder, Melchior Grab, Guillaume Jouvet, Margit Schwikowski, and Hansruedi Maurer
The Cryosphere, 15, 677–694, https://doi.org/10.5194/tc-15-677-2021, https://doi.org/10.5194/tc-15-677-2021, 2021
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We analyse the orientation of ice crystals in an Alpine glacier and compare this orientation with the ice flow direction. We found that the crystals orient in the direction of the largest stress which is in the flow direction in the upper parts of the glacier and in the vertical direction for deeper zones of the glacier. The grains cluster around this maximum stress direction, in particular four-point maxima, most likely as a result of recrystallisation under relatively warm conditions.
Ernst-Jan N. Kuiper, Ilka Weikusat, Johannes H. P. de Bresser, Daniela Jansen, Gill M. Pennock, and Martyn R. Drury
The Cryosphere, 14, 2429–2448, https://doi.org/10.5194/tc-14-2429-2020, https://doi.org/10.5194/tc-14-2429-2020, 2020
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A composite flow law model applied to crystal size distributions from the NEEM deep ice core predicts that fine-grained layers in ice from the last Glacial period localize deformation as internal shear zones in the Greenland ice sheet deforming by grain-size-sensitive creep. This prediction is consistent with microstructures in Glacial age ice.
Ernst-Jan N. Kuiper, Johannes H. P. de Bresser, Martyn R. Drury, Jan Eichler, Gill M. Pennock, and Ilka Weikusat
The Cryosphere, 14, 2449–2467, https://doi.org/10.5194/tc-14-2449-2020, https://doi.org/10.5194/tc-14-2449-2020, 2020
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Fast ice flow occurs in deeper parts of polar ice sheets, driven by high stress and high temperatures. Above 262 K ice flow is further enhanced, probably by the formation of thin melt layers between ice crystals. A model applying an experimentally derived composite flow law, using temperature and grain size values from the deepest 540 m of the NEEM ice core, predicts that flow in fine-grained layers is enhanced by a factor of 10 compared to coarse-grained layers in the Greenland ice sheet.
Chao Qi, David J. Prior, Lisa Craw, Sheng Fan, Maria-Gema Llorens, Albert Griera, Marianne Negrini, Paul D. Bons, and David L. Goldsby
The Cryosphere, 13, 351–371, https://doi.org/10.5194/tc-13-351-2019, https://doi.org/10.5194/tc-13-351-2019, 2019
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Ice deformed in nature develops crystallographic preferred orientations, CPOs, which induce an anisotropy in ice viscosity. Shear experiments of ice revealed a transition in CPO with changing temperature/strain, which is due to the change of dominant CPO-formation mechanism: strain-induced grain boundary migration dominates at higher temperatures and lower strains, while lattice rotation dominates at other conditions. Understanding these mechanisms aids the interpretation of CPOs in natural ice.
Jilu Li, Jose A. Vélez González, Carl Leuschen, Ayyangar Harish, Prasad Gogineni, Maurine Montagnat, Ilka Weikusat, Fernando Rodriguez-Morales, and John Paden
The Cryosphere, 12, 2689–2705, https://doi.org/10.5194/tc-12-2689-2018, https://doi.org/10.5194/tc-12-2689-2018, 2018
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Ice properties inferred from multi-polarization measurements can provide insight into ice strain, viscosity, and ice flow. The Center for Remote Sensing of Ice Sheets used a ground-based radar for multi-channel and multi-polarization measurements at the NEEM site. This paper describes the radar system, antenna configurations, data collection, and processing and analysis of this data set. Comparisons between the radar observations, simulations, and ice core fabric data are in very good agreement.
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The Cryosphere, 12, 1715–1734, https://doi.org/10.5194/tc-12-1715-2018, https://doi.org/10.5194/tc-12-1715-2018, 2018
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We investigate the effect of crystal anisotropy on seismic velocities in glacier ice by calculating seismic phase velocities using the exact c axis angles to describe the crystal orientations in ice-core samples for an alpine and a polar ice core. Our results provide uncertainty estimates for earlier established approximative calculations. Additionally, our findings highlight the variation in seismic velocity at non-vertical incidence as a function of the horizontal azimuth of the seismic plane.
Ilka Weikusat, Ernst-Jan N. Kuiper, Gill M. Pennock, Sepp Kipfstuhl, and Martyn R. Drury
Solid Earth, 8, 883–898, https://doi.org/10.5194/se-8-883-2017, https://doi.org/10.5194/se-8-883-2017, 2017
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Understanding the flow of large ice masses on Earth is a major challenge in our changing climate. Deformation mechanisms are governed by the strong anisotropy of ice. As anisotropy is currently moving into the focus of ice sheet flow studies, we provide a detailed analysis of microstructure data from natural ice core samples which directly relate to anisotropic plasticity. Our findings reveal surprising dislocation activity which seems to contradict the concept of macroscopic ice anisotropy.
Jan Eichler, Ina Kleitz, Maddalena Bayer-Giraldi, Daniela Jansen, Sepp Kipfstuhl, Wataru Shigeyama, Christian Weikusat, and Ilka Weikusat
The Cryosphere, 11, 1075–1090, https://doi.org/10.5194/tc-11-1075-2017, https://doi.org/10.5194/tc-11-1075-2017, 2017
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This study contributes to investigations of the effect of impurities on ice microstructure and flow properties. For the first time we mapped over 5000 micro-inclusions in four samples from the EDML and NEEM polar ice cores. The particle distributions show no correlation with grain boundaries and thus we conclude that particle pinning plays only a secondary role for the microstructure evolution. Alternative mechanisms are discussed.
Florian Steinbach, Paul D. Bons, Albert Griera, Daniela Jansen, Maria-Gema Llorens, Jens Roessiger, and Ilka Weikusat
The Cryosphere, 10, 3071–3089, https://doi.org/10.5194/tc-10-3071-2016, https://doi.org/10.5194/tc-10-3071-2016, 2016
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How glaciers or ice sheets flow is a result of microscopic processes controlled by the properties of individual ice crystals. We performed computer simulations on these processes and the effect of air bubbles between crystals. The simulations show that small-scale ice deformation is locally stronger than in other regions, which is enhanced by bubbles. This causes the ice crystals to recrystallise and change their properties in a way that potentially also affects the large-scale flow properties.
D. Jansen, M.-G. Llorens, J. Westhoff, F. Steinbach, S. Kipfstuhl, P. D. Bons, A. Griera, and I. Weikusat
The Cryosphere, 10, 359–370, https://doi.org/10.5194/tc-10-359-2016, https://doi.org/10.5194/tc-10-359-2016, 2016
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In this study we present examples of typical small-scale folds observed in the NEEM ice core, North Greenland, and discuss their characteristics. Numerical modelling of viscoplastic deformation and dynamic recrystallisation was used to improve the understanding of the formation of the observed structures under simple shear boundary conditions. We conclude that the folds originate from bands of grains with a tilted lattice relative to the strong lattice preferred orientation below 1500 m depth.
E. Gomez-Rivas, A. Griera, and M.-G. Llorens
Solid Earth, 6, 497–514, https://doi.org/10.5194/se-6-497-2015, https://doi.org/10.5194/se-6-497-2015, 2015
Z. Zhao, P. D. Bons, G. Wang, A. Soesoo, and Y. Liu
Solid Earth, 6, 457–473, https://doi.org/10.5194/se-6-457-2015, https://doi.org/10.5194/se-6-457-2015, 2015
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The early Mesozoic tectonic history of the Qiangtang terrane in central Tibet is hotly debated. We argue that the north and south Qiangtang terranes were separated by an ocean (Paleo-Tethys) until the late Triassic. Subduction was mainly to the north, underneath the north Qiangtang terrane. The high-pressure rocks were exhumed in a lithospheric-scale core complex. Together with non-metamorphic sedimentary and ophiolitic mélange, these were finally thrust on top of the south Qiangtang.
A. Diez, O. Eisen, C. Hofstede, A. Lambrecht, C. Mayer, H. Miller, D. Steinhage, T. Binder, and I. Weikusat
The Cryosphere, 9, 385–398, https://doi.org/10.5194/tc-9-385-2015, https://doi.org/10.5194/tc-9-385-2015, 2015
M. Montagnat, N. Azuma, D. Dahl-Jensen, J. Eichler, S. Fujita, F. Gillet-Chaulet, S. Kipfstuhl, D. Samyn, A. Svensson, and I. Weikusat
The Cryosphere, 8, 1129–1138, https://doi.org/10.5194/tc-8-1129-2014, https://doi.org/10.5194/tc-8-1129-2014, 2014
T. Sachau and D. Koehn
Geosci. Model Dev., 7, 243–247, https://doi.org/10.5194/gmd-7-243-2014, https://doi.org/10.5194/gmd-7-243-2014, 2014
Related subject area
Discipline: Ice sheets | Subject: Arctic (e.g. Greenland)
Sensitivity to forecast surface mass balance outweighs sensitivity to basal sliding descriptions for 21st century mass loss from three major Greenland outlet glaciers
Recent warming trends of the Greenland ice sheet documented by historical firn and ice temperature observations and machine learning
Spatially heterogeneous effect of climate warming on the Arctic land ice
Improving modelled albedo over the Greenland ice sheet through parameter optimisation and MODIS snow albedo retrievals
Hydraulic suppression of basal glacier melt in sill fjords
Direct measurement of warm Atlantic Intermediate Water close to the grounding line of Nioghalvfjerdsfjorden (79° N) Glacier, northeast Greenland
Brief communication: Preliminary ICESat-2 (Ice, Cloud and land Elevation Satellite-2) measurements of outlet glaciers reveal heterogeneous patterns of seasonal dynamic thickness change
Uncertainties in projected surface mass balance over the polar ice sheets from dynamically downscaled EC-Earth models
Thinning leads to calving-style changes at Bowdoin Glacier, Greenland
Possible impacts of a 1000 km long hypothetical subglacial river valley towards Petermann Glacier in northern Greenland
Greenland Ice Sheet late-season melt: investigating multiscale drivers of K-transect events
In situ observed relationships between snow and ice surface skin temperatures and 2 m air temperatures in the Arctic
J. Rachel Carr, Emily A. Hill, and G. Hilmar Gudmundsson
The Cryosphere, 18, 2719–2737, https://doi.org/10.5194/tc-18-2719-2024, https://doi.org/10.5194/tc-18-2719-2024, 2024
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The Greenland Ice Sheet is one of the world's largest glaciers and is melting quickly in response to climate change. It contains fast-flowing channels of ice that move ice from Greenland's centre to its coasts and allow Greenland to react quickly to climate warming. As a result, we want to predict how these glaciers will behave in the future, but there are lots of uncertainties. Here we assess the impacts of two main sources of uncertainties in glacier models.
Baptiste Vandecrux, Robert S. Fausto, Jason E. Box, Federico Covi, Regine Hock, Åsa K. Rennermalm, Achim Heilig, Jakob Abermann, Dirk van As, Elisa Bjerre, Xavier Fettweis, Paul C. J. P. Smeets, Peter Kuipers Munneke, Michiel R. van den Broeke, Max Brils, Peter L. Langen, Ruth Mottram, and Andreas P. Ahlstrøm
The Cryosphere, 18, 609–631, https://doi.org/10.5194/tc-18-609-2024, https://doi.org/10.5194/tc-18-609-2024, 2024
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How fast is the Greenland ice sheet warming? In this study, we compiled 4500+ temperature measurements at 10 m below the ice sheet surface (T10m) from 1912 to 2022. We trained a machine learning model on these data and reconstructed T10m for the ice sheet during 1950–2022. After a slight cooling during 1950–1985, the ice sheet warmed at a rate of 0.7 °C per decade until 2022. Climate models showed mixed results compared to our observations and underestimated the warming in key regions.
Damien Maure, Christoph Kittel, Clara Lambin, Alison Delhasse, and Xavier Fettweis
The Cryosphere, 17, 4645–4659, https://doi.org/10.5194/tc-17-4645-2023, https://doi.org/10.5194/tc-17-4645-2023, 2023
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The Arctic is warming faster than the rest of the Earth. Studies have already shown that Greenland and the Canadian Arctic are experiencing a record increase in melting rates, while Svalbard has been relatively less impacted. Looking at those regions but also extending the study to Iceland and the Russian Arctic archipelagoes, we see a heterogeneity in the melting-rate response to the Arctic warming, with the Russian archipelagoes experiencing lower melting rates than other regions.
Nina Raoult, Sylvie Charbit, Christophe Dumas, Fabienne Maignan, Catherine Ottlé, and Vladislav Bastrikov
The Cryosphere, 17, 2705–2724, https://doi.org/10.5194/tc-17-2705-2023, https://doi.org/10.5194/tc-17-2705-2023, 2023
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Greenland ice sheet melting due to global warming could significantly impact global sea-level rise. The ice sheet's albedo, i.e. how reflective the surface is, affects the melting speed. The ORCHIDEE computer model is used to simulate albedo and snowmelt to make predictions. However, the albedo in ORCHIDEE is lower than that observed using satellites. To correct this, we change model parameters (e.g. the rate of snow decay) to reduce the difference between simulated and observed values.
Johan Nilsson, Eef van Dongen, Martin Jakobsson, Matt O'Regan, and Christian Stranne
The Cryosphere, 17, 2455–2476, https://doi.org/10.5194/tc-17-2455-2023, https://doi.org/10.5194/tc-17-2455-2023, 2023
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We investigate how topographical sills suppress basal glacier melt in Greenlandic fjords. The basal melt drives an exchange flow over the sill, but there is an upper flow limit set by the Atlantic Water features outside the fjord. If this limit is reached, the flow enters a new regime where the melt is suppressed and its sensitivity to the Atlantic Water temperature is reduced.
Michael J. Bentley, James A. Smith, Stewart S. R. Jamieson, Margaret R. Lindeman, Brice R. Rea, Angelika Humbert, Timothy P. Lane, Christopher M. Darvill, Jeremy M. Lloyd, Fiamma Straneo, Veit Helm, and David H. Roberts
The Cryosphere, 17, 1821–1837, https://doi.org/10.5194/tc-17-1821-2023, https://doi.org/10.5194/tc-17-1821-2023, 2023
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The Northeast Greenland Ice Stream is a major outlet of the Greenland Ice Sheet. Some of its outlet glaciers and ice shelves have been breaking up and retreating, with inflows of warm ocean water identified as the likely reason. Here we report direct measurements of warm ocean water in an unusual lake that is connected to the ocean beneath the ice shelf in front of the 79° N Glacier. This glacier has not yet shown much retreat, but the presence of warm water makes future retreat more likely.
Christian J. Taubenberger, Denis Felikson, and Thomas Neumann
The Cryosphere, 16, 1341–1348, https://doi.org/10.5194/tc-16-1341-2022, https://doi.org/10.5194/tc-16-1341-2022, 2022
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Outlet glaciers are projected to account for half of the total ice loss from the Greenland Ice Sheet over the 21st century. We classify patterns of seasonal dynamic thickness changes of outlet glaciers using new observations from the Ice, Cloud and land Elevation Satellite-2 (ICESat-2). Our results reveal seven distinct patterns that differ across glaciers even within the same region. Future work can use our results to improve our understanding of processes that drive seasonal ice sheet changes.
Fredrik Boberg, Ruth Mottram, Nicolaj Hansen, Shuting Yang, and Peter L. Langen
The Cryosphere, 16, 17–33, https://doi.org/10.5194/tc-16-17-2022, https://doi.org/10.5194/tc-16-17-2022, 2022
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Using the regional climate model HIRHAM5, we compare two versions (v2 and v3) of the global climate model EC-Earth for the Greenland and Antarctica ice sheets. We are interested in the surface mass balance of the ice sheets due to its importance when making estimates of future sea level rise. We find that the end-of-century change in the surface mass balance for Antarctica is 420 Gt yr−1 (v2) and 80 Gt yr−1 (v3), and for Greenland it is −290 Gt yr−1 (v2) and −1640 Gt yr−1 (v3).
Eef C. H. van Dongen, Guillaume Jouvet, Shin Sugiyama, Evgeny A. Podolskiy, Martin Funk, Douglas I. Benn, Fabian Lindner, Andreas Bauder, Julien Seguinot, Silvan Leinss, and Fabian Walter
The Cryosphere, 15, 485–500, https://doi.org/10.5194/tc-15-485-2021, https://doi.org/10.5194/tc-15-485-2021, 2021
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The dynamic mass loss of tidewater glaciers is strongly linked to glacier calving. We study calving mechanisms under a thinning regime, based on 5 years of field and remote-sensing data of Bowdoin Glacier. Our data suggest that Bowdoin Glacier ungrounded recently, and its calving behaviour changed from calving due to surface crevasses to buoyancy-induced calving resulting from basal crevasses. This change may be a precursor to glacier retreat.
Christopher Chambers, Ralf Greve, Bas Altena, and Pierre-Marie Lefeuvre
The Cryosphere, 14, 3747–3759, https://doi.org/10.5194/tc-14-3747-2020, https://doi.org/10.5194/tc-14-3747-2020, 2020
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The topography of the rock below the Greenland ice sheet is not well known. One long valley appears as a line of dips because of incomplete data. So we use ice model simulations that unblock this valley, and these create a watercourse that may represent a form of river over 1000 km long under the ice. When we melt ice at the bottom of the ice sheet only in the deep interior, water can flow down the valley only when the valley is unblocked. It may have developed while an ice sheet was present.
Thomas J. Ballinger, Thomas L. Mote, Kyle Mattingly, Angela C. Bliss, Edward Hanna, Dirk van As, Melissa Prieto, Saeideh Gharehchahi, Xavier Fettweis, Brice Noël, Paul C. J. P. Smeets, Carleen H. Reijmer, Mads H. Ribergaard, and John Cappelen
The Cryosphere, 13, 2241–2257, https://doi.org/10.5194/tc-13-2241-2019, https://doi.org/10.5194/tc-13-2241-2019, 2019
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Arctic sea ice and the Greenland Ice Sheet (GrIS) are melting later in the year due to a warming climate. Through analyses of weather station, climate model, and reanalysis data, physical links are evaluated between Baffin Bay open water duration and western GrIS melt conditions. We show that sub-Arctic air mass movement across this portion of the GrIS strongly influences late summer and autumn melt, while near-surface, off-ice winds inhibit westerly atmospheric heat transfer from Baffin Bay.
Pia Nielsen-Englyst, Jacob L. Høyer, Kristine S. Madsen, Rasmus Tonboe, Gorm Dybkjær, and Emy Alerskans
The Cryosphere, 13, 1005–1024, https://doi.org/10.5194/tc-13-1005-2019, https://doi.org/10.5194/tc-13-1005-2019, 2019
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The paper facilitates the construction of a satellite-derived 2 m air temperature (T2m) product for Arctic snow/ice areas. The relationship between skin temperature (Tskin) and T2m is analysed using weather stations. The main factors influencing the relationship are seasonal variations, wind speed and clouds. A clear-sky bias is estimated to assess the effect of cloud-limited satellite observations. The results are valuable when validating satellite Tskin or estimating T2m from satellite Tskin.
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Short summary
The modelling of Smith-Johnson et al. (The Cryosphere, 14, 841–854, 2020) suggests that a very large heat flux of more than 10 times the usual geothermal heat flux is required to have initiated or to control the huge Northeast Greenland Ice Stream. Our comparison with known hotspots, such as Iceland and Yellowstone, shows that such an exceptional heat flux would be unique in the world and is incompatible with known geological processes that can raise the heat flux.
The modelling of Smith-Johnson et al. (The Cryosphere, 14, 841–854, 2020) suggests that a very...
