Articles | Volume 17, issue 12
https://doi.org/10.5194/tc-17-5075-2023
© Author(s) 2023. 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-17-5075-2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
30 Nov 2023
Research article |
| 30 Nov 2023
| 30 Nov 2023
Observed and modeled moulin heads in the Pâkitsoq region of Greenland suggest subglacial channel network effects
Geosciences Department, University of Arkansas, Fayetteville, AR, USA
Centre for Hydrogeology and Geothermics, University of Neuchâtel, Neuchâtel, Switzerland
Kristin Poinar
Department of Geology and RENEW Institute, University at Buffalo, Buffalo, NY, USA
Lauren C. Andrews
Global Modeling and Assimilation Office, NASA Goddard Space Flight Center, Greenbelt, MD, USA
Matthew D. Covington
Geosciences Department, University of Arkansas, Fayetteville, AR, USA
Jessica Mejia
Department of Geology and RENEW Institute, University at Buffalo, Buffalo, NY, USA
Geosciences Department, University of South Florida, Tampa, FL, USA
Jason Gulley
Geosciences Department, University of South Florida, Tampa, FL, USA
Victoria Siegel
Sisu Field Solutions LLC, Austin, Texas, USA
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Lauren C. Andrews, Kristin Poinar, and Celia Trunz
The Cryosphere, 16, 2421–2448, https://doi.org/10.5194/tc-16-2421-2022, https://doi.org/10.5194/tc-16-2421-2022, 2022
Short summary
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We introduce a model for moulin geometry motivated by the wide range of sizes and shapes of explored moulins. Moulins comprise 10–14 % of the Greenland englacial–subglacial hydrologic system and act as time-varying water storage reservoirs. Moulin geometry can vary approximately 10 % daily and over 100 % seasonally. Moulin shape modulates the efficiency of the subglacial system that controls ice flow and should thus be included in hydrologic models.
Tim Hageman, Jessica Mejía, Ravindra Duddu, and Emilio Martínez-Pañeda
The Cryosphere, 18, 3991–4009, https://doi.org/10.5194/tc-18-3991-2024, https://doi.org/10.5194/tc-18-3991-2024, 2024
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Due to surface melting, meltwater lakes seasonally form on the surface of glaciers. These lakes drive hydrofractures that rapidly transfer water to the base of ice sheets. This paper presents a computational method to capture the complicated hydrofracturing process. Our work reveals that viscous ice rheology has a great influence on the short-term propagation of fractures, enabling fast lake drainage, whereas thermal effects (frictional heating, conduction, and freezing) have little influence.
Benjamin Reynolds, Sophie Nowicki, and Kristin Poinar
EGUsphere, https://doi.org/10.5194/egusphere-2024-2424, https://doi.org/10.5194/egusphere-2024-2424, 2024
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Stress in glaciers, ice sheets, and ice shelves causes crevasses, which are important drivers of retreat and sea level rise. We find that different assumptions found in the literature lead to significantly (up to a factor of two) different crevasse depths and recommend a calculation based on observed ice flow patterns. We find that other stress calculations likely overpredict ice shelf vulnerability to hydrofracture.
Brandon L. Graham, Jason P. Briner, Nicolás E. Young, Allie Balter-Kennedy, Michele Koppes, Joerg M. Schaefer, Kristin Poinar, and Elizabeth K. Thomas
The Cryosphere, 17, 4535–4547, https://doi.org/10.5194/tc-17-4535-2023, https://doi.org/10.5194/tc-17-4535-2023, 2023
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Glacial erosion is a fundamental process operating on Earth's surface. Two processes of glacial erosion, abrasion and plucking, are poorly understood. We reconstructed rates of abrasion and quarrying in Greenland. We derive a total glacial erosion rate of 0.26 ± 0.16 mm per year. We also learned that erosion via these two processes is about equal. Because the site is similar to many other areas covered by continental ice sheets, these results may be applied to many places on Earth.
Elias C. Massoud, Lauren Andrews, Rolf Reichle, Andrea Molod, Jongmin Park, Sophie Ruehr, and Manuela Girotto
Earth Syst. Dynam., 14, 147–171, https://doi.org/10.5194/esd-14-147-2023, https://doi.org/10.5194/esd-14-147-2023, 2023
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In this study, we benchmark the forecast skill of the NASA’s Goddard Earth Observing System subseasonal-to-seasonal (GEOS-S2S version 2) hydrometeorological forecasts in the High Mountain Asia (HMA) region. Hydrometeorological forecast skill is dependent on the forecast lead time, the memory of the variable within the physical system, and the validation dataset used. Overall, these results benchmark the GEOS-S2S system’s ability to forecast HMA hydrometeorology on the seasonal timescale.
Jason P. Briner, Caleb K. Walcott, Joerg M. Schaefer, Nicolás E. Young, Joseph A. MacGregor, Kristin Poinar, Benjamin A. Keisling, Sridhar Anandakrishnan, Mary R. Albert, Tanner Kuhl, and Grant Boeckmann
The Cryosphere, 16, 3933–3948, https://doi.org/10.5194/tc-16-3933-2022, https://doi.org/10.5194/tc-16-3933-2022, 2022
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The 7.4 m of sea level equivalent stored as Greenland ice is getting smaller every year. The uncertain trajectory of ice loss could be better understood with knowledge of the ice sheet's response to past climate change. Within the bedrock below the present-day ice sheet is an archive of past ice-sheet history. We analyze all available data from Greenland to create maps showing where on the ice sheet scientists can drill, using currently available drills, to obtain sub-ice materials.
Lauren C. Andrews, Kristin Poinar, and Celia Trunz
The Cryosphere, 16, 2421–2448, https://doi.org/10.5194/tc-16-2421-2022, https://doi.org/10.5194/tc-16-2421-2022, 2022
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We introduce a model for moulin geometry motivated by the wide range of sizes and shapes of explored moulins. Moulins comprise 10–14 % of the Greenland englacial–subglacial hydrologic system and act as time-varying water storage reservoirs. Moulin geometry can vary approximately 10 % daily and over 100 % seasonally. Moulin shape modulates the efficiency of the subglacial system that controls ice flow and should thus be included in hydrologic models.
Kristin Poinar and Lauren C. Andrews
The Cryosphere, 15, 1455–1483, https://doi.org/10.5194/tc-15-1455-2021, https://doi.org/10.5194/tc-15-1455-2021, 2021
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This study addresses Greenland supraglacial lake drainages. We analyze ice deformation associated with lake drainages over 18 summers to assess whether
precursorstrain-rate events consistently precede lake drainages. We find that currently available remote sensing data products cannot resolve these events, and thus we cannot predict future lake drainages. Thus, future avenues for evaluating this hypothesis will require major field-based GPS or photogrammetry efforts.
Chad A. Greene, Alex S. Gardner, and Lauren C. Andrews
The Cryosphere, 14, 4365–4378, https://doi.org/10.5194/tc-14-4365-2020, https://doi.org/10.5194/tc-14-4365-2020, 2020
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Seasonal variability is a fundamental characteristic of any Earth surface system, but we do not fully understand which of the world's glaciers speed up and slow down on an annual cycle. Such short-timescale accelerations may offer clues about how individual glaciers will respond to longer-term changes in climate, but understanding any behavior requires an ability to observe it. We describe how to use satellite image feature tracking to determine the magnitude and timing of seasonal ice dynamics.
Kelly M. Brunt, Robert L. Hawley, Eric R. Lutz, Michael Studinger, John G. Sonntag, Michelle A. Hofton, Lauren C. Andrews, and Thomas A. Neumann
The Cryosphere, 11, 681–692, https://doi.org/10.5194/tc-11-681-2017, https://doi.org/10.5194/tc-11-681-2017, 2017
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This manuscript presents an analysis of NASA airborne lidar data based on in situ GPS measurements from the interior of the Greenland Ice Sheet. Results show that for two airborne altimeters, surface elevation biases are less than 0.12 m and measurement precisions are 0.09 m or better. The study concludes that two NASA airborne lidars are sufficiently characterized to form part of a satellite data validation strategy, specifically for ICESat-2, scheduled to launch in 2018.
Matija Perne, Matthew D. Covington, Evan A. Thaler, and Joseph M. Myre
Earth Surf. Dynam., 5, 85–100, https://doi.org/10.5194/esurf-5-85-2017, https://doi.org/10.5194/esurf-5-85-2017, 2017
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Concepts of landscape equilibrium often enable the interpretation of landscape response to various forces. However, we demonstrate that standard conceptions of landscape equilibrium do not apply in layered rocks. We develop a more general mathematical description of steady state based on a constraint of land surface continuity. In the case of rock layers that are nearly horizontal, this continuity steady state makes substantially different predictions about the nature of equilibrium landscapes.
A. J. Luhmann, M. D. Covington, J. M. Myre, M. Perne, S. W. Jones, E. C. Alexander Jr., and M. O. Saar
Hydrol. Earth Syst. Sci., 19, 137–157, https://doi.org/10.5194/hess-19-137-2015, https://doi.org/10.5194/hess-19-137-2015, 2015
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Water temperature is a non-conservative tracer. Variations in recharge temperature are damped and retarded as water moves through an aquifer due to heat exchange between water and rock. This paper presents relationships that describe thermal damping and retardation in karst conduits determined using analytical solutions and numerical simulations, with some support provided by field data. These relationships may be used with field data to estimate unknown flow path geometry in karst aquifers.
M. Perne, M. Covington, and F. Gabrovšek
Hydrol. Earth Syst. Sci., 18, 4617–4633, https://doi.org/10.5194/hess-18-4617-2014, https://doi.org/10.5194/hess-18-4617-2014, 2014
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This is the first modeling study of conduit network evolution in karst aquifers under pressurized and free surface turbulent flow conditions. Under pressurized flow, the evolution is governed by the feedback between the distribution of hydraulic head and the growth of conduits, as has been already revealed by earlier models. We demonstrate the final selection of stable flow paths on the scale of individual junctions, during and after transition to the free-surface flow regime.
Related subject area
Discipline: Ice sheets | Subject: Glacier Hydrology
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Controls on Greenland moulin geometry and evolution from the Moulin Shape model
Supraglacial streamflow and meteorological drivers from southwest Greenland
Hourly surface meltwater routing for a Greenlandic supraglacial catchment across hillslopes and through a dense topological channel network
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A confined–unconfined aquifer model for subglacial hydrology and its application to the Northeast Greenland Ice Stream
Modelling the fate of surface melt on the Larsen C Ice Shelf
Modelled subglacial floods and tunnel valleys control the life cycle of transitory ice streams
Sheng Dong, Lei Fu, Xueyuan Tang, Zefeng Li, and Xiaofei Chen
The Cryosphere, 18, 1241–1257, https://doi.org/10.5194/tc-18-1241-2024, https://doi.org/10.5194/tc-18-1241-2024, 2024
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Subglacial lakes are a unique environment at the bottom of ice sheets, and they have distinct features in radar echo images that allow for visual detection. In this study, we use machine learning to analyze radar reflection waveforms and identify candidate subglacial lakes. Our approach detects more lakes than known inventories and can be used to expand the subglacial lake inventory. Additionally, this analysis may also provide insights into interpreting other subglacial conditions.
Christopher J. L. Wilson, Mark Peternell, Filomena Salvemini, Vladimir Luzin, Frieder Enzmann, Olga Moravcova, and Nicholas J. R. Hunter
The Cryosphere, 18, 819–836, https://doi.org/10.5194/tc-18-819-2024, https://doi.org/10.5194/tc-18-819-2024, 2024
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As the temperature increases within a deforming ice aggregate, composed of deuterium (D2O) ice and water (H2O) ice, a set of meltwater segregations are produced. These are composed of H2O and HDO and are located in conjugate shear bands and in compaction bands which accommodate the deformation and weaken the ice aggregate. This has major implications for the passage of meltwater in ice sheets and the formation of the layering recognized in glaciers.
Laura Melling, Amber Leeson, Malcolm McMillan, Jennifer Maddalena, Jade Bowling, Emily Glen, Louise Sandberg Sørensen, Mai Winstrup, and Rasmus Lørup Arildsen
The Cryosphere, 18, 543–558, https://doi.org/10.5194/tc-18-543-2024, https://doi.org/10.5194/tc-18-543-2024, 2024
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Lakes on glaciers hold large volumes of water which can drain through the ice, influencing estimates of sea level rise. To estimate water volume, we must calculate lake depth. We assessed the accuracy of three satellite-based depth detection methods on a study area in western Greenland and considered the implications for quantifying the volume of water within lakes. We found that the most popular method of detecting depth on the ice sheet scale has higher uncertainty than previously assumed.
Adam Jake Hepburn, Christine F. Dow, Antti Ojala, Joni Mäkinen, Elina Ahokangas, Jussi Hovikoski, Jukka-Pekka Palmu, and Kari Kajuutti
EGUsphere, https://doi.org/10.5194/egusphere-2023-2141, https://doi.org/10.5194/egusphere-2023-2141, 2023
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Terrain formerly occupied by ice sheets in the last ice age allows us to parameterise models of basal water flow using terrain and data unavailable beneath current ice sheets. Using GlaDS, a 2D basal hydrology model, we explore the origin of murtoos, a specific landform found throughout Finland that is thought to mark the upper limit of channels beneath the ice. Our results validate many of the predictions for murtoo origin and demonstrate that such models can be used to explore past ice sheets.
Nicole Clerx, Horst Machguth, Andrew Tedstone, Nicolas Jullien, Nander Wever, Rolf Weingartner, and Ole Roessler
The Cryosphere, 16, 4379–4401, https://doi.org/10.5194/tc-16-4379-2022, https://doi.org/10.5194/tc-16-4379-2022, 2022
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Meltwater runoff is one of the main contributors to mass loss on the Greenland Ice Sheet that influences global sea level rise. However, it remains unclear where meltwater runs off and what processes cause this. We measured the velocity of meltwater flow through snow on the ice sheet, which ranged from 0.17–12.8 m h−1 for vertical percolation and from 1.3–15.1 m h−1 for lateral flow. This is an important step towards understanding where, when and why meltwater runoff occurs on the ice sheet.
Lauren C. Andrews, Kristin Poinar, and Celia Trunz
The Cryosphere, 16, 2421–2448, https://doi.org/10.5194/tc-16-2421-2022, https://doi.org/10.5194/tc-16-2421-2022, 2022
Short summary
Short summary
We introduce a model for moulin geometry motivated by the wide range of sizes and shapes of explored moulins. Moulins comprise 10–14 % of the Greenland englacial–subglacial hydrologic system and act as time-varying water storage reservoirs. Moulin geometry can vary approximately 10 % daily and over 100 % seasonally. Moulin shape modulates the efficiency of the subglacial system that controls ice flow and should thus be included in hydrologic models.
Rohi Muthyala, Åsa K. Rennermalm, Sasha Z. Leidman, Matthew G. Cooper, Sarah W. Cooley, Laurence C. Smith, and Dirk van As
The Cryosphere, 16, 2245–2263, https://doi.org/10.5194/tc-16-2245-2022, https://doi.org/10.5194/tc-16-2245-2022, 2022
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In situ measurements of meltwater discharge through supraglacial stream networks are rare. The unprecedentedly long record of discharge captures diurnal and seasonal variability. Two major findings are (1) a change in the timing of peak discharge through the melt season that could impact meltwater delivery in the subglacial system and (2) though the primary driver of stream discharge is shortwave radiation, longwave radiation and turbulent heat fluxes play a major role during high-melt episodes.
Colin J. Gleason, Kang Yang, Dongmei Feng, Laurence C. Smith, Kai Liu, Lincoln H. Pitcher, Vena W. Chu, Matthew G. Cooper, Brandon T. Overstreet, Asa K. Rennermalm, and Jonathan C. Ryan
The Cryosphere, 15, 2315–2331, https://doi.org/10.5194/tc-15-2315-2021, https://doi.org/10.5194/tc-15-2315-2021, 2021
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We apply first-principle hydrology models designed for global river routing to route flows hourly through 10 000 individual supraglacial channels in Greenland. Our results uniquely show the role of process controls (network density, hillslope flow, channel friction) on routed meltwater. We also confirm earlier suggestions that large channels do not dewater overnight despite the shutdown of runoff and surface mass balance runoff being mistimed and overproducing runoff, as validated in situ.
Kristin Poinar and Lauren C. Andrews
The Cryosphere, 15, 1455–1483, https://doi.org/10.5194/tc-15-1455-2021, https://doi.org/10.5194/tc-15-1455-2021, 2021
Short summary
Short summary
This study addresses Greenland supraglacial lake drainages. We analyze ice deformation associated with lake drainages over 18 summers to assess whether
precursorstrain-rate events consistently precede lake drainages. We find that currently available remote sensing data products cannot resolve these events, and thus we cannot predict future lake drainages. Thus, future avenues for evaluating this hypothesis will require major field-based GPS or photogrammetry efforts.
Léo Decaux, Mariusz Grabiec, Dariusz Ignatiuk, and Jacek Jania
The Cryosphere, 13, 735–752, https://doi.org/10.5194/tc-13-735-2019, https://doi.org/10.5194/tc-13-735-2019, 2019
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Due to the fast melting of glaciers around the world, it is important to characterize the evolution of the meltwater circulation beneath them as it highly impacts their velocity. By using very
high-resolution satellite images and field measurements, we modelized it for two Svalbard glaciers. We determined that for most of Svalbard glaciers it is crucial to include their surface morphology to obtain a reliable model, which is not currently done. Having good models is key to predicting our future.
Sebastian Beyer, Thomas Kleiner, Vadym Aizinger, Martin Rückamp, and Angelika Humbert
The Cryosphere, 12, 3931–3947, https://doi.org/10.5194/tc-12-3931-2018, https://doi.org/10.5194/tc-12-3931-2018, 2018
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The evolution of subglacial channels below ice sheets is very important for the dynamics of glaciers as the water acts as a lubricant. We present a new numerical model (CUAS) that generalizes existing approaches by accounting for two different flow situations within a single porous medium layer: (1) a confined aquifer if sufficient water supply is available and (2) an unconfined aquifer, otherwise. The model is applied to artificial scenarios as well as to the Northeast Greenland Ice Stream.
Sammie Buzzard, Daniel Feltham, and Daniela Flocco
The Cryosphere, 12, 3565–3575, https://doi.org/10.5194/tc-12-3565-2018, https://doi.org/10.5194/tc-12-3565-2018, 2018
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Surface lakes on ice shelves can not only change the amount of solar energy the ice shelf receives, but may also play a pivotal role in sudden ice shelf collapse such as that of the Larsen B Ice Shelf in 2002.
Here we simulate current and future melting on Larsen C, Antarctica’s most northern ice shelf and one on which lakes have been observed. We find that should future lakes occur closer to the ice shelf front, they may contain sufficient meltwater to contribute to ice shelf instability.
Thomas Lelandais, Édouard Ravier, Stéphane Pochat, Olivier Bourgeois, Christopher Clark, Régis Mourgues, and Pierre Strzerzynski
The Cryosphere, 12, 2759–2772, https://doi.org/10.5194/tc-12-2759-2018, https://doi.org/10.5194/tc-12-2759-2018, 2018
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Scattered observations suggest that subglacial meltwater routes drive ice stream dynamics and ice sheet stability. We use a new experimental approach to reconcile such observations into a coherent story connecting ice stream life cycles with subglacial hydrology and bed erosion. Results demonstrate that subglacial flooding, drainage reorganization, and valley development can control an ice stream lifespan, thus opening new perspectives on subglacial processes controlling ice sheet instabilities.
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Short summary
Models simulating water pressure variations at the bottom of glaciers must use large storage parameters to produce realistic results. Whether that storage occurs englacially (in moulins) or subglacially is a matter of debate. Here, we directly simulate moulin volume to constrain the storage there. We find it is not enough. Instead, subglacial processes, including basal melt and input from upstream moulins, must be responsible for stabilizing these water pressure fluctuations.
Models simulating water pressure variations at the bottom of glaciers must use large storage...
