346 results on '"Morlighem, Mathieu"'
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2. A thicker Antarctic ice stream during the mid-Pliocene warm period
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Mas e Braga, Martim, Jones, Richard S., Bernales, Jorge, Andersen, Jane Lund, Fredin, Ola, Morlighem, Mathieu, Koester, Alexandria J., Lifton, Nathaniel A., Harbor, Jonathan M., Suganuma, Yusuke, Glasser, Neil F., Rogozhina, Irina, and Stroeven, Arjen P.
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- 2023
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3. Extensive inland thinning and speed-up of Northeast Greenland Ice Stream
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Khan, Shfaqat A., Choi, Youngmin, Morlighem, Mathieu, Rignot, Eric, Helm, Veit, Humbert, Angelika, Mouginot, Jérémie, Millan, Romain, Kjær, Kurt H., and Bjørk, Anders A.
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- 2022
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4. Ice velocity and thickness of the world’s glaciers
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Millan, Romain, Mouginot, Jérémie, Rabatel, Antoine, and Morlighem, Mathieu
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- 2022
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5. The International Bathymetric Chart of the Southern Ocean Version 2
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Dorschel, Boris, Hehemann, Laura, Viquerat, Sacha, Warnke, Fynn, Dreutter, Simon, Tenberge, Yvonne Schulze, Accettella, Daniela, An, Lu, Barrios, Felipe, Bazhenova, Evgenia, Black, Jenny, Bohoyo, Fernando, Davey, Craig, De Santis, Laura, Dotti, Carlota Escutia, Fremand, Alice C., Fretwell, Peter T., Gales, Jenny A., Gao, Jinyao, Gasperini, Luca, Greenbaum, Jamin S., Jencks, Jennifer Henderson, Hogan, Kelly, Hong, Jong Kuk, Jakobsson, Martin, Jensen, Laura, Kool, Johnathan, Larin, Sergei, Larter, Robert D., Leitchenkov, German, Loubrieu, Benoît, Mackay, Kevin, Mayer, Larry, Millan, Romain, Morlighem, Mathieu, Navidad, Francisco, Nitsche, Frank O., Nogi, Yoshifumi, Pertuisot, Cécile, Post, Alexandra L., Pritchard, Hamish D., Purser, Autun, Rebesco, Michele, Rignot, Eric, Roberts, Jason L., Rovere, Marzia, Ryzhov, Ivan, Sauli, Chiara, Schmitt, Thierry, Silvano, Alessandro, Smith, Jodie, Snaith, Helen, Tate, Alex J., Tinto, Kirsty, Vandenbossche, Philippe, Weatherall, Pauline, Wintersteller, Paul, Yang, Chunguo, Zhang, Tao, and Arndt, Jan Erik
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- 2022
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6. Petermann ice shelf may not recover after a future breakup
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Åkesson, Henning, Morlighem, Mathieu, Nilsson, Johan, Stranne, Christian, and Jakobsson, Martin
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- 2022
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7. Inland Summer Speedup at Zachariæ Isstrøm, Northeast Greenland, Driven by Subglacial Hydrology.
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Khan, Shfaqat A., Morlighem, Mathieu, Ehrenfeucht, Shivani, Seroussi, Helene, Choi, Youngmin, Rignot, Eric, Humbert, Angelika, Pickell, Derek, and Hassan, Javed
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GREENLAND ice , *RUNOFF , *CLIMATE change , *HYDROLOGIC models , *GLACIERS ,GLACIER speed - Abstract
The Northeast Greenland Ice Stream (NEGIS) has experienced substantial dynamic thinning in recent years. Here, we examine the evolving behavior of NEGIS, with focus on summer speedup at Zachariae Isstrøm, one of the NEGIS outlet glaciers, which has exhibited rapid retreat and acceleration, indicative of its vulnerability to changing climate conditions. Through a combination of Sentinel‐1 data, in‐situ GPS observations, and numerical ice flow modeling from 2007, we investigate the mechanisms driving short‐term changes. Our analysis reveals a summer speedup in ice flow both near the terminus and inland, with satellite data detecting changes up to 60 km inland, while GPS data capture changes up to 190 km inland along the glacier center line. We attribute this summer speedup to variations in subglacial hydrology, where surface meltwater runoff influences basal friction over the melt season. Incorporating subglacial hydrology into numerical models makes it possible to replicate observed ice velocity patterns. Plain Language Summary: The Northeast Greenland Ice Stream (NEGIS), a crucial part of the Greenland Ice Sheet, has been experiencing significant dynamic thinning recently. This study focuses on the summer speedup of Zachariae Isstrøm (ZI), one of NEGIS's outlet glaciers, which is rapidly retreating and accelerating, highlighting its sensitivity to climate change. Utilizing Sentinel‐1 satellite data, in‐situ GPS observations, and numerical ice flow modeling, we explore the mechanisms behind short‐term dynamic changes. We find that satellite data reveals short‐term summer (June to August) fluctuations in ice flow speed near the glacier terminus and up to 50–70 km inland. However, GPS data shows that this speedup extends further inland, up to at least 190 km along the main flow line. Only GPS data can detect the smaller‐scale summer speedups in these inland regions, providing critical observations for validating ice flow models. We determine that the seasonal acceleration of ice velocity at Zachariae Isstrøm is due to variations in subglacial hydrology, where surface meltwater runoff reduces basal friction by altering the subglacial hydrologic system during the melt season. Additionally, our study highlights that these findings are applicable beyond NEGIS, with similar speedup patterns observed in other Greenland glaciers. Key Points: GPS data reveal summer speed up at least 190 km inland along the main flowline of Zachariae IsstrømSubglacial hydrology is the main driver of the summer speedup near the terminus and deep inlandRecord high warming in 2019 led to a more intense and longer duration of the summer speedup [ABSTRACT FROM AUTHOR]
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- 2024
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8. The West Antarctic Ice Sheet may not be vulnerable to marine ice cliff instability during the 21st century.
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Morlighem, Mathieu, Goldberg, Daniel, Barnes, Jowan M., Bassis, Jeremy N., Benn, Douglas I., Crawford, Anna J., Gudmundsson, G. Hilmar, and Seroussi, Hélène
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ANTARCTIC ice , *ICE sheets , *TWENTY-first century , *ICE shelves , *SUBGLACIAL lakes , *CLIFFS , *MELTWATER , *GLACIERS - Abstract
The collapse of ice shelves could expose tall ice cliffs at ice sheet margins. The marine ice cliff instability (MICI) is a hypothesis that predicts that, if these cliffs are tall enough, ice may fail structurally leading to self-sustained retreat. To date, projections that include MICI have been performed with a single model based on a simple parameterization. Here, we implement a physically motivated parameterization in three ice sheet models and simulate the response of the Amundsen Sea Embayment after a hypothetical collapse of floating ice. All models show that Thwaites Glacier would not retreat further in the 21st century. In another set of simulations, we force the grounding line to retreat into Thwaites' deeper basin to expose a taller cliff. In these simulations, rapid thinning and velocity increase reduce the calving rate, stabilizing the cliff. These experiments show that Thwaites may be less vulnerable to MICI than previously thought, and model projections that include this process should be re-evaluated. [ABSTRACT FROM AUTHOR]
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- 2024
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9. Numerical stabilization methods for level-set-based ice front migration.
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Cheng, Gong, Morlighem, Mathieu, and Gudmundsson, G. Hilmar
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ICE sheets , *MOTION capture (Human mechanics) , *SEA level , *GLACIERS , *VELOCITY - Abstract
Numerical modeling of ice sheet dynamics is a critical tool for projecting future sea level rise. Among all the processes responsible for the loss of mass of the ice sheets, enhanced ice discharge triggered by the retreat of marine-terminating glaciers is one of the key drivers. Numerical models of ice sheet flow are therefore required to include ice front migration in order to reproduce today's mass loss and to be able to predict their future. However, the discontinuous nature of calving poses a significant numerical challenge for accurately capturing the motion of the ice front. In this study, we explore different stabilization techniques combined with varying reinitialization strategies to enhance the numerical stability and accuracy of solving the level-set function, which tracks the position of the ice front. Through rigorous testing on an idealized domain with a semicircular and a straight-line ice front, including scenarios with diverse front velocities, we assess the performance of these techniques. The findings contribute to advancing our ability to model ice sheet dynamics, specifically calving processes, and provide valuable insights into the most effective strategies for simulating and tracking the motion of the ice front. [ABSTRACT FROM AUTHOR]
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- 2024
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10. Author Correction: Ice velocity and thickness of the world’s glaciers
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Millan, Romain, Mouginot, Jérémie, Rabatel, Antoine, and Morlighem, Mathieu
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- 2023
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11. Projected land ice contributions to twenty-first-century sea level rise
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Edwards, Tamsin L., Nowicki, Sophie, Marzeion, Ben, Hock, Regine, Goelzer, Heiko, Seroussi, Hélène, Jourdain, Nicolas C., Slater, Donald A., Turner, Fiona E., Smith, Christopher J., McKenna, Christine M., Simon, Erika, Abe-Ouchi, Ayako, Gregory, Jonathan M., Larour, Eric, Lipscomb, William H., Payne, Antony J., Shepherd, Andrew, Agosta, Cécile, Alexander, Patrick, Albrecht, Torsten, Anderson, Brian, Asay-Davis, Xylar, Aschwanden, Andy, Barthel, Alice, Bliss, Andrew, Calov, Reinhard, Chambers, Christopher, Champollion, Nicolas, Choi, Youngmin, Cullather, Richard, Cuzzone, Joshua, Dumas, Christophe, Felikson, Denis, Fettweis, Xavier, Fujita, Koji, Galton-Fenzi, Benjamin K., Gladstone, Rupert, Golledge, Nicholas R., Greve, Ralf, Hattermann, Tore, Hoffman, Matthew J., Humbert, Angelika, Huss, Matthias, Huybrechts, Philippe, Immerzeel, Walter, Kleiner, Thomas, Kraaijenbrink, Philip, Le clec’h, Sébastien, Lee, Victoria, Leguy, Gunter R., Little, Christopher M., Lowry, Daniel P., Malles, Jan-Hendrik, Martin, Daniel F., Maussion, Fabien, Morlighem, Mathieu, O’Neill, James F., Nias, Isabel, Pattyn, Frank, Pelle, Tyler, Price, Stephen F., Quiquet, Aurélien, Radić, Valentina, Reese, Ronja, Rounce, David R., Rückamp, Martin, Sakai, Akiko, Shafer, Courtney, Schlegel, Nicole-Jeanne, Shannon, Sarah, Smith, Robin S., Straneo, Fiammetta, Sun, Sainan, Tarasov, Lev, Trusel, Luke D., Van Breedam, Jonas, van de Wal, Roderik, van den Broeke, Michiel, Winkelmann, Ricarda, Zekollari, Harry, Zhao, Chen, Zhang, Tong, and Zwinger, Thomas
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- 2021
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12. Seawater Intrusion in the Observed Grounding Zone of Petermann Glacier Causes Extensive Retreat.
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Ehrenfeucht, Shivani, Rignot, Eric, and Morlighem, Mathieu
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SALTWATER encroachment ,GLACIERS ,ICE sheets ,ICE shelves ,RADAR interferometry ,HYDROSTATIC equilibrium ,ALPINE glaciers ,GLACIAL melting - Abstract
Understanding grounding line dynamics is critical for projecting glacier evolution and sea level rise. Observations from satellite radar interferometry reveal rapid grounding line migration forced by oceanic tides that are several kilometers larger than predicted by hydrostatic equilibrium, indicating the transition from grounded to floating ice is more complex than previously thought. Recent studies suggest seawater intrusion beneath grounded ice may play a role in driving rapid ice loss. Here, we investigate its impact on the evolution of Petermann Glacier, Greenland, using an ice sheet model. We compare model results with observed changes in grounding line position, velocity, and ice elevation between 2010 and 2022. We match the observed retreat, speed up, and thinning using 3‐km‐long seawater intrusion that drive peak ice melt rates of 50 m/yr; but we cannot obtain the same agreement without seawater intrusion. Including seawater intrusion in glacier modeling will increase the sensitivity to ocean warming. Plain Language Summary: Relatively warm seawater melts marine‐terminating glaciers from below. Recent observations suggest that seawater flows below grounded ice at high tide. The presence of seawater at this boundary, referred to as seawater intrusion, has the potential to increase glacier mass loss. We test this hypothesis on Petermann Glacier, Greenland, using an ice sheet flow model. We run the model to reconstruct the glacier's behavior from 2010 to 2022 with and without seawater intrusion. We compare the results with satellite observations of velocity, grounding line position, and ice thinning. When we use enhanced ice melt rates from kilometer‐scale seawater intrusion, we match the observed retreat, speed up, and thinning. When we do not, the model fails to replicate the observations. Seawater intrusion may play a critical role in glacier evolution. Adding this process to ice flow models will increase their sensitivity to ocean warming and projections of ice mass loss and sea level rise. Key Points: Ice melt caused by seawater intrusion in the grounding zone explains the observed grounding line retreat of Petermann GlacierWithout seawater intrusion in the grounding zone, we do not replicate the full extent of observed retreatIncluding seawater intrusion in the grounding zone increases glacier mass loss [ABSTRACT FROM AUTHOR]
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- 2024
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13. Thank You to Our 2023 Peer Reviewers.
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Rajaram, Harihar, Aiyyer, Anantha, Camargo, Suzana, Cappa, Christopher D., Dombard, Andrew J., Donohue, Kathleen A., Feakins, Sarah, Flesch, Lucy, Fulweiler, Robinson, Ganju, Neil, Giannini, Alessandra, Gu, Yu, Huber, Christian, Ivanov, Valeriy, Karnauskas, Kristopher, Korte, Monika, Lewis, Kevin, Lu, Gang, Magnusdottir, Gudrun, and Morlighem, Mathieu
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OPEN scholarship ,SCIENTIFIC community ,DATA quality - Abstract
On behalf of the journal, AGU, and the scientific community, the editors of Geophysical Research Letters would like to sincerely thank those who reviewed manuscripts for us in 2023. The hours reading and commenting on manuscripts not only improve the manuscripts, but also increase the scientific rigor of future research in the field. With the advent of AGU's data policy, many reviewers have also helped immensely to evaluate the accessibility and availability of data, and many have provided insightful comments that helped to improve the data presentation and quality. We greatly appreciate the assistance of the reviewers in advancing open science, which is a key objective of AGU's data policy. We particularly appreciate the timely reviews in light of the demands imposed by the rapid review process at Geophysical Research Letters. We received 4,512 submissions in 2023 and 5,112 reviewers contributed to their evaluation by providing 8,587 reviews in total. We deeply appreciate their contributions. Plain Language Summary: Individuals in italics provided three or more reviews for GRL in 2023. Key Points: The editors thank the 2023 peer‐reviewers [ABSTRACT FROM AUTHOR]
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- 2024
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14. Forty-six years of Greenland Ice Sheet mass balance from 1972 to 2018
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Mouginot, Jérémie, Rignot, Eric, Bjørk, Anders A., van den Broeke, Michiel, Millan, Romain, Morlighem, Mathieu, Noël, Brice, Scheuchl, Bernd, and Wood, Michael
- Published
- 2019
15. Four decades of Antarctic Ice Sheet mass balance from 1979–2017
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Rignot, Eric, Mouginot, Jérémie, Scheuchl, Bernd, van den Broeke, Michiel, van Wessem, Melchior J., and Morlighem, Mathieu
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- 2019
16. Ice dynamics will remain a primary driver of Greenland ice sheet mass loss over the next century
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Choi, Youngmin, Morlighem, Mathieu, Rignot, Eric, and Wood, Michael
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- 2021
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17. Elastic deformation plays a non-negligible role in Greenland’s outlet glacier flow
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Christmann, Julia, Helm, Veit, Khan, Shfaqat Abbas, Kleiner, Thomas, Müller, Ralf, Morlighem, Mathieu, Neckel, Niklas, Rückamp, Martin, Steinhage, Daniel, Zeising, Ole, and Humbert, Angelika
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- 2021
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18. Rate of mass loss from the Greenland Ice Sheet will exceed Holocene values this century
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Briner, Jason P., Cuzzone, Joshua K., Badgeley, Jessica A., Young, Nicolás E., Steig, Eric J., Morlighem, Mathieu, Schlegel, Nicole-Jeanne, Hakim, Gregory J., Schaefer, Joerg M., Johnson, Jesse V., Lesnek, Alia J., Thomas, Elizabeth K., Allan, Estelle, Bennike, Ole, Cluett, Allison A., Csatho, Beata, de Vernal, Anne, Downs, Jacob, Larour, Eric, and Nowicki, Sophie
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- 2020
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19. Deep glacial troughs and stabilizing ridges unveiled beneath the margins of the Antarctic ice sheet
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Morlighem, Mathieu, Rignot, Eric, Binder, Tobias, Blankenship, Donald, Drews, Reinhard, Eagles, Graeme, Eisen, Olaf, Ferraccioli, Fausto, Forsberg, René, Fretwell, Peter, Goel, Vikram, Greenbaum, Jamin S., Gudmundsson, Hilmar, Guo, Jingxue, Helm, Veit, Hofstede, Coen, Howat, Ian, Humbert, Angelika, Jokat, Wilfried, Karlsson, Nanna B., Lee, Won Sang, Matsuoka, Kenichi, Millan, Romain, Mouginot, Jeremie, Paden, John, Pattyn, Frank, Roberts, Jason, Rosier, Sebastian, Ruppel, Antonia, Seroussi, Helene, Smith, Emma C., Steinhage, Daniel, Sun, Bo, Broeke, Michiel R. van den, Ommen, Tas D. van, Wessem, Melchior van, and Young, Duncan A.
- Published
- 2020
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20. Geologic Provinces Beneath the Greenland Ice Sheet Constrained by Geophysical Data Synthesis.
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MacGregor, Joseph A., Colgan, William T., Paxman, Guy J. G., Tinto, Kirsty J., Csathó, Beáta, Darbyshire, Fiona A., Fahnestock, Mark A., Kokfelt, Thomas F., MacKie, Emma J., Morlighem, Mathieu, and Sergienko, Olga V.
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PHYSIOGRAPHIC provinces ,GREENLAND ice ,ICE sheets ,ICE ,TOPOGRAPHIC maps ,GEOLOGY - Abstract
Present understanding of Greenland's subglacial geology is derived mostly from interpolation of geologic mapping of its ice‐free margins and unconstrained by geophysical data. Here we refine the extent of its geologic provinces by synthesizing geophysical constraints on subglacial geology from seismic, gravity, magnetic and topographic data. North of 72°N, no province clearly extends across the whole island, leaving three distinct subglacial regions yet to be reconciled with margin geology. Geophysically coherent anomalies and apparent province boundaries are adjacent to the onset of faster ice flow at both Petermann Glacier and the Northeast Greenland Ice Stream. Separately, based on their subaerial expression, dozens of unusually long, straight and sub‐parallel subglacial valleys cross Greenland's interior and are not yet resolved by current syntheses of its subglacial topography. Plain Language Summary: The Greenland Ice Sheet obscures the rocks beneath 79% of Greenland. By necessity, scientists have relied mostly on studying the rocks exposed along Greenland's edge to understand the island's interior geology. We examine geophysical data from seismometers on the ground, satellites that measure Earth's gravity and magnetic fields and surface topography, and aircraft that measure those same properties and ice thickness. We draw a new map of Greenland's geology beneath the ice sheet by examining where those data show similar signals regarding the nature of the underlying rock, and where they could be related to mapped rock exposures. We also find evidence of some areas with geophysical expressions that are distinct from the rocks found at the island's edges. Some geologic structures, which are entirely covered by ice, may affect how ice flows from Greenland's vast interior toward its coast. Finally, we identify many valleys beneath the ice that are very long and often aligned with each other, but which are not yet fully captured in present maps of the topography beneath the ice. Key Points: We produced a new synthesis of subglacial boundaries for Greenland's geologic provinces from seismic, gravity, magnetic and topography dataThree subglacial regions in central and northern Greenland cannot yet be reconciled with surface‐exposed geologic provincesWe find evidence for a large subglacial valley network that is not fully resolved by subglacial topography syntheses for Greenland [ABSTRACT FROM AUTHOR]
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- 2024
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21. Impact of boundary conditions on the modeled thermal regime of the Antarctic ice sheet.
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Park, In-Woo, Jin, Emilia Kyung, Morlighem, Mathieu, and Lee, Kang-Kun
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ANTARCTIC ice ,ICE sheets ,SUBGLACIAL lakes ,ICE prevention & control ,ICE streams ,CONSERVATION of mass - Abstract
A realistic initialization of ice flow models is critical for predicting future changes in ice sheet mass balance and their associated contribution to sea level rise. The initial thermal state of an ice sheet is particularly important, as it controls ice viscosity and basal conditions, thereby influencing the overall ice velocity. Englacial and subglacial conditions, however, remain poorly understood due to insufficient direct measurements, which complicate the initialization and validation of thermal models. Here, we investigate the impact of using different geothermal heat flux (GHF) datasets and vertical velocity profiles on the thermal state of the Antarctic ice sheet and compare our modeled temperatures to in situ measurements from 15 boreholes. We find that the temperature profile is more sensitive to vertical velocity than to GHF. The basal temperature of grounded ice and the amount of basal melting are influenced by both selection of GHF and vertical velocity. More importantly, we find that the standard approach, which consists of combining basal sliding speed and incompressibility to derive vertical velocities, provides reasonably good results in fast-flow regions (ice velocity >50 m yr -1) but performs poorly in slow-flow regions (ice velocity <50 m yr -1). Furthermore, the modeled temperature profiles in ice streams, where bed geometry is generated using a mass conservation approach, show better agreement with observed borehole temperatures compared to kriging-based bed geometry. [ABSTRACT FROM AUTHOR]
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- 2024
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22. Ocean-Ice Interactions in Inglefield Gulf : Early Results from NASA’s Oceans Melting Greenland Mission
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Willis, Josh K., Carroll, Dustin, Fenty, Ian, Kohli, Gurjot, Khazendar, Ala, Rutherford, Matthew, Trenholm, Nicole, and Morlighem, Mathieu
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- 2018
23. Near-margin ice thickness and subglacial water routing, Leverett Glacier, Greenland
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Ross, Neil, Sole, Andrew J., Livingstone, Stephen J., Igneczi, Ádam, and Morlighem, Mathieu
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- 2018
24. Models and Data: A Critical Relationship for Constraining Uncertainty in Ice-Sheet Model Projections
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Schlegel, Nicole-Jeanne, Seroussi, Helene, Schodlok, Michael, Kazendar, Ala, Larour, Eric, Castleman, Blake, and Morlighem, Mathieu
- Published
- 2021
25. Models and Data: A Critical Relationship for Constraining Uncertainty in Ice-Sheet Model Projections
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Morlighem, Mathieu, Castleman, Blake, Larour, Eric, Kazendar, Ala, Schodlok, Michael, Seroussi, Helene, and Schlegel, Nicole-Jeanne
- Published
- 2021
26. The International Bathymetric Chart of the Arctic Ocean Version 4.0
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Jakobsson, Martin, Mayer, Larry A., Bringensparr, Caroline, Castro, Carlos F., Mohammad, Rezwan, Johnson, Paul, Ketter, Tomer, Accettella, Daniela, Amblas, David, An, Lu, Arndt, Jan Erik, Canals, Miquel, Casamor, José Luis, Chauché, Nolwenn, Coakley, Bernard, Danielson, Seth, Demarte, Maurizio, Dickson, Mary-Lynn, Dorschel, Boris, Dowdeswell, Julian A., Dreutter, Simon, Fremand, Alice C., Gallant, Dana, Hall, John K., Hehemann, Laura, Hodnesdal, Hanne, Hong, Jongkuk, Ivaldi, Roberta, Kane, Emily, Klaucke, Ingo, Krawczyk, Diana W., Kristoffersen, Yngve, Kuipers, Boele R., Millan, Romain, Masetti, Giuseppe, Morlighem, Mathieu, Noormets, Riko, Prescott, Megan M., Rebesco, Michele, Rignot, Eric, Semiletov, Igor, Tate, Alex J., Travaglini, Paola, Velicogna, Isabella, Weatherall, Pauline, Weinrebe, Wilhelm, Willis, Joshua K., Wood, Michael, Zarayskaya, Yulia, Zhang, Tao, Zimmermann, Mark, and Zinglersen, Karl B.
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- 2020
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27. Centennial response of Greenland’s three largest outlet glaciers
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Khan, Shfaqat A., Bjørk, Anders A., Bamber, Jonathan L., Morlighem, Mathieu, Bevis, Michael, Kjær, Kurt H., Mouginot, Jérémie, Løkkegaard, Anja, Holland, David M., Aschwanden, Andy, Zhang, Bao, Helm, Veit, Korsgaard, Niels J., Colgan, William, Larsen, Nicolaj K., Liu, Lin, Hansen, Karina, Barletta, Valentina, Dahl-Jensen, Trine S., Søndergaard, Anne Sofie, Csatho, Beata M., Sasgen, Ingo, Box, Jason, and Schenk, Toni
- Published
- 2020
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28. The relationship between Uncertainty Quantification and Observations in Ice Sheet Modeling
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Morlighem, Mathieu, Haynes, Mark, Beauchamp, Rob, Casteman, Blake, Landau, Damon, Larour, Eric, Limonadi, Daniel, Boening, Carmen, Seroussi, Helene, Khazendar, Ala, Schodlok, Michael, and Schlegel, Nicole-Jeanne
- Published
- 2021
29. The relationship between Uncertainty Quantification and Observations in Ice Sheet Modeling
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Schlegel, Nicole-Jeanne, Schodlok, Michael, Khazendar, Ala, Seroussi, Helene, Boening, Carmen, Limonadi, Daniel, Larour, Eric, Landau, Damon, Casteman, Blake, Beauchamp, Rob, Haynes, Mark, and Morlighem, Mathieu
- Published
- 2021
30. Improving Bed Topography Mapping of Greenland Glaciers Using NASA's Oceans Melting Greenland (OMG) Data
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Morlighem, Mathieu, Rignot, Eric, and Willis, Josh K.
- Published
- 2016
31. Graphics-processing-unit-accelerated ice flow solver for unstructured meshes using the Shallow-Shelf Approximation (FastIceFlo v1.0.1).
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Sandip, Anjali, Räss, Ludovic, and Morlighem, Mathieu
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CENTRAL processing units ,HIGH performance computing ,FLOOD risk ,ANTARCTIC ice ,GRAPHICS processing units ,MESH networks ,PARALLEL processing - Abstract
Ice-sheet flow models capable of accurately projecting their future mass balance constitute tools to improve flood risk assessment and assist sea-level rise mitigation associated with enhanced ice discharge. Some processes that need to be captured, such as grounding-line migration, require high spatial resolution (under the kilometer scale). Conventional ice flow models mainly execute on central processing units (CPUs), which feature limited parallel processing capabilities and peak memory bandwidth. This may hinder model scalability and result in long run times, requiring significant computational resources. As an alternative, graphics processing units (GPUs) are ideally suited for high spatial resolution, as the calculations can be performed concurrently by thousands of threads, processing most of the computational domain simultaneously. In this study, we combine a GPU-based approach with the pseudo-transient (PT) method, an accelerated iterative and matrix-free solution strategy, and investigate its performance for finite elements and unstructured meshes with application to two-dimensional (2-D) models of real glaciers at a regional scale. For both the Jakobshavn and Pine Island glacier models, the number of nonlinear PT iterations required to converge a given number of vertices (N) scales in the order of O(N1.2) or better. We further compare the performance of the PT CUDA C implementation with a standard finite-element CPU-based implementation using the price-to-performance metric. The price of a single Tesla V100 GPU is 1.5 times that of two Intel Xeon Gold 6140 CPUs. We expect a minimum speedup of at least 1.5 times to justify the Tesla V100 GPU price to performance. Our developments result in a GPU-based implementation that achieves this goal with a speedup beyond 1.5 times. This study represents a first step toward leveraging GPU processing power, enabling more accurate polar ice discharge predictions. The insights gained will benefit efforts to diminish spatial resolution constraints at higher computing performance. The higher computing performance will allow for ensembles of ice-sheet flow simulations to be run at the continental scale and higher resolution, a previously challenging task. The advances will further enable the quantification of model sensitivity to changes in upcoming climate forcings. These findings will significantly benefit process-oriented sea-level-projection studies over the coming decades. [ABSTRACT FROM AUTHOR]
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- 2024
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32. Modelling GNSS-observed seasonal velocity changes of the Ross Ice Shelf, Antarctica, using the Ice-sheet and Sea-level System Model (ISSM).
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Baldacchino, Francesca, Golledge, Nicholas R., Horgan, Huw, Morlighem, Mathieu, Alevropoulos-Borrill, Alanna V., Malyarenko, Alena, Gossart, Alexandra, Lowry, Daniel P., and van Haastrecht, Laurine
- Subjects
ICE shelves ,ICE sheets ,AUTOMATIC differentiation ,GLOBAL Positioning System ,VELOCITY ,SEA ice ,ICE cores - Abstract
Recently, seasonal changes in sea ice cover have been found to elevate basal melt rates of the Ross Ice Shelf (RIS) calving front at sensitive regions. Melting at these sensitive regions has been found to impact ice sheet mass balance. However, the influence of these seasonally elevated basal melt rates on RIS flow variability is not yet fully understood. This paper aims to explore whether seasonal perturbations in basal melt rates of the RIS can explain intra-annual variations in ice flow measured by GNSS at four sites across the ice shelf. We use the automatic differentiation tool in the Ice-sheet and Sea-level System Model (ISSM) to identify regions of the RIS where changes in basal melt affect ice velocities at the GNSS sites. Next, we seasonally perturb Massachusetts Institute of Technology general circulation (MITgcm) basal melt rates in ISSM at these sensitive regions to try and replicate the GNSS ice flow observations. The GNSS observations display clear intra-annual velocity variability at the four sites, with two distinct peaks observed in austral summer and austral winter. We can replicate this intra-annual velocity variation for GNSS sites near the calving front by seasonally perturbing the basal melt rates at the identified sensitive regions of the ice shelf. We argue that the perturbed seasonal basal melt variability at sensitive regions along the calving front is a realistic scenario for the RIS. Thus, we suggest that the GNSS-recorded intra-annual velocity variations along the calving front could be partly driven by seasonal changes in basal melting today. We also try to replicate intra-annual velocity variability observed at the Siple Coast by seasonally perturbing basal melt rates at sensitive regions there. However, we are unable to replicate similar magnitudes of velocity variations to the GNSS measurements and suspect that the perturbed seasonal basal melt variability is unrealistic, with no observations of seasonally high basal melt rates at the Siple Coast grounding lines or pinning points. Thus, seasonal changes in basal melt cannot explain the observed intra-annual velocity variability at all the GNSS sites, and further work is needed. Our sensitivity maps highlight regions of the ice shelf where changes in basal melt most influence velocities, and are a valuable addition to fieldwork campaigns and modelling studies. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
33. Impact of time-dependent data assimilation on ice flow model initialization and projections: a case study of Kjer Glacier, Greenland.
- Author
-
Choi, Youngmin, Seroussi, Helene, Morlighem, Mathieu, Schlegel, Nicole-Jeanne, and Gardner, Alex
- Subjects
GREENLAND ice ,ICE sheets ,GLACIERS ,KALMAN filtering ,TIME series analysis - Abstract
Ice sheet models are often initialized with data assimilation of present-day conditions, in which unknown model parameters are estimated using the inverse method. While assimilation of snapshot observations has been widely used for regional- and large-scale ice sheet simulations, data assimilation based on time-dependent data has recently started to emerge to constrain model parameters while capturing the transient evolution of the system. However, this method has been applied only to a few glaciers with fixed ice front positions, using spatially and temporally limited observations, and has not been applied to marine-terminating glaciers of the Greenland Ice Sheet that have been retreating over the last 30 years. In this study, we assimilate time series of surface velocity into a model of Kjer Glacier in West Greenland to better capture the observed acceleration over the past 3 decades. We compare snapshot and transient inverse methods and investigate the impact of initialization procedures on the parameters inferred, as well as model projections. We find that transient-calibrated simulations better capture past trends and better reproduce changes after the calibration period, even when a short period of observations is used. The results show the feasibility and clear benefits of a time-dependent data assimilation for initializing ice sheet models. This approach is now possible with the development of longer observational records, though it remains computationally challenging. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
34. Evaluation of four calving laws for Antarctic ice shelves.
- Author
-
Wilner, Joel A., Morlighem, Mathieu, and Cheng, Gong
- Subjects
- *
ANTARCTIC ice , *ICE shelves , *ICE calving , *ICE prevention & control , *ICE sheets , *ICE streams - Abstract
Many floating ice shelves in Antarctica buttress the ice streams feeding them, thereby reducing the discharge of icebergs into the ocean. The rate at which ice shelves calve icebergs and how fast they flow determine whether they advance, retreat, or remain stable, exerting a first-order control on ice discharge. To parameterize calving within ice sheet models, several empirical and physical calving "laws" have been proposed in the past few decades. Such laws emphasize dissimilar features, including along- and across-flow strain rates (the eigencalving law), a fracture yield criterion (the von Mises law), longitudinal stretching (the crevasse depth law), and a simple ice thickness threshold (the minimum thickness law), among others. Despite the multitude of established calving laws, these laws remain largely unvalidated for the Antarctic Ice Sheet, rendering it difficult to assess the broad applicability of any given law in Antarctica. We address this shortcoming through a set of numerical experiments that evaluate existing calving laws for 10 ice shelves around the Antarctic Ice Sheet. We utilize the Ice-sheet and Sea-level System Model (ISSM) and implement four calving laws under constant external forcing, calibrating the free parameter of each of these calving laws for each ice shelf by assuming that the current position of the ice front is in steady state and finding the set of parameters that best achieves this position over a simulation of 200 years. We find that, in general, the eigencalving and von Mises laws best reproduce observed calving front positions under the steady-state position assumption. These results will streamline future modeling efforts of Antarctic ice shelves by better informing the relevant physics of Antarctic-style calving on a shelf-by-shelf basis. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
35. Antarctic Bedmap data: Findable, Accessible, Interoperable, and Reusable (FAIR) sharing of 60 years of ice bed, surface, and thickness data
- Author
-
Frémand, Alice C., Fretwell, Peter, Bodart, Julien A., Pritchard, Hamish D., Aitken, Alan, Bamber, Jonathan L., Bell, Robin, Bianchi, Cesido, Bingham, Robert G., Blankenship, Donald D., Casassa, Gino, Catania, Ginny, Christianson, Knut, Conway, Howard, Corr, Hugh F.J., Cui, Xiangbin, Damaske, Detlef, Damm, Volkmar, Drews, Reinhard, Eagles, Graeme, Eisen, Olaf, Eisermann, Hannes, Ferraccioli, Fausto, Field, Elena, Forsberg, René, Franke, Steven, Fujita, Shuji, Gim, Yonggyu, Goel, Vikram, Gogineni, Siva Prasad, Greenbaum, Jamin, Hills, Benjamin, Hindmarsh, Richard C.A., Hoffman, Andrew O., Holmlund, Per, Holschuh, Nicholas, Holt, John W., Horlings, Anneka N., Humbert, Anglika, Jacobel, Robert W., Jansen, Daniela, Jenkins, Adrian, Jokat, Wilfried, Jordan, Tom, King, Edward, Kohler, Jack, Krabill, William, Langley, Kirsty, Lee, Joohan, Leitchenkov, German, Leuschen, Carlton, Luyendyk, Bruce, MacGregor, Joseph, MacKie, Emma, Matsuoka, Kenichi, Morlighem, Mathieu, Mouginot, Jérémie, Nitsche, Frank O., Nogi, Yoshifumi, Nost, Ole A., Paden, John, Pattyn, Frank, Popov, Sergey V., Rignot, Eric, Rippin, David M., Rivera, Andrés, Roberts, Jason, Ross, Neil, Ruppel, Anotonia, Schroeder, Dustin M., Siegert, Martin J., Smith, Andrew M., Steinhage, Daniel, Studinger, Michael, Sun, Bo, Tabacco, Ignazio, Tinto, Kirsty, Urbini, Stefano, Vaughan, David, Welch, Brian C., Wilson, Douglas S., Young, Duncan A., and Zirizzotti, Achille
- Abstract
One of the key components of this research has been the mapping of Antarctic bed topography and ice thickness parameters that are crucial for modelling ice flow and hence for predicting future ice loss and the ensuing sea level rise. Supported by the Scientific Committee on Antarctic Research (SCAR), the Bedmap3 Action Group aims not only to produce new gridded maps of ice thickness and bed topography for the international scientific community, but also to standardize and make available all the geophysical survey data points used in producing the Bedmap gridded products. Here, we document the survey data used in the latest iteration, Bedmap3, incorporating and adding to all of the datasets previously used for Bedmap1 and Bedmap2, including ice bed, surface and thickness point data from all Antarctic geophysical campaigns since the 1950s. More specifically, we describe the processes used to standardize and make these and future surveys and gridded datasets accessible under the Findable, Accessible, Interoperable, and Reusable (FAIR) data principles. With the goals of making the gridding process reproducible and allowing scientists to re-use the data freely for their own analysis, we introduce the new SCAR Bedmap Data Portal (https://bedmap.scar.org, last access: 1 March 2023) created to provide unprecedented open access to these important datasets through a web-map interface. We believe that this data release will be a valuable asset to Antarctic research and will greatly extend the life cycle of the data held within it. Data are available from the UK Polar Data Centre: https://data.bas.ac.uk (last access: 5 May 2023). See the Data availability section for the complete list of datasets.
- Published
- 2023
36. Impact of boundary conditions on the modelled thermal regime of the Antarctic ice sheet
- Author
-
Park, In-Woo, Jin, Emilia Kyung, Morlighem, Mathieu, and Lee, Kang-Kun
- Abstract
A realistic initialization of ice flow models is critical for predicting future changes in ice sheet mass balance and their associated contribution to sea level rise. The initial thermal state of an ice sheet is particularly important as it controls ice viscosity and basal conditions, thereby influencing the overall ice velocity. Englacial and subglacial conditions, however, remain poorly understood due to insufficient direct measurements, which complicates the initialization and validation of thermal models. Here, we investigate the impact of using different geothermal heat flux (GHF) datasets and vertical velocity profiles on the thermal state of the Antarctic ice sheet, and compare our modeled temperatures to in situ measurements from 15 boreholes. We find that the vertical velocity plays a more important role in the temperature profile than GHF. More importantly, we find that the standard approach, which consists in combining basal sliding speed and incompressibility to derive vertical velocities, provides reasonably good results in fast flowing regions (ice velocity > 50 m yr-1), but performs poorly in slower moving regions.
- Published
- 2023
37. Evaluation of four calving laws for Antarctic ice shelves
- Author
-
Wilner, Joel Alexander, Morlighem, Mathieu, and Cheng, Gong
- Abstract
Many floating ice shelves in Antarctica buttress the ice streams feeding them, thereby reducing the discharge of icebergs into the ocean. The rate at which ice shelves calve icebergs and how fast they flow determines whether they advance, retreat, or remain stable, exerting a first-order control on ice discharge. To parameterize calving within ice sheet models, several empirical and physical calving “laws” have been proposed in the past few decades. Such laws emphasize dissimilar features, including along- and across-flow strain rates (the eigencalving law), a fracture yield criterion (the von Mises law), longitudinal stretching (the crevasse depth law), and a simple ice thickness threshold (the minimum thickness law), among others. Despite the multitude of established calving laws, these laws remain largely unvalidated for the Antarctic Ice Sheet, rendering it difficult to assess the broad applicability of any given law in Antarctica. We address this shortcoming through a set of numerical experiments that evaluate existing calving laws for ten ice shelves around the Antarctic Ice Sheet. We utilize the Ice-sheet and Sea-level System Model (ISSM) and implement four calving laws under constant external forcing, calibrating the free parameter of each of these calving laws by assuming that the current position of the ice front is in steady state and finding the set of parameters that best achieves this position over a simulation of 200 years. We find that, in general, the eigencalving and von Mises laws best reproduce observed calving front positions under the steady state position assumption. These results will streamline future modeling efforts of Antarctic ice shelves by better informing the relevant physics of Antarctic-style calving on a shelf-by-shelf basis.
- Published
- 2023
38. 10Be dating reveals early-middle Holocene age of the Drygalski Moraines in central West Greenland
- Author
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Cronauer, Sandra L., Briner, Jason P., Kelley, Samuel E., Zimmerman, Susan R.H., and Morlighem, Mathieu
- Published
- 2016
- Full Text
- View/download PDF
39. Holocene deceleration of the Greenland Ice Sheet
- Author
-
MacGregor, Joseph A., Colgan, William T., Fahnestock, Mark A., Morlighem, Mathieu, Catania, Ginny A., Paden, John D., and Gogineni, S. Prasad
- Published
- 2016
40. Numerical stabilization methods for level-set-based ice front migration.
- Author
-
Cheng, Gong, Morlighem, Mathieu, and Gudmundsson, G. Hilmar
- Subjects
- *
ICE sheets , *GLACIERS , *ABSOLUTE sea level change , *SUBGLACIAL lakes , *MOTION capture (Human mechanics) , *MOTION - Abstract
Numerical modeling of ice sheet dynamics is a critical tool for projecting future sea-level rise. Among all the processes responsible for the loss of mass of the ice sheets, enhanced ice discharge triggered by the retreat of marine terminating glaciers is one of the key drivers. Numerical models of ice sheet flow are therefore required to include ice front migration in order to reproduce today's mass loss and be able to predict their future. However, the discontinuous nature of calving poses significant numerical challenge for accurately capturing the motion of the ice front. In this study, we explore different stabilization techniques combined with varying reinitialization strategies to enhance the numerical stability and accuracy of solving the level-set function, which tracks the position of the ice front. Through rigorous testing on an idealized domain with semicircular and a straight-line ice front, including scenarios with diverse front velocities, we assess the performance of these techniques. The findings contribute to advancing our ability to model ice sheet dynamics, specifically calving processes, and provide valuable insights into the most effective strategies for simulating and tracking the motion of the ice front. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
41. Model insights into bed control on retreat of Thwaites Glacier, West Antarctica.
- Author
-
Schwans, Emily, Parizek, Byron R., Alley, Richard B., Anandakrishnan, Sridhar, and Morlighem, Mathieu M.
- Subjects
ICE shelves ,GLACIERS ,ICE sheets ,ANTARCTIC ice ,ABSOLUTE sea level change ,PREDICTION models - Abstract
Thwaites Glacier (TG) plays an important role in future sea-level rise (SLR) contribution from the West Antarctic Ice Sheet. Recent observations show that TG is losing mass, and its grounding zone is retreating. Previous modeling has produced a wide range of results concerning whether, when, and how rapidly further retreat will occur under continued warming. These differences arise at least in part from ill-constrained processes, including friction from the bed, and future atmosphere and ocean forcing affecting ice-shelf and grounding-zone buttressing. Here, we apply the Ice Sheet and Sea-level System Model (ISSM) with a range of specifications of basal sliding behavior in response to varying ocean forcing. We find that basin-wide bed character strongly affects TG's response to sub-shelf melt by modulating how changes in driving stress are balanced by the bed as the glacier responds to external forcing. Resulting differences in dynamic thinning patterns alter modeled grounding-line retreat across Thwaites' catchment, affecting both modeled rates and magnitudes of SLR contribution from this critical sector of the ice sheet. Bed character introduces large uncertainties in projections of TG under equal external forcing, pointing to this as a crucial constraint needed in predictive models of West Antarctica. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
42. Closing Greenland's Mass Balance: Frontal Ablation of Every Greenlandic Glacier From 2000 to 2020.
- Author
-
Kochtitzky, William, Copland, Luke, King, Michalea, Hugonnet, Romain, Jiskoot, Hester, Morlighem, Mathieu, Millan, Romain, Khan, Shfaqat Abbas, and Noël, Brice
- Subjects
GLACIERS ,GREENLAND ice ,ICE sheets - Abstract
In Greenland, 87% of the glacierized area terminates in the ocean, but mass lost at the ice‐ocean interface, or frontal ablation, has not yet been fully quantified. Using measurements and models we calculate frontal ablation of Greenland's 213 outlet and 537 peripheral glaciers and find a total frontal ablation of 481.8 ± 24.0 for 2000–2010 and 510.2 ± 18.6 Gt a−1 for 2010–2020. Ice discharge accounted for ∼90% of frontal ablation during both periods, while mass loss due to terminus retreat comprised the remainder. Only 16 glaciers were responsible for the majority (>50%) of frontal ablation from 2010 to 2020. These estimates, along with the climatic‐basal balance, allow for a more complete accounting of Greenland Ice Sheet and peripheral glacier mass balance. In total, Greenland accounted for ∼90% of Northern Hemisphere frontal ablation for 2000–2010 and 2010–2020. Plain Language Summary: We estimate the mass of ice lost from all Greenland glaciers that entered the ocean during each of the last two decades. This ice loss at the front of these marine‐terminating glaciers is called frontal ablation and is approximately equal to the mass of icebergs entering the ocean. Frontal ablation is important because 87% of glacier area in Greenland ends in the ocean, through 750 outlets, and previous work has only approximated frontal ablation. This study quantifies it for the first time, helping to close the mass budget for the Greenland Ice Sheet and better partition its mass balance into components. We find that Greenland accounts for ∼90% of all Northern Hemisphere frontal ablation and, of that contribution, just 17 glaciers for 2000–2010 and 16 glaciers for 2010–2020 account for more than half of total Greenland frontal ablation. Key Points: Frontal ablation of the Greenland Ice Sheet averaged 510.2 ± 18.6 Gt a−1 for 2010–2020, ∼90% of which came from ice dischargeThe frontal ablation we measured is larger than the total mass loss from the ice sheet, indicating a positive climatic‐basal balanceOnly 16 glaciers account for 50% of the total frontal ablation from the Greenland Ice Sheet [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
43. Progress toward globally complete frontal ablation estimates of marine-terminating glaciers.
- Author
-
Kochtitzky, William, Copland, Luke, Van Wychen, Wesley, Hock, Regine, Rounce, David R., Jiskoot, Hester, Scambos, Ted A., Morlighem, Mathieu, King, Michalea, Cha, Leo, Gould, Luke, Merrill, Paige-Marie, Glazovsky, Andrey, Hugonnet, Romain, Strozzi, Tazio, Noël, Brice, Navarro, Francisco, Millan, Romain, Dowdeswell, Julian A., and Cook, Alison
- Subjects
GLACIERS ,ICE calving ,ICE sheets - Abstract
Knowledge of frontal ablation from marine-terminating glaciers (i.e., mass lost at the calving face) is critical for constraining glacier mass balance, improving projections of mass change, and identifying the processes that govern frontal mass loss. Here, we discuss the challenges involved in computing frontal ablation and the unique issues pertaining to both glaciers and ice sheets. Frontal ablation estimates require numerous datasets, including glacier terminus area change, thickness, surface velocity, density, and climatic mass balance. Observations and models of these variables have improved over the past decade, but significant gaps and regional discrepancies remain, and better quantification of temporal variability in frontal ablation is needed. Despite major advances in satellite-derived large-scale datasets, large uncertainties remain with respect to ice thickness, depth-averaged velocities, and the bulk density of glacier ice close to calving termini or grounding lines. We suggest ways in which we can move toward globally complete frontal ablation estimates, highlighting areas where we need improved datasets and increased collaboration. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
44. Hard rock landforms generate 130 km ice shelf channels through water focusing in basal corrugations
- Author
-
Jeofry, Hafeez, Ross, Neil, Le Brocq, Anne, Graham, Alastair G.C., Li, Jilu, Gogineni, Prasad, Morlighem, Mathieu, Jordan, Thomas, and Siegert, Martin J.
- Published
- 2018
- Full Text
- View/download PDF
45. Transient calibration of the Amundsen sea embayment using twenty years of satellite interferometry and altimetry
- Author
-
Morlighem, Mathieu and Goldberg, Daniel
- Abstract
Accurately projecting mass loss from ice sheets is critical to help societies best prepare for the change in sea level. Despite tremendous improvements, several recent studies show that the agreement between models and the observational record remains poor. The inability of numerical models to reproduce observations raises concerns about their ability to provide accurate projections. Data assimilation approaches are great tools to infer unknown parameters by minimizing the misfit between model and observations. Inversions have been used in glaciology since the 1990s, but only for a given point in time. These “snapshot inversions” are routinely used to infer unknown parameters, such as basal friction, but they do not take advantage of time series of observations to which we have access today. The advent of Automatic Differentiation and its recent integration in the Ice-sheet and Sea-level System Model and STREAMICE makes it possible to assimilate almost any type of data using time dependent models. Here we apply transient calibration to the Amundsen Sea Embayment between 2004 and 2022 using surface velocities from MEaSUREs and ITS_LIVE, and surface altimetry data from Cryosat and ICESat-2. We assess the performance of transient compared to snapshot calibrations in terms of capturing past and current trends in speed change, thinning, grounding line retreat and mass change. We then compare future projections over the next 100 years. This exercise paves the way to future modeling work that makes use of more dense time series to constrain critical model parameters and reduce uncertainty in future sea level rise., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)
- Published
- 2023
46. initMIP-Antarctica: an Ice Sheet Model Initialization Experiment of ISMIP6
- Author
-
Seroussi, Helene, Nowicki, Sophie, Simon, Erika, Abe-Ouchi, Ayako, Albrecht, Torsten, Brondex, Julien, Cornford, Stephen, Dumas, Christophe, Gillet-Chaulet, Fabien, Goelzer, Heiko, Golledge, Nicholas R, Gregory, Jonathan M, Greve, Ralf, Hoffman, Matthew J, Humbert, Angelika, Huybrechts, Philippe, Kleiner, Thomas, Larour, Eric, Leguy, Gunter, Lipscomb, William H, Lowry, Daniel, Mengel, Matthias, Morlighem, Mathieu, Pattyn, Frank, Payne, Anthony J, Pollard, David, Price, Stephen F, Quiquet, Aurélien, Reerink, Thomas J, Reese, Ronja, Rodehacke, Christian B, Schlegel, Nicole-Jeanne, Shepherd, Andrew, Sun, Sainan, Sutter, Johannes, Breedam, Jonas Van, Wal, Roderik S. W. van de, Winkelmann, Ricarda, and Zhang, Tong
- Subjects
Geosciences (General) - Abstract
Ice sheet numerical modeling is an important tool to estimate the dynamic contribution of the Antarctic ice sheet to sea level rise over the coming centuries. The influence of initial conditions on ice sheet model simulations, however, is still unclear. To better understand this influence, an initial state intercomparison exercise (initMIP) has been developed to compare, evaluate, and improve initialization procedures and estimate their impact on century-scale simulations. initMIP is the first set of experiments of the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6), which is the primary Coupled Model Intercomparison Project Phase 6 (CMIP6) activity focusing on the Greenland and Antarctic ice sheets. Following initMIP-Greenland, initMIP-Antarctica has been designed to explore uncertainties associated with model initialization and spin-up and to evaluate the impact of changes in external forcings. Starting from the state of the Antarctic ice sheet at the end of the initialization procedure, three forward experiments are each run for 100 years: a control run, a run with a surface mass balance anomaly, and a run with a basal melting anomaly beneath floating ice. This study presents the results of initMIP-Antarctica from 25 simulations performed by 16 international modeling groups. The submitted results use different initial conditions and initialization methods, as well as ice flow model parameters and reference external forcings. We find a good agreement among model responses to the surface mass balance anomaly but large variations in responses to the basal melting anomaly. These variations can be attributed to differences in the extent of ice shelves and their upstream tributaries, the numerical treatment of grounding line, and the initial ocean conditions applied, suggesting that ongoing efforts to better represent ice shelves in continental-scale models should continue.
- Published
- 2019
- Full Text
- View/download PDF
47. Potential Antarctic Contribution to Sea Level Due to Uncertainties in Ice Sheet Model Forcing and Dynamic Feedbacks
- Author
-
Schlegel, Nicole-Jeanne, Seroussi, Helene, Schodlok, Michael, Larour, Eric, Boening, Carmen, Limonadi, Daniel, Morlighem, Mathieu, Caron, Lambert, and Adhikari, Surendra
- Published
- 2018
48. Potential Antarctic Contribution to Sea Level Due to Uncertainties in Ice Sheet Model Forcing and Dynamic Feedbacks
- Author
-
Adhikari, Surendra, Caron, Lambert, Morlighem, Mathieu, Limonadi, Daniel, Boening, Carmen, Larour, Eric, Schodlok, Michael, Seroussi, Helene, and Schlegel, Nicole-Jeanne
- Abstract
UNKNOWN
- Published
- 2018
49. Impact of boundary conditions on the modeled thermal regime of the Antarctic ice sheet.
- Author
-
In-Woo Park, Kyung Jin, Emilia, Morlighem, Mathieu, and Kang-Kun Lee
- Abstract
A realistic initialization of ice flow models is critical for predicting future changes in ice sheet mass balance and their associated contribution to sea level rise. The initial thermal state of an ice sheet is particularly important as it controls ice viscosity and basal conditions, thereby influencing the overall ice velocity. Englacial and subglacial conditions, however, remain poorly understood due to insufficient direct measurements, which complicates the initialization and validation of thermal models. Here, we investigate the impact of using different geothermal heat flux (GHF) datasets and vertical velocity profiles on the thermal state of the Antarctic ice sheet, and compare our modeled temperatures to in situ measurements from 15 boreholes. We find that the vertical velocity plays a more important role in the temperature profile than GHF. More importantly, we find that the standard approach, which consists in combining basal sliding speed and incompressibility to derive vertical velocities, provides reasonably good results in fast flowing regions (ice velocity > 50 m yr-1), but performs poorly in slower moving regions. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
50. In the Quest of a Parametric Relation Between Ice Sheet Model Inferred Weertman's Sliding‐Law Parameter and Airborne Radar‐Derived Basal Reflectivity Underneath Thwaites Glacier, Antarctica.
- Author
-
Das, Indrani, Morlighem, Mathieu, Barnes, Jowan, Gudmundsson, G. Hilmar, Goldberg, Daniel, and Dias dos Santos, Thiago
- Subjects
- *
ICE sheets , *SUBGLACIAL lakes , *STATISTICAL correlation , *GROUND penetrating radar , *PEARSON correlation (Statistics) - Abstract
Numerical ice sheet models use sliding laws to connect basal shear stress and ice velocity to simulate ice sliding. A sliding‐law parameter β2 is used to control Weertman's sliding law in numerical ice sheet models. Basal reflectivity derived from ice‐penetrating radar also provides information about frozen or thawed conditions underneath glaciers. To assess whether basal reflectivity can be used to constrain β2, we carry out statistical experiments between two recently published datasets: β2 inferred from three numerical ice sheet models (ISSM, Úa and STREAMICE) and airborne radar‐derived relative basal reflectivity from the AGASEA‐BBAS mission over Thwaites Glacier (TG). Our results show no robust correlation between the β2–relative reflectivity pair. Pearson's correlation coefficient, a test of linearity, ranges from −0.26 to −0.38. Spearman's correlation coefficient, which does not require a linear assumption, is also modest (∼−0.35). We conclude that β2 and relative basal reflectivity underneath TG do not infer similar basal conditions. Plain Language Summary: Ice sheet models use equations called sliding laws to simulate how fast or slow ice can flow over the bed of a glacier. One such sliding law is Weertman's sliding law, which is widely used by numerical ice sheet models. A parameter called β2 is used in Weertman's sliding law to match the observed velocity. Another parameter called basal reflectivity, derived from airborne ice penetrating radar data, is widely used to identify whether the bed underneath a glacier is frozen or thawed. Frozen or thawed conditions impact how fast a glacier can slide over its bed. Here, we try to find statistical correlations between β2 and basal reflectivity over Thwaites Glacier (TG), West Antarctica. Our results show that the correlation values are not robust, which suggests that β2 and basal reflectivity do not identify similar conditions at the bed underneath TG. Key Points: Correlation experiments are carried out between Weertman's sliding‐law parameter β2 and radar‐derived relative basal reflectivityThe correlations between β2 and relative basal reflectivity are low, suggesting that they do not identify similar conditions at the bedThe correlations do not improve with any value of the sliding exponent m between 3 and 20 [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
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