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Hoffman AO, Christianson K, Holschuh N, Case E, Kingslake J, Arthern R. The Impact of Basal Roughness on Inland Thwaites Glacier Sliding. Geophys Res Lett 2022; 49:e2021GL096564. [PMID: 36249285 PMCID: PMC9541487 DOI: 10.1029/2021gl096564] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 06/03/2022] [Accepted: 06/07/2022] [Indexed: 06/16/2023]
Abstract
Swath radar technology enables three-dimensional mapping of modern glacier beds over large areas at resolutions that are higher than those typically used in ice-flow models. These data may enable new understanding of processes at the ice-bed interface. Here, we use two densely surveyed swath-mapped topographies (<50 m2 resolution) of Thwaites Glacier to investigate the sensitivity of inferred basal friction proxies to bed roughness magnitude and orientation. Our work suggests that along-flow roughness influences inferred friction more than transverse-flow roughness, which agrees with analytic form-drag sliding theory. Using our model results, we calculate the slip length (the ratio of internal shear to basal slip). We find excellent agreement between the numerically derived slip lengths and slip lengths predicted by analytic form-drag sliding theory, which suggests that unresolved short wavelength bed roughness may control sliding in the Thwaites interior.
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Affiliation(s)
- Andrew O. Hoffman
- Department of Earth and Space SciencesUniversity of WashingtonSeattleWAUSA
- Polar Science CenterApplied Physics LaboratoryUniversity of WashingtonSeattleWAUSA
| | - Knut Christianson
- Department of Earth and Space SciencesUniversity of WashingtonSeattleWAUSA
| | | | - Elizabeth Case
- Department of Earth and Environmental SciencesColumbia UniversityNew YorkNYUSA
| | - Jonathan Kingslake
- Department of Earth and Environmental SciencesColumbia UniversityNew YorkNYUSA
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Hamlington BD, Gardner AS, Ivins E, Lenaerts JTM, Reager JT, Trossman DS, Zaron ED, Adhikari S, Arendt A, Aschwanden A, Beckley BD, Bekaert DPS, Blewitt G, Caron L, Chambers DP, Chandanpurkar HA, Christianson K, Csatho B, Cullather RI, DeConto RM, Fasullo JT, Frederikse T, Freymueller JT, Gilford DM, Girotto M, Hammond WC, Hock R, Holschuh N, Kopp RE, Landerer F, Larour E, Menemenlis D, Merrifield M, Mitrovica JX, Nerem RS, Nias IJ, Nieves V, Nowicki S, Pangaluru K, Piecuch CG, Ray RD, Rounce DR, Schlegel N, Seroussi H, Shirzaei M, Sweet WV, Velicogna I, Vinogradova N, Wahl T, Wiese DN, Willis MJ. Understanding of Contemporary Regional Sea-Level Change and the Implications for the Future. Rev Geophys 2020; 58:e2019RG000672. [PMID: 32879921 PMCID: PMC7375165 DOI: 10.1029/2019rg000672] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 03/17/2020] [Accepted: 03/19/2020] [Indexed: 06/11/2023]
Abstract
Global sea level provides an important indicator of the state of the warming climate, but changes in regional sea level are most relevant for coastal communities around the world. With improvements to the sea-level observing system, the knowledge of regional sea-level change has advanced dramatically in recent years. Satellite measurements coupled with in situ observations have allowed for comprehensive study and improved understanding of the diverse set of drivers that lead to variations in sea level in space and time. Despite the advances, gaps in the understanding of contemporary sea-level change remain and inhibit the ability to predict how the relevant processes may lead to future change. These gaps arise in part due to the complexity of the linkages between the drivers of sea-level change. Here we review the individual processes which lead to sea-level change and then describe how they combine and vary regionally. The intent of the paper is to provide an overview of the current state of understanding of the processes that cause regional sea-level change and to identify and discuss limitations and uncertainty in our understanding of these processes. Areas where the lack of understanding or gaps in knowledge inhibit the ability to provide the needed information for comprehensive planning efforts are of particular focus. Finally, a goal of this paper is to highlight the role of the expanded sea-level observation network-particularly as related to satellite observations-in the improved scientific understanding of the contributors to regional sea-level change.
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Smith B, Fricker HA, Gardner AS, Medley B, Nilsson J, Paolo FS, Holschuh N, Adusumilli S, Brunt K, Csatho B, Harbeck K, Markus T, Neumann T, Siegfried MR, Zwally HJ. Pervasive ice sheet mass loss reflects competing ocean and atmosphere processes. Science 2020; 368:1239-1242. [PMID: 32354841 DOI: 10.1126/science.aaz5845] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Accepted: 04/13/2020] [Indexed: 01/07/2023]
Abstract
Quantifying changes in Earth's ice sheets and identifying the climate drivers are central to improving sea level projections. We provide unified estimates of grounded and floating ice mass change from 2003 to 2019 using NASA's Ice, Cloud and land Elevation Satellite (ICESat) and ICESat-2 satellite laser altimetry. Our data reveal patterns likely linked to competing climate processes: Ice loss from coastal Greenland (increased surface melt), Antarctic ice shelves (increased ocean melting), and Greenland and Antarctic outlet glaciers (dynamic response to ocean melting) was partially compensated by mass gains over ice sheet interiors (increased snow accumulation). Losses outpaced gains, with grounded-ice loss from Greenland (200 billion tonnes per year) and Antarctica (118 billion tonnes per year) contributing 14 millimeters to sea level. Mass lost from West Antarctica's ice shelves accounted for more than 30% of that region's total.
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Affiliation(s)
- Ben Smith
- Polar Science Center, Applied Physics Laboratory, University of Washington, Seattle, WA, USA.
| | - Helen A Fricker
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA
| | - Alex S Gardner
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Brooke Medley
- Cryospheric Science Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - Johan Nilsson
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Fernando S Paolo
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Nicholas Holschuh
- Department of Earth and Space Sciences, University of Washington, Seattle, WA, USA.,Department of Geology, Amherst College, Amherst, MA, USA
| | - Susheel Adusumilli
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA
| | - Kelly Brunt
- Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD, USA
| | - Bea Csatho
- Department of Geological Sciences, University at Buffalo, Buffalo, NY, USA
| | | | - Thorsten Markus
- Cryospheric Science Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - Thomas Neumann
- Cryospheric Science Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | | | - H Jay Zwally
- Cryospheric Science Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA.,Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD, USA
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Alley KE, Scambos TA, Alley RB, Holschuh N. Troughs developed in ice-stream shear margins precondition ice shelves for ocean-driven breakup. Sci Adv 2019; 5:eaax2215. [PMID: 31633022 PMCID: PMC6785253 DOI: 10.1126/sciadv.aax2215] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Accepted: 09/11/2019] [Indexed: 06/10/2023]
Abstract
Floating ice shelves of fast-flowing ice streams are prone to rift initiation and calving originating along zones of rapid shearing at their margins. Predicting future ice-shelf destabilization under a warming ocean scenario, with the resultant reduced buttressing, faster ice flow, and sea-level rise, therefore requires an understanding of the processes that thin and weaken these shear margins. Here, we use satellite data to show that high velocity gradients result in surface troughs along the margins of fast-flowing ice streams. These troughs are advected into ice-shelf margins, where the locally thinned ice floats upward to form basal troughs. Buoyant plumes of warm ocean water beneath ice shelves can be focused into these basal troughs, localizing melting and weakening the ice-shelf margins. This implies that major ice sheet drainages are preconditioned for rapid retreat in response to ocean warming.
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Affiliation(s)
- Karen E. Alley
- Department of Earth Sciences, College of Wooster, Wooster, OH 44691, USA
- Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado Boulder, Boulder, CO 80309, USA
| | - Ted A. Scambos
- Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado Boulder, Boulder, CO 80309, USA
| | - Richard B. Alley
- Department of Geosciences, Penn State University, State College, PA 16802, USA
| | - Nicholas Holschuh
- Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USA
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Albertson A, Joshi N, Fuentes K, Holschuh N, Bapna A, Borse H. Soup Consumption in the United States: Associations with Nutrient Intakes and Body Measures in Adults. J Acad Nutr Diet 2012. [DOI: 10.1016/j.jand.2012.06.087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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