USAP-DC

{"dp_type": "Dataset", "free_text": "Strain Rate"}

[{"awards": "1643120 Iverson, Neal", "bounds_geometry": null, "date_created": "Mon, 16 Sep 2024 00:00:00 GMT", "description": "Accurately modeling the deformation of temperate glacier ice, which is at its pressure-melting temperature and contains liquid water at grain boundaries, is essential for predicting ice sheet discharge to the ocean and associated sea-level rise. Central to such modeling is Glen\u2019s flow law, in which strain rate depends on stress raised to a power of n=3-4. In sharp contrast to this nonlinearity, we find by conducting large-scale, shear-deformation experiments to tertiary creep that temperate ice is linear-viscous (n\u22481.0) over common ranges of liquid water content and stress expected near glacier beds and in ice stream margins. This linearity is likely caused by diffusive pressure-melting and refreezing at grain boundaries and could help stabilize modeled responses of ice sheets to shrinkage-induced stress increases.", "east": null, "geometry": null, "keywords": "Antarctica; Cryosphere", "locations": "Antarctica", "north": null, "nsf_funding_programs": "Antarctic Glaciology", "persons": "Iverson, Neal", "project_titles": "NSFGEO-NERC: Collaborative Research: Two-Phase Dynamics of Temperate Ice", "projects": [{"proj_uid": "p0010197", "repository": "USAP-DC", "title": "NSFGEO-NERC: Collaborative Research: Two-Phase Dynamics of Temperate Ice"}], "repo": "USAP-DC", "repositories": "USAP-DC", "science_programs": null, "south": null, "title": "Tertiary creep rates of temperate ice containing greater than 0.7% liquid water", "uid": "601833", "west": null}, {"awards": "1745043 Simkins, Lauren; 1745055 Stearns, Leigh; 1246353 Anderson, John", "bounds_geometry": ["POLYGON((-180 -60,-144 -60,-108 -60,-72 -60,-36 -60,0 -60,36 -60,72 -60,108 -60,144 -60,180 -60,180 -63,180 -66,180 -69,180 -72,180 -75,180 -78,180 -81,180 -84,180 -87,180 -90,144 -90,108 -90,72 -90,36 -90,0 -90,-36 -90,-72 -90,-108 -90,-144 -90,-180 -90,-180 -87,-180 -84,-180 -81,-180 -78,-180 -75,-180 -72,-180 -69,-180 -66,-180 -63,-180 -60))"], "date_created": "Wed, 10 Nov 2021 00:00:00 GMT", "description": "The dataset here allows exploration of the causes and significance of Antarctic grounding-line sinuosity by coupling observations of contemporary Antarctic grounding lines and paleo-grounding lines expressed as ice-marginal landforms on the Ross Sea continental shelf. Modern grounding lines are derived from the MEaSUREs Version 2 Differential Satellite Radar Interferometry dataset with spatial resolutions of 25-120 m spanning February 1992 to December 2014 (Rignot et al., 2016; Mouginot et al., 2017). The boundaries of individual grounding lines representative of individual glacial catchments (n=664) were delineated by the inflection points of the shear strain rate, \u03b5xy (c.f Van der Veen et al., 2011). Sinuosity was calculated as the ratio of the true length, orthogonal to ice-flow direction, of the grounding lines and the straight line length between end-points and in units of km/km. Raster data were extracted at 1-km points along each grounding line; the mean was calculated for each grounding line and merged in a table with sinuosity data. A dataset of 6,275 paleo-grounding lines expressed as ice-marginal landforms on the deglaciated western Ross Sea continental shelf are used in this study, originally published by Simkins et al., 2018. The ice-marginal landforms were mapped from multibeam echo sounder data that was collected onboard the RVIB Nathaniel B. Palmer (NBP) 15-02 cruise using a Kongsberg EM122 operating in dual swath mode at 12 kHz frequency with 30-60% swath overlap (Cruise DOI: 10.7284/901477). The resulting bathymetry data was gridded at 20-40 m with decimeter vertical elevation resolution depending on water depth and sea-state. Sinuosity is calculated as a ratio of true (mapped) landform length, measured in the across paleo-ice flow direction at the crest of the landform, to the straight line distance between the mapped landform endpoints and in units of km/km. \r\n\r\nTo compare modern and paleo-grounding lines, we use a consistent length scale by segmenting the grounding lines into 2-km sections for the two datasets (modern, n=12,966; paleo, n=5,832), even though this eliminates grounding lines that are less than 2-km long and thus results in 1 modern and 3,873 paleo-grounding lines removed. The full-length and 2-km segmented groundings lines are provided as shapefiles \"InSAR_groundinglines_full\" and \"InSAR_groundinglines_2km\", the paleo-grounding lines are provided as shapefiles \"RossSea_icemarginal_full\" and \"RossSea_icemarginal_2km\", and points marking modern grounding lines retreat from repeat InSAR surveys are provided as shapefile \"InSAR_retreat_points\", all stored together in a geodatabase named \"Antarctic_groundinglines.gbd\". Additional grounding line metrics, including length, sinuosity, bed roughness, and bed slope for modern and paleo-grounding lines, and height-above-buoyancy gradient, ice-flow velocity, presence of pinning points and ice shelves are provided for modern grounding lines. \r\n\r\nThe published dataset was compiled and analyzed in the article \"Controls on circum-Antarctic grounding-line sinuosity \" by Simkins, L.M., Stearns, L.A., and Riverman, K.L, which will be submitted to a peer-review journal in November 2021.\r\n\r\nReferences\r\nMouginot, J., B. Scheuchl, and E. Rignot. 2017. MEaSUREs Antarctic Boundaries for IPY 2007-2009 from Satellite Radar, Version 2. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. \r\n\r\nRignot, E., J. Mouginot, and B. Scheuchl. 2016. MEaSUREs Antarctic Grounding Line from Differential Satellite Radar Interferometry, Version 2. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. \r\n\r\nSimkins, L. M., Greenwood, S. L., \u0026 Anderson, J. B. (2018). Diagnosing ice sheet grounding line stability from landform morphology. The Cryosphere, 12(8), 2707-2726.\r\n\r\nVan der Veen, C. J., J. C. Plummer, \u0026 L. A. Stearns. (2011). Controls on the recent speed up of Jakobshavn Isbr\u00e6, West Greenland. Journal of Glaciology, 57(204), 770-782", "east": 180.0, "geometry": ["POINT(0 -89.999)"], "keywords": "Antarctica; Bed Roughness; Bed Slope; Elevation; Glaciers/ice Sheet; Glaciers/Ice Sheet; Pinning Points", "locations": "Antarctica; Antarctica", "north": -60.0, "nsf_funding_programs": "Antarctic Earth Sciences; Antarctic Earth Sciences; Antarctic Earth Sciences", "persons": "Simkins, Lauren; Stearns, Leigh; Riverman, Kiya", "project_titles": "Collaborative Research: Topographic controls on Antarctic Ice Sheet grounding line retreat - integrating models and observations; Evidence for Paleo Ice Stream Collapse in the Western Ross Sea since the Last Glacial Maximum.", "projects": [{"proj_uid": "p0000395", "repository": "USAP-DC", "title": "Evidence for Paleo Ice Stream Collapse in the Western Ross Sea since the Last Glacial Maximum."}, {"proj_uid": "p0010269", "repository": "USAP-DC", "title": "Collaborative Research: Topographic controls on Antarctic Ice Sheet grounding line retreat - integrating models and observations"}], "repo": "USAP-DC", "repositories": "USAP-DC", "science_programs": null, "south": -90.0, "title": "Circum-Antarctic grounding-line sinuosity", "uid": "601484", "west": -180.0}, {"awards": "1738992 Pettit, Erin C", "bounds_geometry": ["POLYGON((-114 -74,-113 -74,-112 -74,-111 -74,-110 -74,-109 -74,-108 -74,-107 -74,-106 -74,-105 -74,-104 -74,-104 -74.2,-104 -74.4,-104 -74.6,-104 -74.8,-104 -75,-104 -75.2,-104 -75.4,-104 -75.6,-104 -75.8,-104 -76,-105 -76,-106 -76,-107 -76,-108 -76,-109 -76,-110 -76,-111 -76,-112 -76,-113 -76,-114 -76,-114 -75.8,-114 -75.6,-114 -75.4,-114 -75.2,-114 -75,-114 -74.8,-114 -74.6,-114 -74.4,-114 -74.2,-114 -74))"], "date_created": "Mon, 11 Oct 2021 00:00:00 GMT", "description": "This dataset includes GeoTiffs of two-year averages of ice flow velocity (including x- and y-components and flow speed) and longitudinal, transverse, and shear strain rates for the Thwaites Eastern Ice Shelf (TEIS) from 2001-2020. The grids were derived from feature tracking on MODIS, Landsat-7, and Landsat-8 imagery. Each pixel in a grid represents the median value of a stack of all available pixels for each time period. Data are gridded at a 500 m spatial resolution in a polar stereographic (EPSG:3031) projection. Speed units are m/day and strain rates are in units of /day. In addition, we provide videos of each variable (excluding x- and y-velocity components) placed alongside a MODIS image of the same extent and from around the same time to provide context. In addition to the variables noted above, we include videos for flow direction (in degrees from grid north in an EPSG:3031 projection) and a zoomed-in version of flow direction, which were calculated from the provided grids.", "east": -104.0, "geometry": ["POINT(-109 -75)"], "keywords": "Antarctica; Glaciology; Ice Shelf; Ice Velocity; Strain Rate; Thwaites Glacier", "locations": "Antarctica; Thwaites Glacier", "north": -74.0, "nsf_funding_programs": "Antarctic Ocean and Atmospheric Sciences", "persons": "Alley, Karen; Wild, Christian; Scambos, Ted; Muto, Atsu; Pettit, Erin; Truffer, Martin; Wallin, Bruce; Klinger, Marin", "project_titles": "NSF-NERC: Thwaites-Amundsen Regional Survey and Network (TARSAN) Integrating Atmosphere-Ice-Ocean Processes affecting the Sub-Ice-Shelf Environment", "projects": [{"proj_uid": "p0010162", "repository": "USAP-DC", "title": "NSF-NERC: Thwaites-Amundsen Regional Survey and Network (TARSAN) Integrating Atmosphere-Ice-Ocean Processes affecting the Sub-Ice-Shelf Environment"}], "repo": "USAP-DC", "repositories": "USAP-DC", "science_programs": "Thwaites (ITGC)", "south": -76.0, "title": "Two-year velocity and strain-rate averages from the Thwaites Eastern Ice Shelf, 2001-2020", "uid": "601478", "west": -114.0}, {"awards": "1842021 Campbell, Seth", "bounds_geometry": ["POLYGON((-168 -82,-162.3 -82,-156.6 -82,-150.9 -82,-145.2 -82,-139.5 -82,-133.8 -82,-128.1 -82,-122.4 -82,-116.7 -82,-111 -82,-111 -82.5,-111 -83,-111 -83.5,-111 -84,-111 -84.5,-111 -85,-111 -85.5,-111 -86,-111 -86.5,-111 -87,-116.7 -87,-122.4 -87,-128.1 -87,-133.8 -87,-139.5 -87,-145.2 -87,-150.9 -87,-156.6 -87,-162.3 -87,-168 -87,-168 -86.5,-168 -86,-168 -85.5,-168 -85,-168 -84.5,-168 -84,-168 -83.5,-168 -83,-168 -82.5,-168 -82))"], "date_created": "Sat, 12 Dec 2020 00:00:00 GMT", "description": "The dataset includes GPS coordinates for crevasse/fracture locations picked from 350MHz and 400Mhz frequency GPR dataset in the Whillans/Mercer Shear Margin along the SALSA traverse route with associated kinematic outputs for each feature (shear strain rate, vorticity, dilatation). GPS coordinates are in the Antarctic Polar Stereographic projection (EPSG:3031). ", "east": -111.0, "geometry": ["POINT(-139.5 -84.5)"], "keywords": "Antarctica; Crevasses; Glaciology; GPR; GPS; Ice Sheet Flow Model; Ice Shelf Dynamics; Snow/ice; Snow/Ice; Whillans Ice Stream", "locations": "Antarctica; Whillans Ice Stream", "north": -82.0, "nsf_funding_programs": "Antarctic Glaciology", "persons": "Kaluzienski, Lynn", "project_titles": "RAPID Proposal: Constraining kinematics of the Whillans/Mercer Ice Stream Confluence", "projects": [{"proj_uid": "p0010145", "repository": "USAP-DC", "title": "RAPID Proposal: Constraining kinematics of the Whillans/Mercer Ice Stream Confluence"}], "repo": "USAP-DC", "repositories": "USAP-DC", "science_programs": null, "south": -87.0, "title": "2017 GPR Observations of the Whillans and Mercer Ice Streams", "uid": "601403", "west": -168.0}, {"awards": "0838947 Tulaczyk, Slawek", "bounds_geometry": ["POLYGON((-165.28 -84.24,-165.086 -84.24,-164.892 -84.24,-164.698 -84.24,-164.504 -84.24,-164.31 -84.24,-164.116 -84.24,-163.922 -84.24,-163.728 -84.24,-163.534 -84.24,-163.34 -84.24,-163.34 -84.252,-163.34 -84.264,-163.34 -84.276,-163.34 -84.288,-163.34 -84.3,-163.34 -84.312,-163.34 -84.324,-163.34 -84.336,-163.34 -84.348,-163.34 -84.36,-163.534 -84.36,-163.728 -84.36,-163.922 -84.36,-164.116 -84.36,-164.31 -84.36,-164.504 -84.36,-164.698 -84.36,-164.892 -84.36,-165.086 -84.36,-165.28 -84.36,-165.28 -84.348,-165.28 -84.336,-165.28 -84.324,-165.28 -84.312,-165.28 -84.3,-165.28 -84.288,-165.28 -84.276,-165.28 -84.264,-165.28 -84.252,-165.28 -84.24))"], "date_created": "Sun, 09 Sep 2018 00:00:00 GMT", "description": "This dataset contains ice-shelf basal melt rates and vertical strain rates for 11 sites near the Whillans Ice Stream grounding line. These rates were determined using Autonomous Phase-Sensitive Radar. Data processing is described in Begeman et al. 2018, JGR Oceans. These sites are concentrated within an embayment of the Ross Ice Shelf. These melt rates and strain rates were determined over periods ranging from 10 to 38 days in December 2014 to January 2015. ", "east": -163.34, "geometry": ["POINT(-164.31 -84.3)"], "keywords": "Antarctica; Flexure Zone; Glaciers/ice Sheet; Glaciers/Ice Sheet; Glaciology; Ice Shelf; Ice-Shelf Basal Melting; Ice-Shelf Strain Rate", "locations": "Antarctica", "north": -84.24, "nsf_funding_programs": "Antarctic Integrated System Science", "persons": "Begeman, Carolyn", "project_titles": "Collaborative Research: Integrative Study of Marine Ice Sheet Stability \u0026 Subglacial Life Habitats in W Antarctica - Lake \u0026 Ice Stream Subglacial Access Research Drilling (LISSARD)", "projects": [{"proj_uid": "p0000105", "repository": "USAP-DC", "title": "Collaborative Research: Integrative Study of Marine Ice Sheet Stability \u0026 Subglacial Life Habitats in W Antarctica - Lake \u0026 Ice Stream Subglacial Access Research Drilling (LISSARD)"}], "repo": "USAP-DC", "repositories": "USAP-DC", "science_programs": "WISSARD", "south": -84.36, "title": "Basal melt rates of the Ross Ice Shelf near the Whillans Ice Stream grounding line", "uid": "601122", "west": -165.28}, {"awards": "9615502 Harrison, William", "bounds_geometry": ["POINT(-148.822 -81.655)", "POINT(-148.693 -81.595)"], "date_created": "Thu, 22 Feb 2007 00:00:00 GMT", "description": "At the Siple Dome area of Antarctica, much of the ice flow is vertical, which causes vertical ice deformation. To measure this phenomenon, the investigators used a method known as vertical strain rate. This project was a part of the West Antarctic Ice Sheet Cores (WAISCORES) project for deep ice coring in West Antarctica. WAISCORES is supported by the Office of Polar Programs (OPP), National Science Foundation (NSF).\n\nThis data set consists of a table of long-term average strain rates measured between 1999 and 2002 at Siple Dome, Antarctica. The measurements were taken in hot-water boreholes by bridge gauges. Data are available in tab-delimited ASCII text format or PDF via FTP.", "east": -148.693, "geometry": ["POINT(-148.822 -81.655)", "POINT(-148.693 -81.595)"], "keywords": "Antarctica; Geodesy; Geology/Geophysics - Other; Glaciers/ice Sheet; Glaciers/Ice Sheet; Glaciology; Siple Dome; Siple Dome Ice Core; Strain; WAISCORES", "locations": "Antarctica; Siple Dome", "north": -81.595, "nsf_funding_programs": "Antarctic Glaciology", "persons": "Harrison, William; Morack, James; Waddington, Edwin D.; Pettit, Erin; Zumberge, Mark; Elsberg, Daniel", "project_titles": "Ice Dynamics, the Flow Law, and Vertical Strain at Siple Dome", "projects": [{"proj_uid": "p0000601", "repository": "USAP-DC", "title": "Ice Dynamics, the Flow Law, and Vertical Strain at Siple Dome"}], "repo": "USAP-DC", "repositories": "USAP-DC", "science_programs": "Siple Dome Ice Core", "south": -81.655, "title": "Vertical Strain at Siple Dome, Antarctica, 1999-2002", "uid": "609214", "west": -148.822}]

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