22 results on '"Hoffman, Andrew O."'
Search Results
2. Amundsen Sea Embayment accumulation variability measured with GNSS-IR
- Author
-
Hoffman, Andrew O., primary, Maclennan, Michelle, additional, Lenaerts, Jan, additional, Larson, Kristine M., additional, and Chrsitianson, Knut, additional
- Published
- 2023
- Full Text
- View/download PDF
3. Supplementary material to "Amundsen Sea Embayment accumulation variability measured with GNSS-IR"
- Author
-
Hoffman, Andrew O., primary, Maclennan, Michelle, additional, Lenaerts, Jan, additional, Larson, Kristine M., additional, and Chrsitianson, Knut, additional
- Published
- 2023
- Full Text
- View/download PDF
4. Antarctic Bedmap data: Findable, Accessible, Interoperable, and Reusable (FAIR) sharing of 60 years of ice bed, surface, and thickness data
- Author
-
Frémand, Alice C., primary, Fretwell, Peter, additional, Bodart, Julien A., additional, Pritchard, Hamish D., additional, Aitken, Alan, additional, Bamber, Jonathan L., additional, Bell, Robin, additional, Bianchi, Cesidio, additional, Bingham, Robert G., additional, Blankenship, Donald D., additional, Casassa, Gino, additional, Catania, Ginny, additional, Christianson, Knut, additional, Conway, Howard, additional, Corr, Hugh F. J., additional, Cui, Xiangbin, additional, Damaske, Detlef, additional, Damm, Volkmar, additional, Drews, Reinhard, additional, Eagles, Graeme, additional, Eisen, Olaf, additional, Eisermann, Hannes, additional, Ferraccioli, Fausto, additional, Field, Elena, additional, Forsberg, René, additional, Franke, Steven, additional, Fujita, Shuji, additional, Gim, Yonggyu, additional, Goel, Vikram, additional, Gogineni, Siva Prasad, additional, Greenbaum, Jamin, additional, Hills, Benjamin, additional, Hindmarsh, Richard C. A., additional, Hoffman, Andrew O., additional, Holmlund, Per, additional, Holschuh, Nicholas, additional, Holt, John W., additional, Horlings, Annika N., additional, Humbert, Angelika, additional, Jacobel, Robert W., additional, Jansen, Daniela, additional, Jenkins, Adrian, additional, Jokat, Wilfried, additional, Jordan, Tom, additional, King, Edward, additional, Kohler, Jack, additional, Krabill, William, additional, Kusk Gillespie, Mette, additional, Langley, Kirsty, additional, Lee, Joohan, additional, Leitchenkov, German, additional, Leuschen, Carlton, additional, Luyendyk, Bruce, additional, MacGregor, Joseph, additional, MacKie, Emma, additional, Matsuoka, Kenichi, additional, Morlighem, Mathieu, additional, Mouginot, Jérémie, additional, Nitsche, Frank O., additional, Nogi, Yoshifumi, additional, Nost, Ole A., additional, Paden, John, additional, Pattyn, Frank, additional, Popov, Sergey V., additional, Rignot, Eric, additional, Rippin, David M., additional, Rivera, Andrés, additional, Roberts, Jason, additional, Ross, Neil, additional, Ruppel, Anotonia, additional, Schroeder, Dustin M., additional, Siegert, Martin J., additional, Smith, Andrew M., additional, Steinhage, Daniel, additional, Studinger, Michael, additional, Sun, Bo, additional, Tabacco, Ignazio, additional, Tinto, Kirsty, additional, Urbini, Stefano, additional, Vaughan, David, additional, Welch, Brian C., additional, Wilson, Douglas S., additional, Young, Duncan A., additional, and Zirizzotti, Achille, additional
- Published
- 2023
- Full Text
- View/download PDF
5. Inland migration of near-surface crevasses in the Amundsen Sea Sector, West Antarctica.
- Author
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Hoffman, Andrew O., Christianson, Knut, Ching-Yao Lai, Joughin, Ian, Holschuh, Nicholas, Case, Elizabeth, and Kingslake, Jonathan
- Abstract
Since distributed satellite observations of elevation change and velocity became available in the 1990s, Thwaites, Pine Island, Haynes, Pope, and Kohler Glaciers, located in Antarctica's Amundsen Sea Embayment, have thinned and accelerated in response to ocean-induced melting and grounding-line retreat. We develop a crevasse image segmentation algorithm to identify and map surface crevasses on the grounded portions of Thwaites, Pine Island, Haynes, Pope, and Kohler Glaciers between 2015 and 2022 using Sentinel-1A satellite synthetic aperture radar (SAR) imagery. We also develop a geometric 5 model for firn tensile strength dependent on porosity and the tensile strength of ice. On Pine Island and Thwaites Glaciers, which have both accelerated since 2015, crevassing has expanded tens of kilometers upstream of the 2015 extent. From the crevasse time series, we find that crevassing is strongly linked to principal surface stresses and consistent with von Mises fracture theory predictions. Our geometric model, analysis of SAR, and optical imagery, together with ice-penetrating radar data, suggest that these crevasses are near-surface features restricted to the firn. The porosity dependence of the near-surface tensile 10 strength of the ice sheet may explain discrepancies between the tensile strength inferred from remotely-sensed surface crevasse observations and tensile strength measured in laboratory experiments, which often focus on ice (rather than firn) fracture. The near-surface nature of these features suggests that the expansion of crevasses inland has a limited direct impact on glacier mechanics. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
6. 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
7. 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, Cesidio, Bingham, Robert G, Blankenship, Donald D, Casassa, Gino, Catania, Ginny, Christianson, Knut, Conway, Howard, Corr, Hugh FJ, 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 CA, Hoffman, Andrew O, Holmlund, Per, Holschuh, Nicholas, Holt, John W, Horlings, Annika N, Humbert, Angelika, Jacobel, Robert W, Jansen, Daniela, Jenkins, Adrian, Jokat, Wilfried, Jordan, Tom, King, Edward, Kohler, Jack, Krabill, William, Gillespie, Mette Kusk, 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, Zirizzotti, Achille, Frémand, Alice C, Fretwell, Peter, Bodart, Julien A, Pritchard, Hamish D, Aitken, Alan, Bamber, Jonathan L, Bell, Robin, Bianchi, Cesidio, Bingham, Robert G, Blankenship, Donald D, Casassa, Gino, Catania, Ginny, Christianson, Knut, Conway, Howard, Corr, Hugh FJ, 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 CA, Hoffman, Andrew O, Holmlund, Per, Holschuh, Nicholas, Holt, John W, Horlings, Annika N, Humbert, Angelika, Jacobel, Robert W, Jansen, Daniela, Jenkins, Adrian, Jokat, Wilfried, Jordan, Tom, King, Edward, Kohler, Jack, Krabill, William, Gillespie, Mette Kusk, 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
8. Antarctic Bedmap data: Findable, Accessible, Interoperable, and Reusable (FAIR) sharing of 60 years of ice bed, surface, and thickness data
- Author
-
Frémand, Alice, Fretwell, Peter, Bodart, Julien A., Pritchard, Hamish D., Aitken, Alan, Bamber, Jonathan L., Bell, Robin, Bianchi, Cesidio, Bingham, Robert G., Blankenship, Donald, 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 Stevens, Hills, Benjamin, Hindmarsh, Richard C. A., Hoffman, Andrew O., Holmlund, Per, Holschuh, Nicholas, Holt, John W., Horlings, Annika, Humbert, Angelika, Jacobel, Robert, Jansen, Daniela, Jenkins, Adrian, Jokat, Wilfried, Jordan, Tom, King, Edward, Kohler, Jack, Krabill, William, Kusk Gillespie, Mette, Langley, Kirsty, Lee, Joohan, Leitchenkov, German, Leuschen, Carlton, Luyendyk, Bruce, MacGregor, Joseph A., MacKie, Emma, Matsuoka, Kenichi, Morlighem, Mathieu, Mouginot, Jeremie, Nitsche, Frank, Nogi, Yoshifumi, Nost, Ole, Paden, John, Pattyn, Frank, Popov, Sergey V., Rignot, Eric, Rippin, David, Medina-Rivera, Alejandra, 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, Wilson, Douglas S., Young, Duncan A., Zirizzotti, Achille, Frémand, Alice, Fretwell, Peter, Bodart, Julien A., Pritchard, Hamish D., Aitken, Alan, Bamber, Jonathan L., Bell, Robin, Bianchi, Cesidio, Bingham, Robert G., Blankenship, Donald, 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 Stevens, Hills, Benjamin, Hindmarsh, Richard C. A., Hoffman, Andrew O., Holmlund, Per, Holschuh, Nicholas, Holt, John W., Horlings, Annika, Humbert, Angelika, Jacobel, Robert, Jansen, Daniela, Jenkins, Adrian, Jokat, Wilfried, Jordan, Tom, King, Edward, Kohler, Jack, Krabill, William, Kusk Gillespie, Mette, Langley, Kirsty, Lee, Joohan, Leitchenkov, German, Leuschen, Carlton, Luyendyk, Bruce, MacGregor, Joseph A., MacKie, Emma, Matsuoka, Kenichi, Morlighem, Mathieu, Mouginot, Jeremie, Nitsche, Frank, Nogi, Yoshifumi, Nost, Ole, Paden, John, Pattyn, Frank, Popov, Sergey V., Rignot, Eric, Rippin, David, Medina-Rivera, Alejandra, 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, 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 andthe ensuing sea level rise. Supported by the Scientific Committee on Antarctic Research (SCAR), the Bedmap3 Action Group aims not only to produce newgridded maps of ice thickness and bed topography for the internationalscientific community, but also to standardize and make available all thegeophysical survey data points used in producing the Bedmap griddedproducts. Here, we document the survey data used in the latest iteration,Bedmap3, incorporating and adding to all of the datasets previously used forBedmap1 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 futuresurveys 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 provideunprecedented 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 heldwithin 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., info:eu-repo/semantics/published
- Published
- 2023
9. Climatology and surface impacts of atmospheric rivers on West Antarctica
- Author
-
Maclennan, Michelle L., primary, Lenaerts, Jan T. M., additional, Shields, Christine A., additional, Hoffman, Andrew O., additional, Wever, Nander, additional, Thompson-Munson, Megan, additional, Winters, Andrew C., additional, Pettit, Erin C., additional, Scambos, Theodore A., additional, and Wille, Jonathan D., additional
- Published
- 2023
- Full Text
- View/download PDF
10. Amundsen Sea Embayment accumulation variability measured with GNSS-IR.
- Author
-
Hoffman, Andrew O., Maclennan, Michelle L., Lenaerts, Jan, Larson, Kristine M., and Christianson, Knut
- Abstract
In order to improve projections of the future ice-sheet surface mass balance and the interpretation of the isotopic signals of past accumulation preserved in ice cores, it is critical to understand the mechanisms that transport water vapor to the Antarctic continent. Global Navigation Satellite System (GNSS) receivers distributed across Antarctica to monitor ice velocity and solid Earth motion can be used to understand accumulation, ablation, and snow redistribution at the ice-sheet surface. Here, we present a forward model for reflector height change between the GNSS antenna phase center and the snow surface and an inverse framework to determine accumulation rate and near-surface firn densification from the reflector height time series. We use this model to determine accumulation at the sites of three long-term on-ice GNSS receivers located in the Amundsen Sea Embayment (ASE) and at a network of GNSS receivers deployed in 2007-2008, 2008-2009, and 2009-2010 austral summers. From the GNSS-IR accumulation reconstructions, we find that extreme precipitation dominates total precipitation and that extreme event frequency varies seasonally. We use our GNSS-IR accumulation reconstructions together with reanalysis products to characterize the atmospheric conditions that promote extreme snowfall in the ASE. The blocking pressure systems that promote extreme accumulation on Thwaites Glacier are facilitated by tropical teleconnections, specifically convection that promotes Rossby waves trains from the Western Pacific, Indian, and Atlantic Oceans to the Amundsen and Bellingshausen Seas. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
11. The Impact of Basal Roughness on Inland Thwaites Glacier Sliding
- Author
-
Hoffman, Andrew O., primary, Christianson, Knut, additional, Holschuh, Nicholas, additional, Case, Elizabeth, additional, Kingslake, Jonathan, additional, and Arthern, Robert, additional
- Published
- 2022
- Full Text
- View/download PDF
12. The Impact of Basal Roughness on Inland Thwaites Glacier Sliding
- Author
-
Hoffman, Andrew O., Christianson, Knut, Holschuh, Nicholas, Case, Elizabeth, Kingslake, Jonathan, Arthern, Robert, Hoffman, Andrew O., Christianson, Knut, Holschuh, Nicholas, Case, Elizabeth, Kingslake, Jonathan, and Arthern, Robert
- 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.
- Published
- 2022
13. Climatology and Surface Impacts of Atmospheric Rivers on West Antarctica
- Author
-
Maclennan, Michelle L., primary, Lenaerts, Jan T. M., additional, Shields, Christine A., additional, Hoffman, Andrew O., additional, Wever, Nander, additional, Thompson-Munson, Megan, additional, Winters, Andrew C., additional, Pettit, Erin C., additional, Scambos, Theodore A., additional, and Wille, Jonathan D., additional
- Published
- 2022
- Full Text
- View/download PDF
14. Supplementary material to "Climatology and Surface Impacts of Atmospheric Rivers on West Antarctica"
- Author
-
Maclennan, Michelle L., primary, Lenaerts, Jan T. M., additional, Shields, Christine A., additional, Hoffman, Andrew O., additional, Wever, Nander, additional, Thompson-Munson, Megan, additional, Winters, Andrew C., additional, Pettit, Erin C., additional, Scambos, Theodore A., additional, and Wille, Jonathan D., additional
- Published
- 2022
- Full Text
- View/download PDF
15. Geophysics and Thermodynamics at South Pole Lake Indicate Stability and a Regionally Thawed Bed
- Author
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Hills, Benjamin H., primary, Christianson, Knut, additional, Hoffman, Andrew O., additional, Fudge, T. J., additional, Holschuh, Nicholas, additional, Kahle, Emma C., additional, Conway, Howard, additional, Christian, John E., additional, Horlings, Annika N., additional, O’Connor, Gemma K., additional, and Steig, Eric J., additional
- Published
- 2022
- Full Text
- View/download PDF
16. icepack: a new glacier flow modeling package in Python, version 1.0
- Author
-
Shapero, Daniel R., primary, Badgeley, Jessica A., additional, Hoffman, Andrew O., additional, and Joughin, Ian R., additional
- Published
- 2021
- Full Text
- View/download PDF
17. Climatology and Surface Impacts of Atmospheric Rivers on West Antarctica.
- Author
-
Maclennan, Michelle L., Lenaerts, Jan T. M., Shields, Christine A., Hoffman, Andrew O., Wever, Nander, Thompson-Munson, Megan, Winters, Andrew C., Pettit, Erin C., Scambos, Theodore A., and Wille, Jonathan D.
- Abstract
Atmospheric rivers (ARs) transport large amounts of moisture from the mid-to high-latitudes and they are a primary driver of the most extreme snowfall events on Antarctica. ARs also raise surface temperatures when they make landfall over Antarctica, leading to surface melting. In this study, we characterize the climatology and surface impacts of ARs on West Antarctica, focusing on the Amundsen Sea Embayment and Marie Byrd Land. First, we develop a climatology of ARs in this region, using an Antarctic-specific AR detection tool combined with MERRA-2 and ERA5 atmospheric reanalyses. We find that while ARs are infrequent, they cause intense precipitation in short periods of time and account for 11% of the annual surface accumulation. They are driven by the coupling of a blocking high over the Antarctic Peninsula with a low-pressure system known as the Amundsen Sea Low. Next, we use observations from automatic weather stations on Thwaites Eastern Ice Shelf to examine a case study of 3 ARs that made landfall in rapid succession from February 2 to 8, known as an AR family event. We use snow height observations to force the firn model SNOWPACK to reconstruct accumulation and surface melting during the event, and compare these results with accumulation higher up on the glacier derived from surface height changes using interferometric reflectometry. While accumulation dominates the surface impacts of the event on Thwaites Eastern Ice Shelf (>100 kg m
-2 ), we find small amounts of surface melt as well (<5 kg m-2 ). West Antarctica currently experiences minimal surface melting, most of which is absorbed by the firn, but future atmospheric warming could lead to more widespread surface melting in West Antarctica. Combined with a future increase in AR intensity or frequency, this could limit the ability of the firn layer to absorb melt water, which could harm ice shelf stability, and ultimately accelerate mass loss of the West Antarctic Ice Sheet. The results presented here enable us to quantify the past impacts of ARs on West Antarctic surface mass balance and characterize their interannual variability and trends, enabling a better assessment of future AR-driven changes in the surface mass balance. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
18. Brief communication: Heterogenous thinning and subglacial lake activity on Thwaites Glacier, West Antarctica
- Author
-
Hoffman, Andrew O., primary, Christianson, Knut, additional, Shapero, Daniel, additional, Smith, Benjamin E., additional, and Joughin, Ian, additional
- Published
- 2020
- Full Text
- View/download PDF
19. Supplementary material to "Brief Communication: Heterogenous thinning and subglacial lake activity on Thwaites Glacier, West Antarctica"
- Author
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Hoffman, Andrew O., primary, Christianson, Knut, additional, Shapero, Daniel, additional, Smith, Benjamin E., additional, and Joughin, Ian, additional
- Published
- 2020
- Full Text
- View/download PDF
20. A low-cost autonomous rover for polar science
- Author
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Hoffman, Andrew O., Christian Steen-Larsen, Hans, Christianson, Knut, Hvidberg, Christine, Hoffman, Andrew O., Christian Steen-Larsen, Hans, Christianson, Knut, and Hvidberg, Christine
- Abstract
We present the developmental considerations, design, and deployment of an autonomous modular terrestrial rover for ice-sheet exploration that is inexpensive, easy to construct, and allows for instrumentation customization. The total construction cost for this rover is less than USD 3000, approximately one-tenth the cost of existing platforms, and it can be built using facilities frequently available at academic institutions (machine shop, 3-D printer, open-source hardware and software). Instrumentation deployed on this rover can be customized; the rover presented in this study was equipped with a dual-frequency GPS receiver and a digital SLR camera for constructing digital elevation models using structure-from-motion (SfM) photogrammetry. We deployed this prototype rover on the Northeast Greenland Ice Stream to map local variations in snow accumulation and surface topography. The rover conducted four autonomous missions based out of the East Greenland Ice-Core Project (EastGRIP) camp during July 2017, measuring surface elevation transects across the hazardous ice-stream shear margins. During these missions, the rover proved capable of driving over 20km on a single charge with a drawbar pull of 250N, sufficient to tow instrumentation of up to 100kg. The rover also acquired photographs that were subsequently used to construct digital elevation models of a site monitored for spatiotemporal variability in snow accumulation, demonstrating adequate stability for high-resolution imaging applications. Due to its low cost, low-power requirements, and simple modular design, mass deployments of this rover design are practicable. Operation of the rover in hazardous areas circumvents the substantial expense and risk to personnel associated with conventional, crewed deployments. Thus, this rover is an investigatory platform that enables direct exploration of polar environments considered too hazardous for conventional field expeditions.
- Published
- 2019
21. Hoffman, Andrew O.
- Author
-
Hoffman, Andrew O. and Hoffman, Andrew O.
- Published
- 2019
22. A low-cost autonomous rover for polar science
- Author
-
Hoffman, Andrew O., primary, Steen-Larsen, Hans Christian, additional, Christianson, Knut, additional, and Hvidberg, Christine, additional
- Published
- 2019
- Full Text
- View/download PDF
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