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2. Bedmap2: improved ice bed, surface and thickness datasets for Antarctica

Author

Fretwell, P., Pritchard, H. D, Vaughan, D. G, Bamber, J. L, Barrand, N. E, Bell, R., Bianchi, C., Bingham, R. G, Blankenship, D. D, Casassa, G., Catania, G., Callens, D., Conway, H., Cook, A. J, Corr, H. F. J, Damaske, D., Damm, V., Ferraccioli, F., Forsberg, R., Fujita, S., Gim, Y., Gogineni, P., Griggs, J. A, Hindmarsh, R. C. A, Holmlund, P., Holt, J. W, Jacobel, R. W, Jenkins, A., Jokat, W., Jordan, T., King, E. C, Kohler, J., Krabill, W., Riger-Kusk, M., Langley, K. A, Leitchenkov, G., Leuschen, C., Luyendyk, B. P, Matsuoka, K., Mouginot, J., Nitsche, F. O, Nogi, Y., Nost, O. A, Popov, S. V, Rignot, E., Rippin, D. M, Rivera, A., Roberts, J., Ross, N., Siegert, M. J, Smith, A. M, Steinhage, D., Studinger, M., Sun, B., Tinto, B. K, Welch, B. C, Wilson, D., Young, D. A, Xiangbin, C., and Zirizzotti, A.

Subjects
Digital Elevation Model, Satellite Radar, East Antarctica, West Antarctica, Sheet, Stream, Sea, Altimetry, Gravity, Bathymetry
Published
2013

3. Dynamics and mass balance of Taylor Glacier, Antarctica: 1. Geometry and surface velocities

Author

Kavanaugh, JL, Cuffey, KM, Morse, DL, Conway, H, and Rignot, E

Subjects
Meteorology & Atmospheric Sciences
Abstract

Taylor Glacier, Antarctica, exemplifies a little-studied type of outlet glacier, one that flows slowly through a region of rugged topography and dry climate. This glacier, in addition, connects the East Antarctic Ice Sheet with the McMurdo Dry Valleys, a region much studied for geomorphology, paleoclimate, and ecology. Here we report extensive new measurements of surface velocities, ice thicknesses, and surface elevations, acquired with InSAR, GPS, and GPR. The latter two were used to construct elevation models of the glacier's surface and bed. Ice velocities in 2002-2004 closely matched those in 2000 and the mid-1970s, indicating negligible interannual variations of flow. Comparing velocities with bed elevations shows that, along much of the glacier, flow concentrates in a narrow axis of relatively fast flowing ice that overlies a bedrock trough. The flow of the glacier over major undulations in its bed can be regarded as a "cascade"; it speeds up over bedrock highs and through valley narrows and slows down over deep basins and in wide spots. This pattern is an expected consequence of mass conservation for a glacier near steady state. Neither theory nor data from this Taylor Glacier study support the alternative view, recently proposed, that an outlet glacier of this type trickles slowly over bedrock highs and flows fastest over deep basins. Copyright 2009 by the American Geophysical Union.

Published
2009

6. Antarctic Bedmap data: Findable, Accessible, Interoperable, and Reusable (FAIR) sharing of 60 years of ice bed, surface, and thickness data

Author

Frémand, A. C., Fretwell, P., Bodart, J. A., Pritchard, H. D., Aitken, A., Bamber, J. L., Bell, R., Bianchi, C., Bingham, R. G., Blankenship, D. D., Casassa, G., Catania, G., Christianson, K., Conway, H., Corr, H. F. J., Cui, X., Damaske, D., Damm, V., Drews, R., Eagles, G., Eisen, O., Eisermann, H., Ferraccioli, F., Field, E., Forsberg, R., Franke, S., Fujita, S., Gim, Y., Goel, V., Gogineni, S. P., Greenbaum, J., Hills, B., Hindmarsh, R. C. A., Hoffman, A. O., Holmlund, P., Holschuh, N., Holt, J. W., Horlings, A. N., Humbert, A., Jacobel, R. W., Jansen, D., Jenkins, A., Jokat, W., Jordan, T., King, E., Kohler, J., Krabill, W., Kusk Gillespie, M., Langley, K., Lee, J., Leitchenkov, G., Leuschen, C., Luyendyk, B., MacGregor, J., MacKie, E., Matsuoka, K., Morlighem, M., Mouginot, J., Nitsche, F. O., Nogi, Y., Nost, O. A., Paden, J., Pattyn, F., Popov, S. V., Rignot, E., Rippin, D. M., Rivera, A., Roberts, J., Ross, N., Ruppel, A., Schroeder, D. M., Siegert, M. J., Smith, A. M., Steinhage, D., Studinger, M., Sun, B., Tabacco, I., Tinto, K., Urbini, S., Vaughan, D., Welch, B. C., Wilson, D. S., Young, D. A., Zirizzotti, A., Frémand, A. C., Fretwell, P., Bodart, J. A., Pritchard, H. D., Aitken, A., Bamber, J. L., Bell, R., Bianchi, C., Bingham, R. G., Blankenship, D. D., Casassa, G., Catania, G., Christianson, K., Conway, H., Corr, H. F. J., Cui, X., Damaske, D., Damm, V., Drews, R., Eagles, G., Eisen, O., Eisermann, H., Ferraccioli, F., Field, E., Forsberg, R., Franke, S., Fujita, S., Gim, Y., Goel, V., Gogineni, S. P., Greenbaum, J., Hills, B., Hindmarsh, R. C. A., Hoffman, A. O., Holmlund, P., Holschuh, N., Holt, J. W., Horlings, A. N., Humbert, A., Jacobel, R. W., Jansen, D., Jenkins, A., Jokat, W., Jordan, T., King, E., Kohler, J., Krabill, W., Kusk Gillespie, M., Langley, K., Lee, J., Leitchenkov, G., Leuschen, C., Luyendyk, B., MacGregor, J., MacKie, E., Matsuoka, K., Morlighem, M., Mouginot, J., Nitsche, F. O., Nogi, Y., Nost, O. A., Paden, J., Pattyn, F., Popov, S. V., Rignot, E., Rippin, D. M., Rivera, A., Roberts, J., Ross, N., Ruppel, A., Schroeder, D. M., Siegert, M. J., Smith, A. M., Steinhage, D., Studinger, M., Sun, B., Tabacco, I., Tinto, K., Urbini, S., Vaughan, D., Welch, B. C., Wilson, D. S., Young, D. A., and Zirizzotti, A.

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

13. Decoding the dipstick: thickness of Siple Dome, West Antarctica, at the Last Glacial Maximum

Author

Waddington, E.D., Conway, H., Steig, E.J., Alley, R.B., Brook, E.J., Taylor, K.C., and White, J.W.C.

Subjects
Sea level, Ice sheets, Glaciology, Climate, Ice cores, Earth sciences
Abstract

Ice thickness in West Antarctica at the Last Glacial Maximum (LGM) is poorly known, yet is key information for understanding ice streams and interpreting ice cores. Although trim lines, moraine limits, and exposure-age dating provide geologic constraints on ice thickness near the Transantarctic Mountains and in Marie Byrd Land, lack of exposed bedrock hampers traditional geologic methods in a central, ~2 x [10.sup.6] [km.sup.2] region. Here we infer ice-sheet thickness changes in the central Ross Sea Embayment by using a transient ice-flow model to find combinations of accumulation-rate and ice-sheet thickness histories that match the depth-age relationship and the measured layer-thickness pattern in the Siple Dome ice core. After we reject unreasonable accumulation-rate histories, the remaining history pairs indicate thinning of 200-400 m since the LGM. Our estimate is lower than previous reconstructions that were constrained by geologic evidence from the Transantarctic Mountains and by marine data from the Ross Sea floor, which indicate that a grounded ice sheet extended to the continental shelf margin during the last glacial period. Low surface elevations in the central Ross Sea Embayment during the LGM do not preclude thicker ice along its boundaries. However, if this grounded ice sheet came over 1000 km from interior West Antarctica, as is usually assumed, then it had very low surface slope, requiring a very slippery bed. Alternatively, the grounded Ross Sea ice might have flowed from the Transantarctic Mountains and western Marie Byrd Land. Keywords: Antarctic Ice Sheet, ice cores, ice streams, glaciology, sea level, climate.

Published
2005

16. The municipal park : design and development, circa 1840-1880

Author

Conway, H.

Subjects
900, History
Abstract

The aim of this study is to identify the main factors contributing to the development of the municipal park in England, and to relate them to park design and use. Official recognition of the need for parks dated from 1833 and focussed on the needs of the working classes in the largest urban centres. An analysis of park development established the various forms of public park, the main modes of park acquisition and their geographical distribution. In the period between 1845 and 1860 parks were developed mainly in the industrial centres of the north-west. Subsequently, this broadened to include resorts and smaller towns. Manchester was the first of the industrial centres to establish municipal parks. Other important early parks were established in Birkenhead and London (Victoria Park). The processes whereby these parks were established, and their design and use, illustrated the preferences of those in authority and showed that parka were seen not only in physical terms but also in social and political terms. The ways in which the "problem" of working class recreation was identified affected parks. They provided an alternative to the public house, and had an educational role to play. The type of meeting permitted, the choice of sports, and of music, showed clearly that parks were seen as places where the classes could mix, but on middle and ruling class terms. After the passing of the Public Health Act 1875 a major acceleration in park development occurred. At the same time there was a growing awareness that the existing large parks did not solve the problem of access to open space for the densest urban areas. The 1880s saw the development of small recreation grounds in working class districts and the transformation of disused burial grounds into open space for recreation. This indicated that a major change in public opinion regarding the need for accessible open space had occurred. The municipal park provided enormous enjoyment, and it was brought into.. being by a variety of means in which municipal enterprise, politics and social conscience all played a part

Published
1985

18. Estimation of atmospheric transmittance from upper-air humidity

Author

Rasmussen, L.A., Conway, H., and Ferguson, S.A.

Subjects
United States -- Environmental aspects, Surface energy -- Research, Water vapor, Atmospheric -- Research, Humidity -- Research, Atmospheric radiation -- Research, Earth sciences, Petroleum, energy and mining industries
Abstract

A very simple model of atmospheric transmittance uses as its input regularly observed and archived measures of upper air humidity. The five model parameters were determined empirically to optimize the agreement with radiation measured at six sites in the northwestern contiguous U.S. in summer and winter 1990. The model uses the relative humidity at 500 hPa, the relative humidity at either 950 hPa or 800 hPa depending on the altitude of the station, and the precipitable water. Although the model does not use cloud observations explicitly, it is partitioned into a low-humidity stage and a high-humidity stage with markedly different dependences on relative humidity. In the low-humidity stage the transmittance is approximated as the product of factors for dry air and for water vapor. In the high-humidity stage the transmittance is the product of the transmittances of each of the two layers used; the product is a strongly decreasing function of relative humidity, as a representation of the effect of cloud. A split-sample test using measurements for spring and autumn indicated that the model parameters were not badly distorted by conditions unique to the summer and winter seasons. In terms of the average daily global shortwave radiation received at the surface, the rms errors are 31 W [m.sup.-2] in spring, 33 in summer, 30 in autumn, and 18 in winter. The corresponding relative errors are 0.25, 0.17, 0.20, and 0.31. Because of high-frequency temporal variation in the model residuals, the error declines to about half of the daily error for 7-day averages and to about a quarter of the daily error for 30-day averages.

Published
1998

22. The Ross Sea Dipole-temperature, snow accumulation and sea ice variability in the Ross Sea region, Antarctica, over the past 2700 years

Author

Bertler, N, Conway, H, Dahl-Jensen, D, Emanuelsson, D, Winstrup, M, Vallelonga, P, Lee, J, Brook, E, Severinghaus, J, Fudge, T, Keller, E, Troy Baisden, W, Hindmarsh, R, Neff, P, Blunier, T, Edwards, R, Mayewski, P, Kipfstuhl, S, Buizert, C, Canessa, S, Dadic, R, Kjær, H, Kurbatov, A, Zhang, D, Waddington, E, Baccolo, G, Beers, T, Brightley, H, Carter, L, Clemens-Sewall, D, Ciobanu, V, Delmonte, B, Eling, L, Ellis, A, Ganesh, S, Golledge, N, Haines, S, Handley, M, Hawley, R, Hogan, C, Johnson, K, Korotkikh, E, Lowry, D, Mandeno, D, Mckay, R, Menking, J, Naish, T, Noerling, C, Ollive, A, Orsi, A, Proemse, B, Pyne, A, Pyne, R, Renwick, J, Scherer, R, Semper, S, Simonsen, M, Sneed, S, Steig, E, Tuohy, A, Ulayottil Venugopal, A, Valero-Delgado, F, Venkatesh, J, Wang, F, Wang, S, Winski, D, Holly, W, Whiteford, A, Xiao, C, Yang, J, Zhang, X, Bertler, Nancy A. N., Conway, Howard, Dahl-Jensen, Dorthe, Emanuelsson, Daniel B., Winstrup, Mai, Vallelonga, Paul T., Lee, James E., Brook, Ed J., Severinghaus, Jeffrey P., Fudge, Taylor J., Keller, Elizabeth D., Troy Baisden, W., Hindmarsh, Richard C. A., Neff, Peter D., Blunier, Thomas, Edwards, Ross, Mayewski, Paul A., Kipfstuhl, Sepp, Buizert, Christo, Canessa, Silvia, Dadic, Ruzica, Kjær, Helle A., Kurbatov, Andrei, Zhang, Dongqi, Waddington, Edwin D., Baccolo, Giovanni, Beers, Thomas, Brightley, Hannah J., Carter, Lionel, Clemens-Sewall, David, Ciobanu, Viorela G., Delmonte, Barbara, Eling, Lukas, Ellis, Aja, Ganesh, Shruthi, Golledge, Nicholas R., Haines, Skylar, Handley, Michael, Hawley, Robert L., Hogan, Chad M., Johnson, Katelyn M., Korotkikh, Elena, Lowry, Daniel P., Mandeno, Darcy, McKay, Robert M., Menking, James A., Naish, Timothy R., Noerling, Caroline, Ollive, Agathe, Orsi, Anaïs, Proemse, Bernadette C., Pyne, Alexander R., Pyne, Rebecca L., Renwick, James, Scherer, Reed P., Semper, Stefanie, Simonsen, Marius, Sneed, Sharon B., Steig, Eric J., Tuohy, Andrea, Ulayottil Venugopal, Abhijith, Valero-Delgado, Fernando, Venkatesh, Janani, Wang, Feitang, Wang, Shimeng, Winski, Dominic A., Holly, Winton, Whiteford, Arran, Xiao, Cunde, Yang, Jiao, Zhang, Xin, Bertler, N, Conway, H, Dahl-Jensen, D, Emanuelsson, D, Winstrup, M, Vallelonga, P, Lee, J, Brook, E, Severinghaus, J, Fudge, T, Keller, E, Troy Baisden, W, Hindmarsh, R, Neff, P, Blunier, T, Edwards, R, Mayewski, P, Kipfstuhl, S, Buizert, C, Canessa, S, Dadic, R, Kjær, H, Kurbatov, A, Zhang, D, Waddington, E, Baccolo, G, Beers, T, Brightley, H, Carter, L, Clemens-Sewall, D, Ciobanu, V, Delmonte, B, Eling, L, Ellis, A, Ganesh, S, Golledge, N, Haines, S, Handley, M, Hawley, R, Hogan, C, Johnson, K, Korotkikh, E, Lowry, D, Mandeno, D, Mckay, R, Menking, J, Naish, T, Noerling, C, Ollive, A, Orsi, A, Proemse, B, Pyne, A, Pyne, R, Renwick, J, Scherer, R, Semper, S, Simonsen, M, Sneed, S, Steig, E, Tuohy, A, Ulayottil Venugopal, A, Valero-Delgado, F, Venkatesh, J, Wang, F, Wang, S, Winski, D, Holly, W, Whiteford, A, Xiao, C, Yang, J, Zhang, X, Bertler, Nancy A. N., Conway, Howard, Dahl-Jensen, Dorthe, Emanuelsson, Daniel B., Winstrup, Mai, Vallelonga, Paul T., Lee, James E., Brook, Ed J., Severinghaus, Jeffrey P., Fudge, Taylor J., Keller, Elizabeth D., Troy Baisden, W., Hindmarsh, Richard C. A., Neff, Peter D., Blunier, Thomas, Edwards, Ross, Mayewski, Paul A., Kipfstuhl, Sepp, Buizert, Christo, Canessa, Silvia, Dadic, Ruzica, Kjær, Helle A., Kurbatov, Andrei, Zhang, Dongqi, Waddington, Edwin D., Baccolo, Giovanni, Beers, Thomas, Brightley, Hannah J., Carter, Lionel, Clemens-Sewall, David, Ciobanu, Viorela G., Delmonte, Barbara, Eling, Lukas, Ellis, Aja, Ganesh, Shruthi, Golledge, Nicholas R., Haines, Skylar, Handley, Michael, Hawley, Robert L., Hogan, Chad M., Johnson, Katelyn M., Korotkikh, Elena, Lowry, Daniel P., Mandeno, Darcy, McKay, Robert M., Menking, James A., Naish, Timothy R., Noerling, Caroline, Ollive, Agathe, Orsi, Anaïs, Proemse, Bernadette C., Pyne, Alexander R., Pyne, Rebecca L., Renwick, James, Scherer, Reed P., Semper, Stefanie, Simonsen, Marius, Sneed, Sharon B., Steig, Eric J., Tuohy, Andrea, Ulayottil Venugopal, Abhijith, Valero-Delgado, Fernando, Venkatesh, Janani, Wang, Feitang, Wang, Shimeng, Winski, Dominic A., Holly, Winton, Whiteford, Arran, Xiao, Cunde, Yang, Jiao, and Zhang, Xin

Abstract

High-resolution, well-dated climate archives provide an opportunity to investigate the dynamic interactions of climate patterns relevant for future projections. Here, we present data from a new, annually dated ice core record from the eastern Ross Sea, named the Roosevelt Island Climate Evolution (RICE) ice core. Comparison of this record with climate reanalysis data for the 1979-2012 interval shows that RICE reliably captures temperature and snow precipitation variability in the region. Trends over the past 2700 years in RICE are shown to be distinct from those in West Antarctica and the western Ross Sea captured by other ice cores. For most of this interval, the eastern Ross Sea was warming (or showing isotopic enrichment for other reasons), with increased snow accumulation and perhaps decreased sea ice concentration. However, West Antarctica cooled and the western Ross Sea showed no significant isotope temperature trend. This pattern here is referred to as the Ross Sea Dipole. Notably, during the Little Ice Age, West Antarctica and the western Ross Sea experienced colder than average temperatures, while the eastern Ross Sea underwent a period of warming or increased isotopic enrichment. From the 17th century onwards, this dipole relationship changed. All three regions show current warming, with snow accumulation declining in West Antarctica and the eastern Ross Sea but increasing in the western Ross Sea. We interpret this pattern as reflecting an increase in sea ice in the eastern Ross Sea with perhaps the establishment of a modern Roosevelt Island polynya as a local moisture source for RICE

Published
2018

23. The Ross Sea Dipole-temperature, snow accumulation and sea ice variability in the Ross Sea region, Antarctica, over the past 2700 years

Author

Bertler, N., Conway, H., Dahl-Jensen, D., Emanuelsson, D., Winstrup, M., Vallelonga, P., Lee, J., Brook, E., Severinghaus, J., Fudge, T., Keller, E., Troy Baisden, W., Hindmarsh, R., Neff, P., Blunier, T., Edwards, Peter, Mayewski, P., Kipfstuhl, S., Buizert, C., Canessa, S., Dadic, R., Kjær, H., Kurbatov, A., Zhang, D., Waddington, E., Baccolo, G., Beers, T., Brightley, H., Carter, L., Clemens-Sewall, D., Ciobanu, V., Delmonte, B., Eling, L., Ellis, A., Ganesh, S., Golledge, N., Haines, S., Handley, M., Hawley, R., Hogan, C., Johnson, K., Korotkikh, E., Lowry, D., Mandeno, D., McKay, R., Menking, J., Naish, T., Noerling, C., Ollive, A., Orsi, A., Proemse, B., Pyne, A., Pyne, R., Renwick, J., Scherer, R., Semper, S., Simonsen, M., Sneed, S., Steig, E., Tuohy, A., Ulayottil Venugopal, A., Valero-Delgado, F., Venkatesh, J., Wang, F., Wang, S., Winski, D., Holly, W., Whiteford, A., Xiao, C., Yang, J., Zhang, X., Bertler, N., Conway, H., Dahl-Jensen, D., Emanuelsson, D., Winstrup, M., Vallelonga, P., Lee, J., Brook, E., Severinghaus, J., Fudge, T., Keller, E., Troy Baisden, W., Hindmarsh, R., Neff, P., Blunier, T., Edwards, Peter, Mayewski, P., Kipfstuhl, S., Buizert, C., Canessa, S., Dadic, R., Kjær, H., Kurbatov, A., Zhang, D., Waddington, E., Baccolo, G., Beers, T., Brightley, H., Carter, L., Clemens-Sewall, D., Ciobanu, V., Delmonte, B., Eling, L., Ellis, A., Ganesh, S., Golledge, N., Haines, S., Handley, M., Hawley, R., Hogan, C., Johnson, K., Korotkikh, E., Lowry, D., Mandeno, D., McKay, R., Menking, J., Naish, T., Noerling, C., Ollive, A., Orsi, A., Proemse, B., Pyne, A., Pyne, R., Renwick, J., Scherer, R., Semper, S., Simonsen, M., Sneed, S., Steig, E., Tuohy, A., Ulayottil Venugopal, A., Valero-Delgado, F., Venkatesh, J., Wang, F., Wang, S., Winski, D., Holly, W., Whiteford, A., Xiao, C., Yang, J., and Zhang, X.

Abstract

High-resolution, well-dated climate archives provide an opportunity to investigate the dynamic interactions of climate patterns relevant for future projections. Here, we present data from a new, annually dated ice core record from the eastern Ross Sea, named the Roosevelt Island Climate Evolution (RICE) ice core. Comparison of this record with climate reanalysis data for the 1979-2012 interval shows that RICE reliably captures temperature and snow precipitation variability in the region. Trends over the past 2700 years in RICE are shown to be distinct from those in West Antarctica and the western Ross Sea captured by other ice cores. For most of this interval, the eastern Ross Sea was warming (or showing isotopic enrichment for other reasons), with increased snow accumulation and perhaps decreased sea ice concentration. However, West Antarctica cooled and the western Ross Sea showed no significant isotope temperature trend. This pattern here is referred to as the Ross Sea Dipole. Notably, during the Little Ice Age, West Antarctica and the western Ross Sea experienced colder than average temperatures, while the eastern Ross Sea underwent a period of warming or increased isotopic enrichment. From the 17th century onwards, this dipole relationship changed. All three regions show current warming, with snow accumulation declining in West Antarctica and the eastern Ross Sea but increasing in the western Ross Sea. We interpret this pattern as reflecting an increase in sea ice in the eastern Ross Sea with perhaps the establishment of a modern Roosevelt Island polynya as a local moisture source for RICE.

Published
2018

30. A Reexamination of Residual Stresses in Thin Films and of the Validity of Stoney's Estimate

Author

Hui, C. Y., Conway, H. D., and Lin, Y. Y.

Subjects
Electronic packaging -- Research, Stress analysis (Engineering) -- Research, Electronics
Abstract

The residual stresses in thin films are explained using elementary mechanics. In particular, the range of validity of the well-known Stoney's formula is examined using a strength of materials approach. An improved formula is obtained. The results of these analyses can also be used to compute energy release rates for cracks in thin film systems. Some simple examples of such applications are given. [S1043-7398(00)01603-0]

Published
2000

31. Entrainment at cold glacier beds

Author

Cuffey, K. M., Conway, H., Gades, A. M., Hallet, B., Lorrain, R., Severinghaus, J. P., Steig, E. J., Vaughn, B., and White, J. W. C.

Subjects
Glacial climates -- Research, Isotopes -- Research, Glacial erosion -- Research, Ice -- Antarctica, Earth sciences
Abstract

Here we present measurements of the gas content and isotopic composition of debris-rich basal layers of a polar glacier, Meserve Glacier, Antarctica, which has a basal temperature of -17 [degrees] C. These measurements show that debris entrainment has occurred without alteration of the glacial ice, and provide the most direct evidence to date that active entrainment occurs at the beds of cold glaciers, without bulk freezing of water. Entrainment at subfreezing temperatures may have formed the U-shaped trough containing Meserve Glacier. In addition to possibly allowing some cold-based glaciers to be important geomorphic agents, entrainment at subfreezing temperatures provides a general mechanism for formation of the dirty basal layers of polar glaciers and ice sheets, which are rheologically distinct and can limit the time span of ice-core analyses. Furthermore, accumulating evidence suggests that geomorphologists should abandon the assumption that cold-based glaciers do not slide and abrade their beds. Keywords: glacial erosion, glacial entrainment, glacial valleys, ice cores, Antarctic Dry Valleys.

Published
2000

32. A community-based geological reconstruction of Antarctic Ice Sheet deglaciation since the Last Glacial Maximum

Author

RAISED Consortium, Bentley, J, Cofaigh, O, Anderson, B, Conway, H., Davies, B, Graham, C, Hillenbrand, D, Hodgson, A, Jamieson, R, Larter, D, Mackintosh, A, Smith, A, Verleyen, E., Ackert, P, Bart, J, Berg, S, Brunstein, D, Canals, M, Colhoun, A, Crosta, X, Dickens, A, Domack, E, Dowdeswell, A, Dunbar, R, Ehrmann, W, Evans, J, Favier, V, Fink, D, Fogwill, J, Glasser, F, Gohl, K, Golledge, R, Goodwin, I, Gore, B, Greenwood, L, Hall, L, Hall, K, Hedding, W, Hein, S, Hocking, P, Jakobsson, M, Johnson, S, Jomelli, V, Jones, S, Klages, P, Kristoffersen, Y, Kuhn, G, Leventer, A, Licht, K, Lilly, K, Lindow, J, Livingstone, J, Masse, G, McGlone, S, McKay, M, Melles, M, Miura, H, Mulvaney, R., Nel, W, Nitsche, O, O'Brien, E, Post, L, Roberts, J, Saunders, M, Selkirk, M, Simms, R, Spiegel, C, Stolldorf, D, Sugden, E, van der Putten, N., van Ommen, T, Verfaillie, D, Vyverman, W., Wagner, B, White, A, Witus, E, and Zwartz, D

Abstract

A robust understanding of Antarctic Ice Sheet deglacial history since the Last Glacial Maximum is important in order to constrain ice sheet and glacial-isostatic adjustment models, and to explore the forcing mechanisms responsible for ice sheet retreat. Such understanding can be derived from a broad range of geological and glaciological datasets and recent decades have seen an upsurge in such data gathering around the continent and Sub-Antarctic islands. Here, we report a new synthesis of those datasets, based on an accompanying series of reviews of the geological data, organised by sector. We present a series of timeslice maps for 20 ka, 15 ka, 10 ka and 5 ka, including grounding line position and ice sheet thickness changes, along with a clear assessment of levels of confidence. The reconstruction shows that the Antarctic Ice sheet did not everywhere reach the continental shelf edge at its maximum, that initial retreat was asynchronous, and that the spatial pattern of deglaciation was highly variable, particularly on the inner shelf. The deglacial reconstruction is consistent with a moderate overall excess ice volume and with a relatively small Antarctic contribution to meltwater pulse la. We discuss key areas of uncertainty both around the continent and by time interval, and we highlight potential priorities for future work. The synthesis is intended to be a resource for the modelling and glacial geological community.

Published
2014

33. Constraining the recent mass balance of pine island and thwaites glaciers, west antarctica, with airborne observations of snow accumulation

Author

Medley, B., Joughin, I., Smith, B. E., Das, S. B., Steig, E. J., Conway, H., Gogineni, S., Lewis, C., Criscitiello, A. S., McConnell, J. R., Van Den Broeke, M. R., Lenaerts, J. T M, Bromwich, D. H., Nicolas, J. P., Leuschen, C., Sub Dynamics Meteorology, Marine and Atmospheric Research, Sub Dynamics Meteorology, and Marine and Atmospheric Research

Subjects
lcsh:GE1-350, Glacier ice accumulation, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Ice stream, lcsh:QE1-996.5, Accumulation zone, Glacier, Future sea level, Glacier morphology, 010502 geochemistry & geophysics, 01 natural sciences, lcsh:Geology, Glacier mass balance, 13. Climate action, Climatology, Cryosphere, lcsh:Environmental sciences, Geology, 0105 earth and related environmental sciences, Water Science and Technology, Earth-Surface Processes
Abstract

In Antarctica, uncertainties in mass input and output translate directly into uncertainty in glacier mass balance and thus in sea level impact. While remotely sensed observations of ice velocity and thickness over the major outlet glaciers have improved our understanding of ice loss to the ocean, snow accumulation over the vast Antarctic interior remains largely unmeasured. Here, we show that an airborne radar system, combined with ice-core glaciochemical analysis, provide the means necessary to measure the accumulation rate at the catchment-scale along the Amundsen Sea coast of West Antarctica. We used along-track radar-derived accumulation to generate a 1985–2009 average accumulation grid that resolves moderate- to large-scale features (>25 km) over the Pine Island–Thwaites glacier drainage system. Comparisons with estimates from atmospheric models and gridded climatologies generally show our results as having less accumulation in the lower-elevation coastal zone but greater accumulation in the interior. Ice discharge, measured over discrete time intervals between 1994 and 2012, combined with our catchment-wide accumulation rates provide an 18-year mass balance history for the sector. While Thwaites Glacier lost the most ice in the mid-1990s, Pine Island Glacier's losses increased substantially by 2006, overtaking Thwaites as the largest regional contributor to sea-level rise. The trend of increasing discharge for both glaciers, however, appears to have leveled off since 2008.

Published
2014

42. Airborne-radar and ice-core observations of annual snow accumulation over Thwaites Glacier, West Antarctica confirm the spatiotemporal variability of global and regional atmospheric models

Author

Medley, B., Joughin, I., Das, S.B., Steig, E. J., Conway, H., Gogineni, S., Criscitiello, A.S., McConnell, J.R., Smith, B.E., van den Broeke, M.R., Lenaerts, J.T.M., Bromwich, D.H., Nicolas, J.P., Marine and Atmospheric Research, and Sub Dynamics Meteorology

Abstract

We use an airborne-radar method, verified with ice-core accumulation records, to determine the spatiotemporal variations of snow accumulation over Thwaites Glacier, West Antarctica between 1980 and 2009. We also present a regional evaluation of modeled accumulation in Antarctica. Comparisons between radar-derived measurements and model outputs show that three global models capture the interannual variability well (r > 0.9), but a high-resolution regional model (RACMO2) has better absolute accuracy and captures the observed spatial variability (r = 0.86). Neither the measured nor modeled accumulation records over Thwaites Glacier show any trend since 1980. Although an increase in accumulation may potentially accompany the observed warming in the region, the projected trend is too small to detect over the 30 year record.

Published
2013

49. Melting and refreezing beneath Roi Baudouin Ice Shelf (East Antarctica) inferred from radar, GPS, and ice core data

Author

Pattyn, F., Matsuoka, K., Callens, D., Conway, H., Depoorter, M., Docquier, D., Hubbard, B., Samyn, D., and Tison, J.-L.

Abstract

Ice-penetrating radar profiles across the grounding line of a small ice-rise promontory located within the Roi Baudouin Ice Shelf in the Dronning Maud Land sector of East Antarctica show downward dipping englacial radar-detected reflectors. Model results indicate that this reflector pattern is best fit by including basal melting of at least 15 cm a-1. This rate of melting is low compared with rates observed on larger ice shelves in both West and East Antarctica. Ice cores extracted from a rift system close to the ice-rise promontory show several meters of marine ice accreted beneath the shelf. These observations of low rates of basal melting, and limited distribution of accreted marine ice suggest that either Antarctic surface water may reach the ice shelf base or that circulation beneath the shelf is likely dominated by the production of high salinity shelf water rather than the incursion of circumpolar deep water, implying a weak sub-shelf circulation system here. Many of the ice shelves located along the coast of Dronning Maud Land are, like Roi Baudouin Ice Shelf, characterized by frequent ice rises and promontories. Therefore, it is highly likely that these are also of shallow bathymetry and are subject to similarly weak side-shelf basal melting and refreezing.

Published
2012

50. A community-based geological reconstruction of Antarctic Ice Sheet deglaciation since the Last Glacial Maximum

Author

Bentley, MJ, Ocofaigh, C, Anderson, JB, Conway, H, Davies, B, Graham, AGC, Hillenbrand, CD, Hodgson, DA, Jamieson, SSR, Larter, RD, Mackintosh, A, Smith, JA, Verleyen, E, Ackert, RP, Bart, PJ, Berg, S, Brunstein, D, Canals, M, Colhoun, EA, Crosta, X, Dickens, WA, Domack, E, Dowdeswell, JA, Dunbar, R, Ehrmann, W, Evans, J, Favier, V, Fink, D, Fogwill, CJ, Glasser, NF, Gohl, K, Golledge, NR, Goodwin, I, Gore, DB, Greenwood, SL, Hall, BL, Hall, K, Hedding, DW, Hein, AS, Hocking, EP, Jakobsson, M, Johnson, JS, Jomelli, V, Jones, RS, Klages, JP, Kristoffersen, Y, Kuhn, G, Leventer, A, Licht, K, Lilly, K, Lindow, J, Livingstone, SJ, Massé, G, McGlone, MS, McKay, RM, Melles, M, Miura, H, Mulvaney, R, Nel, W, Nitsche, FO, O'Brien, PE, Post, AL, Roberts, SJ, Saunders, KM, Selkirk, PM, Simms, AR, Spiegel, C, Stolldorf, TD, Sugden, DE, van der Putten, N, van Ommen, T, Verfaillie, D, Vyverman, W, Wagner, B, White, DA, Witus, AE, Zwartz, D, Bentley, MJ, Ocofaigh, C, Anderson, JB, Conway, H, Davies, B, Graham, AGC, Hillenbrand, CD, Hodgson, DA, Jamieson, SSR, Larter, RD, Mackintosh, A, Smith, JA, Verleyen, E, Ackert, RP, Bart, PJ, Berg, S, Brunstein, D, Canals, M, Colhoun, EA, Crosta, X, Dickens, WA, Domack, E, Dowdeswell, JA, Dunbar, R, Ehrmann, W, Evans, J, Favier, V, Fink, D, Fogwill, CJ, Glasser, NF, Gohl, K, Golledge, NR, Goodwin, I, Gore, DB, Greenwood, SL, Hall, BL, Hall, K, Hedding, DW, Hein, AS, Hocking, EP, Jakobsson, M, Johnson, JS, Jomelli, V, Jones, RS, Klages, JP, Kristoffersen, Y, Kuhn, G, Leventer, A, Licht, K, Lilly, K, Lindow, J, Livingstone, SJ, Massé, G, McGlone, MS, McKay, RM, Melles, M, Miura, H, Mulvaney, R, Nel, W, Nitsche, FO, O'Brien, PE, Post, AL, Roberts, SJ, Saunders, KM, Selkirk, PM, Simms, AR, Spiegel, C, Stolldorf, TD, Sugden, DE, van der Putten, N, van Ommen, T, Verfaillie, D, Vyverman, W, Wagner, B, White, DA, Witus, AE, and Zwartz, D

Abstract

A robust understanding of Antarctic Ice Sheet deglacial history since the Last Glacial Maximum is important in order to constrain ice sheet and glacial-isostatic adjustment models, and to explore the forcing mechanisms responsible for ice sheet retreat. Such understanding can be derived from a broad range of geological and glaciological datasets and recent decades have seen an upsurge in such data gathering around the continent and Sub-Antarctic islands. Here, we report a new synthesis of those datasets, based on an accompanying series of reviews of the geological data, organised by sector. We present a series of timeslice maps for 20ka, 15ka, 10ka and 5ka, including grounding line position and ice sheet thickness changes, along with a clear assessment of levels of confidence. The reconstruction shows that the Antarctic Ice sheet did not everywhere reach the continental shelf edge at its maximum, that initial retreat was asynchronous, and that the spatial pattern of deglaciation was highly variable, particularly on the inner shelf. The deglacial reconstruction is consistent with a moderate overall excess ice volume and with a relatively small Antarctic contribution to meltwater pulse 1a. We discuss key areas of uncertainty both around the continent and by time interval, and we highlight potential priorit. © 2014 The Authors.

Published
2014

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