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23 results on '"Bohlander, J."'

1. Timing of recent accelerations of Pine Island Glacier, Antarctica

Author

Joughin, I, Rignot, E, Rosanova, CE, Lucchitta, BK, and Bohlander, J

Subjects
Meteorology & Atmospheric Sciences
Abstract

We have used Interferometric Synthetic Aperture Radar (InSAR) data and sequential Landsat imagery to identify and temporally constrain two acceleration events on Pine Island Glacier (PIG). These two events are separated by a period of at least seven years (1987 - 1994). The change in discharge between two flux gates indicates that the majority of the increase in discharge associated with the second acceleration originates well inland (>80 km) from the grounding line. An analysis indicates that changes in driving stress consistent with observed thinning rates are sufficient in magnitude to explain much of the acceleration.

Published
2003

4. Extent of Low-accumulation 'Wind Glaze' Areas on the East Antarctic Plateau: Implications for Continental Ice Mass Balance

Author

Scambos, Theodore A, Frezzotti, Massimo, Haran, T, Bohlander, J, Lenaerts, J. T. M, Van Den Broeke, M. R, Jezek, K, Long, D, Urbini, S, Farness, K, Neumann, T, Albert, M, and Winther, J.-G

Subjects
Geosciences (General), Earth Resources And Remote Sensing
Abstract

Persistent katabatic winds form widely distributed localized areas of near-zero net surface accumulation on the East Antarctic ice sheet (EAIS) plateau. These areas have been called 'glaze' surfaces due to their polished appearance. They are typically 2-200 square kilometers in area and are found on leeward slopes of ice-sheet undulations and megadunes. Adjacent, leeward high-accumulation regions (isolated dunes) are generally smaller and do not compensate for the local low in surface mass balance (SMB). We use a combination of satellite remote sensing and field-gathered datasets to map the extent of wind glaze in the EAIS above 1500m elevation. Mapping criteria are derived from distinctive surface and subsurface characteristics of glaze areas resulting from many years of intense annual temperature cycling without significant burial. Our results show that 11.2 plus or minus 1.7%, or 950 plus or minus 143 x 10(exp 3) square kilometers, of the EAIS above 1500m is wind glaze. Studies of SMB interpolate values across glaze regions, leading to overestimates of net mass input. Using our derived wind-glaze extent, we estimate this excess in three recent models of Antarctic SMB at 46-82 Gt. The lowest-input model appears to best match the mean in regions of extensive wind glaze.

Published
2012
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5. Getting around Antarctica: New High-Resolution Mappings of the Grounded and Freely-Floating Boundaries of the Antarctic Ice Sheet Created for the International Polar Year

Author

Bindschadler, R, Choi, H, Wichlacz, A, Bingham, R, Bohlander, J, Brunt, K, Corr, H, Drews, R, Fricker, H, Hall, M, Hindmarsh, R, Kohler, J, Padman, L, Rack, W, Rotschkly, G, Urbini, S, Vornberger, P, and Young, N

Subjects
Geosciences (General)
Abstract

Two ice-dynamic transitions of the Antarctic ice sheet - the boundary of grounded ice features and the freely-floating boundary - are mapped at 15-m resolution by participants of the International Polar Year project ASAID using customized software combining Landsat-7 imagery and ICESat/GLAS laser altimetry. The grounded ice boundary is 53 610 km long; 74% abuts to floating ice shelves or outlet glaciers, 19% is adjacent to open or sea-ice covered ocean, and 7% of the boundary ice terminates on land. The freely-floating boundary, called here the hydrostatic line, is the most landward position on ice shelves that expresses the full amplitude of oscillating ocean tides. It extends 27 521 km and is discontinuous. Positional (one-sigma) accuracies of the grounded ice boundary vary an order of magnitude ranging from +/- 52m for the land and open-ocean terminating segments to +/- 502m for the outlet glaciers. The hydrostatic line is less well positioned with errors over 2 km. Elevations along each line are selected from 6 candidate digital elevation models based on their agreement with ICESat elevation values and surface shape inferred from the Landsat imagery. Elevations along the hydrostatic line are converted to ice thicknesses by applying a firn-correction factor and a flotation criterion. BEDMAP-compiled data and other airborne data are compared to the ASAID elevations and ice thicknesses to arrive at quantitative (one-sigma) uncertainties of surface elevations of +/-3.6, +/-9.6, +/-11.4, +/-30 and +/-100m for five ASAID-assigned confidence levels. Over one-half of the surface elevations along the grounded ice boundary and over one-third of the hydrostatic line elevations are ranked in the highest two confidence categories. A comparison between ASAID-calculated ice shelf thicknesses and BEDMAP-compiled data indicate a thin-ice bias of 41.2+/-71.3m for the ASAID ice thicknesses. The relationship between the seaward offset of the hydrostatic line from the grounded ice boundary only weakly matches a prediction based on beam theory. The mapped products along with the customized software to generate them and a variety of intermediate products are available from the National Snow and Ice Data Center.

Published
2011
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6. Glacier Acceleration and Thinning after Ice Shelf Collapse in the Larsen B Embayment, Antarctica

Author

Scambos, T. A, Bohlander, J. A, Shuman, C. A, and Skvarca, P

Subjects
Geophysics
Abstract

Ice velocities derived from five Landsat 7 images acquired between January 2000 and February 2003 show a two- to six-fold increase in centerline speed of four glaciers flowing into the now-collapsed section of the Larsen B Ice Shelf. Satellite laser altimetry from ICEsat indicates the surface of Hektoria Glacier lowered by up to 38 +/- 6 m a six-month period beginning one year after the break-up in March 2002. Smaller elevation losses are observed for Crane and Jorum glaciers over a later 5-month period. Two glaciers south of the collapse area, Flask and Leppard, show little change in speed or elevation. Seasonal variations in speed preceding the large post-collapse velocity increases suggest that both summer melt percolation and changes in the stress field due to shelf removal play a major role in glacier dynamics.

Published
2004

7. Detailed ice loss pattern in the northern Antarctic Peninsula: widespread decline driven by ice front retreats

Author

Scambos, T. A., Berthier, E., Haran, T., Shuman, C. A., Cook, A. J., Ligtenberg, S. R M, Bohlander, J., Sub Dynamics Meteorology, Marine and Atmospheric Research, Sub Dynamics Meteorology, and Marine and Atmospheric Research

Subjects
lcsh:GE1-350, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Ice stream, lcsh:QE1-996.5, Antarctic sea ice, 010502 geochemistry & geophysics, Glacier morphology, 01 natural sciences, Ice shelf, lcsh:Geology, Oceanography, 13. Climate action, Ice tongue, Sea ice, Cryosphere, Ice sheet, Geology, lcsh:Environmental sciences, 0105 earth and related environmental sciences, Water Science and Technology, Earth-Surface Processes
Abstract

The northern Antarctic Peninsula (nAP, < 66° S) is one of the most rapidly changing glaciated regions on earth, yet the spatial patterns of its ice mass loss at the glacier basin scale have to date been poorly documented. We use satellite laser altimetry and satellite stereo-image topography spanning 2001–2010, but primarily 2003–2008, to map ice elevation change and infer mass changes for 33 glacier basins covering the mainland and most large islands in the nAP. Rates of ice volume and ice mass change are 27.7± 8.6 km3 a−1 and 24.9± 7.8 Gt a−1, equal to −0.73 m a−1 w.e. for the study area. Mass loss is the highest for eastern glaciers affected by major ice shelf collapses in 1995 and 2002, where twelve glaciers account for 60% of the total imbalance. However, losses at smaller rates occur throughout the nAP, at both high and low elevation, despite increased snow accumulation along the western coast and ridge crest. We interpret the widespread mass loss to be driven by decades of ice front retreats on both sides of the nAP, and extended throughout the ice sheet due to the propagation of kinematic waves triggered at the fronts into the interior.

Published
2018

8. Conservation translocations of Hawaiian monk seals: accounting for variability in body condition improves evaluation of translocation efficacy.

Author

Baker, J. D., Barbieri, M. M., Johanos, T. C., Littnan, C. L., Bohlander, J. L., Kaufman, A. C., Harting, A. L., Farry, S. C., and Yoshinaga, C. H.

Subjects
DISTRIBUTION (Probability theory), HAWAIIANS, MONKS, QUANTITATIVE research, SURVIVAL analysis (Biometry)
Abstract

To assess the efficacy of conservation translocations, survival of released individuals is typically compared to that of control groups. Such comparisons assume that treatment groups consist of otherwise equivalent individuals. When that assumption is unmet, incorporating physiological parameters may improve assessment of translocation programs. During 2012–2014, 19 weaned female Hawaiian monk seal pups were translocated to sites where survival prospects were expected to be more favorable than at their natal locations. We compared survival from weaning to age two years of translocated pups to two control groups; pups remaining at source sites and pups native to destination sites. To account for the known relationship between weaning girth and survival, we generated probability distributions of the number of survivors at source and destination sites given the weaning girths of translocated seals. Data were available to calculate girth‐adjusted survival probabilities for 13 of the translocated pups. Of these, we estimated that only one pup would have been expected to have survived had the translocated pups remained at their natal site. Seven of the 13 translocated seals survived, a value just below the median (eight) expected to have survived at the destination site. Thus, translocation substantially improved survival. Had we not accounted for weaning girth effects on survival, we would have erroneously concluded that the translocation program had yielded no survival benefit. Identifying and integrating correlates of survival into quantitative analyses associated with conservation translocations can reduce bias and lead to greater success. [ABSTRACT FROM AUTHOR]

Published
2021
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9. Glacier Acceleration and Thinning after Ice Shelf Collapse in the Larsen B Embayment, Antarctica

Author

Scambos, T. A., Bohlander, J. A., Shuman, Christopher, and Skvarca, P.

Abstract

Ice velocities derived from five Landsat 7 images acquired between January 2000 and February 2003 show a two- to six-fold increase in centerline speed of four glaciers flowing into the now-collapsed section of the Larsen B Ice Shelf. Satellite laser altimetry from ICESat indicates the surface of Hektoria Glacier lowered by up to 38 �� 6 m in a six-month period beginning one year after the break-up in March 2002. Smaller elevation losses are observed for Crane and Jorum glaciers over a later 5-month period. Two glaciers south of the collapse area, Flask and Leppard, show little change in speed or elevation. Seasonal variations in speed preceding the large post-collapse velocity increases suggest that both summer melt percolation and changes in the stress field due to shelf removal play a major role in glacier dynamics.

Published
2014
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10. Detailed ice loss pattern in the northern Antarctic Peninsula: Widespread decline driven by ice front retreats

Author

Scambos, T. A., Berthier, E., Haran, T., Shuman, C. A., Cook, A. J., Ligtenberg, S. R M, Bohlander, J., Scambos, T. A., Berthier, E., Haran, T., Shuman, C. A., Cook, A. J., Ligtenberg, S. R M, and Bohlander, J.

Abstract

The northern Antarctic Peninsula (nAP, < 66° S) is one of the most rapidly changing glaciated regions on earth, yet the spatial patterns of its ice mass loss at the glacier basin scale have to date been poorly documented. We use satellite laser altimetry and satellite stereo-image topography spanning 2001-2010, but primarily 2003-2008, to map ice elevation change and infer mass changes for 33 glacier basins covering the mainland and most large islands in the nAP. Rates of ice volume and ice mass change are 27.7 ± 8.6 km3 a-1 and 24.9±7.8Gta-1, equal to -0.73 ma-1 w.e. for the study area. Mass loss is the highest for eastern glaciers affected by major ice shelf collapses in 1995 and 2002, where twelve glaciers account for 60% of the total imbalance. However, losses at smaller rates occur throughout the nAP, at both high and low elevation, despite increased snow accumulation along the western coast and ridge crest. We interpret the widespread mass loss to be driven by decades of ice front retreats on both sides of the nAP, and extended throughout the ice sheet due to the propagation of kinematic waves triggered at the fronts into the interior.

Published
2014

14. Getting around Antarctica: New high-resolution mappings of the grounded and freely-floating boundaries of the Antarctic ice sheet created for the International Polar Year

Author

Bindschadler, R., Choi, H., Wichlacz, A., Bingham, B., Bohlander, J., Brunt, K., Corr, H., Drews, Reinhard, Fricker, H., Hall, M., Hindmarsh, R., Kohler, J., Padman, L., Rack, Wolfgang, Rotschky, G., Urbini, S., Vornberger, P., Young, N., Bindschadler, R., Choi, H., Wichlacz, A., Bingham, B., Bohlander, J., Brunt, K., Corr, H., Drews, Reinhard, Fricker, H., Hall, M., Hindmarsh, R., Kohler, J., Padman, L., Rack, Wolfgang, Rotschky, G., Urbini, S., Vornberger, P., and Young, N.

Abstract

The boundary of grounded ice and the location of ice transitioning to a freely floating state are mapped at 15‐m resolution around the entire continent of Antarctica. These data products are produced by participants of the International Polar Year project ASAID using customized software combining Landsat‐7 imagery and ICESat laser altimetry. The grounded ice boundary is 53,610 km long; 74% of it abuts to floating ice shelves or outlet glaciers, 19% is adjacent to open or sea‐ice covered ocean, and 7% of the boundary are land terminations with bare rock. Elevations along each line are selected from 6 candidate digital elevation models: two created from the input ICESat laser altimetry and Landsat data, two from stereo satellite imagery, and two from compilations of primarily radar altimetry. Elevation selection and an assignment of confidence in the elevation value are based on agreement with ICESat elevation values and shape of the surface inferred from the Landsat imagery. Elevations along the freely‐floating boundary (called the hydrostatic line) are converted to ice thicknesses by applying a firn‐correction factor and a flotation criterion. The relationship between the seaward offset of the hydrostatic line from the grounding line only weakly matches a prediction based on beam theory. Airborne data are used to validate the technique of grounding line mapping, elevation selection and ice thickness derivation. The mapped products along with the customized software to generate them and a variety of intermediate products are available from the National Snow and Ice Data Center.

Published
2011

15. Getting around Antarctica: new high-resolution mappings of the grounded and freely-floating boundaries of the Antarctic ice sheet created for the International Polar Year

Author

Bindschadler, R., primary, Choi, H., additional, Wichlacz, A., additional, Bingham, R., additional, Bohlander, J., additional, Brunt, K., additional, Corr, H., additional, Drews, R., additional, Fricker, H., additional, Hall, M., additional, Hindmarsh, R., additional, Kohler, J., additional, Padman, L., additional, Rack, W., additional, Rotschky, G., additional, Urbini, S., additional, Vornberger, P., additional, and Young, N., additional

Published
2011
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21. Extent of low accumulation 'wind glaze' areas on the East Antarctic plateau: implications for continental ice mass balance

Author

Ted Scambos, Kenneth C. Jezek, Mary R. Albert, Jan-Gunnar Winther, Jennifer Bohlander, David G. Long, Thomas Neumann, M. R. van den Broeke, Terry Haran, K. Farness, Stefano Urbini, Jan T. M. Lenaerts, Massimo Frezzotti, Scambos, T. A., Frezzotti, M., Haran, T., Bohlander, J., Lenaerts, J. T. M., Van Den Broeke, M. R., Jezek, K., Long, D., Urbini, S., Farness, K., Neumann, T., Albert, M., and Winther, J. -G.

Subjects
010506 paleontology, geography, Katabatic wind, geography.geographical_feature_category, Plateau, 010504 meteorology & atmospheric sciences, Glaze, Elevation, Antarctic ice sheet, Atmospheric sciences, 01 natural sciences, Glacier mass balance, 13. Climate action, Climatology, Ice sheet, Digital elevation model, Geology, 0105 earth and related environmental sciences, Earth-Surface Processes
Abstract

Persistent katabatic winds form widely distributed localized areas of near-zero net surface accumulation on the East Antarctic ice sheet (EAIS) plateau. These areas have been called 'glaze' surfaces due to their polished appearance. They are typically 2-200 km2 in area and are found on leeward slopes of ice-sheet undulations and megadunes. Adjacent, leeward high-accumulation regions (isolated dunes) are generally smaller and do not compensate for the local low in surface mass balance (SMB). We use a combination of satellite remote sensing and field-gathered datasets to map the extent of wind glaze in the EAIS above 1500 m elevation. Mapping criteria are derived from distinctive surface and subsurface characteristics of glaze areas resulting from many years of intense annual temperature cycling without significant burial. Our results show that 11.2 ± 1.7%, or 950 ± 143 × 103km2, of the EAIS above 1500 m is wind glaze. Studies of SMB interpolate values across glaze regions, leading to overestimates of net mass input. Using our derived wind-glaze extent, we estimate this excess in three recent models of Antarctic SMB at 46-82 Gt. The lowest-input model appears to best match the mean in regions of extensive wind glaze.

Published
2012
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22. Social support and patterns of adjustment to breast cancer.

Author

Hoskins CN, Baker S, Sherman D, Bohlander J, Bookbinder M, Budin W, Ekstrom D, Knauer C, and Maislin G

Subjects
Breast Neoplasms rehabilitation, Breast Neoplasms surgery, Clinical Nursing Research, Family, Female, Humans, Male, Marriage, Middle Aged, Patient Satisfaction, Postoperative Period, Psychological Tests, Social Environment, Stress, Psychological, Adaptation, Psychological, Breast Neoplasms psychology, Social Support
Abstract

The effect of marital support and support from other adults on the emotional and physical adjustment of 128 women with breast cancer was examined. Role function and satisfaction with health care also were evaluated as predictors of adjustment. Intact data series were obtained at 7-10 days, at 1, 2, 3, and 6 months, and 1 year postsurgery. Emotional adjustment could be predicted by satisfaction with a spouse's response to interactional and emotional needs and by support from other adults. The relationships were significant at concurrent times, across contiguous times, and predicting from the 7-10 day postsurgical period to both the 6-month and 1-year end points. Physical adjustment was not predicted by support but satisfaction with health care was predictive of perceived overall health status. Functional status in vocational, domestic, and social roles was significantly related to emotional and physical adjustment at all phases with few exceptions.

Published
1996

23. Differentiation of self: an examination of the concept.

Author

Bohlander JR

Subjects
Child, Preschool, Humans, Infant, Infant, Newborn, Psychiatric Nursing, Child Development, Models, Psychological, Self Concept
Abstract

Differentiation of self is a concept that has been used interchangeably with the similar concepts of individuation and psychological differentiation. The construction of a sound empirical knowledge base for differentiation of self has been hindered by the lack of conceptual-operational fit found in many studies. Using a modification of the concept analysis approach proposed by Walker and Avant (1988), a detailed description of differentiation of self is presented, delineating it from similar concepts. Differentiation of self is defined as the ability to distinguish between thoughts and feelings in an emotional relationship system. As the cornerstone concept in the Bowen theory (1985b), knowledge about differentiation of self has important clinical implications for nurses and other health professionals who strive to improve the assessment and intervention process in their work with individuals and families.

Published
1995
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