Geospatial simulations of airborne ice-penetrating radar surveying reveal elevation under-measurement bias for ice-sheet bed topography
Airborne radio-echo sounding (RES) surveys are widely used to measure ice-sheet bed topography. Measuring bed topography as accurately and widely as possible is of critical importance to modelling ice dynamics and hence to constraining better future ice response to climate change. Measurement accura...
| Main Authors: | , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Cambridge University Press
2020-04-01
|
| Series: | Annals of Glaciology |
| Subjects: | |
| Online Access: | https://www.cambridge.org/core/product/identifier/S026030552000035X/type/journal_article |
| _version_ | 1811157281773977600 |
|---|---|
| author | Oliver T. Bartlett Steven J. Palmer Dustin M. Schroeder Emma J. MacKie Timothy T. Barrows Alastair G. C. Graham |
| author_facet | Oliver T. Bartlett Steven J. Palmer Dustin M. Schroeder Emma J. MacKie Timothy T. Barrows Alastair G. C. Graham |
| author_sort | Oliver T. Bartlett |
| collection | DOAJ |
| description | Airborne radio-echo sounding (RES) surveys are widely used to measure ice-sheet bed topography. Measuring bed topography as accurately and widely as possible is of critical importance to modelling ice dynamics and hence to constraining better future ice response to climate change. Measurement accuracy of RES surveys is influenced both by the geometry of bed topography and the survey design. Here we develop a novel approach for simulating RES surveys over glaciated terrain, to quantify the sensitivity of derived bed elevation to topographic geometry. Furthermore, we investigate how measurement errors influence the quantification of glacial valley geometry. We find a negative bias across RES measurements, where off-nadir return measurement error is typically −1.8 ± 11.6 m. Topographic highlands are under-measured an order of magnitude more than lowlands. Consequently, valley depth and cross-sectional area are largely under-estimated. While overall estimates of ice thickness are likely too high, we find large glacier valley cross-sectional area to be under-estimated by −2.8 ± 18.1%. Therefore, estimates of ice flux through large outlet glaciers are likely too low when this effect is not taken into account. Additionally, bed mismeasurements potentially impact our appreciation of outlet-glacier stability. |
| first_indexed | 2024-04-10T05:04:39Z |
| format | Article |
| id | doaj.art-429e3d0e634345638764827fdf8398be |
| institution | Directory Open Access Journal |
| issn | 0260-3055 1727-5644 |
| language | English |
| last_indexed | 2024-04-10T05:04:39Z |
| publishDate | 2020-04-01 |
| publisher | Cambridge University Press |
| record_format | Article |
| series | Annals of Glaciology |
| spelling | doaj.art-429e3d0e634345638764827fdf8398be2023-03-09T12:27:39ZengCambridge University PressAnnals of Glaciology0260-30551727-56442020-04-0161465710.1017/aog.2020.35Geospatial simulations of airborne ice-penetrating radar surveying reveal elevation under-measurement bias for ice-sheet bed topographyOliver T. Bartlett0https://orcid.org/0000-0002-0347-7926Steven J. Palmer1https://orcid.org/0000-0003-3977-8509Dustin M. Schroeder2Emma J. MacKie3https://orcid.org/0000-0002-6303-5249Timothy T. Barrows4Alastair G. C. Graham5Department of Geography, University of Exeter, Exeter, UKDepartment of Geography, University of Exeter, Exeter, UKDepartment of Geophysics, Stanford University, Stanford, CA, USA Department of Electrical Engineering, Stanford University, Stanford, CA, USADepartment of Geophysics, Stanford University, Stanford, CA, USASchool of Earth, Atmospheric and Life Sciences, University of Wollongong, Wollongong, Australia Department of Geography, University of Portsmouth, Portsmouth, UKCollege of Marine Science, University of South Florida, St Petersburg, FL33701, USAAirborne radio-echo sounding (RES) surveys are widely used to measure ice-sheet bed topography. Measuring bed topography as accurately and widely as possible is of critical importance to modelling ice dynamics and hence to constraining better future ice response to climate change. Measurement accuracy of RES surveys is influenced both by the geometry of bed topography and the survey design. Here we develop a novel approach for simulating RES surveys over glaciated terrain, to quantify the sensitivity of derived bed elevation to topographic geometry. Furthermore, we investigate how measurement errors influence the quantification of glacial valley geometry. We find a negative bias across RES measurements, where off-nadir return measurement error is typically −1.8 ± 11.6 m. Topographic highlands are under-measured an order of magnitude more than lowlands. Consequently, valley depth and cross-sectional area are largely under-estimated. While overall estimates of ice thickness are likely too high, we find large glacier valley cross-sectional area to be under-estimated by −2.8 ± 18.1%. Therefore, estimates of ice flux through large outlet glaciers are likely too low when this effect is not taken into account. Additionally, bed mismeasurements potentially impact our appreciation of outlet-glacier stability.https://www.cambridge.org/core/product/identifier/S026030552000035X/type/journal_articleGlaciological instruments and methodsGreenland Ice Sheetradio-echo soundingsubglacial topography |
| spellingShingle | Oliver T. Bartlett Steven J. Palmer Dustin M. Schroeder Emma J. MacKie Timothy T. Barrows Alastair G. C. Graham Geospatial simulations of airborne ice-penetrating radar surveying reveal elevation under-measurement bias for ice-sheet bed topography Annals of Glaciology Glaciological instruments and methods Greenland Ice Sheet radio-echo sounding subglacial topography |
| title | Geospatial simulations of airborne ice-penetrating radar surveying reveal elevation under-measurement bias for ice-sheet bed topography |
| title_full | Geospatial simulations of airborne ice-penetrating radar surveying reveal elevation under-measurement bias for ice-sheet bed topography |
| title_fullStr | Geospatial simulations of airborne ice-penetrating radar surveying reveal elevation under-measurement bias for ice-sheet bed topography |
| title_full_unstemmed | Geospatial simulations of airborne ice-penetrating radar surveying reveal elevation under-measurement bias for ice-sheet bed topography |
| title_short | Geospatial simulations of airborne ice-penetrating radar surveying reveal elevation under-measurement bias for ice-sheet bed topography |
| title_sort | geospatial simulations of airborne ice penetrating radar surveying reveal elevation under measurement bias for ice sheet bed topography |
| topic | Glaciological instruments and methods Greenland Ice Sheet radio-echo sounding subglacial topography |
| url | https://www.cambridge.org/core/product/identifier/S026030552000035X/type/journal_article |
| work_keys_str_mv | AT olivertbartlett geospatialsimulationsofairborneicepenetratingradarsurveyingrevealelevationundermeasurementbiasforicesheetbedtopography AT stevenjpalmer geospatialsimulationsofairborneicepenetratingradarsurveyingrevealelevationundermeasurementbiasforicesheetbedtopography AT dustinmschroeder geospatialsimulationsofairborneicepenetratingradarsurveyingrevealelevationundermeasurementbiasforicesheetbedtopography AT emmajmackie geospatialsimulationsofairborneicepenetratingradarsurveyingrevealelevationundermeasurementbiasforicesheetbedtopography AT timothytbarrows geospatialsimulationsofairborneicepenetratingradarsurveyingrevealelevationundermeasurementbiasforicesheetbedtopography AT alastairgcgraham geospatialsimulationsofairborneicepenetratingradarsurveyingrevealelevationundermeasurementbiasforicesheetbedtopography |