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Glaciers are particularly well suited to investigation by radar because the [[Electrical conductivity|conductivity]], imaginary part of the [[permittivity]], and the [[Permittivity#Dielectric absorption processes|dielectric absorption]] of ice are small at [[Radio frequency|radio frequencies]] resulting in low loss [[Dissipation factor|tangent]], [[Skin effect|skin depth]], and [[Attenuation|attenuation values]]. This allows echoes from the base of the ice sheet to be detected through ice thicknesses greater than 4&nbsp;km.<ref name=":1">{{Cite journal|last=Bamber|first=J. L.|last2=Griggs|first2=J. A.|last3=Hurkmans|first3=R. T. W. L.|last4=Dowdeswell|first4=J. A.|last5=Gogineni|first5=S. P.|last6=Howat|first6=I.|last7=Mouginot|first7=J.|last8=Paden|first8=J.|last9=Palmer|first9=S.|last10=Rignot|first10=E.|last11=Steinhage|first11=D.|date=2013-03-22|title=A new bed elevation dataset for Greenland|url=https://tc.copernicus.org/articles/7/499/2013/|journal=The Cryosphere|language=en|volume=7|issue=2|pages=499–510|doi=10.5194/tc-7-499-2013|issn=1994-0424}}</ref> <ref name=Bedmap2>{{cite journal |last1=Fretwell|first1=P. |last2=Pritchard|first2= H. D. |last3=Vaughan|first3= D. G. |last4=Bamber|first4= J. L. |last5=Barrand|first5= N. E. |last6=Bell|first6= R. |last7=Bianchi|first7= C. |last8=Bingham|first8=R. G. |last9=Blankenship|first9= D. D. |last10=Casassa|first10= G. |last11=Catania|first11= G. |last12=Callens|first12= D. |last13=Conway|first13= H. |last14=Cook|first14= A. J. |last15=Corr|first15= H. F. J. |last16=Damaske|first16=D. |last17=Damm|first17= V. |last18=Ferraccioli|first18= F. |last19=Forsberg|first19= R. |last20=Fujita|first20= S. |last21=Gim|first21= Y. |last22=Gogineni|first22= P. |last23=Griggs|first23= J. A. |last24=Hindmarsh|first24=R. C. A. |last25=Holmlund|first25= P. |last26=Holt|first26= J. W. |last27=Jacobel|first27= R. W. |last28=Jenkins|first28= A. |last29=Jokat|first29= W. |last30=Jordan|first30= T. |last31=King|first31= E. C. |last32=Kohler|first32=J. |last33=Krabill|first33= W. |last34=Riger|first34= M. |last35=Langley|first35= K. A. |last36=Leitchenkov|first36= G. |last37=Leuschen|first37= C. |last38=Luyendyk|first38= B. P. |last39=Matsuoka|first39=K. |last40=Mouginot|first40= J. |last41=Nitsche|first41= F. O. |last42=Nogi|first42= Y. |last43=Nost|first43= O. A. |last44=Popov|first44= S. V. |last45=Rignot|first45= E. |last46=Rippin|first46= D. M. |last47=Rivera|first47=A. |last48=Roberts|first48= J. |last49=Ross|first49= N. |last50=Siegert|first50= M. J. |last51=Smith|first51= A. M. |last52=Steinhage|first52= D. |last53=Studinger|first53= M. |last54=Sun|first54= B. |last55=Tinto|first55=B. K.|last56=Welch|first56= B. C. |last57=Wilson|first57= D. |last58=Young|first58= D. A. |last59=Xiangbin|first59= C. |last60=Zirizzotti|first60= A. | display-authors = 5 |title=Bedmap2: improved ice bed, surface and thickness datasets for Antarctica |journal=The Cryosphere |volume=7 |issue=1 |page=390 | date = 28 February 2013|url=http://www.the-cryosphere.net/7/375/2013/tc-7-375-2013.pdf |accessdate=6 January 2014|doi=10.5194/tc-7-375-2013 |bibcode=2013TCry....7..375F }}</ref>The subsurface observation of ice masses using radio waves has been an integral and evolving [[Geophysics|geophysical]] technique in [[glaciology]] for over half a century.<ref>{{Cite web|last=Allen|first=Christopher|date=September 26, 2008|title=A Brief History Of Radio – Echo Sounding Of Ice|url=https://earthzine.org/a-brief-history-of-radio-echo-sounding-of-ice-2/|url-status=live}}</ref><ref name=":2">{{Cite journal|last=Dowdeswell|first=J A|last2=Evans|first2=S|date=2004-10-01|title=Investigations of the form and flow of ice sheets and glaciers using radio-echo sounding|url=https://iopscience.iop.org/article/10.1088/0034-4885/67/10/R03|journal=Reports on Progress in Physics|volume=67|issue=10|pages=1821–1861|doi=10.1088/0034-4885/67/10/R03|issn=0034-4885}}</ref><ref>{{Cite book|last=Drewry|first=DJ|title=Antarctica: Glaciological and Geophysical Folio, Vol. 2|publisher=University of Cambridge, Scott Polar Research Institute Cambridge|year=1983}}</ref><ref>{{Cite journal|last=Gudmandsen|first=P.|date=December 1969|title=Airborne Radio Echo Sounding of the Greenland Ice Sheet|url=https://www.jstor.org/stable/1795099?origin=crossref|journal=The Geographical Journal|volume=135|issue=4|pages=548|doi=10.2307/1795099}}</ref><ref>{{Cite journal|last=Robin|first=G. de Q.|date=1975|title=Radio-Echo Sounding: Glaciological Interpretations and Applications|url=https://www.cambridge.org/core/product/identifier/S0022143000034262/type/journal_article|journal=Journal of Glaciology|language=en|volume=15|issue=73|pages=49–64|doi=10.3189/S0022143000034262|issn=0022-1430}}</ref><ref>{{cite thesis|type=PhD|last=Steenson|first=BO|date=1951|title=Radar Methods for the Exploration of Glaciers|publisher=California Institute of Technology}}</ref><ref>{{Cite book|last=Stern|first=W|title=Principles, methods and results of electrodynamic thickness measurement of glacier ice|publisher=Zeitschrift fur Gletscherkunde 18, 24|year=1930}}</ref><ref>{{Cite journal|last=Turchetti|first=Simone|last2=Dean|first2=Katrina|last3=Naylor|first3=Simon|last4=Siegert|first4=Martin|date=September 2008|title=Accidents and opportunities: a history of the radio echo-sounding of Antarctica, 1958–79|url=https://www.cambridge.org/core/product/identifier/S0007087408000903/type/journal_article|journal=The British Journal for the History of Science|language=en|volume=41|issue=3|pages=417–444|doi=10.1017/S0007087408000903|issn=0007-0874}}</ref> Its most widespread uses have been the measurement of ice thickness, subglacial topography, and ice sheet stratigraphy.<ref>{{Cite journal|last=Bingham|first=R. G.|last2=Siegert|first2=M. J.|date=2007-03-01|title=Radio-Echo Sounding Over Polar Ice Masses|url=http://jeeg.geoscienceworld.org/cgi/doi/10.2113/JEEG12.1.47|journal=Journal of Environmental & Engineering Geophysics|language=en|volume=12|issue=1|pages=47–62|doi=10.2113/JEEG12.1.47|issn=1083-1363}}</ref><ref name=":2" /><ref name=":1" /> It has also been used to observe the subglacial and conditions of ice sheets and glaciers, including hydrology, thermal state, accumulation, flow history, ice fabric, and bed geology.<ref name=":0" /> In planetary science, ice penetrating radar has also been used to explore the subsurface of the Polar Ice Caps on Mars and comets.<ref>{{Cite journal|last=Picardi|first=G.|date=2005-12-23|title=Radar Soundings of the Subsurface of Mars|url=https://www.sciencemag.org/lookup/doi/10.1126/science.1122165|journal=Science|language=en|volume=310|issue=5756|pages=1925–1928|doi=10.1126/science.1122165|issn=0036-8075}}</ref><ref>{{Cite journal|last=Kofman|first=W.|last2=Herique|first2=A.|last3=Barbin|first3=Y.|last4=Barriot|first4=J.-P.|last5=Ciarletti|first5=V.|last6=Clifford|first6=S.|last7=Edenhofer|first7=P.|last8=Elachi|first8=C.|last9=Eyraud|first9=C.|last10=Goutail|first10=J.-P.|last11=Heggy|first11=E.|date=2015-07-31|title=Properties of the 67P/Churyumov-Gerasimenko interior revealed by CONSERT radar|url=https://www.sciencemag.org/lookup/doi/10.1126/science.aab0639|journal=Science|language=en|volume=349|issue=6247|pages=aab0639–aab0639|doi=10.1126/science.aab0639|issn=0036-8075}}</ref><ref>{{Cite journal|last=Seu|first=Roberto|last2=Phillips|first2=Roger J.|last3=Biccari|first3=Daniela|last4=Orosei|first4=Roberto|last5=Masdea|first5=Arturo|last6=Picardi|first6=Giovanni|last7=Safaeinili|first7=Ali|last8=Campbell|first8=Bruce A.|last9=Plaut|first9=Jeffrey J.|last10=Marinangeli|first10=Lucia|last11=Smrekar|first11=Suzanne E.|date=2007-05-18|title=SHARAD sounding radar on the Mars Reconnaissance Orbiter|url=http://doi.wiley.com/10.1029/2006JE002745|journal=Journal of Geophysical Research|language=en|volume=112|issue=E5|pages=E05S05|doi=10.1029/2006JE002745|issn=0148-0227}}</ref> Missions are planned to explore the icy moons of Jupiter.<ref>{{Cite journal|last=Blankenship|first=DD|date=2018|others=and 5 others|title=Reasons for Europa|journal=42nd COSPAR Scientific Assembly|volume=42}}</ref><ref>{{Cite journal|last=Bruzzone|first=L|last2=Alberti|first2=G|last3=Catallo|first3=C|last4=Ferro|first4=A|last5=Kofman|first5=W|last6=Orosei|first6=R|date=May 2011|title=Subsurface Radar Sounding of the Jovian Moon Ganymede|url=http://ieeexplore.ieee.org/document/5738315/|journal=Proceedings of the IEEE|volume=99|issue=5|pages=837–857|doi=10.1109/JPROC.2011.2108990|issn=0018-9219}}</ref>
Glaciers are particularly well suited to investigation by radar because the [[Electrical conductivity|conductivity]], imaginary part of the [[permittivity]], and the [[Permittivity#Dielectric absorption processes|dielectric absorption]] of ice are small at [[Radio frequency|radio frequencies]] resulting in low loss [[Dissipation factor|tangent]], [[Skin effect|skin depth]], and [[Attenuation|attenuation values]]. This allows echoes from the base of the ice sheet to be detected through ice thicknesses greater than 4&nbsp;km.<ref name=":1">{{Cite journal|last=Bamber|first=J. L.|last2=Griggs|first2=J. A.|last3=Hurkmans|first3=R. T. W. L.|last4=Dowdeswell|first4=J. A.|last5=Gogineni|first5=S. P.|last6=Howat|first6=I.|last7=Mouginot|first7=J.|last8=Paden|first8=J.|last9=Palmer|first9=S.|last10=Rignot|first10=E.|last11=Steinhage|first11=D.|date=2013-03-22|title=A new bed elevation dataset for Greenland|url=https://tc.copernicus.org/articles/7/499/2013/|journal=The Cryosphere|language=en|volume=7|issue=2|pages=499–510|doi=10.5194/tc-7-499-2013|issn=1994-0424}}</ref> <ref name=Bedmap2>{{cite journal |last1=Fretwell|first1=P. |last2=Pritchard|first2= H. D. |last3=Vaughan|first3= D. G. |last4=Bamber|first4= J. L. |last5=Barrand|first5= N. E. |last6=Bell|first6= R. |last7=Bianchi|first7= C. |last8=Bingham|first8=R. G. |last9=Blankenship|first9= D. D. |last10=Casassa|first10= G. |last11=Catania|first11= G. |last12=Callens|first12= D. |last13=Conway|first13= H. |last14=Cook|first14= A. J. |last15=Corr|first15= H. F. J. |last16=Damaske|first16=D. |last17=Damm|first17= V. |last18=Ferraccioli|first18= F. |last19=Forsberg|first19= R. |last20=Fujita|first20= S. |last21=Gim|first21= Y. |last22=Gogineni|first22= P. |last23=Griggs|first23= J. A. |last24=Hindmarsh|first24=R. C. A. |last25=Holmlund|first25= P. |last26=Holt|first26= J. W. |last27=Jacobel|first27= R. W. |last28=Jenkins|first28= A. |last29=Jokat|first29= W. |last30=Jordan|first30= T. |last31=King|first31= E. C. |last32=Kohler|first32=J. |last33=Krabill|first33= W. |last34=Riger|first34= M. |last35=Langley|first35= K. A. |last36=Leitchenkov|first36= G. |last37=Leuschen|first37= C. |last38=Luyendyk|first38= B. P. |last39=Matsuoka|first39=K. |last40=Mouginot|first40= J. |last41=Nitsche|first41= F. O. |last42=Nogi|first42= Y. |last43=Nost|first43= O. A. |last44=Popov|first44= S. V. |last45=Rignot|first45= E. |last46=Rippin|first46= D. M. |last47=Rivera|first47=A. |last48=Roberts|first48= J. |last49=Ross|first49= N. |last50=Siegert|first50= M. J. |last51=Smith|first51= A. M. |last52=Steinhage|first52= D. |last53=Studinger|first53= M. |last54=Sun|first54= B. |last55=Tinto|first55=B. K.|last56=Welch|first56= B. C. |last57=Wilson|first57= D. |last58=Young|first58= D. A. |last59=Xiangbin|first59= C. |last60=Zirizzotti|first60= A. | display-authors = 5 |title=Bedmap2: improved ice bed, surface and thickness datasets for Antarctica |journal=The Cryosphere |volume=7 |issue=1 |page=390 | date = 28 February 2013|url=http://www.the-cryosphere.net/7/375/2013/tc-7-375-2013.pdf |accessdate=6 January 2014|doi=10.5194/tc-7-375-2013 |bibcode=2013TCry....7..375F }}</ref>The subsurface observation of ice masses using radio waves has been an integral and evolving [[Geophysics|geophysical]] technique in [[glaciology]] for over half a century.<ref>{{Cite web|last=Allen|first=Christopher|date=September 26, 2008|title=A Brief History Of Radio – Echo Sounding Of Ice|url=https://earthzine.org/a-brief-history-of-radio-echo-sounding-of-ice-2/|url-status=live}}</ref><ref name=":2">{{Cite journal|last=Dowdeswell|first=J A|last2=Evans|first2=S|date=2004-10-01|title=Investigations of the form and flow of ice sheets and glaciers using radio-echo sounding|url=https://iopscience.iop.org/article/10.1088/0034-4885/67/10/R03|journal=Reports on Progress in Physics|volume=67|issue=10|pages=1821–1861|doi=10.1088/0034-4885/67/10/R03|issn=0034-4885}}</ref><ref>{{Cite book|last=Drewry|first=DJ|title=Antarctica: Glaciological and Geophysical Folio, Vol. 2|publisher=University of Cambridge, Scott Polar Research Institute Cambridge|year=1983}}</ref><ref>{{Cite journal|last=Gudmandsen|first=P.|date=December 1969|title=Airborne Radio Echo Sounding of the Greenland Ice Sheet|url=https://www.jstor.org/stable/1795099?origin=crossref|journal=The Geographical Journal|volume=135|issue=4|pages=548|doi=10.2307/1795099}}</ref><ref>{{Cite journal|last=Robin|first=G. de Q.|date=1975|title=Radio-Echo Sounding: Glaciological Interpretations and Applications|url=https://www.cambridge.org/core/product/identifier/S0022143000034262/type/journal_article|journal=Journal of Glaciology|language=en|volume=15|issue=73|pages=49–64|doi=10.3189/S0022143000034262|issn=0022-1430}}</ref><ref>{{cite thesis|type=PhD|last=Steenson|first=BO|date=1951|title=Radar Methods for the Exploration of Glaciers|publisher=California Institute of Technology}}</ref><ref>{{Cite book|last=Stern|first=W|title=Principles, methods and results of electrodynamic thickness measurement of glacier ice|publisher=Zeitschrift fur Gletscherkunde 18, 24|year=1930}}</ref><ref>{{Cite journal|last=Turchetti|first=Simone|last2=Dean|first2=Katrina|last3=Naylor|first3=Simon|last4=Siegert|first4=Martin|date=September 2008|title=Accidents and opportunities: a history of the radio echo-sounding of Antarctica, 1958–79|url=https://www.cambridge.org/core/product/identifier/S0007087408000903/type/journal_article|journal=The British Journal for the History of Science|language=en|volume=41|issue=3|pages=417–444|doi=10.1017/S0007087408000903|issn=0007-0874}}</ref> Its most widespread uses have been the measurement of ice thickness, subglacial topography, and ice sheet stratigraphy.<ref>{{Cite journal|last=Bingham|first=R. G.|last2=Siegert|first2=M. J.|date=2007-03-01|title=Radio-Echo Sounding Over Polar Ice Masses|url=http://jeeg.geoscienceworld.org/cgi/doi/10.2113/JEEG12.1.47|journal=Journal of Environmental & Engineering Geophysics|language=en|volume=12|issue=1|pages=47–62|doi=10.2113/JEEG12.1.47|issn=1083-1363}}</ref><ref name=":2" /><ref name=":1" /> It has also been used to observe the subglacial and conditions of ice sheets and glaciers, including hydrology, thermal state, accumulation, flow history, ice fabric, and bed geology.<ref name=":0" /> In planetary science, ice penetrating radar has also been used to explore the subsurface of the Polar Ice Caps on Mars and comets.<ref>{{Cite journal|last=Picardi|first=G.|date=2005-12-23|title=Radar Soundings of the Subsurface of Mars|url=https://www.sciencemag.org/lookup/doi/10.1126/science.1122165|journal=Science|language=en|volume=310|issue=5756|pages=1925–1928|doi=10.1126/science.1122165|issn=0036-8075}}</ref><ref>{{Cite journal|last=Kofman|first=W.|last2=Herique|first2=A.|last3=Barbin|first3=Y.|last4=Barriot|first4=J.-P.|last5=Ciarletti|first5=V.|last6=Clifford|first6=S.|last7=Edenhofer|first7=P.|last8=Elachi|first8=C.|last9=Eyraud|first9=C.|last10=Goutail|first10=J.-P.|last11=Heggy|first11=E.|date=2015-07-31|title=Properties of the 67P/Churyumov-Gerasimenko interior revealed by CONSERT radar|url=https://www.sciencemag.org/lookup/doi/10.1126/science.aab0639|journal=Science|language=en|volume=349|issue=6247|pages=aab0639–aab0639|doi=10.1126/science.aab0639|issn=0036-8075}}</ref><ref>{{Cite journal|last=Seu|first=Roberto|last2=Phillips|first2=Roger J.|last3=Biccari|first3=Daniela|last4=Orosei|first4=Roberto|last5=Masdea|first5=Arturo|last6=Picardi|first6=Giovanni|last7=Safaeinili|first7=Ali|last8=Campbell|first8=Bruce A.|last9=Plaut|first9=Jeffrey J.|last10=Marinangeli|first10=Lucia|last11=Smrekar|first11=Suzanne E.|date=2007-05-18|title=SHARAD sounding radar on the Mars Reconnaissance Orbiter|url=http://doi.wiley.com/10.1029/2006JE002745|journal=Journal of Geophysical Research|language=en|volume=112|issue=E5|pages=E05S05|doi=10.1029/2006JE002745|issn=0148-0227}}</ref> Missions are planned to explore the icy moons of Jupiter.<ref>{{Cite journal|last=Blankenship|first=DD|date=2018|others=and 5 others|title=Reasons for Europa|journal=42nd COSPAR Scientific Assembly|volume=42}}</ref><ref>{{Cite journal|last=Bruzzone|first=L|last2=Alberti|first2=G|last3=Catallo|first3=C|last4=Ferro|first4=A|last5=Kofman|first5=W|last6=Orosei|first6=R|date=May 2011|title=Subsurface Radar Sounding of the Jovian Moon Ganymede|url=http://ieeexplore.ieee.org/document/5738315/|journal=Proceedings of the IEEE|volume=99|issue=5|pages=837–857|doi=10.1109/JPROC.2011.2108990|issn=0018-9219}}</ref>


==Measurements and Applications==
==Principle==
Radioglaciology uses [[nadir]] facing [[Radar|radars]] to probe the subsurface of [[Glacier|glaciers]], [[Ice sheet|ice sheets]], [[Ice cap|ice caps]], and [[Icy moon|icy moons]] and to detect [[Reflection (physics)|reflected]] and [[Scattering|scattered]] energy from within and beneath the ice. <ref name=":2" /> This geometry tends to emphasize [[Coherence (physics)|coherent]] and [[Specular reflection|specular]] reflected energy resulting in distinct forms or the radar equation. <ref>{{Cite journal|last=Haynes|first=Mark S.|date=2020-04|title=Surface and subsurface radar equations for radar sounders|url=https://www.cambridge.org/core/product/identifier/S0260305520000166/type/journal_article|journal=Annals of Glaciology|language=en|volume=61|issue=81|pages=135–142|doi=10.1017/aog.2020.16|issn=0260-3055}}</ref><ref name=":3">{{Cite journal|last=Peters|first=M.E.|last2=Blankenship|first2=D.D.|last3=Carter|first3=S.P.|last4=Kempf|first4=S.D.|last5=Young|first5=D.A.|last6=Holt|first6=J.W.|date=2007-09|title=Along-Track Focusing of Airborne Radar Sounding Data From West Antarctica for Improving Basal Reflection Analysis and Layer Detection|url=http://ieeexplore.ieee.org/document/4294104/|journal=IEEE Transactions on Geoscience and Remote Sensing|volume=45|issue=9|pages=2725–2736|doi=10.1109/TGRS.2007.897416|issn=0196-2892}}</ref> Collected radar data typical undergoes [[signal processing]] ranging from stacking (or pre-summing) to [[Seismic migration|migration]] to [[Synthetic-aperture radar|Synthetic Aperture Radar (SAR)]] focusing in 1, 2, or 3 dimensions. <ref>{{Cite journal|last=Ferro|first=A.|date=2019-06-18|title=Squinted SAR focusing for improving automatic radar sounder data analysis and enhancement|url=https://doi.org/10.1080/01431161.2019.1573339|journal=International Journal of Remote Sensing|volume=40|issue=12|pages=4762–4786|doi=10.1080/01431161.2019.1573339|issn=0143-1161}}</ref><ref>{{Cite journal|last=Zhang|first=Qiuwang|last2=Kandic|first2=Ivana|last3=Barfield|first3=Jeffrey T.|last4=Kutryk|first4=Michael J.|date=2013|title=Coculture with Late, but Not Early, Human Endothelial Progenitor Cells Up Regulates IL-1βExpression in THP-1 Monocytic Cells in a Paracrine Manner|url=http://dx.doi.org/10.1155/2013/859643|journal=Stem Cells International|volume=2013|pages=1–7|doi=10.1155/2013/859643|issn=1687-966X}}</ref><ref>{{Cite journal|last=Paden|first=John|last2=Akins|first2=Torry|last3=Dunson|first3=David|last4=Allen|first4=Chris|last5=Gogineni|first5=Prasad|date=2010/ed|title=Ice-sheet bed 3-D tomography|url=https://www.cambridge.org/core/journals/journal-of-glaciology/article/icesheet-bed-3d-tomography/665FF385052909BD4F5540E1CD91C3DA|journal=Journal of Glaciology|language=en|volume=56|issue=195|pages=3–11|doi=10.3189/002214310791190811|issn=0022-1430}}</ref><ref name=":3" /> This data is collected using ice penetrating radar systems which range from commercial (or bespoke) [[Ground-penetrating radar|ground penetrating radar (GPR) systems]] <ref>{{Cite journal|last=Booth|first=Adam D.|last2=Clark|first2=Roger|last3=Murray|first3=Tavi|date=2010-06|title=Semblance response to a ground-penetrating radar wavelet and resulting errors in velocity analysis|url=http://doi.wiley.com/10.3997/1873-0604.2010008|journal=Near Surface Geophysics|language=en|volume=8|issue=3|pages=235–246|doi=10.3997/1873-0604.2010008}}</ref><ref>{{Cite journal|last=Tulaczyk|first=Slawek M.|last2=Foley|first2=Neil T.|date=2020-12-08|title=The role of electrical conductivity in radar wave reflection from glacier beds|url=https://tc.copernicus.org/articles/14/4495/2020/|journal=The Cryosphere|language=English|volume=14|issue=12|pages=4495–4506|doi=10.5194/tc-14-4495-2020|issn=1994-0416}}</ref> to coherent, [[Chirp|chirped]] airborne sounders <ref>{{Cite journal|last=Gogineni|first=S.|last2=Tammana|first2=D.|last3=Braaten|first3=D.|last4=Leuschen|first4=C.|last5=Akins|first5=T.|last6=Legarsky|first6=J.|last7=Kanagaratnam|first7=P.|last8=Stiles|first8=J.|last9=Allen|first9=C.|last10=Jezek|first10=K.|date=2001-12-27|title=Coherent radar ice thickness measurements over the Greenland ice sheet|url=http://doi.wiley.com/10.1029/2001JD900183|journal=Journal of Geophysical Research: Atmospheres|language=en|volume=106|issue=D24|pages=33761–33772|doi=10.1029/2001JD900183}}</ref><ref>{{Cite journal|last=Rodriguez-Morales|first=Fernando|last2=Byers|first2=Kyle|last3=Crowe|first3=Reid|last4=Player|first4=Kevin|last5=Hale|first5=Richard D.|last6=Arnold|first6=Emily J.|last7=Smith|first7=Logan|last8=Gifford|first8=Christopher M.|last9=Braaten|first9=David|last10=Panton|first10=Christian|last11=Gogineni|first11=Sivaprasad|date=2014-05|title=Advanced Multifrequency Radar Instrumentation for Polar Research|url=https://ieeexplore.ieee.org/document/6557071/|journal=IEEE Transactions on Geoscience and Remote Sensing|volume=52|issue=5|pages=2824–2842|doi=10.1109/TGRS.2013.2266415|issn=0196-2892}}</ref><ref>{{Cite journal|last=Yan|first=J.|last2=Gogineni|first2=P.|last3=O'Neill|first3=C.|date=2018-07|title=L-Band Radar Sounder for Measuing Ice Basal Conditions and Ice-Shelf Melt Rate|url=https://ieeexplore.ieee.org/document/8518210/|journal=IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium|pages=4135–4137|doi=10.1109/IGARSS.2018.8518210}}</ref> to swath-imaging<ref>{{Cite journal|last=Holschuh|first=N.|last2=Christianson|first2=K.|last3=Paden|first3=J.|last4=Alley|first4=R.B.|last5=Anandakrishnan|first5=S.|date=2020-03-01|title=Linking postglacial landscapes to glacier dynamics using swath radar at Thwaites Glacier, Antarctica|url=https://pubs.geoscienceworld.org/gsa/geology/article/48/3/268/579962/Linking-postglacial-landscapes-to-glacier-dynamics|journal=Geology|language=en|volume=48|issue=3|pages=268–272|doi=10.1130/G46772.1|issn=0091-7613}}</ref>, multi-frequency<ref>{{Cite journal|last=Carrer|first=Leonardo|last2=Bruzzone|first2=Lorenzo|date=2017-12|title=Solving for ambiguities in radar geophysical exploration of planetary bodies by mimicking bats echolocation|url=http://www.nature.com/articles/s41467-017-02334-1|journal=Nature Communications|language=en|volume=8|issue=1|pages=2248|doi=10.1038/s41467-017-02334-1|issn=2041-1723|pmc=PMC5740182|pmid=29269728}}</ref>, or [[Polarimetry|polarimetric]]<ref>{{Cite journal|last=Dall|first=Jorgen|last2=Corr|first2=Hugh F. J.|last3=Walker|first3=Nick|last4=Rommen|first4=Bjorn|last5=Lin|first5=Chung-Chi|date=2018-07|title=Sounding the Antarctic ice sheet from space: a feasibility study based on airborne P-band radar data|url=https://ieeexplore.ieee.org/document/8518826/|journal=IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium|location=Valencia|publisher=IEEE|pages=4142–4145|doi=10.1109/IGARSS.2018.8518826|isbn=978-1-5386-7150-4}}</ref> implementations of such systems. Additionally, stationary, phase-sensitive, and [[Continuous-wave radar#Modulated continuous-wave|Frequency Modulated Continuous Wave (FMCW)]] radars <ref>{{Cite journal|last=Brennan|first=Paul V.|last2=Lok|first2=Lai Bun|last3=Nicholls|first3=Keith|last4=Corr|first4=Hugh|date=2014|title=Phase-sensitive FMCW radar system for high-precision Antarctic ice shelf profile monitoring|url=https://ietresearch.onlinelibrary.wiley.com/doi/abs/10.1049/iet-rsn.2013.0053|journal=IET Radar, Sonar & Navigation|language=en|volume=8|issue=7|pages=776–786|doi=10.1049/iet-rsn.2013.0053|issn=1751-8792}}</ref><ref>{{Cite journal|last=Lok|first=L. B.|last2=Brennan|first2=P. V.|last3=Ash|first3=M.|last4=Nicholls|first4=K. W.|date=2015-07|title=Autonomous phase-sensitive radio echo sounder for monitoring and imaging antarctic ice shelves|url=https://ieeexplore.ieee.org/document/7292636/|journal=2015 8th International Workshop on Advanced Ground Penetrating Radar (IWAGPR)|pages=1–4|doi=10.1109/IWAGPR.2015.7292636}}</ref><ref>{{Cite journal|last=Vaňková|first=Irena|last2=Nicholls|first2=Keith W.|last3=Xie|first3=Surui|last4=Parizek|first4=Byron R.|last5=Voytenko|first5=Denis|last6=Holland|first6=David M.|date=2020/04|title=Depth-dependent artifacts resulting from ApRES signal clipping|url=https://www.cambridge.org/core/journals/annals-of-glaciology/article/depthdependent-artifacts-resulting-from-apres-signal-clipping/74C8B78B415646A16B15CF418749D9E0|journal=Annals of Glaciology|language=en|volume=61|issue=81|pages=108–113|doi=10.1017/aog.2020.56|issn=0260-3055}}</ref> have been used to observe snow<ref>{{Cite journal|last=Marshall|first=Hans-Peter|last2=Koh|first2=Gary|date=2008-04-01|title=FMCW radars for snow research|url=https://www.sciencedirect.com/science/article/pii/S0165232X07000833|journal=Cold Regions Science and Technology|series=Research in Cryospheric Science and Engineering|language=en|volume=52|issue=2|pages=118–131|doi=10.1016/j.coldregions.2007.04.008|issn=0165-232X}}</ref>, ice shelf melt rates<ref>{{Cite journal|last=Corr|first=H. F. J.|last2=Jenkins|first2=A.|last3=Nicholls|first3=K. W.|last4=Doake|first4=C. S. M.|date=2002-04|title=Precise measurement of changes in ice-shelf thickness by phase-sensitive radar to determine basal melt rates: ICE MELT RATES REVEALED BY RADAR|url=http://doi.wiley.com/10.1029/2001GL014618|journal=Geophysical Research Letters|language=en|volume=29|issue=8|pages=73–1–74-4|doi=10.1029/2001GL014618}}</ref>, englacial hydrology<ref>{{Cite journal|last=Kendrick|first=A. K.|last2=Schroeder|first2=D. M.|last3=Chu|first3=W.|last4=Young|first4=T. J.|last5=Christoffersen|first5=P.|last6=Todd|first6=J.|last7=Doyle|first7=S. H.|last8=Box|first8=J. E.|last9=Hubbard|first9=A.|last10=Hubbard|first10=B.|last11=Brennan|first11=P. V.|date=2018-10-16|title=Surface Meltwater Impounded by Seasonal Englacial Storage in West Greenland|url=https://onlinelibrary.wiley.com/doi/abs/10.1029/2018GL079787|journal=Geophysical Research Letters|language=en|volume=45|issue=19|doi=10.1029/2018GL079787|issn=0094-8276}}</ref>, ice sheet structure<ref>{{Cite journal|last=Young|first=Tun Jan|last2=Schroeder|first2=Dustin M.|last3=Christoffersen|first3=Poul|last4=Lok|first4=Lai Bun|last5=Nicholls|first5=Keith W.|last6=Brennan|first6=Paul V.|last7=Doyle|first7=Samuel H.|last8=Hubbard|first8=Bryn|last9=Hubbard|first9=Alun|date=2018-08|title=Resolving the internal and basal geometry of ice masses using imaging phase-sensitive radar|url=https://www.cambridge.org/core/product/identifier/S0022143018000540/type/journal_article|journal=Journal of Glaciology|language=en|volume=64|issue=246|pages=649–660|doi=10.1017/jog.2018.54|issn=0022-1430}}</ref>, and vertical ice flow<ref>{{Cite journal|last=Kingslake|first=Jonathan|last2=Hindmarsh|first2=Richard C. A.|last3=Aðalgeirsdóttir|first3=Guðfinna|last4=Conway|first4=Howard|last5=Corr|first5=Hugh F. J.|last6=Gillet‐Chaulet|first6=Fabien|last7=Martín|first7=Carlos|last8=King|first8=Edward C.|last9=Mulvaney|first9=Robert|last10=Pritchard|first10=Hamish D.|date=2014|title=Full-depth englacial vertical ice sheet velocities measured using phase-sensitive radar|url=https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2014JF003275|journal=Journal of Geophysical Research: Earth Surface|language=en|volume=119|issue=12|pages=2604–2618|doi=10.1002/2014JF003275|issn=2169-9011}}</ref>. [[Interferometric synthetic-aperture radar|Interferometric]] analysis of airborne systems have also been demonstrated to measure vertical ice flow<ref>{{Cite journal|last=Castelletti|first=D.|last2=Schroeder|first2=D. M.|last3=Jordan|first3=T. M.|last4=Young|first4=D.|date=2020|title=Permanent Scatterers in Repeat-Pass Airborne VHF Radar Sounder for Layer-Velocity Estimation|url=https://ieeexplore.ieee.org/document/9143148/|journal=IEEE Geoscience and Remote Sensing Letters|pages=1–5|doi=10.1109/LGRS.2020.3007514|issn=1558-0571}}</ref>. Additionally, radioglaciological instruments have been developed to operate on autonomous platforms<ref>{{Cite journal|last=Arcone|first=Steven A.|last2=Lever|first2=James H.|last3=Ray|first3=Laura E.|last4=Walker|first4=Benjamin S.|last5=Hamilton|first5=Gordon|last6=Kaluzienski|first6=Lynn|date=2016-01-01|title=Ground-penetrating radar profiles of the McMurdo Shear Zone, Antarctica, acquired with an unmanned rover: Interpretation of crevasses, fractures, and folds within firn and marine ice|url=https://library.seg.org/doi/10.1190/geo2015-0132.1|journal=GEOPHYSICS|language=en|volume=81|issue=1|pages=WA21–WA34|doi=10.1190/geo2015-0132.1|issn=0016-8033}}</ref>, on in-situ probes<ref>{{Cite journal|last=Bagshaw|first=E. A.|last2=Lishman|first2=B.|last3=Wadham|first3=J. L.|last4=Bowden|first4=J. A.|last5=Burrow|first5=S. G.|last6=Clare|first6=L. R.|last7=Chandler|first7=D.|date=2014/ed|title=Novel wireless sensors for in situ measurement of sub-ice hydrologic systems|url=https://www.cambridge.org/core/journals/annals-of-glaciology/article/novel-wireless-sensors-for-in-situ-measurement-of-subice-hydrologic-systems/3DB2AA304A87519CBF9AB72579E3FDB3|journal=Annals of Glaciology|language=en|volume=55|issue=65|pages=41–50|doi=10.3189/2014AoG65A007|issn=0260-3055}}</ref>, in low-cost deployments<ref>{{Cite journal|last=Mingo|first=Laurent|last2=Flowers|first2=Gwenn E.|last3=Crawford|first3=Anna J.|last4=Mueller|first4=Derek R.|last5=Bigelow|first5=David G.|date=2020/04|title=A stationary impulse-radar system for autonomous deployment in cold and temperate environments|url=https://www.cambridge.org/core/journals/annals-of-glaciology/article/stationary-impulseradar-system-for-autonomous-deployment-in-cold-and-temperate-environments/7AA6AF76E87AA2E8AFE4317152BC1FB5|journal=Annals of Glaciology|language=en|volume=61|issue=81|pages=99–107|doi=10.1017/aog.2020.2|issn=0260-3055}}</ref>, using [[Software-defined radio|Software Defined Radios]]<ref>{{Cite journal|last=Liu|first=Peng|last2=Mendoza|first2=Jesus|last3=Hu|first3=Hanxiong|last4=Burkett|first4=Peter G.|last5=Urbina|first5=Julio V.|last6=Anandakrishnan|first6=Sridhar|last7=Bilen|first7=Sven G.|date=2019-03|title=Software-Defined Radar Systems for Polar Ice-Sheet Research|url=https://ieeexplore.ieee.org/document/8654719/|journal=IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing|volume=12|issue=3|pages=803–820|doi=10.1109/JSTARS.2019.2895616|issn=1939-1404}}</ref>, and exploiting ambient radio signals for passive sounding<ref>{{Cite journal|last=Peters|first=Sean T.|last2=Schroeder|first2=Dustin M.|last3=Castelletti|first3=Davide|last4=Haynes|first4=Mark|last5=Romero-Wolf|first5=Andrew|date=2018-12|title=In Situ Demonstration of a Passive Radio Sounding Approach Using the Sun for Echo Detection|url=https://ieeexplore.ieee.org/document/8418789/|journal=IEEE Transactions on Geoscience and Remote Sensing|volume=56|issue=12|pages=7338–7349|doi=10.1109/TGRS.2018.2850662|issn=0196-2892}}</ref><ref>{{Cite journal|last=Romero-Wolf|first=Andrew|last2=Vance|first2=Steve|last3=Maiwald|first3=Frank|last4=Heggy|first4=Essam|last5=Ries|first5=Paul|last6=Liewer|first6=Kurt|date=2015-03-01|title=A passive probe for subsurface oceans and liquid water in Jupiter’s icy moons|url=https://www.sciencedirect.com/science/article/pii/S0019103514006009|journal=Icarus|language=en|volume=248|pages=463–477|doi=10.1016/j.icarus.2014.10.043|issn=0019-1035}}</ref>.
The primary goal of many radioglaciological surveys is to measure the thickness of a body of ice, which is an important [[boundary condition]] for ice-flow models. Ice thicknesses greater than 4&nbsp;km have been measured in [[East Antarctica]].<ref name="Bedmap2" /> Internal [[Reflection (physics)|reflection]]s have also been detected in many [[glacier#Types of glaciers|alpine glaciers]] and all modern ice sheets. These layers represent the internal [[stratigraphy]] and can also be used to constrain ice-flow models. The shapes of these internal reflections generally follow the [[bedrock]] [[topography]] at longer horizontal scales, while at shorter horizontal scales they are influenced by ice-flow mechanics <ref name=MechsOnIsochroneArch >{{Cite journal|last1=Hindmarsh |first1=R.C.A. |last2=Leysinger Vieli|first2=G.J-M.C. |last3=Raymond |first3=M.J. |last4=Gudmundsson |first4=G.H. | display-authors = 2 |title= Draping or Overriding: The Effect of Horizontal Stress Gradients on Internal Layer Architecture in Ice-Sheets |journal=Journal of Geophysical Research |volume=111 |issue=F02018 |url=https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2005JF000309 |date=2011 |accessdate=3 March 2021|doi=10.1029/2010JF001785}}</ref>
. They are often assumed to be [[isochronous]]. Disturbances in these reflections that are unrelated to bedrock topography can be used to understand past ice flow, for example the [[anticline]]s arising from the [[Raymond Effect]].


The most common scientific application for radioglaciological observations is measuring ice thickness and bed topography. This includes [[Interpolation|interpolated]] “bed maps”<ref>{{Cite journal|last=Bamber|first=J. L.|last2=Griggs|first2=J. A.|last3=Hurkmans|first3=R. T. W. L.|last4=Dowdeswell|first4=J. A.|last5=Gogineni|first5=S. P.|last6=Howat|first6=I.|last7=Mouginot|first7=J.|last8=Paden|first8=J.|last9=Palmer|first9=S.|last10=Rignot|first10=E.|last11=Steinhage|first11=D.|date=2013-03-22|title=A new bed elevation dataset for Greenland|url=https://tc.copernicus.org/articles/7/499/2013/|journal=The Cryosphere|language=English|volume=7|issue=2|pages=499–510|doi=10.5194/tc-7-499-2013|issn=1994-0416}}</ref><ref>{{Cite journal|last=MacKie|first=E. J.|last2=Schroeder|first2=D. M.|last3=Caers|first3=J.|last4=Siegfried|first4=M. 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J.|date=2007/ed|title=Three-dimensional flow influences on radar layer stratigraphy|url=https://www.cambridge.org/core/journals/annals-of-glaciology/article/threedimensional-flow-influences-on-radar-layer-stratigraphy/94F7AA070907CD0A93D932218BB35D54|journal=Annals of Glaciology|language=en|volume=46|pages=22–28|doi=10.3189/172756407782871729|issn=0260-3055}}</ref><ref>{{Cite journal|last=Pettit|first=Erin C.|last2=Waddington|first2=Edwin D.|last3=Harrison|first3=William D.|last4=Thorsteinsson|first4=Throstur|last5=Elsberg|first5=Daniel|last6=Morack|first6=John|last7=Zumberge|first7=Mark A.|date=2011|title=The crossover stress, anisotropy and the ice flow law at Siple Dome, West Antarctica|url=https://www.cambridge.org/core/product/identifier/S0022143000204620/type/journal_article|journal=Journal of Glaciology|language=en|volume=57|issue=201|pages=39–52|doi=10.3189/002214311795306619|issn=0022-1430}}</ref>, and [[Fabric (geology)|fabric]]<ref>{{Cite journal|last=Jordan|first=Thomas M.|last2=Schroeder|first2=Dustin M.|last3=Castelletti|first3=Davide|last4=Li|first4=Jilu|last5=Dall|first5=Jorgen|date=2019-11|title=A Polarimetric Coherence Method to Determine Ice Crystal Orientation Fabric From Radar Sounding: Application to the NEEM Ice Core Region|url=https://ieeexplore.ieee.org/document/8755860/|journal=IEEE Transactions on Geoscience and Remote Sensing|volume=57|issue=11|pages=8641–8657|doi=10.1109/TGRS.2019.2921980|issn=0196-2892}}</ref><ref>{{Cite journal|last=Martín|first=Carlos|last2=Gudmundsson|first2=G. Hilmar|last3=Pritchard|first3=Hamish D.|last4=Gagliardini|first4=Olivier|date=2009-10-14|title=On the effects of anisotropic rheology on ice flow, internal structure, and the age-depth relationship at ice divides|url=http://doi.wiley.com/10.1029/2008JF001204|journal=Journal of Geophysical Research|language=en|volume=114|issue=F4|pages=F04001|doi=10.1029/2008JF001204|issn=0148-0227}}</ref> as well as absence or disturbances of that stratigraphy<ref>{{Cite journal|last=Bell|first=R. E.|last2=Ferraccioli|first2=F.|last3=Creyts|first3=T. T.|last4=Braaten|first4=D.|last5=Corr|first5=H.|last6=Das|first6=I.|last7=Damaske|first7=D.|last8=Frearson|first8=N.|last9=Jordan|first9=T.|last10=Rose|first10=K.|last11=Studinger|first11=M.|date=2011-03-25|title=Widespread Persistent Thickening of the East Antarctic Ice Sheet by Freezing from the Base|url=https://www.sciencemag.org/lookup/doi/10.1126/science.1200109|journal=Science|language=en|volume=331|issue=6024|pages=1592–1595|doi=10.1126/science.1200109|issn=0036-8075}}</ref><ref>{{Cite journal|last=Drews|first=R.|last2=Eisen|first2=O.|last3=Weikusat|first3=I.|last4=Kipfstuhl|first4=S.|last5=Lambrecht|first5=A.|last6=Steinhage|first6=D.|last7=Wilhelms|first7=F.|last8=Miller|first8=H.|date=2009-08-25|title=Layer disturbances and the radio-echo free zone in ice sheets|url=https://tc.copernicus.org/articles/3/195/2009/|journal=The Cryosphere|language=English|volume=3|issue=2|pages=195–203|doi=10.5194/tc-3-195-2009|issn=1994-0416}}</ref><ref>{{Cite journal|last=Winter|first=Kate|last2=Woodward|first2=John|last3=Ross|first3=Neil|last4=Dunning|first4=Stuart A.|last5=Hein|first5=Andrew S.|last6=Westoby|first6=Matthew J.|last7=Culberg|first7=Riley|last8=Marrero|first8=Shasta M.|last9=Schroeder|first9=Dustin M.|last10=Sugden|first10=David E.|last11=Siegert|first11=Martin J.|date=2019|title=Radar-Detected Englacial Debris in the West Antarctic Ice Sheet|url=https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL084012|journal=Geophysical Research Letters|language=en|volume=46|issue=17-18|pages=10454–10462|doi=10.1029/2019GL084012|issn=1944-8007}}</ref>. Radioglaciology data has also been used extensively to study [[Subglacial lake|subglacial lakes]]<ref>{{Cite journal|last=Carter|first=Sasha P.|last2=Blankenship|first2=Donald D.|last3=Peters|first3=Matthew E.|last4=Young|first4=Duncan A.|last5=Holt|first5=John W.|last6=Morse|first6=David L.|date=2007-03|title=Radar-based subglacial lake classification in Antarctica: ANTARCTIC SUBGLACIAL LAKES|url=http://doi.wiley.com/10.1029/2006GC001408|journal=Geochemistry, Geophysics, Geosystems|language=en|volume=8|issue=3|pages=n/a–n/a|doi=10.1029/2006GC001408}}</ref><ref>{{Cite journal|last=Ilisei|first=Ana-Maria|last2=Khodadadzadeh|first2=Mahdi|last3=Ferro|first3=Adamo|last4=Bruzzone|first4=Lorenzo|date=2019-06|title=An Automatic Method for Subglacial Lake Detection in Ice Sheet Radar Sounder Data|url=https://ieeexplore.ieee.org/document/8590794/|journal=IEEE Transactions on Geoscience and Remote Sensing|volume=57|issue=6|pages=3252–3270|doi=10.1109/TGRS.2018.2882911|issn=0196-2892}}</ref><ref>{{Cite journal|last=Oswald|first=G. K. A.|last2=Robin|first2=G. De Q.|date=1973-10|title=Lakes Beneath the Antarctic Ice Sheet|url=http://www.nature.com/articles/245251a0|journal=Nature|language=en|volume=245|issue=5423|pages=251–254|doi=10.1038/245251a0|issn=0028-0836}}</ref><ref>{{Cite journal|last=Palmer|first=Steven J.|last2=Dowdeswell|first2=Julian A.|last3=Christoffersen|first3=Poul|last4=Young|first4=Duncan A.|last5=Blankenship|first5=Donald D.|last6=Greenbaum|first6=Jamin S.|last7=Benham|first7=Toby|last8=Bamber|first8=Jonathan|last9=Siegert|first9=Martin J.|date=2013|title=Greenland subglacial lakes detected by radar|url=https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2013GL058383|journal=Geophysical Research Letters|language=en|volume=40|issue=23|pages=6154–6159|doi=10.1002/2013GL058383|issn=1944-8007}}</ref><ref>{{Cite journal|last=Rutishauser|first=Anja|last2=Blankenship|first2=Donald D.|last3=Sharp|first3=Martin|last4=Skidmore|first4=Mark L.|last5=Greenbaum|first5=Jamin S.|last6=Grima|first6=Cyril|last7=Schroeder|first7=Dustin M.|last8=Dowdeswell|first8=Julian A.|last9=Young|first9=Duncan A.|date=2018-04-01|title=Discovery of a hypersaline subglacial lake complex beneath Devon Ice Cap, Canadian Arctic|url=https://advances.sciencemag.org/content/4/4/eaar4353|journal=Science Advances|language=en|volume=4|issue=4|pages=eaar4353|doi=10.1126/sciadv.aar4353|issn=2375-2548|pmc=PMC5895444|pmid=29651462}}</ref><ref>{{Cite journal|last=Siegert|first=Martin J.|date=2018|title=A 60-year international history of Antarctic subglacial lake exploration|url=http://sp.lyellcollection.org/lookup/doi/10.1144/SP461.5|journal=Geological Society, London, Special Publications|language=en|volume=461|issue=1|pages=7–21|doi=10.1144/SP461.5|issn=0305-8719}}</ref> and glacial [[hydrology]]<ref>{{Cite journal|last=Wolovick|first=Michael J.|last2=Bell|first2=Robin E.|last3=Creyts|first3=Timothy T.|last4=Frearson|first4=Nicholas|date=2013|title=Identification and control of subglacial water networks under Dome A, Antarctica|url=https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2012JF002555|journal=Journal of Geophysical Research: Earth Surface|language=en|volume=118|issue=1|pages=140–154|doi=10.1029/2012JF002555|issn=2169-9011}}</ref> including englacial water<ref>{{Cite journal|last=Björnsson|first=Helgi|last2=Gjessing|first2=Yngvar|last3=Hamran|first3=Svein-Erik|last4=Hagen|first4=Jon Ove|last5=LiestøL|first5=Olav|last6=Pálsson|first6=Finnur|last7=Erlingsson|first7=Björn|date=1996|title=The thermal regime of sub-polar glaciers mapped by multi-frequency radio-echo sounding|url=https://www.cambridge.org/core/product/identifier/S0022143000030495/type/journal_article|journal=Journal of Glaciology|language=en|volume=42|issue=140|pages=23–32|doi=10.3189/S0022143000030495|issn=0022-1430}}</ref><ref>{{Cite journal|last=Bradford|first=John H.|last2=Harper|first2=Joel T.|date=2005|title=Wave field migration as a tool for estimating spatially continuous radar velocity and water content in glaciers|url=https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2004GL021770|journal=Geophysical Research Letters|language=en|volume=32|issue=8|doi=10.1029/2004GL021770|issn=1944-8007}}</ref><ref>{{Cite journal|last=Murray|first=Tavi|last2=Stuart|first2=Graham W.|last3=Fry|first3=Matt|last4=Gamble|first4=Nicola H.|last5=Crabtree|first5=Mike D.|date=2000/ed|title=Englacial water distribution in a temperate glacier from surface and borehole radar velocity analysis|url=https://www.cambridge.org/core/journals/journal-of-glaciology/article/englacial-water-distribution-in-a-temperate-glacier-from-surface-and-borehole-radar-velocity-analysis/49C1E579B840B9CAFD23296F30FBC805|journal=Journal of Glaciology|language=en|volume=46|issue=154|pages=389–398|doi=10.3189/172756500781833188|issn=0022-1430}}</ref>, firn aquifers<ref>{{Cite journal|last=Forster|first=Richard R.|last2=Box|first2=Jason E.|last3=van den Broeke|first3=Michiel R.|last4=Miège|first4=Clément|last5=Burgess|first5=Evan W.|last6=van Angelen|first6=Jan H.|last7=Lenaerts|first7=Jan T. M.|last8=Koenig|first8=Lora S.|last9=Paden|first9=John|last10=Lewis|first10=Cameron|last11=Gogineni|first11=S. Prasad|date=2014-02|title=Extensive liquid meltwater storage in firn within the Greenland ice sheet|url=https://www.nature.com/articles/ngeo2043|journal=Nature Geoscience|language=en|volume=7|issue=2|pages=95–98|doi=10.1038/ngeo2043|issn=1752-0908}}</ref>, and their temporal evolution<ref>{{Cite journal|last=Chu|first=W.|last2=Schroeder|first2=D. M.|last3=Siegfried|first3=M. R.|date=2018-11-16|title=Retrieval of Englacial Firn Aquifer Thickness From Ice-Penetrating Radar Sounding in Southeastern Greenland|url=http://doi.wiley.com/10.1029/2018GL079751|journal=Geophysical Research Letters|language=en|volume=45|issue=21|pages=11,770–11,778|doi=10.1029/2018GL079751}}</ref><ref>{{Cite journal|last=Kendrick|first=A. K.|last2=Schroeder|first2=D. M.|last3=Chu|first3=W.|last4=Young|first4=T. J.|last5=Christoffersen|first5=P.|last6=Todd|first6=J.|last7=Doyle|first7=S. H.|last8=Box|first8=J. E.|last9=Hubbard|first9=A.|last10=Hubbard|first10=B.|last11=Brennan|first11=P. V.|date=2018-10-16|title=Surface Meltwater Impounded by Seasonal Englacial Storage in West Greenland|url=https://onlinelibrary.wiley.com/doi/abs/10.1029/2018GL079787|journal=Geophysical Research Letters|language=en|volume=45|issue=19|doi=10.1029/2018GL079787|issn=0094-8276}}</ref><ref>{{Cite journal|last=Kulessa|first=B.|last2=Booth|first2=A. D.|last3=Hobbs|first3=A.|last4=Hubbard|first4=A. L.|date=2008|title=Automated monitoring of subglacial hydrological processes with ground-penetrating radar (GPR) at high temporal resolution: scope and potential pitfalls|url=https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2008GL035855|journal=Geophysical Research Letters|language=en|volume=35|issue=24|doi=10.1029/2008GL035855|issn=1944-8007}}</ref>. Ice penetrating radar data has also been used to investigate the subsurface of [[Ice shelf|ice shelves]] including their grounding zones<ref>{{Cite journal|last=Catania|first=G. A.|last2=Conway|first2=H.|last3=Raymond|first3=C. F.|last4=Scambos|first4=T. A.|date=2006|title=Evidence for floatation or near floatation in the mouth of Kamb Ice Stream, West Antarctica, prior to stagnation|url=https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2005JF000355|journal=Journal of Geophysical Research: Earth Surface|language=en|volume=111|issue=F1|doi=10.1029/2005JF000355|issn=2156-2202}}</ref><ref>{{Cite journal|last=Greenbaum|first=J. S.|last2=Blankenship|first2=D. D.|last3=Young|first3=D. A.|last4=Richter|first4=T. G.|last5=Roberts|first5=J. L.|last6=Aitken|first6=A. R. A.|last7=Legresy|first7=B.|last8=Schroeder|first8=D. M.|last9=Warner|first9=R. C.|last10=van Ommen|first10=T. D.|last11=Siegert|first11=M. J.|date=2015-04|title=Ocean access to a cavity beneath Totten Glacier in East Antarctica|url=http://www.nature.com/articles/ngeo2388|journal=Nature Geoscience|language=en|volume=8|issue=4|pages=294–298|doi=10.1038/ngeo2388|issn=1752-0894}}</ref>, melt rates<ref>{{Cite journal|last=Khazendar|first=Ala|last2=Rignot|first2=Eric|last3=Schroeder|first3=Dustin M.|last4=Seroussi|first4=Helene|last5=Schodlok|first5=Michael P.|last6=Scheuchl|first6=Bernd|last7=Mouginot|first7=Jeremie|last8=Sutterley|first8=Tyler C.|last9=Velicogna|first9=Isabella|date=2016-12|title=Rapid submarine ice melting in the grounding zones of ice shelves in West Antarctica|url=http://www.nature.com/articles/ncomms13243|journal=Nature Communications|language=en|volume=7|issue=1|pages=13243|doi=10.1038/ncomms13243|issn=2041-1723|pmc=PMC5093338|pmid=27780191}}</ref><ref>{{Cite journal|last=Pattyn|first=F.|last2=Matsuoka|first2=K.|last3=Callens|first3=D.|last4=Conway|first4=H.|last5=Depoorter|first5=M.|last6=Docquier|first6=D.|last7=Hubbard|first7=B.|last8=Samyn|first8=D.|last9=Tison|first9=J. L.|date=2012|title=Melting and refreezing beneath Roi Baudouin Ice Shelf (East Antarctica) inferred from radar, GPS, and ice core data|url=https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2011JF002154|journal=Journal of Geophysical Research: Earth Surface|language=en|volume=117|issue=F4|doi=10.1029/2011JF002154|issn=2156-2202}}</ref>, brine distribution<ref>{{Cite journal|last=Grima|first=Cyril|last2=Greenbaum|first2=Jamin S.|last3=Lopez Garcia|first3=Erika J.|last4=Soderlund|first4=Krista M.|last5=Rosales|first5=Arami|last6=Blankenship|first6=Donald D.|last7=Young|first7=Duncan A.|date=2016-07-16|title=Radar detection of the brine extent at McMurdo Ice Shelf, Antarctica, and its control by snow accumulation: BRINE EXTENT AT MCMURDO ICE SHELF|url=http://doi.wiley.com/10.1002/2016GL069524|journal=Geophysical Research Letters|language=en|volume=43|issue=13|pages=7011–7018|doi=10.1002/2016GL069524}}</ref>, and basal channels<ref>{{Cite journal|last=Le Brocq|first=Anne M.|last2=Ross|first2=Neil|last3=Griggs|first3=Jennifer A.|last4=Bingham|first4=Robert G.|last5=Corr|first5=Hugh F. J.|last6=Ferraccioli|first6=Fausto|last7=Jenkins|first7=Adrian|last8=Jordan|first8=Tom A.|last9=Payne|first9=Antony J.|last10=Rippin|first10=David M.|last11=Siegert|first11=Martin J.|date=2013-11|title=Evidence from ice shelves for channelized meltwater flow beneath the Antarctic Ice Sheet|url=http://www.nature.com/articles/ngeo1977|journal=Nature Geoscience|language=en|volume=6|issue=11|pages=945–948|doi=10.1038/ngeo1977|issn=1752-0894}}</ref>.
The cause of the observed internal reflections partly depends on the frequency of the radar system used to detect them. There are three primary types of reflections:{{Citation needed|date=March 2015}}
* In the [[firn]] and at depths where densification is occurring, small changes in [[density]] alter the real part of the permittivity, which can cause reflections. Once densification is complete, changes in density in an ice column are not expected to be large enough to cause radar reflections.
* High [[concentration]]s of [[volcano|volcanic]] [[acid]]s, e.g., [[sulfuric acid]] or [[hydrochloric acid]], increase the conductivity of the surface [[snow]] over which they are deposited. Acidity increases the conductivity, which produces a reflection. Reflections due to volcanic layers are possible at any depth.
* Individual [[crystal]]s of ice display dielectric [[anisotropy]]. Layers that have a preferred crystal fabric direction different from that above it can therefore also cause reflections.

Ice-penetrating radar systems, particularly the [[antenna (radio)|antenna]]e, are often homemade systems made of commercially available components. However, commercial ground-penetrating radar systems are sometimes used.


==Planetary exploration==
==Planetary exploration==

Revision as of 20:12, 4 March 2021

Radioglaciology is the study of glaciers, ice sheets, ice caps and icy moons using ice penetrating radar. It employs a geophysical method similar to ground-penetrating radar and typically operates at frequencies in the MF, HF, VHF and UHF portions of the radio spectrum.[1][2][3][4] This technique is also commonly referred to as “Ice Penetrating Radar (IPR)” or “Radio Echo Sounding (RES)”.

Glaciers are particularly well suited to investigation by radar because the conductivity, imaginary part of the permittivity, and the dielectric absorption of ice are small at radio frequencies resulting in low loss tangent, skin depth, and attenuation values. This allows echoes from the base of the ice sheet to be detected through ice thicknesses greater than 4 km.[5] [6]The subsurface observation of ice masses using radio waves has been an integral and evolving geophysical technique in glaciology for over half a century.[7][8][9][10][11][12][13][14] Its most widespread uses have been the measurement of ice thickness, subglacial topography, and ice sheet stratigraphy.[15][8][5] It has also been used to observe the subglacial and conditions of ice sheets and glaciers, including hydrology, thermal state, accumulation, flow history, ice fabric, and bed geology.[1] In planetary science, ice penetrating radar has also been used to explore the subsurface of the Polar Ice Caps on Mars and comets.[16][17][18] Missions are planned to explore the icy moons of Jupiter.[19][20]

Measurements and Applications

Radioglaciology uses nadir facing radars to probe the subsurface of glaciers, ice sheets, ice caps, and icy moons and to detect reflected and scattered energy from within and beneath the ice. [8] This geometry tends to emphasize coherent and specular reflected energy resulting in distinct forms or the radar equation. [21][22] Collected radar data typical undergoes signal processing ranging from stacking (or pre-summing) to migration to Synthetic Aperture Radar (SAR) focusing in 1, 2, or 3 dimensions. [23][24][25][22] This data is collected using ice penetrating radar systems which range from commercial (or bespoke) ground penetrating radar (GPR) systems [26][27] to coherent, chirped airborne sounders [28][29][30] to swath-imaging[31], multi-frequency[32], or polarimetric[33] implementations of such systems. Additionally, stationary, phase-sensitive, and Frequency Modulated Continuous Wave (FMCW) radars [34][35][36] have been used to observe snow[37], ice shelf melt rates[38], englacial hydrology[39], ice sheet structure[40], and vertical ice flow[41]. Interferometric analysis of airborne systems have also been demonstrated to measure vertical ice flow[42]. Additionally, radioglaciological instruments have been developed to operate on autonomous platforms[43], on in-situ probes[44], in low-cost deployments[45], using Software Defined Radios[46], and exploiting ambient radio signals for passive sounding[47][48].

The most common scientific application for radioglaciological observations is measuring ice thickness and bed topography. This includes interpolated “bed maps”[49][50][51], widely used in ice sheet modeling and sea level rise projections, studies exploring specific ice-sheet regions[52][53][54][55][56], and observations of glacier beds[57][58][59][60]. The strength and character of radar echoes from the bed of the ice sheet are also used to investigate the reflectivity[61][62] of the bed, the attenuation[63][64][65] of radar in the ice, and the morphology of the bed[66][67][68].In addition bed echoes, radar returns from englacial layers[69] are used in studies of the radio stratigraphy of ice sheets[70][71][72][73][74] including investigations of ice accumulation[75][76][77][78][79], flow[80][81][82][83], and fabric[84][85] as well as absence or disturbances of that stratigraphy[86][87][88]. Radioglaciology data has also been used extensively to study subglacial lakes[89][90][91][92][93][94] and glacial hydrology[95] including englacial water[96][97][98], firn aquifers[99], and their temporal evolution[100][101][102]. Ice penetrating radar data has also been used to investigate the subsurface of ice shelves including their grounding zones[103][104], melt rates[105][106], brine distribution[107], and basal channels[108].

Planetary exploration

There are currently two ice-penetrating radars orbiting Mars: MARSIS and SHARAD. An ice-penetrating radar system is planned for the 2022 Jupiter Icy Moons Orbiter,[109] and such systems were also proposed for two orbiters that were part of the cancelled Europa Jupiter System Mission.

References

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External links

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