Radioglaciology is the study of
glacier
A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its Ablation#Glaciology, ablation over many years, often Century, centuries. It acquires dis ...
s,
ice sheet
In glaciology, an ice sheet, also known as a continental glacier, is a mass of glacial ice that covers surrounding terrain and is greater than . The only current ice sheets are in Antarctica and Greenland; during the Last Glacial Period at Las ...
s,
ice cap
In glaciology, an ice cap is a mass of ice that covers less than of land area (usually covering a highland area). Larger ice masses covering more than are termed ice sheets.
Description
Ice caps are not constrained by topographical features ...
s and
icy moon Icy commonly refers to conditions involving ice, a frozen state, usually referring to frozen water.
Icy or Icey may also refer to:
People
* Icy Spicy Leoncie, an Icelandic-Indian musician
Arts, entertainment, and media Music
* ICY (band), a voca ...
s using
ice penetrating radar. It employs a
geophysical
Geophysics () is a subject of natural science concerned with the physical processes and physical properties of the Earth and its surrounding space environment, and the use of quantitative methods for their analysis. The term ''geophysics'' som ...
method similar to
ground-penetrating radar
Ground-penetrating radar (GPR) is a geophysical method that uses radar pulses to image the subsurface. It is a non-intrusive method of surveying the sub-surface to investigate underground utilities such as concrete, asphalt, metals, pipes, cables o ...
and typically operates at
frequencies
Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
in the
MF,
HF,
VHF
Very high frequency (VHF) is the ITU designation for the range of radio frequency electromagnetic waves (radio waves) from 30 to 300 megahertz (MHz), with corresponding wavelengths of ten meters to one meter.
Frequencies immediately below VHF ...
and
UHF
Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter (on ...
portions of the
radio spectrum
The radio spectrum is the part of the electromagnetic spectrum with frequencies from 0 Hz to 3,000 GHz (3 THz). Electromagnetic waves in this frequency range, called radio waves, are widely used in modern technology, particula ...
.
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
Conductivity may refer to:
*Electrical conductivity, a measure of a material's ability to conduct an electric current
**Conductivity (electrolytic), the electrical conductivity of an electrolyte in solution
**Ionic conductivity (solid state), elec ...
, imaginary part of the
permittivity
In electromagnetism, the absolute permittivity, often simply called permittivity and denoted by the Greek letter ''ε'' ( epsilon), is a measure of the electric polarizability of a dielectric. A material with high permittivity polarizes more in ...
, and the
dielectric absorption Dielectric absorption is the name given to the effect by which a capacitor, that has been charged for a long time, discharges only incompletely when briefly discharged. Although an ideal capacitor would remain at zero volts after being discharged, r ...
of ice are small at
radio frequencies
Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the upper ...
resulting in low loss
tangent
In geometry, the tangent line (or simply tangent) to a plane curve at a given point is the straight line that "just touches" the curve at that point. Leibniz defined it as the line through a pair of infinitely close points on the curve. More ...
,
skin depth
Skin effect is the tendency of an alternating electric current (AC) to become distributed within a conductor such that the current density is largest near the surface of the conductor and decreases exponentially with greater depths in the con ...
, and
attenuation values. This allows echoes from the base of the ice sheet to be detected through ice thicknesses greater than 4 km.
The subsurface observation of ice masses using radio waves has been an integral and evolving
geophysical
Geophysics () is a subject of natural science concerned with the physical processes and physical properties of the Earth and its surrounding space environment, and the use of quantitative methods for their analysis. The term ''geophysics'' som ...
technique in
glaciology
Glaciology (; ) is the scientific study of glaciers, or more generally ice and natural phenomena that involve ice.
Glaciology is an interdisciplinary Earth science that integrates geophysics, geology, physical geography, geomorphology, climato ...
for over half a century.
Its most widespread uses have been the measurement of ice thickness, subglacial topography, and ice sheet stratigraphy.
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.
In planetary science, ice penetrating radar has also been used to explore the subsurface of the Polar Ice Caps on Mars and comets.
Missions are planned to explore the icy moons of Jupiter.
Measurements and applications
Radioglaciology uses
nadir
The nadir (, ; ar, نظير, naẓīr, counterpart) is the direction pointing directly ''below'' a particular location; that is, it is one of two vertical directions at a specified location, orthogonal to a horizontal flat surface.
The direc ...
facing
radar
Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...
s to probe the subsurface of
glacier
A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its Ablation#Glaciology, ablation over many years, often Century, centuries. It acquires dis ...
s,
ice sheet
In glaciology, an ice sheet, also known as a continental glacier, is a mass of glacial ice that covers surrounding terrain and is greater than . The only current ice sheets are in Antarctica and Greenland; during the Last Glacial Period at Las ...
s,
ice cap
In glaciology, an ice cap is a mass of ice that covers less than of land area (usually covering a highland area). Larger ice masses covering more than are termed ice sheets.
Description
Ice caps are not constrained by topographical features ...
s, and
icy moon Icy commonly refers to conditions involving ice, a frozen state, usually referring to frozen water.
Icy or Icey may also refer to:
People
* Icy Spicy Leoncie, an Icelandic-Indian musician
Arts, entertainment, and media Music
* ICY (band), a voca ...
s and to detect
reflected and
scattered
Scattered may refer to:
Music
* ''Scattered'' (album), a 2010 album by The Handsome Family
* "Scattered" (The Kinks song), 1993
* "Scattered", a song by Ace Young
* "Scattered", a song by Lauren Jauregui
* "Scattered", a song by Green Day from ' ...
energy from within and beneath the ice.
This geometry tends to emphasize
coherent
Coherence, coherency, or coherent may refer to the following:
Physics
* Coherence (physics), an ideal property of waves that enables stationary (i.e. temporally and spatially constant) interference
* Coherence (units of measurement), a deri ...
and
specular
Specular reflection, or regular reflection, is the mirror-like reflection of waves, such as light, from a surface.
The law of reflection states that a reflected ray of light emerges from the reflecting surface at the same angle to the surfac ...
reflected energy resulting in distinct forms of the radar equation.
Collected radar data typically undergoes
signal processing
Signal processing is an electrical engineering subfield that focuses on analyzing, modifying and synthesizing ''signals'', such as audio signal processing, sound, image processing, images, and scientific measurements. Signal processing techniq ...
ranging from stacking (or pre-summing) to
migration
Migration, migratory, or migrate may refer to: Human migration
* Human migration, physical movement by humans from one region to another
** International migration, when peoples cross state boundaries and stay in the host state for some minimum le ...
to
Synthetic Aperture Radar (SAR) focusing in 1, 2, or 3 dimensions.
This data is collected using ice penetrating radar systems which range from commercial (or bespoke)
ground penetrating radar (GPR) systems to coherent,
chirp
A chirp is a signal in which the frequency increases (''up-chirp'') or decreases (''down-chirp'') with time. In some sources, the term ''chirp'' is used interchangeably with sweep signal. It is commonly applied to sonar, radar, and laser system ...
ed airborne sounders to swath-imaging, multi-frequency, or
polarimetric
Polarimetry is the measurement and interpretation of the polarization of transverse waves, most notably electromagnetic waves, such as radio or light waves. Typically polarimetry is done on electromagnetic waves that have traveled through or ...
implementations of such systems. Additionally, stationary, phase-sensitive, and
Frequency Modulated Continuous Wave (FMCW) radars have been used to observe snow, ice shelf melt rates, englacial hydrology,
ice sheet structure, and vertical ice flow.
Interferometric
Interferometry is a technique which uses the ''interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber op ...
analysis of airborne systems have also been demonstrated to measure vertical ice flow. Additionally, radioglaciological instruments have been developed to operate on autonomous platforms, on in-situ probes, in low-cost deployments, using
Software Defined Radios, and exploiting ambient radio signals for passive sounding.
The most common scientific application for radioglaciological observations is measuring ice thickness and bed topography. This includes
interpolated
In the mathematical field of numerical analysis, interpolation is a type of estimation, a method of constructing (finding) new data points based on the range of a discrete set of known data points.
In engineering and science, one often has a n ...
"bed maps",
[ widely used in ice sheet modeling and sea level rise projections, studies exploring specific ice-sheet regions, and observations of glacier beds. The strength and character of radar echoes from the bed of the ice sheet are also used to investigate the ]reflectivity
The reflectance of the surface of a material is its effectiveness in reflecting radiant energy. It is the fraction of incident electromagnetic power that is reflected at the boundary. Reflectance is a component of the response of the electronic ...
of the bed, the attenuation
In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at variable att ...
of radar in the ice, and the morphology
Morphology, from the Greek and meaning "study of shape", may refer to:
Disciplines
* Morphology (archaeology), study of the shapes or forms of artifacts
* Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies ...
of the bed. In addition bed echoes, radar returns from englacial layers are used in studies of the radio stratigraphy
Stratigraphy is a branch of geology concerned with the study of rock (geology), rock layers (Stratum, strata) and layering (stratification). It is primarily used in the study of sedimentary rock, sedimentary and layered volcanic rocks.
Stratigrap ...
of ice sheets including investigations of ice accumulation, flow, and fabric
Textile is an umbrella term that includes various fiber-based materials, including fibers, yarns, filaments, threads, different fabric types, etc. At first, the word "textiles" only referred to woven fabrics. However, weaving is not the ...
as well as absence or disturbances of that stratigraphy. Radioglaciology data has also been used extensively to study subglacial lake
A subglacial lake is a lake that is found under a glacier, typically beneath an ice cap or ice sheet. Subglacial lakes form at the boundary between ice and the underlying bedrock, where gravitational pressure decreases the pressure melting point ...
s and glacial hydrology
Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and environmental watershed sustainability. A practitioner of hydrology is calle ...
including englacial water, firn aquifers, and their temporal evolution. Ice penetrating radar data has also been used to investigate the subsurface of ice shelves
An ice shelf is a large floating platform of ice that forms where a glacier or ice sheet flows down to a coastline and onto the ocean surface. Ice shelves are only found in Antarctica, Greenland, Northern Canada, and the Russian Arctic. The b ...
including their grounding zones, melt rates, brine distribution, and basal channels.
Planetary exploration
There are currently two ice-penetrating radars orbiting Mars
Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury (planet), Mercury. In the English language, Mars is named for the Mars (mythology), Roman god of war. Mars is a terr ...
: MARSIS
MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) is a low frequency, pulse-limited radar sounder and altimeter developed by the University of Rome La Sapienza and Alenia Spazio (today Thales Alenia Space Italy). The Italian MARS ...
and SHARAD
Sharad/Sarath/Sharath ( sa, शरद्)is the autumn season or ritu in the Hindu calendar. It roughly corresponds to the western months of mid-September to mid-November. Sharad is preceded by Varsha and followed by Hemant. The Hindu calendar c ...
. An ice penetrating radar was also part of the ROSETTA mission
''Rosetta'' was a space probe built by the European Space Agency launched on 2 March 2004. Along with ''Philae'', its lander module, ''Rosetta'' performed a detailed study of comet 67P/Churyumov–Gerasimenko (67P). During its journey to the c ...
to comet
A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena ar ...
67P/Churyumov–Gerasimenko
67P/Churyumov–Gerasimenko (abbreviated as 67P or 67P/C–G) is a Jupiter-family comet, originally from the Kuiper belt, with a current orbital period of 6.45 years, a rotation period of approximately 12.4 hours and a maximum velocity of . Chu ...
. Ice penetrating radars are also included in the payloads of two planned missions to the icy moon Icy commonly refers to conditions involving ice, a frozen state, usually referring to frozen water.
Icy or Icey may also refer to:
People
* Icy Spicy Leoncie, an Icelandic-Indian musician
Arts, entertainment, and media Music
* ICY (band), a voca ...
s of Jupiter
Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but ...
: JUICE
Juice is a drink made from the extraction or Cold-pressed juice, pressing of the natural liquid contained in fruit and vegetables. It can also refer to liquids that are flavored with concentrate or other biological food sources, such as meat ...
and Europa Clipper
Europa Clipper (previously known as Europa Multiple Flyby Mission) is an interplanetary mission in development by NASA comprising an orbiter. Planned for launch in October 2024, the spacecraft is being developed to study the Galilean moon Europ ...
.
IGS symposia
The International Glaciological Society (IGS) holds a periodic series of symposia focused on radioglaciology. In 2008, the "Symposium on Radioglaciology and its Applications" was hosted at the Technical University of Madrid
The Technical University of Madrid or sometimes called Polytechnic University of Madrid ( es, Universidad Politécnica de Madrid, UPM) is a public university, located in Madrid, Spain. It was founded in 1971 as the result of merging different Te ...
. In 2013, the "Symposium on Radioglaciology" was hosted at the University of Kansas
The University of Kansas (KU) is a public research university with its main campus in Lawrence, Kansas, United States, and several satellite campuses, research and educational centers, medical centers, and classes across the state of Kansas. Tw ...
. In 2019, the "Symposium of Five Decades of Radioglaciolgy" was hosted at Stanford University
Stanford University, officially Leland Stanford Junior University, is a private research university in Stanford, California. The campus occupies , among the largest in the United States, and enrolls over 17,000 students. Stanford is consider ...
.
Further reading
The following books and papers cover important topics in radioglaciology
* Allen C (2008
of-ice-2/ A brief history of radio-echo sounding of ice.
Earthzine.
* Bingham RG and Siegert MJ (2007) Radio-echo sounding over polar ice masses. Journal of Environmental and Engineering Geophysics 12(1), 47–62.
* Bogorodsky, VV, Bentley CR, and Gudmandsen PE (1985) Radioglaciology. D. Reidel Publishing
* Dowdeswell JA and Evans S (2004) Investigations of the form and flow of ice sheets and glaciers using radio-echo sounding. Reports on Progress in Physics 67(10), 1821–1861.
* Haynes M (2020) Surface and subsurface radar equations for radar sounders. Annals of Glaciology 61(81), 135–142.
* Hubbard B and Glasser NF (2005). Field Techniques in Glaciology and Glacial Geomorphology. John Wiley & Sons.
* Navarro F and Eisen O (2009). 11. Ground-penetrating radar in glaciological in Remote Sensing of Glaciers, Pellikka P and Rees GW (editors).
* Pettinelli E and 6 others (2015) Dielectric properties of Jovian satellite ice analogs for subsurface radar exploration: a review. Reviews of Geophysics 53(3), 593–641.
* Schroeder DM, Bingham RG, Blankenship, DD, Christianson, K, Eisen, O, Flowers, GE, Karlsson, NB, Koutnik MR, Paden JD, Siegert, MJ (2020) Five decades of radioglaciology. Annals of Glaciology 61(81), 1-13.
* Turchetti S, Dean K, Naylor S and Siegert M (2008) Accidents and opportunities: a history of the radio echo-sounding of Antarctica, 1958–79. The British Journal for the History of Science 41(3), 417–444.
Research institutions
Research and education in radioglaciology is undertaken at universities and research institutes around the world. These groups found in institutions and departments that span physical geography
Physical geography (also known as physiography) is one of the three main branches of geography. Physical geography is the branch of natural science which deals with the processes and patterns in the natural environment such as the atmosphere, h ...
, geophysics
Geophysics () is a subject of natural science concerned with the physical processes and physical properties of the Earth and its surrounding space environment, and the use of quantitative methods for their analysis. The term ''geophysics'' som ...
, earth science
Earth science or geoscience includes all fields of natural science related to the planet Earth. This is a branch of science dealing with the physical, chemical, and biological complex constitutions and synergistic linkages of Earth's four spheres ...
, planetary science
Planetary science (or more rarely, planetology) is the scientific study of planets (including Earth), celestial bodies (such as moons, asteroids, comets) and planetary systems (in particular those of the Solar System) and the processes of their f ...
, electrical engineering
Electrical engineering is an engineering discipline concerned with the study, design, and application of equipment, devices, and systems which use electricity, electronics, and electromagnetism. It emerged as an identifiable occupation in the l ...
, and related disciplines.
References
{{reflist
Glaciology