CR5.4 | Radar investigations of icy and rocky (sub)surfaces
EDI
Radar investigations of icy and rocky (sub)surfaces
Co-organized by GI5/PS7
Convener: Kirk M. ScanlanECSECS | Co-conveners: Anja RutishauserECSECS, Christopher GerekosECSECS, Marie G. P. CavitteECSECS
Orals
| Fri, 19 Apr, 10:45–12:30 (CEST)
 
Room 1.34
Posters on site
| Attendance Fri, 19 Apr, 16:15–18:00 (CEST) | Display Fri, 19 Apr, 14:00–18:00
 
Hall X4
Orals |
Fri, 10:45
Fri, 16:15
Radar is a prominent tool to study ice on Earth and is quickly becoming widespread in the study of other planetary bodies. In this session, we hope to bring together all those interested in radar to showcase their work, take inspiration from each other and develop new interdisciplinary collaborations. We aim for this session to encompass many targets, instruments and applications, including:

Targets: snow, firn, land ice, sea ice, lake ice, river ice and permafrost on Earth as well as the surfaces and interiors of Mars, Europa, The Moon, Titan, Venus, Small bodies, etc.
Instruments: airborne and spaceborne sounders, altimeters, SAR and passive microwave radiometers as well as drones, GPR, ApRES and other stationary radars, etc.
Acquisition and processing: hardware, passive measurements, datasets, algorithm development, etc.
Analysis and Interpretation techniques: reflectometry, interferometry, thermometry, specularity, EM simulations, etc.
Applications: surface-, englacial and basal structure, roughness, hydrology, geothermal heat flux, material properties, modeling, Earth and extraterrestrial synergies, etc.

We especially encourage the participation of Early Career Researchers and those from underrepresented groups.

Orals: Fri, 19 Apr | Room 1.34

Chairpersons: Kirk M. Scanlan, Anja Rutishauser, Christopher Gerekos
10:45–10:50
Planetary Applications
10:50–11:10
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EGU24-18640
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solicited
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Highlight
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On-site presentation
Elena Pettinelli

Radar sounder (or Ice-penetrating radar) is one of the most suitable geophysical instruments to explore planets and moons given the very dry and/or cold conditions of their crusts, which favor the penetration of the radio waves at great depth. The first ever planetary subsurface radar was tested on the Moon, during the Apollo 17 mission: the ALSE (Apollo Lunar Sounder Experiment) multifrequency radar sounder operating onboard the Apollo Service Module (ASM) (Porcello et al., 1974). After this successful experiment more than twenty years passed before another radar sounder was included in the payload of a planetary mission. MARSIS was launched in 2003, on board Mars Express, and SHARAD in 2007 onboard Mars Reconnaissance Orbiter. Since the successful deployed on Mars, such radars collected data for more than 15 years, mapping the structures of the Martian poles and discovering the first extraterrestrial stable body of subglacial liquid water below the South pole cap. Six orbiting radar sounders have been employed so far to explore the Moon, Mars and the 67P/GC comet, and some of them are still in full operation today. The Jupiter icy moons will be the next destination of a new generations of radars: RIME, already on his way to Ganymede onboard JUICE and REASON that will be launch this year onboard Europa Clipper. These radars will explore the icy shells of Europa, Ganymede and Callisto to establish their habitability conditions and in search for evidence of liquid water. Finally, also Venus will be investigated in the next decade by a similar radar to help understand the geological and climatic evolution of the Earth twin.

In this talk I will discuss the new opportunities and challenges for the radar sounder community in the years to come.

How to cite: Pettinelli, E.: In search for liquid water using radio waves: from Earth to the icy moons of Jupiter, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18640, https://doi.org/10.5194/egusphere-egu24-18640, 2024.

11:10–11:20
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EGU24-13404
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ECS
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On-site presentation
Kristian Chan, Cyril Grima, Christopher Gerekos, and Donald Blankenship

Knowledge of (near-)surface properties and their spatial heterogeneity can reveal much about the processes that dominate the evolution of the top few-to-tens of meters of icy worlds. Radar reflectometry has been demonstrated to be a valuable technique for characterizing near-surface ice on Earth and Mars with mature plans for it to be applied to future observations of the Jovian icy moons, collected by the Europa Clipper and Juice missions. Both missions host nadir-pointing ice-penetrating radar instruments: the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON) on Europa Clipper operating at center frequencies of 60 MHz and 9 MHz, with bandwidths of 10 MHz and 1 MHz, respectively, and the Radar for Icy Moons Exploration (RIME) on Juice at a single 9 MHz center frequency but bandwidths of 1 and 2.8 MHz.

Previous applications of reflectometry rested on the assumptions implicit in the Radar Statistical Reconnaissance (RSR) technique, which has been regularly used to characterize bulk near-surface properties (e.g., porosity) and surface roughness, each predominantly dependent on the coherent and incoherent components of the total surface return, respectively. However, these previous applications of RSR utilized observations collected at near constant altitude. Europa Clipper and Juice will both perform flybys of their targets of interest with altitude that rapidly changes across the observation window. Thus, an understanding of how altitude (convolved with changes in the surface geology) can affect the balance between observed coherent and incoherent backscattered energy is necessary to confidently apply RSR on Europa and Ganymede.

Here, we simulate the radar surface echo from synthetic Europa-like terrains, using a version of the multilayer Stratton-Chu coherent simulator that computes the scattering contributions from every frequency component within the bandwidth of the emitted chirp. We then apply RSR to deconvolve the total simulated surface power into its coherent and incoherent components. We assess the coherent content of the total power to changes in altitude, by comparing the coherent power derived from simulated surface echoes at the REASON/RIME shared center frequency (9 MHz) but different bandwidths (1 vs. 2.8 MHz). Coherent and incoherent geometric power falls off at different rates with altitude. Thus, the coherent content of the total return at a particular altitude over the target of interest could affect our ability to invert for near-surface properties. Note in particular that different terrain types (e.g., chaos terrain versus ridged plains on Europa) may be better observed at different altitudes from the perspective of reflectometry. In addition, our results provide valuable insight into targets and altitudes suitable for cross calibrating RIME and REASON [9/1 MHz] for comparative radar studies across the Jovian icy moons.

How to cite: Chan, K., Grima, C., Gerekos, C., and Blankenship, D.: Characterizing the altitude dependence of radar reflectometry for the (near-)surface of icy worlds, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13404, https://doi.org/10.5194/egusphere-egu24-13404, 2024.

11:20–11:30
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EGU24-10754
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Highlight
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On-site presentation
Marilena Amoroso, Enrico Flamini, Eleonora Ammanito, Michele Viotti, Raffaele Mugnuolo, Timothy Haltigin, Etienne Boulais, Tomohiro Usui, David M. Hollibaugh Baker, Richard M. Davis, Michael S. Kelley, Bob Collom, Sébastien Lafrance, and Patrick Plourde

The primary goal of the International Mars Ice Mapper (I-MIM) mission concept is to identify and characterize accessible water-ice and its overburden in the upper 0-10 m of the Martian subsurface in preparation for future human-robotic exploration. The I-MIM concept mission has been developed by the Italian, Canadian, Japanese, and US space Agency Partners (ASI, CSA, JAXA, and NASA).

In 2021, the Agency Partners competitively selected a Measurement Definition Team (MDT) to define the core measurements for the mission’s primary payload, to suggest possible augmentations, and to develop a concept of operations. In August 2022, the MDT released a Final Report [1], concluding that the mission’s primary instrument, a Synthetic Aperture Radar (SAR) centred at 930 MHz, would satisfy all of the Reconnaissance Objectives (ROs) and would provide the opportunity to accomplish unique new science covering a broad range of international science priorities. In order to expand the capabilities of I-MIM to undertake high-priority science investigations, the MDT also recommended that the concept team consider the inclusion of complementary payloads identified as highest priority: a very high frequency (VHF) radar sounder, a high-resolution optical imager, and a sub-millimetre sounder for atmospheric profiling.

Based on the MDT inputs, the Agency Partners have updated the I-MIM mission architecture to consist of three spacecraft elements with complementary science payloads:

Element 1 – Ice-Mapping Orbiter: Provided by JAXA, with two radar instruments and an atmospheric sensor: a CSA-provided polarimetric L-band (930 MHz) SAR, an ASI-provided Very High Frequency (VHF) Shallow Radar Sounder (100-200 MHz), and a JAXA-provided sub-millimetre sounder. Moreover, an ASI-provided Large Deployable Reflector (LDR) would support the SAR and act as part of the ASI-provided telecommunications subsystem.

Element 2– Demonstration Lander: A JAXA-provided demonstration lander would piggyback on the main orbiter to provide ground-truthing capabilities with a potential complementary small instrument package.

Element 3 – Free-flying Smallsat: A NASA-provided, free-flying smallsat with a high-resolution imager would provide high-resolution imaging for context and continuity under a small low-cost mission profile and to meet the requirements for multiple scientific investigations and future mission site selection.

Mapping the unstudied near surface of Mars thanks to the synergic observations L-band SAR and the VHF Sounder, augmented by the High-resolution Imager, has the potential to fill a major data gap unmet by prior instruments sent to Mars and provide a broad evaluation of the abundance of water ice reservoirs at medium latitudes.

In order to characterize variability in the ionosphere both the SAR and the sub-millimeter sounder further addresses key questions about the connections in Mars’s dynamic climate regions and seasonal interactions of shallow subsurface volatiles with the atmospheric structure, of critical importance to both science and human-robotic mission planning.

In the International Moon to Mars objectives context, I-MIM would provide core information about the role of water ice and other volatiles in prior and active changes globally on Mars, identifying landed locations in ice-rich areas that represent potential habitable environments, for future robotic and human missions.

References: [1] I-MIM MDT Final Report (2022) 239 pp., online: https://science.nasa.gov/researchers/ice-mapper-measurement-definition-team

How to cite: Amoroso, M., Flamini, E., Ammanito, E., Viotti, M., Mugnuolo, R., Haltigin, T., Boulais, E., Usui, T., Hollibaugh Baker, D. M., Davis, R. M., Kelley, M. S., Collom, B., Lafrance, S., and Plourde, P.: International Mars Ice Mapper Mission: Detection, mapping and characterization of subsurface water ice and overburden on Mars with Synthetic Aperture Radar combined with VHF Sounding and High-Resolution Imaging, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10754, https://doi.org/10.5194/egusphere-egu24-10754, 2024.

Terrestrial Applications
11:30–11:40
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EGU24-12330
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On-site presentation
Hoyeon Shi, Gorm Dybkjær, Suman Singha, Sang-Moo Lee, Rasmus Tonboe, and Fabrizio Baordo

Sea ice thickness is derived from its freeboard measured by satellite radar altimeters. However, the radar freeboard, which is initially estimated freeboard by interpreting the observed waveform, needs correction before sea ice thickness estimation so that it coincides with the height of the snow-ice interface from the sea surface. The so-called radar freeboard correction is thus an essential procedure for sea ice thickness estimation from satellite radar altimeter data, such as those from the CryoSat-2 mission. Today, most studies do the correction taking into account a slower wave propagation speed in the snow layer on sea ice under the assumption that the main scattering horizon is the snow-ice interface. However, while several recent studies have raised questions on that assumption, there is also a possibility that a retracker, which is an algorithm that estimates radar freeboard from waveform, has systematic bias. Accordingly, this study revisits the conventional way of doing the radar freeboard correction. First, we directly compare the CryoSat-2-derived radar freeboards from different retrackers with reference airborne freeboard measurements to introduce alternative correction methods for each retracker. Then, those correction methods are combined with a recently developed methodology where snow depth, sea ice thickness, freeboard, and ice draft are retrieved simultaneously. In order to compare the performance of different correction methods, including the conventional light speed correction, retrievals are done using the updated methodology, and those results are assessed using various reference datasets. Those are snow depth and freeboard from airborne observation, ice draft from mooring observation, and freeboard from satellite laser altimeter observation. In addition, the correction methods are combined with another independent retrieval method that estimates snow depth and sea ice thickness by combining satellite laser and radar altimeter measurements. Lastly, the consistency between the results from the two retrieval methods is examined for each radar freeboard correction method.

How to cite: Shi, H., Dybkjær, G., Singha, S., Lee, S.-M., Tonboe, R., and Baordo, F.: Retracker-dependent radar freeboard correction methods for satellite radar altimetry-based sea ice thickness estimation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12330, https://doi.org/10.5194/egusphere-egu24-12330, 2024.

11:40–11:50
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EGU24-1096
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ECS
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On-site presentation
Unai Letamendia, Iván Ramírez, Francisco Navarro, Beatriz Benjumea, and Emanuel Schiavi

Ground-penetrating radar (GPR) has been shown to be an effective tool to infer the hydrothermal structure of polythermal glaciers. Knowledge of this structure is fundamental to the study of their dynamics. The cold-temperate transition surface (CTS) is the englacial boundary between cold and temperate ice. It can be identified by GPR because of the contrast in permittivity between dry cold ice and water-rich temperate ice. However, the interpretation of the CTS using GPR has traditionally been a very time-consuming and manual process. Here we show a procedure based on machine learning for detecting CTS automatically. The data used for training a convolutional neural network were collected in both Svalbard, in the Arctic (radar with central frequency of 25 MHz), and the South Shetland Islands in the Antarctic Peninsula region (200 MHz central frequency). Various metrics revealed success rates in the classification in the order of 90%. The size of the training dataset is limited, so current work is focused on enlarging its size by using random variations of synthetic radargrams generated by forward modelling with gprMax.

How to cite: Letamendia, U., Ramírez, I., Navarro, F., Benjumea, B., and Schiavi, E.: Automatic detection of cold-temperate transition surface in polythermal glaciers using GPR and machine learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1096, https://doi.org/10.5194/egusphere-egu24-1096, 2024.

11:50–12:00
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EGU24-266
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ECS
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On-site presentation
Charlotte Carter, Steven Franke, Veit Helm, Daniela Jansen, Coen Hofstede, John Paden, and Olaf Eisen

Here we present an extensive swath radar dataset collected in the onset region of the Northeast Greenland Ice Stream, surrounding the East Greenland Ice Core Project site (EGRIP). We produce a new digital elevation model (DEM) of the subglacial topography at a resolution of 25 m, covering a study area of 40 km by 60 km. The data was collected using the AWI airborne ultra-wideband radar system, in profiles mainly perpendicular to the ice flow direction with a spacing of 2 km so that the swaths overlapped.

The high-resolution subglacial topography DEM shows subglacial landforms beneath an active ice stream, located approximately 600 km into the interior of the ice sheet. These landforms indicate spatially variable bed conditions which are partly reflected in the surface velocity field. Some features appear to be crag and tail formations up to 4 km in length, with steep stoss-side slopes and tapering lee-side tails which are oriented in the direction of ice flow. Megascale glacial lineations up to 7 km in length are evident, but appear restricted to the inner ice stream within the modern shear margins, where the ice flow velocity increases from approximately 11 m/a to 58 m/a. Meltwater channels curve around a high point in the topography, which are on the scale of tunnel valleys formed from subglacial meltwater incision. Seismic data located in a channel at the eastern shear margin indicates soft sedimentation inflow. In summary, differences in landform morphology can be seen within and outside of the ice stream shear margins, indicating that NEGIS ice flow may have been transitory in this region.

This survey provides a new insight into the active subglacial environment of a Greenlandic ice stream, matching in quality surveys from ice-free land surface or marine areas. Further analysis will contribute to the understanding of how glacially sculpted landscapes are formed, as well as the effects of small-scale topography on the dynamics and the surface of the overlying ice sheet, in particular ice streams. Moreover, the dataset emphasises the usage of swath radar mapping of bedforms and thus a more widespread application of this method in all radar surveys.

How to cite: Carter, C., Franke, S., Helm, V., Jansen, D., Hofstede, C., Paden, J., and Eisen, O.: High resolution subglacial topography from airborne swath radar beneath the Northeast Greenland Ice Stream (NEGIS), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-266, https://doi.org/10.5194/egusphere-egu24-266, 2024.

12:00–12:10
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EGU24-11581
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ECS
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On-site presentation
Álvaro Arenas-Pingarrón, Alex M. Brisbourne, Carlos Martín, Hugh F.J. Corr, Carl Robinson, and Tom A. Jordan

The flow of polar ice is controlled by its viscosity that is spatially variable and depends, among other factors, on the orientations of the anisotropic crystals of ice, often referred as crystal orientation fabric. Ice crystalizes in planes represented by the c-axis, a direction perpendicular to the main plane of the crystals, and it is highly anisotropic: the viscosity along the c-axis is two orders of magnitude greater than across, and hence it can be a key factor for ice flow modelling. Interestingly, the ice crystals rotate to accommodate ice flow, similarly to how dominoes tend to align under strain, and ice c-axis orientation evolves to be perpendicular to the direction of the maximum strain rate. Thus, ice flow and crystal orientation fabric are related. However, critically for our work, c-axis evolution is not instantaneous and, particularly in currently slow deforming ice, crystal orientation fabric contains traces or past ice flow conditions. Here, we use data from the British Antarctic Survey (BAS) airborne radar PASIN2 for deep ice sounding in Rutford Ice Stream, collected during the 2019-2020 season, to derive crystal orientation fabric. Because electromagnetic waves propagate at different speeds depending on the wave polarisation being parallel or perpendicular to the c-axis, an optical phenomenon called birefringence, we compare signals from different antenna orientations in our array to derive englacial crystal orientation fabric. We then compare our radar-derived crystal orientation fabric with strain rate derived from satellite ice flow observations. To aid the interpretation, we use a numerical model that bounds the prediction of ice fabric from ice flow under different assumptions. We find that Carlson Inlet, now stagnant, show traces of past fast flow on its crystal orientation fabric. This agrees with previous studies that suggest flow-switching and water-piracy between neighbouring Carlson Inlet and Rutford Ice Stream (Vaughan et al., 2008). Our method provides a framework to investigate the timing and the causes of the flow-switching event. More in general, we demonstrate the use of existing and future airborne polarimetric data to investigate recent changes in the cryosphere.

How to cite: Arenas-Pingarrón, Á., M. Brisbourne, A., Martín, C., F.J. Corr, H., Robinson, C., and A. Jordan, T.: Evidence of Ice Flow Switching from Carlson Inlet to Rutford Ice Stream Based on Polarimetric Radar, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11581, https://doi.org/10.5194/egusphere-egu24-11581, 2024.

12:10–12:20
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EGU24-18077
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ECS
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On-site presentation
Falk M. Oraschewski, M. Reza Ershadi, Clara Henry, and Reinhard Drews

The fabric anisotropy of ice and its flow dynamics are co-dependent. Parameters used in models that solve the evolution of ice fabric are currently unconstrained, for which comparisons with observations are needed. In observations and models, the ice fabric can be represented by a crystal orientation tensor, describing the spatial distribution of ice crystal orientations. Because ice crystals are not only mechanically, but also dielectrically anisotropic, the fabric anisotropy causes birefringence and anisotropic scattering and can be inferred by polarimetric radar surveys. In recent years, the advancement of polarimetric radar methods has resulted in a surge of available observational data. However, all existing methods are performed with a nadir-looking radar geometry. As a consequence, these approaches are only sensitive to horizontal fabric anisotropy, making the assumption necessary that one eigenvector of the crystal orientation tensor is aligned in vertical (nadir) direction. We aim to develop an approach to measure the actual orientation of this eigenvector. 

Here, we present the results of a polarimetric wide-angle common midpoint (CMP) survey conducted on Ekström Ice Shelf, Dronning Maud Land, Antarctica, using the Autonomous phase-sensitive Radio Echo Sounder (ApRES). Our CMP survey had a maximum antenna offset of 200 m, with an ice shelf thickness of 250 m. For several englacial reflectors, we observe offset-dependent phase shifts between orthogonal antenna orientations. We explore these phase variations by modelling the off-nadir radio wave propagation in the birefringent ice. These wide-angle radar surveys have the potential to infer the full crystal orientation tensor, required for a constitutive paramerization of glacial flow.

How to cite: Oraschewski, F. M., Ershadi, M. R., Henry, C., and Drews, R.: Can polarimetric wide-angle radar surveys teach us more about ice fabric anisotropy?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18077, https://doi.org/10.5194/egusphere-egu24-18077, 2024.

12:20–12:30
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EGU24-61
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ECS
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On-site presentation
Daniel May, Dustin Schroeder, Paul Summers, Thomas Teisberg, Anna Broome, and Nicole Bienert

Radio-echo sounding (RES) is a widely used tool in the field of glaciology with which critical information about englacial and subglacial conditions can be derived. However, RES observations have historically been limited to zero-offset or small-offset surveys, typically employing one transmitting and one receiving antenna. The poor spatial and azimuthal coverage of the subsurface associated with these sparse geometries limits the ability to robustly constrain key englacial and subglacial properties including ice temperature, bed material composition, water content, ice fabric, and firn density. Furthermore, using radar only in zero- or small-offset configurations limits its potential to provide high resolution imaging of bed geometry. The maximum achievable offset in ground-based radar surveys is typically limited by the relatively high-loss coaxial cable which connects the radar transmitter and receiver. To overcome this limitation, two multi-offset ground-based radar systems, both built around an autonomous phase-sensitive radio-echo sounder (ApRES) as a transmitter, have been developed and deployed by the Radio Glaciology Group at Stanford. The first system forgoes cabled connection between a transmitting ApRES unit and a software-defined radio (SDR) based receiver, instead relying on a post-acquisition processing flow to ensure coherent summation of repeated measurements to achieve sufficient signal-to-noise ratios. The second system replaces the standard high-loss coaxial cable with low-loss fiber optic cable in order to extend the maximum achievable offset between transmitter and receiver. This requires outfitting the ApRES radar system with hardware to convert radio-frequency signals into optical signals that can be transmitted over fiber optic cable (RFoF). Both systems were deployed during the 2023-24 Antarctic field season as part of the Thwaites Interdisciplinary Margin Evolution project in order to collect multi-offset RES data on both floating and grounded ice. These surveys are aimed at detecting englacial temperature anomalies and the estimation of dielectric properties of englacial and subglacial materials through amplitude-versus-offset analysis of radar data. The dense multi-offset coverage in surveys described here was built up by frequent repositioning of only four SDR-based and one ApRES-based receiver; however, future surveys with these systems could have 10s or 100s of radar receivers simultaneously recording, allowing for survey geometries commonly employed in active source seismic imaging to be applied to radar imaging. 

How to cite: May, D., Schroeder, D., Summers, P., Teisberg, T., Broome, A., and Bienert, N.: Multi-Offset Radio-Echo Sounding for Estimation of Englacial and Subglacial Thermal Conditions and Material Properties, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-61, https://doi.org/10.5194/egusphere-egu24-61, 2024.

Posters on site: Fri, 19 Apr, 16:15–18:00 | Hall X4

Display time: Fri, 19 Apr 14:00–Fri, 19 Apr 18:00
Chairpersons: Anja Rutishauser, Christopher Gerekos, Marie G. P. Cavitte
X4.25
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EGU24-1721
Daniel Farinotti, Raphael Moser, Barthelemy Anhorn, Christophe Ogier, Andreas Bauder, Benedikt Pohl, Benedikt Soja, and Hansruedi Maurer

The Airborne Ice Radar of ETH Zurich (AIRETH) is a dual-polarization, helicopter-borne GPR system that was developed for glaciological applications. At the core of AIRETH are two pairs of commercial, orthogonally oriented, bistatic dipole antennas operating at a center frequency of 25 HMz or higher. The system has extensively been operated in the past, e.g. for collecting close to 2,500 km of GPR data for estimating the ice thickness of glaciers across the Swiss Alps.

Here, we present a series of amendments that have recently performed to the AIRETH system in order to increase its versatility and operability. The corresponding work notably included:
1. a re-design of AIRETH’s air-frame, aiming at decreasing the system’s overall weight, as well as at increasing the system’s stability and ease of operation;
2. a newly developed positioning system, which is now based on the integration of information obtained from a set of four low-cost Global Navigation Satellite System (GNSS) sensors placed at the corners of the main air-frame in combination with an Inertial measurement unit (IMU); and
3. an experimental antenna shielding based on low-cost materials, aiming at minimizing the ringing noise caused by the proximity of the GPR system to the carrying helicopter.

The contribution will focus on the advances that were achieved compared to the previous AIRETH setup, and will point out the challenges faced during system re-design. The capabilities of the new system will, moreover, be illustrated by presenting some recent datasets acquired over Alpine glaciers.

How to cite: Farinotti, D., Moser, R., Anhorn, B., Ogier, C., Bauder, A., Pohl, B., Soja, B., and Maurer, H.: AIRETH 2.0 – a revamped helicopter-borne GPR for glaciological applications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1721, https://doi.org/10.5194/egusphere-egu24-1721, 2024.

X4.26
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EGU24-8982
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ECS
First results from the high-density 4D GPR datasets acquired on three Swiss alpine glaciers using our drone-based GPR system.
(withdrawn)
Bastien Ruols, Ludovic Baron, Johanna Klahold, Alexi Morin, Mélissa Francey, and James Irving
X4.27
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EGU24-16685
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ECS
Johanna Klahold, Benjamin Schwarz, Alexander Bauer, Gabriela Clara Racz, Bastien Ruols, and James Irving

Ground-penetrating radar (GPR) has become a well-established tool in the field of glaciology thanks to its capacity for high-resolution imaging and the excellent propagation characteristics of radar waves in snow and ice. In this context, 3D surveying and processing techniques hold significant promise for examining the internal structure and dynamics of glaciers, yet 3D studies are rarely done due to time and cost constraints. In particular, the field of glacier hydrology could immensely benefit from the acquisition and dedicated processing of high-density 3D GPR data sets, as observations of hydrological conditions inside the glacier and at its base are of critical importance for model calibration and validation.

In this contribution, we attempt to exploit the full potential of high-resolution 3D GPR data to study glacier hydrology. A novel drone-based GPR acquisition system enables us to collect high-density 3D data with unprecedented spatial coverage. Our corresponding processing scheme considers two complementary components: the prominent reflected arrivals, and the faint (often neglected) diffracted wavefield. Reflection amplitudes at the ice-bedrock interface are used to delineate subglacial channels, whereas diffraction imaging methods borrowed from exploration seismology facilitate the localization of englacial conduits.

We present results from two case studies in the Swiss Alps: the Haut Glacier d’Arolla and the Glacier d’Otemma. Our workflow provides complementary maps of the subglacial drainage system and of well-developed englacial channels. For the Glacier d’Otemma, we combine these results with supplementary methods (photogrammetry, dye tracing, time lapse cameras, steam drilling, and hydrological modeling) to obtain a more comprehensive characterization of the drainage system.

How to cite: Klahold, J., Schwarz, B., Bauer, A., Racz, G. C., Ruols, B., and Irving, J.: Mapping Glacier Hydrology in 3D: Novel GPR Acquisition and Processing Techniques, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16685, https://doi.org/10.5194/egusphere-egu24-16685, 2024.

X4.28
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EGU24-12324
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ECS
Chris Pierce, Mark Skidmore, Lucas Beem, Don Blankenship, Ed Adams, and Christopher Gerekos

Sub-glacial canyon features up to 580m deep between broad, flat mesas were identified beneath Devon Ice Cap, Devon Island, Nunavut, Canada during a recent Radar Echo Sounding (RES) survey. The largest canyon connects a hypothesized area of distributed sub-glacial water near the ice cap's summit with the marine-terminating Sverdrup outlet glacier. This canyon represents a probable drainage route for the hypothesized sub-glacial water system. Radar bed reflectivity is consistently 30 dB lower along the canyon floor than on the mesas, contradicting the signature expected in the presence of sub-glacial water. We compare these data with radar backscattering simulations to demonstrate that the reflectivity pattern may be topographically induced. Our simulated results indicated a 10m wide canal-like water feature is unlikely along the canyon floor averaging ~300m wide, however, smaller features may be difficult to detect via RES.

We calculated basal temperature profiles along the canyon using a 2-D finite difference method, and found basal conditions at the canyon floor may be significantly warmer than at the mesas. Despite elevated temperatures, there is limited evidence that the basal environment along the canyon floor could support a connected drainage system between the Devon Ice Cap summit and Sverdrup Glacier.

The complex terrain beneath Devon Ice Cap demonstrates some limitations for RES. Future studies should carefully consider attenuation correction methods near steep or complex terrain, and seek validation of RES analyses with multiple methods, as we have demonstrated here.  

How to cite: Pierce, C., Skidmore, M., Beem, L., Blankenship, D., Adams, E., and Gerekos, C.: Exploring Canyons Beneath Devon Ice Cap for Sub-Glacial Drainage Using Radar and Thermodynamic Modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12324, https://doi.org/10.5194/egusphere-egu24-12324, 2024.

X4.29
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EGU24-18028
Daniela Jansen, Steven Franke, Catherine Bauer, Tobias Binder, Dorthe Dahl-Jensen, Jan Eichler, Olaf Eisen, Yuanbang Hu, Johanna Kerch, Maria Gema Llorens, Heinrich Miller, Niklas Neckel, John Paden, Tamara de Riese, Till Sachau, Nicolas Stoll, Ilka Weikusat, Frank Wilhelms, Yu Zhang, and Paul Dirk Bons

Only a few localised ice streams drain most ice from the Greenland Ice Sheet. Thus, understanding ice stream behaviour and their temporal variability is crucially important to predict future sea-level change. The interior trunk of the 700 km-long North-East Greenland Ice Stream (NEGIS) is remarkable for the lack of any clear bedrock channel to explain its presence. Here we use isochronous radar reflections from an airborne radar survey as passive tracers of ice deformation. We present the first-ever 3-dimensional analysis of folding and advection of stratigraphic horizons within an ice stream, which shows that the localised flow and shear margins in the upstream part were fully developed only ca. 2000 years ago. This indicates that this type of streaming in the interior of an ice sheet can be triggered on short time scales.

How to cite: Jansen, D., Franke, S., Bauer, C., Binder, T., Dahl-Jensen, D., Eichler, J., Eisen, O., Hu, Y., Kerch, J., Llorens, M. G., Miller, H., Neckel, N., Paden, J., de Riese, T., Sachau, T., Stoll, N., Weikusat, I., Wilhelms, F., Zhang, Y., and Bons, P. D.: Folded ice in the upper North East Greenland Ice Stream reveal timing of the onset of streaming, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18028, https://doi.org/10.5194/egusphere-egu24-18028, 2024.

X4.30
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EGU24-17445
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ECS
Anja Rutishauser, Reinhard Drews, Reza M. Ershadi, Falk M. Oraschewski, Kirk M. Scanlan, Nanna B. Karlsson, Carlos Martin, Anne M. Solgaard, Camilla S. Andresen, and Andreas P. Ahlstrøm

The crystal orientation fabric (COF) of ice sheets, characterized as the net alignment of ice crystals, can contain a record of past ice sheet dynamics and potentially climatic conditions. In turn, the COF significantly influences ice viscosity, thus impacting present-day ice deformation and flow velocities. Due to its dielectric properties, anisotropic COF can be detected with polarimetric radar measurements, including Autonomous phase-sensitive Radio-Echo Sounders (ApRES).

Here, we present findings from polarimetric ApRES measurements conducted at Camp Century North-West Greenland, and two sites in Southwest Greenland: Dye-2 and KAN-U. At Camp Century, the ApRES measurements indicate some COF anisotropy throughout the ice column, with a distinct boundary at the depth of the Holocene-Wisconsin ice transition, previously identified in a nearby ice core. We investigate the origin of this boundary in the ApRES data, and whether such signatures can be used to identify glacial-interglacial transitions from polarimetric radar data.

At both sites in Southwest Greenland, the signal is strongly attenuated and falls below the noise level beyond 500 m depth, likely due to significant scattering within a heterogeneous firn column. However, Dye-2 exhibits strong COF anisotropy in the uppermost 100-500 m of the ice column, despite the region’s slow ice flow. Conversely, KAN-U displays no evidence of  COF anisotropy. We investigate causes of the peculiar localized anisotropy at Dye-2, hypothesizing it as a residual imprint of a historic fast flowing, far inland-reaching ice stream.

How to cite: Rutishauser, A., Drews, R., Ershadi, R. M., Oraschewski, F. M., Scanlan, K. M., Karlsson, N. B., Martin, C., Solgaard, A. M., Andresen, C. S., and Ahlstrøm, A. P.: ApRES observations of ice fabric in Greenland: From a climatic transition in the North to a potential historical ice stream remnant in the South, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17445, https://doi.org/10.5194/egusphere-egu24-17445, 2024.

X4.31
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EGU24-1398
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ECS
Alexandra Zuhr, Steven Franke, Daniel Steinhage, Daniela Jansen, Olaf Eisen, and Reinhard Drews

Contrary to the rest of the Antarctic ice sheet, East Antarctica currently gains mass due to an increase in snow accumulation over the last decades. How or if this increase is linked to anthropogenic warming is not yet clear and requires better understanding of the surface mass balance history over the last centuries, and also the dependency of snow accumulation with the local surface slopes across different spatial scales.

Here, we present a novel airborne dataset using the multichannel ultra-wideband radar system from the Alfred Wegener Institute in Germany with a decadal vertical resolution for the plateau area in Dronning Maud Land. We assess the spatial and temporal variability of surface mass balance and snow accumulation for the past centuries for an area of ~200,000 km2. With this contribution, we aim to (1) show the potential to use ultra-wideband radar systems to reconstruct the recent surface mass balance and accumulation rates in low-accumulation regions, (2) present information on large spatial scales, and (3) discuss potential overlap of interests and/or data in this and/or other areas on the plateau of East Antarctica.

How to cite: Zuhr, A., Franke, S., Steinhage, D., Jansen, D., Eisen, O., and Drews, R.: Spatial and temporal changes in surface mass balance derived from airborne radio sounding for the plateau area in Dronning Maud Land, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1398, https://doi.org/10.5194/egusphere-egu24-1398, 2024.

X4.32
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EGU24-18237
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ECS
Hameed Moqadam, Claudius Zelenka, and Olaf Eisen

The task of mapping of deep internal reflection horizons (IRH) of ice sheets has been a crucial step for a variety of glaciological studies, for instance relating ice core age-depth relationships, tuning ice sheet models, and extend dated layers beyond ice core sites. However, mapping a sufficient number of IRHs is a time-consuming and error-proned task. Thus, there have been ongoing endeavors for automatized pipelines to perform this.

In this work, a complete pipeline for automatic mapping of deep IRH, which determine ice layer boundaries, is presented. This pipeline is tested on radargrams from Dronning Maud Land Antarctica and shows good performance in mapping a number of deep IRHs. The model shows great promise to be used on snow radargrams and obtaining recent accumulation rates as well.

We have applied convolutional neural networks (CNN) to achieve this. The training data is composed of a small set of complete hand-labeled radargrams as well as radargrams that are labeled using conventional feature extraction methods. This task requires dense pixel-level predictions, and ground-truth collection is time-consuming and prone to errors, therefore a group of modifications have been implemented on the model. The role of post-processing is discussed, since the output of the model is a raw image and much work is done on the model output. The potential of such a deep mapped stratigraphy is discussed and various applications are pointed out.

How to cite: Moqadam, H., Zelenka, C., and Eisen, O.: Mapping of deep internal reflection horizons, method modifications and applications., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18237, https://doi.org/10.5194/egusphere-egu24-18237, 2024.

X4.33
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EGU24-14822
Yong-Gil Park, Chol-Young Lee, Joo-Han Lee, and Dong-Chan Joo

The structure of Antarctic ice preserves the sequence of ice deposition, offering insights into ancient environmental conditions. Organisms discovered beneath the ice sheets, spanning from hundreds to thousands of meters in thickness, hold information on survival in extreme environments. Antarctic ice investigations are conducted using radar systems mounted on helicopters or vehicles, generating vast datasets covering hundreds of kilometers. Analyzing this large-scale data is essential to reduce time and cost for detecting ice structures and subglacial lakes. In this study, we developed algorithms for ice structure analysis and subglacial lake detection using big data analysis techniques, specifically outlier detection methods applied to radar signal values. Utilizing radar signal values represented in an 800x83,344 matrix, we employed the Spark platform with specifications of 400 cores and 1.6TB of memory for data analysis. To facilitate data processing in Spark, the data was transformed into a 3x66,675,200 dataframe after uploading to HDFS. Outlier detection, using the Moving Interquartile Range (IQR), identified abrupt changes in signal values based on columns, adjusting the IQR's range and scale to optimize the results. Detected outlier values were normalized within a 0-255 range and visualized based on intensity. Results revealed that using the Moving IQR for radar imagery processing effectively detected localized changes as the range increased; however, detection rates decreased with larger scales. Analyzing radar exploration results in a big data environment is anticipated to significantly reduce time and costs compared to traditional methods, contributing to Antarctic exploration and climate change response efforts.

 

How to cite: Park, Y.-G., Lee, C.-Y., Lee, J.-H., and Joo, D.-C.: Big Data Analysis of Antarctic Ice Structures and Subglacial Lakes: Utilizing Moving IQR for Radar Intensity Processing, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14822, https://doi.org/10.5194/egusphere-egu24-14822, 2024.

X4.34
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EGU24-5342
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ECS
Steven Franke, Michael Wolovick, Reinhard Drews, Daniela Jansen, Kenichi Matsuoka, and Paul Bons

Understanding the material properties and physical conditions of basal ice is crucial for a comprehensive understanding of Antarctic ice-sheet dynamics. Yet, direct data are sparse and difficult to acquire, necessitating geophysical data for analysis. We employed high-resolution ultra-wideband radar to map high-backscatter zones near the glacier bed within East Antarctica's Jutulstraumen drainage basin. In addition, we used radar forward modelling to constrain their material composition. Our results reveal along-flow oriented sediment-laden basal ice units connected to the basal substrate, extending to several hundred meters thick. Three-dimensional thermomechanical modelling suggests these units initially form via basal freeze-on of subglacial water originating upstream. We suggest that basal freeze-on and the entrainment and transport of subglacial material play a significant role in an accurate representation of the material, physical, and rheological properties of the Antarctic ice sheet's basal ice, ultimately enhancing the accuracy and reliability of ice-sheet modelling.

How to cite: Franke, S., Wolovick, M., Drews, R., Jansen, D., Matsuoka, K., and Bons, P.: Sediment-laden basal ice units near the onset of a fast-flowing glacier in East Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5342, https://doi.org/10.5194/egusphere-egu24-5342, 2024.

X4.35
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EGU24-14072
Jason Bott, Don Blankenship, Shuai Yan, Lucas Beem, and Duncan Young

In NASA’s MEaSUREs Ice Velocity Data, a distinctive 8.5km diameter patch of slow-moving to stationary ice (0-15m/year) can be observed near the grounding line of Haynes Glacier, amidst much faster-flowing ice (300-1300 m/year). Additionally, a number of anomalously drawn-down englacial radar reflections are observed in multiple aerogeophysical surveys with the McCORDs (Multichannel Coherent Radar Depth Sounder) Instrument upstream of this ice velocity anomaly. 

The potential source of this velocity anomaly is hypothesized to be either anomalous geothermal flux or high frictional heat upstream, coupled to a thinning of the ice column as it nears the grounding line. These factors, taken together, imply a scenario where the warmer ice at the base of the ice column melts away while colder ice enters from above at the accumulation rate along the flowline. Upstream, with the ice column's relatively high thickness (~1000m), the basal ice experiences sufficient pressure to induce significant down draw of layers from substantial melting that is consistent with basal friction and/or a source of anomalous geothermal flux; the result is significant thermal advection of the much colder surface accumulation deep into the ice column. Downstream, where the ice thins, the  reduced pressure results in freezing of the anomalously cold ice to the bed, leading to the observed velocity anomaly.The testing of this hypothesis requires reconciling of the vertical velocity profile necessary to produce the down draw with either expected frictional melt or anomalous geothermal flux along the flowline (given the accumulation gradient). We present here this coupled thermal and kinematic modeling of Haynes Glacier from the site of the down draw to the sticky spot near the grounding line. With our models of temperature variations and ice flow characteristics within the Haynes Glacier system, we can further refine our understanding of the importance of heterogeneous geothermal flux for cryosphere evolution  - which may prove to be vitally important to fully understand fast-flowing and vulnerable ice streams in the Amundsen Embayment of West Antarctica. This, in turn, may have further implications for the study of heterogeneous heat flux and volcanic activity within the broader context of West Antarctica.

How to cite: Bott, J., Blankenship, D., Yan, S., Beem, L., and Young, D.: The Potential Role of Anomalous Geothermal Flux for Enhanced Basal Melting and Suppressed Ice Velocity at Haynes Glacier, West Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14072, https://doi.org/10.5194/egusphere-egu24-14072, 2024.

X4.36
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EGU24-12995
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Highlight
Duncan Young, John Paden, Megan Kerr, Shivangini Singh, Shravan Kaundinya, Shuai Yan, Alejandra Vega González, Jamin Greenbaum, Dillon Buhl, Gregory Ng, Kristian Chan, Bradley Schroeder, Gonzalo Echeverry, Thomas Richter, Scott Kempf, Fernando Rodriguez-Morales, Richard Hale, Donald Blankenship, and Edward Brook

The Center for Oldest Ice Exploration (COLDEX) is a US initiative funded to search for climate records over the last 5 million years, including locating sites for an accessible continuous ice core going back 1.5 million years.  As part of this effort, COLDEX has mapped the southern flank of Dome A, East Antarctica using an instrumented Basler, including dual frequency radar observations of the ice sheet and ice bed, as well as potential fields measurements (see presentation by Kerr in EGU session G4.3) across two field seasons from Amundsen-Scott South Pole Station.  The aerogeophysical system included both the UTIG VHF MARFA radar system operating at 52.5-67.5 MHz, as well as a new large high resolution UHF array from CReSIS operating at 670-750 MHz operating simultanously.  A goal of this project was to obtain airborne repeat interferometry for segments of the survey, as well as directly feed ice sheet models using englacial isochrons (see Singh presentation in EGU session CR5.6).  These goals lead to a survey explicitly designed around ice sheet flow lines.  

While prior work had sampled the region at lithospheric scales, the COLDEX survey had two components - the first was to map the region at crustal scales (line spacing of 15 km), and the second was to map subareas at ice sheet scales (line spacing of 3 km).  Immediate observations include an extensive basal unit and strong discontinuity in englacial stratigraphy that runs across the survey area and appears correlated with changes in bed interface properties.  The airborne campaign will be used to inform follow up ground campaigns to understand processes relevant for old ice preservation.

How to cite: Young, D., Paden, J., Kerr, M., Singh, S., Kaundinya, S., Yan, S., Vega González, A., Greenbaum, J., Buhl, D., Ng, G., Chan, K., Schroeder, B., Echeverry, G., Richter, T., Kempf, S., Rodriguez-Morales, F., Hale, R., Blankenship, D., and Brook, E.: Comprehensive multi frequency airborne mapping of the southern flank of Dome A: results of the COLDEX airborne program., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12995, https://doi.org/10.5194/egusphere-egu24-12995, 2024.

X4.37
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EGU24-11801
Alain Herique, Dirk Plettemeier, and Wlodek Kofman

Our knowledge of the internal structure of asteroids relies entirely on inferences from remote sensing observations of the surface and theoretical modeling. Is the body a monolithic piece of rock or a rubble-pile, and how high is the porosity? What is the typical size distribution of the constituent blocks? Are these blocks homogeneous or heterogeneous? Direct measurements of an asteroid’s deep interior structure are needed to better understand asteroid accretion and their dynamic evolution. The characterization of the asteroids’ internal structure is crucial for science, planetary defense and exploration. In orbit Radar sounding is the most mature instruments capable of achieving the objective of characterizing the internal structure and heterogeneity, for the benefit of science as well as for planetary defense or exploration.

This is the goal of JuRa, the Juventas radar, onboard the ESA HERA mission. JuRa is a monostatic radar, BPSK coded at 60MHz carrier frequency and 20MHz bandwidth, inherited from CONSERT/Rosetta. The instrument design is under integration on Juventas cubesat for the ESA HERA mission. HERA will be launched this autumn to deeply investigate the Didymos binary system and especially its moonlet Dimorphos, five years after the DART/NASA impact. The main objective of JuRA is to characterize the asteroid interior, to identify internal geological structure such as layers, voids and sub-aggregates, to bring out the aggregate structure and to characterize its constituent blocks in terms of size distribution from submetric to global scale. The second objective is to estimate the average permittivity and to monitor its spatial variation in order to retrieve information on its composition and porosity.

This radar is also proposed to probe Asteroid 99942 Apophis in 2029, a potentially dangerous asteroid which will then approach Earth as close as 32000 kilometers on the DROID JPL/CNES and the RAMSES ESA proposed missions. This radar, which is a modified version of JuRa, will be able to operate in both monostatic and bistatic modes between orbiting or landed CubeSats. The knowledge of Apophis’ internal structure is crucial to improve our ability to study its stability conditions and to model its response to the gravitational constraints induced by Earth close approach. The Multipass processing will allow us to build a 3D tomographic image of the interior at different scales from submeter to global.

In this talk will present the instrument, its status, performances and goals as well as the science objectives in the context of the different targets.

How to cite: Herique, A., Plettemeier, D., and Kofman, W.: Radar tomography of asteroid deep interior. JuRa / HERA to DIDYMOS and Ra proposed to APOPHIS , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11801, https://doi.org/10.5194/egusphere-egu24-11801, 2024.

X4.38
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EGU24-11645
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ECS
Carolyn Michael, Livia Jakob, Noel Gourmelen, Sophie Dubber, Karla Boxall, Andrea Incatasciato, Martin Ewart, Jerome Bouffard, and Alessandro Di Bella

The Greenland and Antarctic ice sheets are contributing to a quarter of current sea level change and have the potential to raise sea level by several metres in the future. The surface elevation of ice sheets, and its temporal evolution, is one of the essential climate variables, it forms the basis observation for mass balance monitoring and the projection of sea level contribution under future climate scenarios. This work explores the creation of a seamless and gapless annual digital elevation model (DEM) derived from CryoSat radar altimetry measurements to aid in the ongoing study of their ever-changing topography.

 

CryoSat-2 waveforms can be processed using two distinct techniques; (1) the conventional Point-Of-Closest-Approach (POCA), sampling a single elevation beneath the satellite, and (2) Swath processing which produces a swath of elevation measurements across the satellite ground track beyond the POCA, increasing spatial and temporal resolution. CryoSat operates in its Synthetic Aperture Radar Interferometric (SARIn) mode over the margins of the ice sheets allowing both processing techniques, however, within the ice sheet interior, CryoSat switches to its Low Resolution Mode (LRM), allowing solely the POCA technique for data processing. To achieve a comprehensive DEM encompassing the entirety of the ice sheet, whilst optimising data coverage, it is imperative to integrate and reconcile the outputs obtained from these distinct processing methodologies. This investigation uses two data sets provided by ESA’s CryoSat thematic product range: the CryoSat-2 ThEMatic PrOducts (CryoTEMPO) land ice data set that applies the POCA processing technique and covers the entirety of the ice sheets and the CryoTEMPO-EOLIS (Elevation Over Land Ice from Swath) data set that provides a comprehensive point cloud data set specific to the ice sheet margins.

 

In this investigation, the EOLIS and CryoTEMPO land ice datasets are aggregated into a spatial grid, utilising a Gaussian Radial Basis Function kernel to consider both, the spatial and temporal distribution of data points. To integrate EOLIS measurements from the margins of the ice sheet with CryoTEMPO land ice measurements from its interior, adjustments for variations in penetration are necessary to facilitate a seamless transition and mitigate the impact of anomalies. The combined and adjusted dataset is then post-processed to remove outliers while missing data is interpolated to generate a continuous DEM. Various spatio-temporal interpolation methods - such as External Drift Kriging, radial basis function, and DINCAE (Data Interpolating Convolutional Auto-Encoder) - have been explored and compared for their effectiveness.

 

This poster will provide and summarise an overview of the gridding, merging, and interpolation methodologies. Additionally, an assessment of the performance of different interpolation methods and their accuracies will be presented with comparisons to existing DEMs.

How to cite: Michael, C., Jakob, L., Gourmelen, N., Dubber, S., Boxall, K., Incatasciato, A., Ewart, M., Bouffard, J., and Di Bella, A.: A Seamless Ice Sheet Digital Elevation Model using CryoSat, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11645, https://doi.org/10.5194/egusphere-egu24-11645, 2024.

X4.39
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EGU24-6717
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ECS
Tian Tian, Alexander Fraser, Petra Heil, Thomas Lavergne, Xuanji Wang, Yinghui Liu, and Jay Hoffman

Remotely sensed ice motion is a crucial component in sea, lake, or river ice research. Over the past few decades, the ice movement has been detected and retrieved predominantly through the application of the Maximum Cross-Correlation (MCC) technique by analyzing the overlapped consecutive satellite images.

Traditionally, ice motion products have been derived from daily averaged satellite imagery, commonly referred to as 'daily-map' (DM) ice motion. This DM ice motion product has gained widespread usage in sea ice studies due to its inherent timescale and extensive coverage.

Recently, a new approach known as the swath-to-swath (S2S) method has emerged, deriving ice motion from individual satellite swath pairs. The S2S ice motion product has proven valuable in sea ice kinematics research, revealing a robust relationship between ice kinematics and thickness, characterized by its diverse timescale. Consequently, these two types of satellite-derived ice motion products contribute distinct perspectives to ice kinematics research.

The latest generation of NOAA's Geostationary Operational Environmental Satellites (GOES), specifically the GOES-R Series, offers sea/lake/river ice observations at a relatively high resolution. A recent development involves the MCC approach generating a new DM ice motion product with a 2 km resolution using GOES-R reflectance imagery (0.5 km resolution). This ice motion dataset holds potential for final users engaged in analyzing small-scale sea/lake/river ice status and its changes.

How to cite: Tian, T., Fraser, A., Heil, P., Lavergne, T., Wang, X., Liu, Y., and Hoffman, J.: Satellite-derived sea ice motion data: daily-maps (DM) and swath-to-swath (S2S), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6717, https://doi.org/10.5194/egusphere-egu24-6717, 2024.

X4.40
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EGU24-8824
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ECS
Kirk M. Scanlan and Sebastian B. Simonsen

Satellite remote sensing is one of the few ways to comprehensively monitor changes in the Greenland Ice Sheet ‘s surface conditions through both time and space. From orbit, satellites can efficiently collect repeated measurements covering the entire ice sheet surface and elucidate the processes controlling how Greenland responds to a changing climate. Active radar and passive microwave measurements are especially valuable datasets, as cloud cover or illumination conditions are not limiting factors.

In this vein, recent research has shown how near-surface properties (i.e., density and roughness) across Greenland can be derived through the Radar Statistical Reconnaissance analysis of Ku-band ESA CryoSat-2 and Ka-band CNES/ISRO SARAL surface echo powers. While this approach yields densities at individual depths in the near-surface, a fuller result would include constraining a continuous density profile as a function of depth. At the same time, L-band ESA SMOS passive microwave brightness temperatures are sensitive to the entire snow-firn-ice column. However, the inversion of brightness temperatures for a property of interest in a specific layer (e.g., snow wetness, density, etc.) requires numerous assumptions regarding the subsurface conditions.

The EO4GRHO project seeks to merge these two approaches to investigate whether the inversion of SMOS brightness temperatures using a subsurface structure pre-conditioned with results derived from the analysis of radar altimetry surface echoes (i.e., density at known depth(s)) can provide a more complete picture of how Greenland Ice Sheet near-surface densities vary with depth, time, and space. Here, EO4GRHO leverages a decade (2013-2023) of contemporaneous CryoSat-2, SARAL, and SMOS measurements, makes use of modelled brightness temperatures from the Snow Microwave Radiative Transfer model software and, finally, hundreds of in-situ measurements. The ultimate aim of EO4GRHO is to operationally produce observation-based maps and time series for the near-surface density structure of the Greenland Ice Sheet that can be incorporated in future mass balance calculations.

How to cite: Scanlan, K. M. and Simonsen, S. B.: EO4GRHO: A multi-satellite synthesis constraining the near-surface density profile of the Greenland Ice Sheet through time and space, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8824, https://doi.org/10.5194/egusphere-egu24-8824, 2024.