Methods
Glaciers are super dynamic! Understanding ice flow dynamics requires an in depth understanding of complex physics, fluid dynamics, and material properties. The unique characteristics of glacial ice make it particularly challenging to study because most of our observations are limited to the surface.. but there is so much happening within the ice itself that can tell us about how it is flowing and changing over time!
To conduct my research, I use to main types of radar systems to image subsurface characteristics of glacial ice:
Each radar system has the ability to tell us about glacial properties that would be difficult to deduce otherwise. Because the alpine glaciers I study have a fairly small footprints, I rely upon data collected during field work rather than using airborne data or satellite derived measurements. IPR is primarily used to profile englacial stratigraphy of the ice and basal topography. ApRES is primarily used for measuring vertical velocity of the ice pack (englacial deformation).
To conduct my research, I use to main types of radar systems to image subsurface characteristics of glacial ice:
- Ice Penetrating Radar (IPR), also called Ground Penetrating Radar (GPR)
- Autonomous phase-sensitive Radar (ApRES)
Each radar system has the ability to tell us about glacial properties that would be difficult to deduce otherwise. Because the alpine glaciers I study have a fairly small footprints, I rely upon data collected during field work rather than using airborne data or satellite derived measurements. IPR is primarily used to profile englacial stratigraphy of the ice and basal topography. ApRES is primarily used for measuring vertical velocity of the ice pack (englacial deformation).
GPR
Radar units emit an electromagnetic wave through a transmitter (or transmitting antenna). Energy from the emitted wave reflects off of layers with different dielectric properties. These reflections are received by the radar unit (receiving antenna). We can calculate the depth of the reflected layer using physics and the material properties of glacial ice.
10 MHz GPR survey on the Begguya (Mt. Hunter) plateau in 2022.
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Cartoon of GPR theory. By calculating the two-way travel time (TWTT) between the emitted and recieved electromagnetic pulse, we can derive the ice depth using simple equations relating by relating the velocity of the radar wave to the electromagnetic properties of the material.
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Radargram collected from a 2022 GPR survey on the Begguya summit plateau in Denali National Park, showing ice depth and basal topography surrounding the drilling site of the 2013 Denali ice core. Figure published in Fang et al (2023).
ApRES
Phase-sensitive radar is uniquely suited to detect englacial deformation with high-resolution. By conducting measurements at the same location after time has passed, we can derive the vertical velocity (w) of englacial layers.