The Department of Defense (DoD) Arctic Strategy has indicated that in the sub-Arctic and Alaska, DoD's natural and built infrastructures are adversely affected by landscape changes such as thaw subsidence and slope instability caused by permafrost degradation, groundwater extraction, and coastal erosion. “Land subsidence” is the term used to address all types of downward land motions, whereas the upward motion is called uplift. Land subsidence is a growing problem that presents pressing and localized challenges by damaging infrastructure and exacerbating relative coastal change and associated flooding hazards. This project will demonstrate and validate Spaceborne Interferometric Synthetic Aperture Radar (InSAR) as a revolutionary active imaging technology providing large-scale high-resolution measurements of land subsidence at millimetric-level accuracy and 10 m in near real-time. This project presents an advanced algorithm developed in-house and thoroughly validated in various settings and conditions for performing multitemporal interferometric analysis of any SAR images to create maps of land subsidence at unprecedented resolution and accuracy at DoD sites in Alaska. Using this algorithm, accurate maps of land subsidence time series, rates, and uncertainties at 10 m at nine DoD sites in Alaska from 2015 to 2025 will be generated. The technology and products will enable DoD to address several outstanding challenges, including (i) How does land subsidence at and near DoD assets vary in time and space due to various natural factors? (ii) How does changing land elevation affect inundation hazards? (iii) How is DoD infrastructure vulnerability changing due to land subsidence?

Alaska, where many military sites and associated natural and built infrastructure and operations are located, is on the front lines of landscape vulnerabilities (e.g., permafrost degradation, land subsidence, landslides, coastal erosion and flooding). However, assessment of the pace and consequences of these impacts remains elusive, particularly over large spatial scales and for all DoD sites. Tracing local, regional, and global changes with high spatial resolution over several decades is essential. In addition to in situ networks, this task is increasingly fulfilled by Earth observation satellites, particularly imaging radars, which have been acquiring measurements of the land, atmosphere, and oceans since the 1990s. Synthetic Aperture Radar (SAR) is an active imaging system that illuminates an area of the Earth's surface using microwaves. InSAR measures phase differences between two or more SAR images to measure the change in distance between the satellite and the ground surface with millimetric precision. This technique has revolutionized the geodetic and intelligence communities' capacity by producing surface deformation maps with unprecedented resolution and accuracy on demand. Unlike optical systems that rely on reflected solar radiation or thermal radiation emitted by Earth, SAR imaging instruments work independently of light and heat, providing day-and-night imagery of Earth. In addition, clouds, fog, and precipitation do not significantly affect most microwaves, so images can also be acquired regardless of weather conditions. This project will demonstrate how InSAR can transform DoD's ability to monitor tiny ground motions at any time and in any location worldwide.

While many multi-decadal SAR data sets are already available, the major limitation hindering their effective use by DoD is the lack of dedicated data centers offering high-quality and efficient analysis tools to process them at a fine spatial resolution and high accuracy on demand. From a DoD perspective, there is a pressing need to build transparent computational platforms for end-users with flexible data requirements and quality. Timely access to land subsidence measurements is vital, for instance, to ensure the readiness and safety of DoD infrastructure. This project will offer an inexpensive and relatively risk-free framework to enable DoD end-users to obtain actionable data regarding ground surface motion remotely without requiring a field survey and boots on the ground.

(Anticipated Project Completion-2026)