From Surface Deformation to Permafrost Process Inference: A Systematic Review of InSAR Applications, Validation, and Quantitative Evidence

Abstract

Interferometric synthetic aperture radar (InSAR) maps ground motion in permafrost regions, but deformation does not uniquely identify the underlying process. This systematic review assessed how far the field has progressed from deformation detection toward validated process inference. A Web of Science Core Collection search on 16 July 2026 returned 409 records; 262 publications met the core scope, and 175 contributed 372 coherent scientific results and 727 companion metrics. Research expanded rapidly after 2020 and diversified from seasonal mapping toward active-layer thickness (ALT), ground ice, hydrology, infrastructure, and predictive modelling. Evidence maturity nevertheless declined along the inference chain. Descriptive deformation/quality and model/algorithm results comprised 58.3% of the evidence, whereas direct validation against field observations, global navigation satellite system (GNSS) measurements, or levelling comprised 4.6%. Only 12.4% of results reported a defensible analytic sample size and 33.9% provided usable uncertainty. ALT evaluations using probing, ground-penetrating radar (GPR), or model references estimated non-equivalent quantities and could not support one pooled accuracy measure. The radar line-of-sight (LOS) displacement is also a projected, non-unique response whose process interpretation depends on motion geometry and thermal, hydrological, and mechanical assumptions. No evidence family met the prespecified requirements for global meta-analysis. Progress toward cumulative inference requires explicit estimands, matched independent validation, uncertainty propagation, and transparent dataset dependence.