Aufeis (icings) are unique cryohydrological features in frozen ground regions, acting as critical solid-water reservoirs by freezing and storing a substantial portion (up to 40%) of the winter baseflow in some basins. Ecologically, they also serve as keystone habitats that provide crucial unfrozen overwintering refugia for cryophilic fish and other aquatic organisms. Concurrently, their formation and evolution pose significant geohazards to engineering infrastructure such as roads, bridges, tunnels, and culverts. In the context of global warming, a synthesis of both long-term in-situ and remote sensing observations confirms that icings are undergoing significant degradation, characterized by shrinking areas, accelerated melt rates, and fragmentation of perennial ice bodies. However, the mechanisms governing their formation and evolution, as well as their broader impacts on eco-hydrological processes and sustainable development in these regions, remain inadequately understood. This study comprehensively reviews the current understanding of icing formation, distribution, and controlling factors (e.g., geology, climate, and permafrost). It traces the evolution of research methodologies, from foundational field surveys and historical mapping to modern approaches combining satellite remote sensing (e.g., NDSI and machine learning) and geophysical techniques (e.g., GPR, ERT, and NMR). This review also highlights the eco-hydrological and hazard-related impacts of changes in ice-riving. We further discuss future research directions, noting a shift in focus, from the broad river systems of the Arctic and subarctic regions to understudied areas such as High Mountain Asia. Future research priorities are identified, calling for a paradigm shift from two-dimensional spatial monitoring towards integrated, three-dimensional quantitative analysis and prediction. Key frontiers include: elucidating the fundamental physical mechanisms of icing formation through coupled modeling; leveraging artificial intelligence to combine multi-source data (e.g., satellite, UAV, geophysical) for accurate estimation of icing volume; quantifying the cascading impacts of icing degradation on geomorphology and ecosystems; and developing robust predictive models for water resource management and geohazard mitigation related to icing evolution. Such advancements are crucial for providing the robust scientific basis needed for sustainable development in Earth’s rapidly changing cold regions.