Scientists map rock glaciers on plateau

Chinese scientists have identified 132,867 rock glaciers across 16,500 square kilometers of the Qinghai-Tibet Plateau in the first comprehensive inventory of its kind.

While glaciers are what come to mind when people think of the plateau's "solid reservoir", the number and significance of rock glaciers — periglacial landforms made of ice-rich debris that slowly move downhill in cold alpine environments — have been seriously underestimated.

The figure exceeds the total number of rock glaciers previously known worldwide, suggesting a long-standing underestimation of their quantity and their role in the plateau's frozen water reserves.

The study was published recently in the journal Science Bulletin. The dataset has been made public through the National Tibetan Plateau Data Center.

Although not true glaciers, rock glaciers serve as indicators of mountain permafrost and potential reservoirs of solid-water. The Qinghai-Tibet Plateau, dubbed a core part of the "Asian Water Tower", is home to one of the largest concentrations of mid — to low-latitude permafrost on Earth, nurturing many rock glaciers.

However, a comprehensive and unified dataset tracking the movement of rock glaciers has been elusive, largely due to the challenges posed by the region's high altitude, rugged terrain and the labor-intensive nature of manual data interpretation.

The research team integrated high-resolution optical remote sensing imagery, radar data and digital elevation models to develop a deep-learning method for automatically detecting rock glaciers across the plateau. They employed multi-temporal radar techniques to extract surface deformation rates and obtained kinematic data for 99.3 percent of the cataloged features.

In addition to location and boundaries, the inventory records the morphological type, terrain attributes, glacier connectivity and motion status for each unit, supporting research into rock glacier activity and periglacial geomorphic dynamics.

Notably, the team estimated that ice stored within the plateau's rock glaciers is equivalent to roughly 92 to 186 cubic kilometers, which is comparable to the storage capacity of dozens of large reservoirs.

"This represents a solid-water reserve in the Asian Water Tower that has been largely underestimated," said Feng Min, a professor at the Institute of Tibetan Plateau Research of the Chinese Academy of Sciences who led the study.

"This discovery could have substantial implications for long-term hydrological regulation in regions lacking glaciers or where glaciers are rapidly retreating," Feng added.

The dataset also provides insights into geohazard risks. Rock glaciers creep continuously and, where they intersect roads or river valleys, can trigger ground deformation, river blockages and debris flows. By documenting the spatial relationship between rock glaciers and nearby infrastructure, the inventory offers a new tool for assessing mountain hazards, Feng noted.

"When mapping permafrost, we used to lack direct geomorphic evidence. Rock glaciers are natural markers that indicate where frozen ground exists," Feng said.

He said that the dataset is expected to support permafrost monitoring, water resource assessment, cryospheric hazard identification and surface process modeling, while providing an important baseline for reassessing the global extent and water storage of rock glaciers in cold mountain regions.

limenghan@chinadaily.com.cn