Six decades of satellite remote sensing reveal widespread glacier pulsations in the Hissar-Alay (Central Asia)

Central Asia hosts a high density of surge‑type glaciers (locally known as pulsating), which exhibit heterogeneous surge characteristics and poorly understood driving mechanisms. Historical monitoring of glacier dynamics in the region is scarce, particularly in the transitional area of the Hissar‑Alay (Pamir-Alay): there, as few as five surging glaciers are reported in existing inventories since the 1970s, and only the Abramov glacier pulsation of 1972 was studied in situ. However, a high prevalence of pulsating glaciers was postulated by Glazirin and Schetinnikov (1980), who used a Bayesian classification model of glacier morphology to predict around 200 occurrences in the Hissar‑Alay – almost 25% of the investigated sample.

Here, we systematically investigate pulsating behavior of glaciers in the Hissar-Alay, using a newly compiled dataset of optical satellite imagery from 1964 to present. We include data from film-based reconnaissance satellites (Key Hole program), SPOT 1 to 7, RapidEye, and Pléiades: these provide superior spatial resolution and temporal coverage compared to the commonly used Landsat and ASTER datasets.

Our analysis reveals asynchronous terminus advances and surge‑like patterns of ice thickness, within an overall context of mass loss. These findings confirm the occurrence of widespread glacier pulsation in the region, despite challenges in the differentiation of actual surge events from glacier advances. We note that existing inventories of surge-type glaciers are highly incomplete and biased towards larger glaciers. The model of Glazirin and Schetinnikov (1980) accurately predicted pulsating behavior at several previously unobserved glaciers; however, we also find a comparable number of misclassifications (both false positive and false negative), confirming that glacier morphology is an imperfect predictor of surging behavior.

Pulsations can induce rapid changes in glacier geometry and surface properties: these may undermine representativity of the computed glacier‑wide mass balance trends, including at reference glaciers like Abramov. Frequently updated topographic data are essential for large-scale modeling and geodetic studies in the region. However, even at pulsating glaciers, point measurements of mass balance remain valuable for calibration and validation of energy and mass balance models. Further investigation of spatio-temporal patterns of the found glacier pulsations will contribute to a better understanding of the drivers of surge behavior in Central Asia.