What Drives the Glacier Retreat, and How Do We See It? A Study of Measurement Methods and Environmental Drivers of Retreat in the Amundsenisen Glacial System, Svalbard

The Arctic is warming approximately four times faster than the global mean, accelerating retreat of marine-terminating glaciers. Changes in glacier extent are linked to environmental factors, and their accurate quantification depends on the measurement methods used. This study compares five terminus change quantification methods applied to Austre Torellbreen, analyses terminus position changes of four outlet glaciers of the Amundsenisen Glacial System—Paierlbreen, Austre Torellbreen, Vestre Torellbreen, and Recherchebreen—in SW Svalbard, over 1975–2022, and assesses environmental controls on glacier retreat. Curvilinear box and GTT emerge as the most broadly applicable methods. Multi-centreline, Rectangle box, and Curvilinear box methods form the most internally consistent group, while GTT diverges moderately from this group. The Centreline method deviates most strongly from all others and is unsuitable for short-term analysis. A ~15° change in fjord orientation caused the Rectangle box to underestimate cumulative recession by ~330 m relative to the Curvilinear box, confirming that rectilinear approaches are limited to glaciers with low fjord sinuosity. Fjord depth and surge phase are likely key modulators of the environmental signal: deep-water, marine-terminating fronts show the strongest associations with sea surface temperature and runoff, whereas shallow fjords and restricted near-terminus water circulation weaken the oceanic imprint. Land-terminating sections of glaciers retreat approximately 3.4 times more slowly than marine counterparts and show no significant annual correlations with environmental variables. The terminus record constrains the timing and magnitude of surge-related frontal advance at Paierlbreen (1993–1995, ~280 m), Vestre Torellbreen (2008–2013, ~170 m), and Recherchebreen (2018–2020, ~660 m).