Changes in glacier dynamics during land-to-lake glaciers transition in Patagonian glaciers.

Glacier retreat and the transition from land to lake termini can accelerate mass loss through various feedback mechanisms. This study examines the dynamic changes during the land-to-lake transition of four neighboring glaciers (Exploradores, Grosse, Reichter and Gualas) located in the maritime-humid climate of the western Northern Patagonian Icefields, where ablation rates on glacier terminal tongues can reach up to 20 m w.e. annually.

We conducted the first bathymetric surveys on the glacier’s proglacial lakes and integrated data on ice velocity, elevation changes, front retreat, and front depth to identify the main controls on glacier retreat. Three transition stages were observed: (i) initial thinning with slow front retreat, (ii) increased glacier velocity and terminus flotation leading to rapid disintegration into large tabular icebergs, and (iii) formation of a stable calving front on prograde or <5º retrograde bedrock slopes, with a slowdown in velocity followed by smaller calving events. One debris-covered glacier left large sections of dead ice, while debris-free glaciers efficiently produced large tabular icebergs (>500 m).

While Grosse, Gualas and Reicher Glacier developed a calving front, Exploradores Glacier is currently in stage (i) to (ii), characterized by increased velocity and flotation. Identifying this stage is critical for Exploradores Glacier not only for glaciological interest, but also due to a rapid increase in lake area in the coming years, which will heighten the risk for tourists accessing the terminal glacier tongue, a major attraction visited by up to 9,000 tourists annually. Due to insufficient ice bedrock information to fully assess flotation conditions, we discuss the potential of using ice velocity (widely available nowadays through satellite), geometry and elevation changes to predict rapid retreat stages.

In the Patagonian Icefields, overdeepened areas currently covered by ice are expected to fill with water as glaciers retreat. Understanding the impacts and processes during glacial lake development will enhance the interpretation of paleo-records and predictions of glacier responses to climate change in future environmental systems.