Field activities at Glaciar Pío XI, the Southern Patagonia Icefield, in 2024（南パタゴニア氷原Pío XI氷河における2024年野外観測）

抄録

Glaciar Pío XI is an advancing outlet glacier in the Southern Patagonia Icefield. We conducted a field campaign to better understand the mechanisms driving this glacier’s variation and its influence on the proglacial environments. In this report, we present an overview of our field activities and preliminary results from meteorological, glaciological, and ocean measurements, which took place in December 2024 in the southern terminus region. Precipitation measured over a five-day period (13.0 mm) was significantly different from reanalysis- and satellite-based datasets, whereas temperature and wind conditions were generally consistent with the reanalysis data. Surface melt rate ranged from 54 ± 11 to 123 ± 25 mm d⁻¹ (90 ± 6 mm d⁻¹ on average) showing the first in situ surface ablation measurements reported from the western side of the icefield. Repeated aerial surveys with uncrewed aerial vehicles showed the glacier flowing at rates up to 4.0 m d⁻¹ in the region and the ice front pushed a proglacial moraine ridge at a rate of approximately 0.4 m d⁻¹. Fjord measurements showed a stratification of fresh, cold and turbid surface water and relatively warm and saline deepwater, indicating an influence of glacial meltwater discharge. A sediment trap installed on the ocean floor ∼500 m from the glacier front collected 95 mm thick sediment after three days, corresponding to a sedimentation rate of 35.8 ± 0.6 kg m⁻² d⁻¹. Our data demonstrate the importance of in-situ measurements for an accurate understanding of the climatic conditions in the region and the proglacial environments dynamically evolving under the influence of the advancing glacier.