10:00 〜 10:15
[MIS23-05] Rapid drainage of Lago Greve, a large proglacial lake in Patagonia, observed by satellite in 2020
キーワード：氷河湖、衛星リモートセンシング、パタゴニア
As a consequence of recent warming climate, the number, area, and volume of glacial lakes are increasing all over the world. While storage in the glacial lakes prevent immediate contribution of glacial meltwater to sea level rise, they threaten societies in mountain regions by posing a risk of glacial lake outburst flood (GLOF). Along the margins of the Patagonia Icefields, glacial lakes are expanding under the influence of glacier retreats. However, due to the remoteness of the lake locations, observations of GLOF are sparse and flood mechanisms are poorly understood. In May 2020, satellite imagery showed a sudden drop in the water level of Lago Greve, the largest proglacial lake in the western side of the Southern Patagonia Icefield. In this presentation, we report the rapid water drainage by analyzing several types of satellite based remote sensing data.
Before the drainage event, the lake area increased by 3.1±2.6 km2 from September 2016 to April 2020 and the lake level was stable (0.19±0.15 m) from November 2018 to February 2020. Thereafter, the lake area decreased by 15.0±2.6 km2 during April–November 2020 and the lake level dropped by 18.7±0.2 m during February–July 2020. Satellite image indicates that a gorge at the northern lake margin collapsed and drained lake water through a deepened water channel.
The amount of discharge during April–November 2020 was estimated as 3.7±0.6 km3 (3.6±0.6 Gt) from the changes in the water level and lake area. Satellite gravimetry in May–August showed a negative gravity change centered on the lake compared to the March 2020. The magnitude of this gravity change was consistent with the amount of drained water. The loss of water from the lake is equivalent to 25–32% of annual ice mass loss from the Southern Patagonia Icefield.
Before the drainage event, the lake area increased by 3.1±2.6 km2 from September 2016 to April 2020 and the lake level was stable (0.19±0.15 m) from November 2018 to February 2020. Thereafter, the lake area decreased by 15.0±2.6 km2 during April–November 2020 and the lake level dropped by 18.7±0.2 m during February–July 2020. Satellite image indicates that a gorge at the northern lake margin collapsed and drained lake water through a deepened water channel.
The amount of discharge during April–November 2020 was estimated as 3.7±0.6 km3 (3.6±0.6 Gt) from the changes in the water level and lake area. Satellite gravimetry in May–August showed a negative gravity change centered on the lake compared to the March 2020. The magnitude of this gravity change was consistent with the amount of drained water. The loss of water from the lake is equivalent to 25–32% of annual ice mass loss from the Southern Patagonia Icefield.