Seminar by Ugo Nanni, PhD/Doctoral Research Fellow, Dept of Geosciences.
Advances in mapping and understanding short-term variations in glacier-surface velocities from optical remote sensing images
Abstract: Accurate ice flow measurements are essential to evaluate ice flow models. Satellite imagery provides large spatial coverage and is thus an efficient approach for retrieving glacier flow characteristics in remote areas at large or even global scales. On short timescales (weeks to months), the expected glacier displacement is often on the same order as the signal-to-noise ratio for the commonly used satellite imagery, which limits the retrieval of accurate glacier velocity fields. Large-scale assessments of velocity changes over short time scales and over complex areas such as mountain ranges are thus still missing but are critical in order to better understand how physical processes controlling glacier dynamics are affected by meteorological conditions. In this study we investigate short term (weekly to monthly) glacier surface velocity changes in a mountain range (Western Pamir) that hosts a wide variety of glaciers in term of geometry and dynamics. Our results reveal strong seasonal patterns that can be resolved at a 10-day timescale. In sring/summer we observe velocities that can increase by up to 300% compared to a slow winter period. This dynamics show a clear upglacier migration of the acceleration and results from the evolution of the subglacial drainage system. In fall, we observe a second episode of glacier acceleration that has been rarely observed. This episode is of shorter duration (1-2 months) than the spring/summer episodes, and often affects the lower part of the ablation zone with a clear down glacier migration. We suggest that it results from a pressurization of the drainage system in response to (1) rapid water input due to supraglacial pond drainage and/or (2) progressive closing of the drainage system at the end of the melt season. Our observations therefore allow to characterise the response of the subglacial drainage system and its influence on ice dynamics, to change in air temperature at a 10-day resolution and at a mountain range scale. Such observations are crucial to understand the response of glaciers to changes in climatic conditions.
It is possible to attend physically or to participate digitally at the seminar
Videolink to the lecture will be sent to the mailinglists alle@geo and geohyd-info@geo. If you want to subscribe to the geohyd-info@geo list send an email to Anita.
This lecture use Zoom | Download the Zoom Client for Meetings
About the seminar
This seminar is offered by the Section for Geography and Hydrology, Dept. of Geosciences, University of Oslo. The GEOHYD-seminars are announced as lunch seminars so bring your lunch if you want to.
The seminars are open for everyone interested, and especially students are welcome.
The Lunch Seminar Team
– Louise and Henning