Analyses of UAV and GNSS based flow velocity variations of the rock glacier Lazaun (Ötztal Alps, South Tyrol, Italy)

Rock glaciers are geomorphological phenomena of mountain permafrost which slowly move downslope as a consequence of the ice deformation. During the last few decades, many rock glaciers in the Alps are showing an increase of flow velocities which is most probably caused by climate change. However, the factors influencing the flow velocities (e.g. air temperature, meltwater infiltration, internal rock glacier characteristics) are not fully understood. Data about the annual, inter-annual and diurnal rock glacier flow velocities are essential to understand the influence of climatic factors on rock glaciers.This study focused on the Finstertal rock glacier, located in the Eastern Alps, where flow velocities are reconstructed since the 1970s based on aerial imagery, airborne and terrestrial laser scan data. Since 2014, a terrestrial laser scanning (TLS) based monitoring is implemented. The maximum flow velocities of the Finstertal rock glacier increased from 0.1 m/year (time period 1970-1997) to 1.4 m/year (time period 2015-2016) and is currently about 1.3 m/ year (time period 2018-2019).The accuracy of aerial imagery and laser scan data is in the range of centimetres and well suited to analyse the annual variability of rock glaciers. Imagery and laser scan data are not suited for shorter time intervals, where the absolute displacement of a rock glacier is smaller than the measurement accuracy. Consequently, for the understanding of interannual and diurnal variations in rock glacier flow velocities, other measurement methods are needed. Ground-based interferometric synthetic aperture radar (GBInSAR) is able to detect spatial deformations in the range of sub-centimeters.Therefore, to get a more detailed understanding of the rock glacier flow velocity variations, a GBInSAR was installed on Finstertal hydroelectric dam to measure the rock glacier flow velocities between October to November 2019. In this study, preliminary results on diurnal flow velocity variations of Finstertal rock glacier, based on GBInSAR, are presented, and compared to annual variations derived from aerial imagery and laser scan data.

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Short-term velocity variations at three rock glaciers and their relationship with meteorological conditions

Earth Surface Dynamics ◽

10.5194/esurf-4-103-2016 ◽

2016 ◽

Vol 4 (1) ◽

pp. 103-123 ◽

Cited By ~ 35

Author(s):

V. Wirz ◽

S. Gruber ◽

R. S. Purves ◽

J. Beutel ◽

I. Gärtner-Roer ◽

...

Keyword(s):

Pore Water Pressure ◽

Water Pressure ◽

Ground Surface ◽

Climatic Conditions ◽

Water Infiltration ◽

High Temporal Resolution ◽

Rock Glacier ◽

Short Term ◽

Rock Glaciers ◽

Velocity Variations

Abstract. In recent years, strong variations in the speed of rock glaciers have been detected, raising questions about their stability under changing climatic conditions. In this study, we present continuous time series of surface velocities over 3 years of six GPS stations located on three rock glaciers in Switzerland. Intra-annual velocity variations are analysed in relation to local meteorological factors, such as precipitation, snow(melt), and air and ground surface temperatures. The main focus of this study lies on the abrupt velocity peaks, which have been detected at two steep and fast-moving rock glacier tongues ( ≥  5 m a−1), and relationships to external meteorological forcing are statistically tested.The continuous measurements with high temporal resolution allowed us to detect short-term velocity peaks, which occur outside cold winter conditions, at these two rock glacier tongues. Our measurements further revealed that all rock glaciers experience clear intra-annual variations in movement in which the timing and the amplitude is reasonably similar in individual years. The seasonal decrease in velocity was typically smooth, starting 1–3 months after the seasonal decrease in temperatures, and was stronger in years with colder temperatures in mid winter. Seasonal acceleration was mostly abrupt and rapid compared to the winter deceleration, always starting during the zero curtain period. We found a statistically significant relationship between the occurrence of short-term velocity peaks and water input from heavy precipitation or snowmelt, while no velocity peak could be attributed solely to high temperatures. The findings of this study further suggest that, in addition to the short-term velocity peaks, the seasonal acceleration is also influenced by water infiltration, causing thermal advection and an increase in pore water pressure. In contrast, the amount of deceleration in winter seems to be mainly controlled by winter temperatures.

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Mesenteric flow velocity variations as a function of angle of insonation

Journal of Vascular Surgery ◽

10.1016/0741-5214(90)90215-v ◽

1990 ◽

Vol 11 (5) ◽

pp. 688-694 ◽

Cited By ~ 47

Author(s):

Robert J. Rizzo ◽

Gail Sandager ◽

Patricia Astleford ◽

Kathleen Payne ◽

Linda Peterson-Kennedy ◽

...

Keyword(s):

Flow Velocity ◽

Velocity Variations

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The flow of Fireweed rock glacier, Alaska, U.S.A.

Journal of Glaciology ◽

10.3189/172756504781830213 ◽

2004 ◽

Vol 50 (168) ◽

pp. 76-86 ◽

Cited By ~ 11

Author(s):

Adam K. Bucki ◽

Keith A. Echelmeyer

Keyword(s):

Mass Balance ◽

Rectangular Channel ◽

Shear Plane ◽

Rock Glacier ◽

South Central ◽

Glacier Ice ◽

Internal Deformation ◽

Velocity Variations

AbstractFireweed rock glacier is a large rock glacier in south central Alaska, U.S.A. It flows relatively fast, with velocities up to 3.5 ma–1, and exhibits both seasonal and annual velocity variations, some of which are related to periodic terminus calving and increased rainfall. Our analysis reveals that motion is likely concentrated in a pseudo-rectangular channel within the larger parabolic channel with a “shear plane” at ~27 m depth. There is likely motion along the shear plane as well as internal deformation above it. We estimate that the ice—rock mixture is up to seven times softer than clean glacier ice with a temperature of –2°C. Calving at the terminus is an important component of the mass balance of this rock glacier.

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