scholarly journals Seasonal ice dynamics in the lower ablation zone of Dagongba Glacier, southeastern Tibetan Plateau, from multitemporal UAV images

2021 ◽  
pp. 1-15
Author(s):  
Yin Fu ◽  
Qiao Liu ◽  
Guoxiang Liu ◽  
Bo Zhang ◽  
Rui Zhang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Seasonal Dynamics ◽  
Warm Season ◽  
Cold Season ◽  
Surface Elevation ◽  
Surface Velocity ◽  
Ablation Zone ◽  
Glacier Surface ◽  
Ice Dynamics ◽  
Southeastern Tibetan Plateau

Abstract Most glaciers on the Tibetan Plateau have experienced continuous mass losses in response to global warming. However, the seasonal dynamics of glaciers on the southeastern Tibetan Plateau have rarely been reported in terms of glacier surface elevation and velocity. This paper presents a first attempt to explore the seasonal dynamics of the debris-covered Dagongba Glacier within the southeastern Tibetan Plateau. We use the multitemporal unoccupied aerial vehicle images collected over the lower ablation zone on 8 June and 17 October 2018, and 13 May 2019, and then perform an analysis concerning climatic fluctuations. The results reveal that the mean surface elevation decrease of the Dagongba Glacier during the warm season ( $2.81\pm 0.44$ m) was remarkably higher than the cold season ( $0.72\pm 0.45$ m). Particularly notable glacier surface elevation changes were found around supraglacial lakes and ice cliffs where ice ablation rates were $\sim$ 3 times higher than the average. In addition, a larger longitudinal decline of glacier surface velocity was observed in the warm season than that in the cold season. In terms of further comparative analysis, the Dagongba Glacier experienced a decrease in surface velocity between 1982–83 and 2018–19, with a decrease in the warm season possibly twice as large as that in the cold season.

scholarly journals Seasonal Dynamics of a Temperate Tibetan Glacier Revealed by High-Resolution UAV Photogrammetry and In Situ Measurements

2020 ◽  
Vol 12 (15) ◽  
pp. 2389
Author(s):  
Wei Yang ◽  
Chuanxi Zhao ◽  
Matthew Westoby ◽  
Tandong Yao ◽  
Yongjie Wang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Warm Season ◽  
Cold Season ◽  
Seasonal Dynamic ◽  
Surface Elevation ◽  
The Tibetan Plateau ◽  
Ablation Zone ◽  
Spring Precipitation ◽  
Ice Surface ◽  
Seasonal Signals

The seasonal dynamic changes of Tibetan glaciers have seen little prior investigation, despite the increase in geodetic studies of multi-year changes. This study compares seasonal glacier dynamics (“cold” and “warm” seasons) in the ablation zone of Parlung No. 4 Glacier, a temperate glacier in the monsoon-influenced southeastern Tibetan Plateau, by using repeat unpiloted aerial vehicle (UAV) surveys combined with Structure-from-Motion (SfM) photogrammetry and ground stake measurements. Our results showed that the surveyed ablation zone had a mean change of −2.7 m of ice surface elevation during the period of September 2018 to October 2019 but is characterized by significant seasonal cyclic variations with ice surface elevation lifting (+2.0 m) in the cold season (September 2018 to June 2019) but lowering (−4.7 m) in the warm season (June 2019 to October 2019). Over an annual timescale, surface lowering was greatly suppressed by the resupply of ice from the glacier’s accumulation area—the annual emergence velocity compensates for about 55% of surface ablation in our study area. Cold season emergence velocities (3.0 ± 1.2 m) were ~5-times larger than those observed in the warm season (0.6 ± 1.0 m). Distinct spring precipitation patterns may contribute to these distinct seasonal signals. Such seasonal dynamic conditions are possibly critical for different glacier responses to climate change in this region of the Tibetan Plateau, and perhaps further afield.

scholarly journals Influence of recent warming and ice dynamics on glacier surface elevations in the Canadian High Arctic, 1995–2014

2018 ◽  
Vol 64 (245) ◽  
pp. 450-464 ◽  
Author(s):  
COLLEEN A. MORTIMER ◽  
MARTIN SHARP ◽  
WESLEY VAN WYCHEN
Keyword(s):  
Land Surface ◽  
High Arctic ◽  
Surface Elevation ◽  
Surface Velocity ◽  
Glacier Surface ◽  
Ice Dynamics ◽  
Thickness Change ◽  
Near Surface ◽  
Elevation Changes ◽  
Moderate Resolution Imaging Spectroradiometer

ABSTRACTRepeat airborne laser altimetry measurements show widespread thinning (surface lowering) of glaciers in Canada's Queen Elizabeth Islands since 1995. Thinning rates averaged for 50 m elevation bins, were more than three times higher during the period 2005/06 to 2012/14 pentad than during the previous two pentads. Strongly negative thickness change (dh/dt) anomalies from 2005/06 to 2012/14, relative to the 1995–2012/14 mean, suggest that most of the measured thinning occurred during the most recent 5–6 year period when mean summer land surface temperatures (LSTs) were anomalously high and the mean summer black-sky shortwave broadband albedos (BSA) were anomalously low, relative to the 2000/01–15/16 period, and upper-air (700 hPa) and near surface (2 m) air temperatures were between 0.8°C and 1.5°C higher than 1995–2012 mean. Comparisons of dh/dt with mean summer LST and BSA measurements from the Moderate Resolution Imaging Spectroradiometer and with surface longitudinal strain rates computed from surface velocity fields derived from RADARSAT 1/2 and Landat-7 ETM + data suggest that surface elevation changes were driven mainly by changes in climate. An exception to this occurs along many fast-flowing outlet glaciers where ice dynamics appear also to have played an important role in surface elevation changes.

scholarly journals Variations in the surface velocity of an alpine cirque glacier

2018 ◽  
Vol 64 (248) ◽  
pp. 969-976 ◽  
Author(s):  
J. W. SANDERS ◽  
K. M. CUFFEY ◽  
K. R. MACGREGOR ◽  
J. L. KAVANAUGH ◽  
C. F. DOW
Keyword(s):  
Water System ◽  
Heavy Rain ◽  
Temporal Variations ◽  
Surface Velocity ◽  
Channel Network ◽  
Glacier Surface ◽  
Ice Dynamics ◽  
Speed Up ◽  
Water Volumes ◽  
One Year

ABSTRACTFollowing pioneering work in Norway, cirque glaciers have widely been viewed as rigidly rotating bodies. This model is incorrect for basin-filling cirque glaciers, as we have demonstrated at West Washmawapta Glacier, a small glacier in the Canadian Rocky Mountains. Here we report observations at the same glacier that assess whether complex temporal variations of flow also occur. For parts of three summers, we measured daily displacements of the glacier surface. In one year, four short-duration speed-up events were recorded. Three of the events occurred during the intervals of warmest weather, when melt was most rapid; the fourth event occurred immediately following heavy rain. We interpret the speed-up events as manifestations of enhanced water inputs to the glacier bed and associated slip lubrication by increased water volumes and pressures. No further speed-ups occurred in the final month of the melt season, despite warm temperatures and several rainstorms; the dominant subglacial water system likely transformed from one of poorly connected cavities to one with an efficient channel network. The seasonal evolution of hydrology and flow resembles behaviors documented at other, larger temperate glaciers and indicates that analyses of cirque erosion cannot rely on simple assumptions about ice dynamics.

scholarly journals Seasonal Surface Change of Urumqi Glacier No. 1, Eastern Tien Shan, China, Revealed by Repeated High-Resolution UAV Photogrammetry

2021 ◽  
Vol 13 (17) ◽  
pp. 3398
Author(s):  
Puyu Wang ◽  
Hongliang Li ◽  
Zhongqin Li ◽  
Yushuo Liu ◽  
Chunhai Xu ◽  
...  
Keyword(s):  
Tien Shan ◽  
Surface Elevation ◽  
Surface Velocity ◽  
Elevation Change ◽  
The West ◽  
Glacier Surface ◽  
Surface Change ◽  
Ablation Area ◽  
Glacier Terminus ◽  
Surface Changes

The seasonal surface changes of glaciers in Tien Shan have seen little prior investigation despite the increase in geodetic studies of multi-year changes. In this study, we analyzed the potential of an Unmanned Aerial Vehicle (UAV) to analyze seasonal surface change processes of the Urumqi Glacier No. 1 in eastern Tien Shan. We carried out UAV surveys at the beginning and the end of the ablation period in 2018. The high-precision evolution of surface elevation, geodetic mass changes, surface velocity, and terminus change in the surveyed ablation area were correspondingly derived in combination with ground measurements, including stake/snow-pit observation and GPS measurement. The derived mean elevation change in the surveyed ablation area was −1.64 m, corresponding to the geodetic mass balance of approximately −1.39 m w.e. during the ablation period in 2018. The mean surface velocity was 3.3 m/yr and characterized by the spatial change of the velocity, which was less in the East Branch than in the West Branch. The UAV survey results were a little less than those from the ground measurements, and the correlation coefficient was 0.88 for the surface elevation change and 0.87 for surface displacement. The relative error of the glacier terminus change was 4.5% for the East Branch and 6.2% for the West Branch. These results show that UAV photogrammetry is ideal for assessing seasonal glacier surface changes and has a potential application in the monitoring of detailed glacier changes.

scholarly journals Debris cover and the thinning of Kennicott Glacier, Alaska, Part C: feedbacks between melt, ice dynamics, and surface processes

2019 ◽  
Author(s):  
Leif S. Anderson ◽  
William H. Armstrong ◽  
Robert S. Anderson ◽  
Pascal Buri
Keyword(s):  
Mass Balance ◽  
Lower Limb ◽  
Surface Velocity ◽  
Glacier Surface ◽  
Ice Dynamics ◽  
Part C ◽  
High Resolution Imagery ◽  
Debris Cover ◽  
Process Domains

Abstract. The mass balance of many valley glaciers is enhanced by the presence of melt hotspots within otherwise continuous debris cover. We assess the effect of debris, melt hotspots, and ice dynamics on the thinning of Kennicott Glacier in three companion papers. In Part A we report in situ measurements from the debris-covered tongue. In Part B, we develop a method to delineate ice cliffs using high-resolution imagery and produce distributed mass balance estimates. Here in Part C we describe feedbacks controlling rapid thinning under thick debris. Despite the extreme abundance of ice cliffs on Kennicott Glacier, average melt rates are strongly suppressed downglacier due to thick debris. The estimated melt pattern therefore appears to reflect Østrem’s curve (the debris thickness-melt relationship). As Kennicott Glacier has thinned over the last century Østrem’s curve has manifested itself in two process domains on the glacier surface. The portion of the glacier affected by the upper-limb of Østrem’s curve corresponds to high melt, melt gradients, and ice dynamics, as well as high ice cliff and stream occurrence. The portion of the glacier affected by the lower-limb of Østrem’s curve corresponds to low melt, melt gradients, and ice dynamics, as well as high ice cliff and stream occurrence. The upglacier end of the zone of maximum thinning on Kennicott Glacier occurs at the boundary between these process domains and the bend in Østrem’s curve. The expansion of debris upglacier appears to be linked to changes in the surface velocity pattern through time. In response to climate warming, debris itself may therefore control where rapid thinning occurs on debris-covered glaciers. Ice cliffs are most abundant at the upglacier end of the zone of maximum thinning.

scholarly journals Isotopic constraints on atmospheric sulfate formation pathways in the Mt. Everest region, southern Tibetan Plateau

2021 ◽  
Author(s):  
Kun Wang ◽  
Shohei Hattori ◽  
Mang Lin ◽  
Sakiko Ishino ◽  
Becky Alexander ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Warm Season ◽  
Cold Season ◽  
Sulfur Cycle ◽  
Formation Mechanisms ◽  
The Tibetan Plateau ◽  
Sampling Campaign ◽  
Water Ph ◽  
Southern Tibetan Plateau ◽  
Sulfate Formation

Abstract. As an important atmosphere constituent, sulfate aerosols exert profound impacts on climate, ecological environment, and human health. The Tibetan Plateau (TP), identified as the Third Pole, contains the largest land ice masses outside the poles and has attracted wide attention on its environment and climatic change. However, the mechanisms of sulfate formation in this specific region remain poorly characterized. Oxygen-17 anomaly (Δ17O) has been used as a probe to constrain the relative importance of different pathways leading to sulfate formation. Here, we report the Δ17O values in atmospheric sulfate collected at a remote site in the Mt. Everest region to decipher the possible formation mechanisms of sulfate in such a pristine environment. Throughout the sampling campaign (April–September 2018), the Δ17O in non-dust sulfate show an average of 1.7 ± 0.5 ‰ which is higher than most existing data in modern atmospheric sulfate. The seasonality of Δ17O in non-dust sulfate exhibits high values in the pre-monsoon and low values in the monsoon, opposite to the seasonality in Δ17O for both sulfate and nitrate (i.e., minima in warm season and maxima in cold season) observed from diverse geographic sites. This high Δ17O in non-dust sulfate found in this region clearly indicates the important role of the S(IV) + O3 pathway in atmospheric sulfate formation promoted by high cloud water pH condition. Overall, our study provides an observational constraint on atmospheric acidity in altering sulfate formation pathways particularly in dust-rich environments, and such identification of key processes provides an important basis for a better understanding of the sulfur cycle in the TP.

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