/pdf/modelling-outburst-floods-from-moraine-dammed-glacial-lakes-1c5qr1h3yb.pdf

Modelling outburst floods from moraine-dammed glacial lakes

https://repositorio.ul.pt/bitstream/10451/36205/1/Oliva%20Marc_2017%283%29.pdf

Recent regional climate cooling on the Antarctic Peninsula and associated impacts on the cryosphere.

The meltwater released by the glaciers in the Central Tien Shan feeds in particular the Tarim River which is the main artery for the oases at the northern margin of the Taklamakan desert. The correct assessment of the contribution of the glaciers' meltwater to the total runoff is hampered by the lack of long-term measurements of glacier mass budgets. Digital terrain models (DTMs) for the different regions in the Central Tien Shan were generated based on ~ 1975 KH-9 Hexagon imagery and compared to the SRTM3 DTM acquired in February 2000. Moreover, glacier area changes for the period ~ 1975–2008 have been measured by means of multi-temporal optical satellite imagery. The geodetic mass budget estimates for a glacierized area of 5000 km 2 revealed increasing mass loss east to west and from the inner to the outer ranges. Highest mass loss accompanied by the most pronounced glacier retreat was found for the Ak-Shirak massif with a region-wide mass balance of − 0.51 ± 0.36 m w.e. a − 1 and a rate of area change of − 0.27 ± 0.15% a − 1 , whilst moderate mass loss was observed for the Inylchek (0.20 ± 0.44 m w.e. a − 1 ) and Tomur area (0.33 ± 0.30 m w.e. a − 1 ) despite partly debris cover. These latter regions also revealed the lowest glacier shrinkage within the entire Central Tien Shan. The total glacier mass loss of 0.35 ± 0.34 m w.e. a − 1 is, however, within the global average whilst the glacier area shrinkage is comparatively low. On average, the investigated glacierized area of ~ 6600 km 2 shrank by 0.11 ± 0.15% a − 1 only. We could also identify several surge-type glaciers. The results are consistent with in-situ mass balance measurements for Karabatkak Glacier and previously published results of the Ak-Shirak range proving the suitability of declassified imagery for glacier change investigations. The contribution to the runoff of Aksu River, the largest tributary of the Tarim River, due to glacier imbalance has been determined at ~ 20% for the 1975–2000 period.

Region-wide glacier mass budgets and area changes for the Central Tien Shan between ~ 1975 and 1999 using Hexagon KH-9 imagery

Like in many other parts of the world, the glaciers in northern Tien Shan are receding, and the permafrost is thawing. Concomitantly, glacial lakes are developing. Historically, outbursts of these glacial lakes have resulted in severe hazards for infrastructures and livelihood. Multi-temporal space imageries are an ideal means to study and monitor glaciers and glacial lakes over large areas. Geomorphometric analysis and modelling allows to estimate the potential danger for glacial lake outburst floods (GLOFs). This paper presents a comprehensive approach by coupling of remote sensing, geomorphometric analyses aided with GIS modelling for the identification of potentially dangerous glacial lakes. We suggest a classification scheme based on an additive ratio scale in order to prioritise sites for detailed investigations. The identification and monitoring of glacial lakes was carried out semi-automatically using band ratioing and the normalised difference water index (NDWI) based on multi-temporal space imagery from the years 1971 to 2008 using Corona, ASTER and Landsat data. The results were manually edited when required. The probability of the growth of a glacial lake was estimated by analysing glacier changes, glacier motion and slope analysis. A permafrost model was developed based on geomorphometric parameters, solar radiation and regionalised temperature conditions which permitted to assess the influence of potential permafrost thawing. Finally, a GIS-based model was applied to simulate the possibly affected area of lake outbursts. The findings of this study indicate an increasing number and area of glacial lakes in the northern Tien Shan region. We identified several lakes with a medium to high potential for an outburst after a classification according to their outburst probability and their downstream impact. These lakes should be investigated more in detail.

Identification of potentially dangerous glacial lakes in the northern Tien Shan

Changes of glacial lakes and implications were assessed for the Tian Shan Mountains from 1990 to 2010, based on Landsat Thematic Mapper/Enhanced Thematic Mapper Plus images. The total area of glacial lakes has expanded greatly over the last 20 years, at an average rate of 0.69 ± 0.12 km2 a−1 or 0.8 ± 0.1% a−1. Eastern Tian Shan contributed nearly half that increase (≈0.34 ± 0.03 km2 a−1), followed by northern Tian Shan at 0.17 ± 0.03 km2 a−1. Both widespread climate warming and glacier shrinking led to glacial lake areal expansion, while small to medium (<0.6 km2) lakes responded most sensitively to glacier retreat. The closer the hydrologic connection of lakes to glaciers, the greater the areal expansion rate. An average ≈0.007 ± 0.002 Gt a−1 of glacier meltwater has been temporarily held in lakes over the past two decades. The increasing quantity of melt available for lake formation and growth may simultaneously increase the frequency and damage of glacial lake outburst floods or debris flows in this region. Sixty potentially dangerous glacial lakes are identified, among which 12 have an outburst probability status of ‘high’, 25 ‘medium’ and 23 ‘low’.

https://iopscience.iop.org/article/10.1088/1748-9326/8/4/044052/pdf

Changes of glacial lakes and implications in Tian Shan, central Asia, based on remote sensing data from 1990 to 2010

This study describes the origin, bedrock geology, geomorphology, hydrological stability and physical and chemical characteristics of a representative set of 29 lakes in the ice-free parts of the Ulu Peninsula, James Ross Island, located close to the northern tip of the Antarctic Peninsula. Based on these features, six different types of lakes were defined: stable shallow lakes on higher-altitude levelled surfaces, shallow coastal lakes, stable lakes in old moraines, small unstable lakes in young moraines, deep cirque lakes and kettle lakes. We observed a significant relationship between lake type and water chemistry. Bedrock, lake age and morphometry together with altitude were the most important factors underlying the observed limnological variability. Our results further suggested possible nitrogen limitation in the lake ecosystems. However, physical factors such as low temperature and light were also likely to be limiting.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0954102012000934

Freshwater lakes of Ulu Peninsula, James Ross Island, north-east Antarctic Peninsula: origin, geomorphology and physical and chemical limnology

Outburst flood hazard: Case studies from the Tien-Shan Mountains, Kyrgyzstan

An interdisciplinary study of glacier-related hazards in the Petrov lake region (Ak-Shiirak Range, the Inner Tien-Shan, Kyrgyzstan) has been undertaken to identify potential dangers to the area. A cooperative effort from experts in the fields of hydrology, glaciology, geomorphology and geophysics has been employed in this study. For the hazard assessment, evolution of the Petrov glacier and lake was reconstructed using historical reports, aerial photographs and satellite images. Geomorphological mapping and geophysical soundings was applied to the lake territory and the moraine dam. This has identified potentially hazardous areas of the dam including subsurface drainage zones and cracks that could cause a sudden extremely high discharge. In the past three decades, the Petrov lake has doubled in size, while in recent years, its area has been increasing by more than 92,000 square metres per year. Although there is no evidence for an imminent outburst, the dramatic increase in the lake’s size emphasizes the importance of this study.

/pdf/the-evolution-of-petrov-lake-and-moraine-dam-rupture-risk-1dshlcfq9t.pdf

The evolution of Petrov lake and moraine dam rupture risk (Tien-Shan, Kyrgyzstan)

The unique environment of the most acidified permanently meromictic lake in the Czech Republic

A combination of remotely sensed data, field mapping, bathymetric survey and geophysical soundings is used to describe the recent changes in the terminal area of Petrov glacier, the largest glacier in the Akshiirak massif, central Tien Shan. According to our results, three periods of accelerated glacier retreat (1977-80, 1990-95 and 2008-09) can be distinguished since 1977. The largest recession occurred in 1990-95 when the glacier retreated by 54 ± 8ma-1. Accelerated glacier retreat affected the enlargement rate of Petrov lake, which increased by 0.04-0.1 km2 a-1 and by 1.3-2.2 × 106m3a-1 in the last three decades. Since 1995, the mean annual retreat rate of the lake-calving northern glacier section has been up to three times higher than the retreat rate of the land-terminating southern section. The calving flux ranged from 2.5 to 4.6 × 106m3a-1 in 2003-09, resulting in a total glacier mass loss of (17.7 ± 0.4) × 106m3. The calving terminus of Petrov glacier was >65 m thick in 2009 according to ground-penetrating radar measurements.

/pdf/changes-of-petrov-glacier-and-its-proglacial-lake-in-the-53k93tlovn.pdf

Miroslav Šobr

Papers

Freshwater lakes of Ulu Peninsula, James Ross Island, north-east Antarctic Peninsula: origin, geomorphology and physical and chemical limnology

Outburst flood hazard: Case studies from the Tien-Shan Mountains, Kyrgyzstan

The evolution of Petrov lake and moraine dam rupture risk (Tien-Shan, Kyrgyzstan)

The unique environment of the most acidified permanently meromictic lake in the Czech Republic

Changes of Petrov glacier and its proglacial lake in the Akshiirak massif, central Tien Shan, since 1977