Southern Inylchek Glacier Research Articles

Simultaneous drainage events from supraglacial lakes on the southern Inylchek Glacier, Central Asia

AbstractTo understand the mechanism of simultaneous drainage event related to supraglacial lakes on a debris-covered glacier, we investigated water-level variations of supraglacial lakes on the southern Inylchek Glacier in Kyrgyzstan. To examine these variations, we used daily aerial images for 2017–2019 from an uncrewed aerial vehicle that were converted to 15 cm-digital surface models and ortho-images. Our main results are as follows: (1) When one lake drained, the water levels of other lakes simultaneously increased, indicating that drainage water is shared with several lakes through a main englacial conduit. In one drainage event, a branched off englacial conduit clearly connected to a main englacial conduit. (2) Sometimes several lakes discharged simultaneously, indicating that several lakes had connected to a main englacial conduit that had opened. Such cases can cause larger-scale drainage than that from the opening of a branched off englacial conduit. (3) Simultaneous drainage occurred twice in the same year, each time through a different conduit, indicating that the main englacial conduit can be abandoned and reused. (4) In some lakes, the water level on the hydraulic gradient line increased gradually with nearly the same increase rate just before drainage. Such an increase may be an indicator of a possible simultaneous drainage event.

Deriving a time series of 3D glacier motion to investigate interactions of a large mountain glacial system with its glacial lake: Use of Synthetic Aperture Radar Pixel Offset-Small Baseline Subset technique

We investigated the interactions of Lake Merzbacher with the Southern Inylchek Glacier (Central Tien Shan) using the Synthetic Aperture Radar (SAR) Pixel Offset-Small Baseline Subset (PO-SBAS) to derive a time series of three-dimensional (3D) glacier motion. The measurements of 3D glacier velocity were ∼17% more precise than a previous study that did not use the SBAS estimation. The velocities of the glacier were up to 58 cm/day east, 70 cm/day north, and 113 cm/day vertically. Combining these data with Landsat images indicated that movement of the glacier is sensitive to changes of Lake Merzbacher. Specifically, the entry of more lake water into the glacier during the ablation season increased englacial ablation due to thermal erosion. Moreover, ice calving begins when the lake water gradually lifts the ice dam. Calving can cause greater loss of glacier mass than normal ablation. Trying to replenish the front mass loss, the distributary accelerates and the mass loss further intensifies. A time series of the vertical velocity indicates that the glacier tongue has a huge englacial cavity. We suggest that the lake outburst is directly related to the crack of this cavity. Bursting of the lake triggers a mini-surge at the glacier tongue. The vertical velocity at the ice dam was ∼+60 cm/day before the lake outburst, and ∼−113 cm/day afterwards. After drainage of the lake, flow velocities at the distributary, do not sharply decrease because pre-drainage mass loss needs to be replenished by fast flow. Based on comparisons with previous measurements, our results indicate that the lake had an increasing influence on the glacier from 2005 to 2009. This study demonstrates that a time series of 3D glacier motion based on the PO-SBAS technique is effective for assessing the dynamics of a mountain glacial system and interactions with its glacial lake.

Seasonal drainage of supraglacial lakes on debris-covered glaciers in the Tien Shan Mountains, Central Asia

Using field surveys in 2013, 2014, and 2016 plus satellite data from the 1999–2015 period, we analyze the seasonal drainage cycle of supraglacial lakes on seven debris-covered glaciers in the central Tien Shan. We characterize this cycle by the number of lakes and their water levels. The cycle of the Southern Inylchek Glacier starts to increase in the beginning of April, reaches a maximum in May–June, and decreases sharply in June–July. The increase in April to June comes from an inflow of meltwater from snow and ice, and the subsequent decrease arises from a greater connectivity to the englacial drainage network. For the Southern Inylchek Glacier, 94% of the supraglacial lakes that exist and appear during 2013–2015 drain during all three years, indicating that most lakes could connect to the englacial drainage network for three years. Concerning the water level, lakes in close proximity and with the same base-level tend to synchronize their seasonal water levels through the englacial channels. Although the maximum water level of the three-year, field-measured lake is about the same from 2014 through 2016, the date of maximum water level varies between mid-May and mid-June. During this period, the lifetime and size of the supraglacial lakes are controlled by the timing of their connectivity to the englacial drainage network.

Mass changes of Southern and Northern Inylchek Glacier, Central Tian Shan, Kyrgyzstan, during ∼1975 and 2007 derived from remote sensing data

Abstract. Glacier melt is an essential source of freshwater for the arid regions surrounding the Tian Shan. However, the knowledge about glacier volume and mass changes over the last decades is limited. In the present study, glacier area, glacier dynamics and mass changes are investigated for the period ~1975–2007 for Southern Inylchek Glacier (SIG) and Northern Inylchek Glacier (NIG), the largest glacier system in Central Tian Shan separated by the regularly draining Lake Merzbacher. The area of NIG increased by 2.0 ± 0.1 km2 (~1.3%) in the period ~1975–2007. In contrast, SIG has shrunk continuously in all investigated periods since ~1975. Velocities of SIG in the central part of the ablation region reached ~100–120 m a−1 in 2002/2003, which was slightly higher than the average velocity in 2010/2011. The central part of SIG flows mainly towards Lake Merzbacher rather than towards its terminus. The measured velocities at the distal part of the terminus downstream of Lake Merzbacher were below the uncertainty, indicating very low flow with even stagnant parts. Geodetic glacier mass balances have been calculated using multi-temporal digital elevation models from KH-9 Hexagon (representing the year 1975), SRTM3 (1999), ALOS PRISM (2006) and SPOT-5 high-resolution geometrical (HRG) data (2007). In general, a continuous mass loss for both SIG and NIG could be observed between ~1975 and 2007. SIG lost mass at a rate of 0.43 ± 0.10 m w.e. a−1 and NIG at a rate of 0.25 ± 0.10 m w.e. a−1 within the period ~1975–1999. For the period 1999–2007, the highest mass loss of 0.57 ± 0.46 m w.e. a−1 was found for NIG, whilst SIG showed a potential moderate mass loss of 0.28 ± 0.46 m w.e. a−1. Both glaciers showed a small retreat during this period. Between ~1975 and 1999, we identified a thickening at the front of NIG with a maximum surface elevation increase of about 150 m as a consequence of a surge event. In contrast significant thinning (>0.5 m a−1) and comparatively high velocities close to the dam of Lake Merzbacher were observed for SIG, indicating that Lake Merzbacher enhances glacier mass loss.

Sub‐debris melt rates on southern inylchek glacier, central tian shan

.Melt rates of glacier surfaces are strongly influenced by the existence of a debris cover. Dependent on thickness and other physical parameters, the debris layer can enhance or reduce ablation as compared to bare ice conditions. Supraglacial moraines appear very frequently on Central Asian glaciers, greatly affecting water yield from these high mountain regions. In summer 2005, a network of 22 ablation stakes was drilled into locations with varying debris thicknesses on southern Inylchek Glacier in the central Tian Shan. Mean ablation rates varied from 2.8 to 6.7 cm/day, strongly correlated with moraine thickness. Parallel observation of air temperature allowed the application of a simple degree‐day approach and the calculation of ablation rates. Efforts to improve calculations of melt rates by incorporating relative air humidity to account for latent heat fluxes failed. This proves that air temperature is already a very good melt indicator. Ice albedo measurements show that reflectivity might be controlled by the occurrence of evaporation or condensation, but this topic needs further investigation.

Post‐drainage ice dam response at lake merzbacher, inylchek glacier, kyrgyzstan

.The Inylchek glacier system in Central Tian Shan, Kyrgyzstan, comprises a large glacier‐dammed lake which usually drains once a year through a subglacial drainage system. Detailed GPS measurements on the ice dam and the analysis of Aster scenes from several subsequent years provide insight into the post‐drainage dam response and the changed ice dynamic conditions. We demonstrate that during high water levels in the lake a large part of the ice dam is afloat, lifting the ice surface up to almost 20 m in the central dam region. During this phase of extensive flotation strong calving is facilitated, which is supported by the high density of ice debris in the lake. In general, surface ice velocities are about 1.5‐2 times higher during summer than winter. Closer to the lake, however, ice velocities increase considerably after the drainage event, showing values more than three times the annual mean. The increased mass flux during the phase of high lake level needs to be compensated by replenishment of the lost ice from the dam. Therefore the ice velocities show compressive flow during the remaining part of the year. These results show that Southern Inylchek glacier is strongly influenced by the existence of the lake.

Glaciological results of the 2005 expedition to Inylchek Glacier, Central Tian Shan

Like many other glaciers in Central Asia, Southern Inylchek glacier in the Kyrgyz Tian Shan is covered by supraglacial moraine, which drastically influences melt rates and complicates the estimation of ablation. The quantification of sub-debris melt from simple parameters is still an unsolved problem, but also essential to predict future yield from high mountains. Snow cover and glacier ice are the main water storages for the surrounding arid lowlands and a better understanding of ablation processes is the prerequisite for a sustainable water resources management. Another interesting feature of Southern Inylchek glacier is the existence of an ice dammed lake in a tributary valley, which is drained regularly by outburst floods. Improvements in predicting these floods would lower the risk potential for the downstream population. The main objectives of a group of glaciologists which participated in an expedition to the glacier in 2005 were to investigate melt rates on debris covered glacier parts and to quantify the ice flux into the glacier lake. The results of their field experiments are reported in this paper.

Glacial regime of the highest Tien Shan mountain, Pobeda-Khan Tengry massif

AbstractMajor processes controlling the existence of a large sub-continental glacier system were identified on the basis of glaciological, meteorological and isotopic analyses using expeditionary and long-term data. Observations were made on the southern Inylchek glacier located in the Pobeda-Khan Tengry massif, the largest sub-continental glacier system on the northern periphery of central Asia. More than 1200 glaciers with a total area of about 4320 km2 comprise the massif. Melt is for the most part caused by radiation and is most intensive during periods of anticyclonic weather with fohn development. The proportion of solar radiation input in relation to heat balance is more than 90%. Evaporation and condensation are negligible during most times and comprise 7% of heat expenditure. Accumulation was associated with cold cyclonic weather. Four ice-formation zones were identified, the upper boundary of liquid runoff is at 5200 m and the recryslallization zone is above 5900 m. The calculated net glacier mass is negative, −318 kg m−2 a−1, and indicates the degradation of modern Pobeda-Khan Tengry glaciers.

Glacial regime of the highest Tien Shan mountain, Pobeda-Khan Tengry massif

AbstractMajor processes controlling the existence of a large sub-continental glacier system were identified on the basis of glaciological, meteorological and isotopic analyses using expeditionary and long-term data. Observations were made on the southern Inylchek glacier located in the Pobeda-Khan Tengry massif, the largest sub-continental glacier system on the northern periphery of central Asia. More than 1200 glaciers with a total area of about 4320 km2comprise the massif. Melt is for the most part caused by radiation and is most intensive during periods of anticyclonic weather with fohn development. The proportion of solar radiation input in relation to heat balance is more than 90%. Evaporation and condensation are negligible during most times and comprise 7% of heat expenditure. Accumulation was associated with cold cyclonic weather. Four ice-formation zones were identified, the upper boundary of liquid runoff is at 5200 m and the recryslallization zone is above 5900 m. The calculated net glacier mass is negative, −318 kg m−2a−1, and indicates the degradation of modern Pobeda-Khan Tengry glaciers.