scholarly journals Modelling channelized surface drainage of supraglacial lakes

2015 ◽  
Vol 61 (225) ◽  
pp. 185-199 ◽  
Author(s):  
J. Kingslake ◽  
F. Ng ◽  
A. Sole
Keyword(s):  
Surface Water ◽  
Ice Sheets ◽  
Frictional Heat ◽  
Lake Area ◽  
Ice Dynamics ◽  
Surface Drainage ◽  
Supraglacial Lakes ◽  
Lake Model ◽  
Lake Drainage ◽  
Area Expansion

AbstractSupraglacial lakes can drain to the bed of ice sheets, affecting ice dynamics, or over their surface, relocating surface water. Focusing on surface drainage, we first discuss observations of lake drainage. In particular, for the first time, lakes are observed to drain >70 km across the Nivlisen ice shelf, East Antarctica. Inspired by these observations, we develop a model of lake drainage through a channel that incises into an ice-sheet surface by frictional heat dissipated in the flow. Modelled lake drainage can be stable or unstable. During stable drainage, the rate of lake-level drawdown exceeds the rate of channel incision, so discharge from the lake decreases with time; this can prevent the lake from emptying completely. During unstable drainage, discharge grows unstably with time and always empties the lake. Model lakes are more prone to drain unstably when the initial lake area, the lake input and the channel slope are larger. These parameters will vary during atmospheric-warming-induced ablation-area expansion, hence the mechanisms revealed by our analysis can influence the dynamic response of ice sheets to warming through their impact on surface-water routing and storage.

scholarly journals Investigating Controls on the Formation and Distribution of Wintertime Storage of Water in Supraglacial Lakes

2020 ◽  
Vol 8 ◽  
Author(s):  
Derrick Julius Lampkin ◽  
Lora Koenig ◽  
Casey Joseph ◽  
Jason Eric Box
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Lake Area ◽  
Channel Networks ◽  
Supraglacial Lakes ◽  
Lake Model ◽  
Temporal Occurrence ◽  
Atmospheric Factors ◽  
And Behavior ◽  
Percolation Zone

Supraglacial lakes over the Greenland Ice Sheet can demonstrate multi-model drainage states. Lakes can demonstrate incomplete drainage, where residual melt can become buried under ice and snow and survive throughout the winter. We evaluate atmospheric factors that influence the propensity for the formation of buried lakes over the ice sheet. We examine the spatial and temporal occurrence and behavior of buried lakes over the Jakobshavn Isbrae and Zachariae Isstrøm outlet basins and assess the magnitude of insolation necessary to preserve melt water using a numerical lake model from 2009 to 2012. Buried lakes tend to occur at higher elevations within the ablation zone and those present at elevations > 1000 m tend to reoccur over several seasons. Lakes without buried water are relatively small (∼1 km2), whereas lakes with buried water are larger (∼6–10 km2). Lake area is correlated with the number of seasons sub-surface water persists. Buried lakes are relatively deep and associated with complex supraglacial channel networks. Winter stored water could be a precursor to the formation of supraglacial channels. Simulations of the insulation potential of accumulated snow and ice on the surface of lakes indicate substantial regional differences and inter-annual variability. With the possibility of inland migration of supraglacial lakes, buried lakes could be important in the evolution of ablation/percolation zone hydrology.

scholarly journals Modelled present and future thaw lake area expansion/contraction trends throughout the continuous permafrost zone

2014 ◽  
Vol 8 (4) ◽  
pp. 3603-3627 ◽  
Author(s):  
Y. Mi ◽  
J. van Huissteden ◽  
A. J. Dolman
Keyword(s):  
Greenhouse Gas ◽  
Ground Subsidence ◽  
Permafrost Degradation ◽  
Lake Area ◽  
Dominant Feature ◽  
Lake Drainage ◽  
Area Expansion ◽  
Thaw Lakes ◽  
Lake Dynamics ◽  
Lake Basins

Abstract. Thaw lakes and drained lake basins are a dominant feature of Arctic lowlands. Thaw lakes are a source of the greenhouse gas methane (CH4), which is produced under anaerobic conditions, while drained lake basins are carbon sinks due to sedimentation. Besides feedbacks on climate, the development of thaw lakes due to the melt-out of ground ice and subsequent ground subsidence, can have significant impacts on the regional morphology, hydrology, geophysics and biogehemistry. Permafrost degradation as a result of climate warming, which is proceeding considerably faster in high latitude regions than the global average, could lead to either an increases in lake area due to lake expansion, or decrease due to lake drainage. However, which process will dominate is elusive. Therefore understanding thaw lake dynamics and quantifying the feedbacks related to thaw lake expansion and contraction are urgent questions to solve. We apply a stochastic model, THAWLAKE, on four representative Arctic sites, to reproduce recent lake dynamics (1963–2012) and predict for the future changes under various anticipated climate scenarios. The model simulations of current thaw lake cycles and expansion rates are comparable with data. Future lake expansions are limited by lake drainage. We suggest further improvements in the area of enhancing the hydrology component, and operation on larger scales to gauge the impacts on lacustrine morphology and greenhouse gas emissions.

scholarly journals Seasonal Evolution of Supraglacial Lakes on Baltoro Glacier From 2016 to 2020

2021 ◽  
Vol 9 ◽  
Author(s):  
Anna Wendleder ◽  
Andreas Schmitt ◽  
Thilo Erbertseder ◽  
Pablo D’Angelo ◽  
Christoph Mayer ◽  
...  
Keyword(s):  
Time Series ◽  
Standardized Precipitation Index ◽  
Remote Sensing Data ◽  
Lake Area ◽  
Reanalysis Dataset ◽  
Ice Dynamics ◽  
Seasonal Evolution ◽  
Supraglacial Lakes ◽  
Lake Evolution ◽  
Observation Period

The existence of supraglacial lakes influences debris-covered glaciers in two ways. The absorption of solar radiation in the water leads to a higher ice ablation, and water draining through the glacier to its bed leads to a higher velocity. Rising air temperatures and changes in precipitation patterns provoke an increase in the supraglacial lakes in number and total area. However, the seasonal evolution of supraglacial lakes and thus their potential for influencing mass balance and ice dynamics have not yet been sufficiently analyzed. We present a summertime series of supraglacial lake evolution on Baltoro Glacier in the Karakoram from 2016 to 2020. The dense time series is enabled by a multi-sensor and multi-temporal approach based on optical (Sentinel-2 and PlanetScope) and Synthetic Aperture Radar (SAR; Sentinel-1 and TerraSAR-X) remote sensing data. The mapping of the seasonal lake evolution uses a semi-automatic approach, which includes a random forest classifier applied separately to each sensor. A combination of linear regression and the Hausdorff distance is used to harmonize between SAR- and optical-derived lake areas, producing consistent and internally robust time series dynamics. Seasonal variations in the lake area are linked with the Standardized Precipitation Index (SPI) and Standardized Temperature Index (STI) based on air temperature and precipitation data derived from the climate reanalysis dataset ERA5-Land. The largest aggregated lake area was found in 2018 with 5.783 km2, followed by 2019 with 4.703 km2, and 2020 with 4.606 km2. The years 2016 and 2017 showed the smallest areas with 3.606 and 3.653 km2, respectively. Our data suggest that warmer spring seasons (April–May) with higher precipitation rates lead to increased formation of supraglacial lakes. The time series decomposition shows a linear increase in the lake area of 11.12 ± 9.57% per year. Although the five-year observation period is too short to derive a significant trend, the tendency for a possible increase in the supraglacial lake area is in line with the pronounced positive anomalies of the SPI and STI during the observation period.

scholarly journals Development and application of a time-lapse photograph analysis method to investigate the link between tidewater glacier flow variations and supraglacial lake drainage events

2013 ◽  
Vol 59 (214) ◽  
pp. 287-302 ◽  
Author(s):  
Brad Danielson ◽  
Martin Sharp
Keyword(s):  
Time Lapse ◽  
Velocity Variation ◽  
Lake Area ◽  
Flow Acceleration ◽  
Supraglacial Lakes ◽  
Glacier Terminus ◽  
Tidewater Glacier ◽  
Glacier Flow ◽  
Lake Drainage ◽  
Time Lapse Photography

AbstractMarine-terminating glaciers may experience seasonal and short-term flow variations, which can impact rates of ice flux through the glacier terminus. We explore the relationship between variability in the flow of a large tidewater glacier (Belcher Glacier, Nunavut, Canada), the seasonal cycle of surface meltwater production and the rapid drainage of supraglacial lakes. We demonstrate a novel method for analyzing time-lapse photography to quantify lake area change rates (a proxy for net filling and drainage rates) and develop a typology of lake drainage styles. GPS records of ice motion reveal four flow acceleration events which can be linked to lake drainage events discovered in the time-lapse photography. These events are superimposed on a longer pattern of velocity variation that is linked to seasonal variation in surface melting. At the terminus of the glacier, the ice displacement associated with the lake drainage events constitutes ∼10% of the seasonally accelerated displacement or 0.4% of the total annual ice displacement (336 m a−1). While the immediate ice response to these individual perturbations may be small, these drainage events may enhance overall seasonal acceleration by opening and/or sustaining meltwater conduits to the glacier bed.

scholarly journals A Novel Method for Automated Supraglacial Lake Mapping in Antarctica Using Sentinel-1 SAR Imagery and Deep Learning

2021 ◽  
Vol 13 (2) ◽  
pp. 197
Author(s):  
Mariel Dirscherl ◽  
Andreas J. Dietz ◽  
Christof Kneisel ◽  
Claudia Kuenzer
Keyword(s):  
Mass Loss ◽  
Ice Sheets ◽  
Greenland Ice Sheet ◽  
Detection Algorithm ◽  
Training Data ◽  
Ice Dynamics ◽  
Supraglacial Lakes ◽  
Spatio Temporal ◽  
Sar Imagery ◽  
Sentinel 2

Supraglacial meltwater accumulation on ice sheets can be a main driver for accelerated ice discharge, mass loss, and global sea-level-rise. With further increasing surface air temperatures, meltwater-induced hydrofracturing, basal sliding, or surface thinning will cumulate and most likely trigger unprecedented ice mass loss on the Greenland and Antarctic ice sheets. While the Greenland surface hydrological network as well as its impacts on ice dynamics and mass balance has been studied in much detail, Antarctic supraglacial lakes remain understudied with a circum-Antarctic record of their spatio-temporal development entirely lacking. This study provides the first automated supraglacial lake extent mapping method using Sentinel-1 synthetic aperture radar (SAR) imagery over Antarctica and complements the developed optical Sentinel-2 supraglacial lake detection algorithm presented in our companion paper. In detail, we propose the use of a modified U-Net for semantic segmentation of supraglacial lakes in single-polarized Sentinel-1 imagery. The convolutional neural network (CNN) is implemented with residual connections for optimized performance as well as an Atrous Spatial Pyramid Pooling (ASPP) module for multiscale feature extraction. The algorithm is trained on 21,200 Sentinel-1 image patches and evaluated in ten spatially or temporally independent test acquisitions. In addition, George VI Ice Shelf is analyzed for intra-annual lake dynamics throughout austral summer 2019/2020 and a decision-level fused Sentinel-1 and Sentinel-2 maximum lake extent mapping product is presented for January 2020 revealing a more complete supraglacial lake coverage (~770 km2) than the individual single-sensor products. Classification results confirm the reliability of the proposed workflow with an average Kappa coefficient of 0.925 and a F1-score of 93.0% for the supraglacial water class across all test regions. Furthermore, the algorithm is applied in an additional test region covering supraglacial lakes on the Greenland ice sheet which further highlights the potential for spatio-temporal transferability. Future work involves the integration of more training data as well as intra-annual analyses of supraglacial lake occurrence across the whole continent and with focus on supraglacial lake development throughout a summer melt season and into Antarctic winter.

scholarly journals Assessing Climate Change Trends and Their Relationships with Alpine Vegetation and Surface Water Dynamics in the Everest Region, Nepal

Atmosphere ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 987
Author(s):  
Mana Raj Rai ◽  
Amnat Chidthaisong ◽  
Chaiwat Ekkawatpanit ◽  
Pariwate Varnakovida
Keyword(s):  
Climate Change ◽  
Surface Water ◽  
River Basin ◽  
Climate Impacts ◽  
Glacial Lake ◽  
Annual Precipitation ◽  
Series Data ◽  
Lake Area ◽  
Alpine Vegetation ◽  
Koshi River Basin

The Himalayas, especially the Everest region, are highly sensitive to climate change. Although there are research works on this region related to cryospheric work, the ecological understandings of the alpine zone and climate impacts are limited. This study aimed to assess the changes in surface water including glacier lake and streamflow and the spatial and temporal changes in alpine vegetation and examine their relationships with climatic factors (temperature and precipitation) during 1995–2019 in the Everest region and the Dudh Koshi river basin. In this study, Landsat time-series data, European Commission’s Joint Research Center (JRC) surface water data, ECMWF Reanalysis 5th Generation (ERA5) reanalysis temperature data, and meteorological station data were used. It was found that the glacial lake area and volume are expanding at the rates of 0.0676 and 0.0198 km3/year, respectively; the average annual streamflow is decreasing at the rate of 2.73 m3/s/year. Similarly, the alpine vegetation greening as indicated by normalized difference vegetation index (NDVI) is increasing at the rate of 0.00352 units/year. On the other hand, the annual mean temperature shows an increasing trend of 0.0329 °C/year, and the annual precipitation also shows a significant negative monotonic trend. It was also found that annual NDVI is significantly correlated with annual temperature. Likewise, the glacial lake area expansion is strongly correlated with annual minimum temperature and annual precipitation. Overall, we found a significant alteration in the alpine ecosystem of the Everest region that could impact on the water–energy–food nexus of the Dudh Koshi river basin.

The response of large ice sheets to climatic change

1992 ◽  
Vol 338 (1285) ◽  
pp. 235-242 ◽  
Keyword(s):  
Mass Balance ◽  
Sea Level ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Sea Level Change ◽  
Mixing Ratio ◽  
Ice Dynamics ◽  
Environmental Models ◽  
Level Change ◽  
The Antarctic

The prediction of short-term (100 year) changes in the mass balance of ice sheets and longer-term (1000 years) variations in their ice volumes is important for a range of climatic and environmental models. The Antarctic ice sheet contains between 24 M km 3 and 29 M km 3 of ice, equivalent to a eustatic sea level change of between 60m and 72m. The annual surface accumulation is estimated to be of the order of 2200 Gtonnes, equivalent to a sea level change of 6 mm a -1 . Analysis of the present-day accumulation regime of Antarctica indicates that about 25% ( ca. 500 Gt a -1 ) of snowfall occurs in the Antarctic Peninsula region with an area of only 6.8% of the continent. To date most models have focused upon solving predictive algorithms for the climate-sensitivity of the ice sheet, and assume: (i) surface mass balance is equivalent to accumulation (i.e. no melting, evaporation or deflation); (ii) percentage change in accumulation is proportional to change in saturation mixing ratio above the surface inversion layer; and (iii) there is a linear relation between mean annual surface air tem perature and saturation mixing ratio. For the A ntarctic Peninsula with mountainous terrain containing ice caps, outlet glaciers, valley glaciers and ice shelves, where there can be significant ablation at low levels and distinct climatic regimes, models of the climate response must be more complex. In addition, owing to the high accumulation and flow rates, even short- to medium -term predictions must take account of ice dynamics. Relationships are derived for the mass balance sensitivity and, using a model developed by Hindmarsh, the transient effects of ice dynamics are estimated. It is suggested that for a 2°C rise in mean annual surface tem perature over 40 years, ablation in the A ntarctic Peninsula region would contribute at least 1.0 mm to sea level rise, offsetting the fall of 0.5 mm contributed by increased accum ulation.

scholarly journals Winter drainage of surface lakes on the Greenland Ice Sheet from Sentinel-1 SAR imagery

2021 ◽  
Vol 15 (3) ◽  
pp. 1587-1606
Author(s):  
Corinne L. Benedek ◽  
Ian C. Willis
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Shape From Shading ◽  
Lake Area ◽  
Ice Flow ◽  
Surface Mass ◽  
Flow Acceleration ◽  
Optical Imagery ◽  
Sar Imagery ◽  
Lake Drainage

Abstract. Surface lakes on the Greenland Ice Sheet play a key role in its surface mass balance, hydrology and biogeochemistry. They often drain rapidly in the summer via hydrofracture, which delivers lake water to the ice sheet base over timescales of hours to days and then can allow meltwater to reach the base for the rest of the summer. Rapid lake drainage, therefore, influences subglacial drainage evolution; water pressures; ice flow; biogeochemical activity; and ultimately the delivery of water, sediments and nutrients to the ocean. It has generally been assumed that rapid lake drainage events are confined to the summer, as this is typically when observations are made using satellite optical imagery. Here we develop a method to quantify backscatter changes in satellite radar imagery, which we use to document the drainage of six different lakes during three winters (2014/15, 2015/16 and 2016/17) in fast-flowing parts of the Greenland Ice Sheet. Analysis of optical imagery from before and after the three winters supports the radar-based evidence for winter lake drainage events and also provides estimates of lake drainage volumes, which range between 0.000046 ± 0.000017 and 0.0200 ± 0.002817 km3. For three of the events, optical imagery allows repeat photoclinometry (shape from shading) calculations to be made showing mean vertical collapse of the lake surfaces ranging between 1.21 ± 1.61 and 7.25 ± 1.61 m and drainage volumes of 0.002 ± 0.002968 to 0.044 ± 0.009858 km3. For one of these three, time-stamped ArcticDEM strips allow for DEM differencing, which demonstrates a mean collapse depth of 2.17 ± 0.28 m across the lake area. The findings show that lake drainage can occur in the winter in the absence of active surface melt and notable ice flow acceleration, which may have important implications for subglacial hydrology and biogeochemical processes.

scholarly journals Marine Ice Sheet Instability and Ice Shelf Buttressing Influenced Deglaciation of the Minch Ice Stream, Northwest Scotland

2018 ◽  
Author(s):  
Niall Gandy ◽  
Lauren J. Gregoire ◽  
Jeremy C. Ely ◽  
Christopher D. Clark ◽  
David M. Hodgson ◽  
...  
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Last Deglaciation ◽  
Ice Shelf ◽  
Dynamical Processes ◽  
Ice Dynamics ◽  
Surface Mass ◽  
Ice Shelves ◽  
Ice Stream ◽  
The Last Deglaciation

Abstract. Uncertainties in future sea level projections are dominated by our limited understanding of the dynamical processes that control instabilities of marine ice sheets. A valuable case to examine these processes is the last deglaciation of the British-Irish Ice Sheet. The Minch Ice Stream, which drained a large proportion of ice from the northwest sector of the British-Irish Ice Sheet during the last deglaciation, is well constrained, with abundant empirical data which could be used to inform, validate and analyse numerical ice sheet simulations. We use BISICLES, a higher-order ice sheet model, to examine the dynamical processes that controlled the retreat of the Minch Ice Stream. We simulate retreat from the shelf edge under constant "warm" surface mass balance and subshelf melt, to isolate the role of internal ice dynamics from external forcings. The model simulates a slowdown of retreat as the ice stream becomes laterally confined at a "pinning-point" between mainland Scotland and the Isle of Lewis. At this stage, the presence of ice shelves became a major control on deglaciation, providing buttressing to upstream ice. Subsequently, the presence of a reverse slope inside the Minch Strait produces an acceleration in retreat, leading to a "collapsed" state, even when the climate returns to the initial "cold" conditions. Our simulations demonstrate the importance of the Marine Ice Sheet Instability and ice shelf buttressing during the deglaciation of parts of the British-Irish Ice Sheet. Thus, geological data could be used to constrain these processes in ice sheet models used for projecting the future of our contemporary ice sheets.

Simulasi Perancangan Drainase Muka Tanah pada Bandar Udara Achmad Yani Semarang Sebagai Salah Satu Usaha Pencegahan Banjir

WARTA ARDHIA ◽  
2013 ◽  
Vol 39 (4) ◽  
pp. 305-316
Author(s):  
Ataline Muliasari ◽  
Lupi Wahyuningsih
Keyword(s):  
Surface Water ◽  
Cross Section ◽  
Land Surface ◽  
Drainage Channel ◽  
Water Drainage ◽  
Hydraulic Radius ◽  
Channel Depth ◽  
Cross Sectional ◽  
Surface Drainage ◽  
Sectional Shape

Drainage is defined as surface water drainage, either by gravity or by pump which aims to prevent inundation, maintain and lower the water level im order to avoid the amount of water. Ahmad Yani Airport has a poor drainage systems. Furthermore, land subsidence in Semarang area potential for experiencing flooding when the rainy season with a fairly high rainfall. Based on the results of processing the data showed that it is needed the land surface drainage channel with a cross-sectional shape of a trapezium. When the width of the base of the cross section is 3 meters , then the required channel depth is 3.9 meters with a hydraulic radius is 0.82-meter, and hydraulic depth is 3.05 meters. Drainase didefinisikan sebagai pembuangan air permukaan, baik secara gravitasi maupun dengan pompa yang bertujuan untuk mencegah terjadinya genangan, menjaga dan menurunkan permukaan air sehingga genangan air dapat dihindarkan. Bandar Udara Ahmad Yani dengan kondisi sistem drainase yang kurang baik dan penurunan permukaan tanah di wilayah Semarang, maka bila musim penghujan tiba dengan curah hujan yang cukup tinggi selalu berpotensi untuk mengalami banjir. Berdasarkan hasil pengolahan data juga didapatkan hasil bahwa untuk menyesuaikan antara curah hujan di wilayah Semarang dengan luas area Bandar udara Achmad Yani diperlukan saluran drainase muka tanah berupa saluran dengan bentuk penampang trapezium. Bila lebar dasar dari penampang trapezim tersebut adalah 3 meter, maka diperlukan saluran sedalam 3,9 meter dengan Jari-jari hydraulic 0,82 meter, dan kedalaman hydraulic 3,05 meter.

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