Ice tectonics during the rapid tapping of a supraglacial lake on the Greenland Ice Sheet

Abstract. The hydraulic fracture of ice during the rapid tapping of supraglacial lakes is proposed as one mechanism to establish efficient surface-to-bed hydraulic pathways through kilometre-thick ice. This study presents detailed records of lake discharge, ice motion, and passive seismicity capturing the behaviour and processes preceding, during and following the rapid (~2 h) tapping of a large (~4 km2) supraglacial lake through 1.1 km of the western margin of the Greenland Ice Sheet. Peak discharge (3300 m3s−1) was coincident with maximal rates of horizontal displacement and vertical uplift, indicating that surface water accessed the ice-bed interface causing widespread hydraulic separation and enhanced basal motion. The differential motion of four GPS located around the lake, record the opening and closure of fractures suggesting that on short time-scales the brittle fracture of ice dominates ice flow. We hypothesise that during lake tapping, drainage occurred through a ~3 km long longitudinal fracture with a mean width of ~0.4 m. The perennial location of the supraglacial lake and the observed pattern of fracturing and surface uplift evince control by the local subglacial topography and the gradient of hydraulic potential. Our observations support the assertion that water-filled crevasses can propagate without longitudinal extension. The tapping of the lake coincided with the rapid drainage of a cluster of supraglacial lakes located within the same elevation band coincident with a notable and isolated peak in the catchment-wide, proglacial Watson River hydrograph.

Download Full-text

Seasonally evolving hydraulic transmissivity beneath Greenland supraglacial lakes

10.21203/rs.3.rs-104092/v1 ◽

2020 ◽

Author(s):

Ching-Yao Lai ◽

Laura Stevens ◽

Danielle Chase ◽

Timothy Creyts ◽

Mark Behn ◽

...

Keyword(s):

Ice Sheet ◽

Drainage System ◽

Greenland Ice Sheet ◽

Dye Tracing ◽

Surface Uplift ◽

Supraglacial Lakes ◽

Drainage Networks ◽

Order Of Magnitude ◽

Novel Method ◽

Lake Drainage

Abstract Surface meltwater reaching the base of the Greenland Ice Sheet transits through drainage networks, modulating the flow of the ice sheet. Dye-tracing studies indicate that drainage efficiency evolves seasonally along the drainage pathway. However, the local evolution of drainage systems further inland, where ice thicknesses exceed 1000 m, remains largely unknown. Here, we develop a novel method to infer transmissivity of the drainage system based on surface uplift relaxation following rapid lake drainage events. Combining field observations of five lake drainage events with a mathematical model and laboratory experiments, we show that the surface uplift decreases exponentially with time, as the water in the blister formed beneath the drained lake permeates through the subglacial drainage system. This deflation obeys a universal relaxation law with a timescale that reveals hydraulic transmissivity and indicates a two-order-of-magnitude increase in subglacial transmissivity as the melt season progresses, suggesting significant changes in basal hydrology beneath the lakes.

Download Full-text

Hydraulic transmissivity inferred from ice-sheet relaxation following Greenland supraglacial lake drainages

Nature Communications ◽

10.1038/s41467-021-24186-6 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Ching-Yao Lai ◽

Laura A. Stevens ◽

Danielle L. Chase ◽

Timothy T. Creyts ◽

Mark D. Behn ◽

...

Keyword(s):

Laboratory Experiments ◽

Ice Sheet ◽

Drainage System ◽

Greenland Ice Sheet ◽

Field Observations ◽

Surface Uplift ◽

Drainage Networks ◽

Order Of Magnitude ◽

Lake Drainage ◽

Magnitude Increase

AbstractSurface meltwater reaching the base of the Greenland Ice Sheet transits through drainage networks, modulating the flow of the ice sheet. Dye and gas-tracing studies conducted in the western margin sector of the ice sheet have directly observed drainage efficiency to evolve seasonally along the drainage pathway. However, the local evolution of drainage systems further inland, where ice thicknesses exceed 1000 m, remains largely unknown. Here, we infer drainage system transmissivity based on surface uplift relaxation following rapid lake drainage events. Combining field observations of five lake drainage events with a mathematical model and laboratory experiments, we show that the surface uplift decreases exponentially with time, as the water in the blister formed beneath the drained lake permeates through the subglacial drainage system. This deflation obeys a universal relaxation law with a timescale that reveals hydraulic transmissivity and indicates a two-order-of-magnitude increase in subglacial transmissivity (from 0.8 ± 0.3 $${\rm{m}}{{\rm{m}}}^{3}$$ m m 3 to 215 ± 90.2 $${\rm{m}}{{\rm{m}}}^{3}$$ m m 3 ) as the melt season progresses, suggesting significant changes in basal hydrology beneath the lakes driven by seasonal meltwater input.

Download Full-text

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

Frontiers in Earth Science ◽

10.3389/feart.2020.00370 ◽

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.

Download Full-text

Use of Remote-Sensing Data in Modelling Run-Off from the Greenland Ice Sheet

Annals of Glaciology ◽

10.1017/s0260305500000641 ◽

1987 ◽

Vol 9 ◽

pp. 215-217 ◽

Cited By ~ 5

Author(s):

H.H. Thomsen ◽

R.J. Braithwaite

Keyword(s):

Drainage Basin ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Remote Sensing Data ◽

Landsat Data ◽

Local Surface ◽

Drainage Patterns ◽

Lack Of Information ◽

Run Off ◽

Subglacial Topography

Run-off modelling is needed in Greenland to extend the short series of measurements. However, the delineation of hydrological basins on the Greenland ice sheet is difficult because of the lack of information about surface and subglacial drainage patterns. Low Sun-angle Landsat data have been used for mapping local surface features which has led to an improvement in basin delineations and thereby run-off simulations. Work is now in progress to map subglacial topography by electromagnetic reflection (EMR) from a helicopter. This information will be used for calculating hydraulic potentials within the basin and to assess the possibilities of future changes in drainage-basin delineation.

Download Full-text

A comparison of supraglacial lake observations derived from MODIS imagery at the western margin of the Greenland ice sheet

Journal of Glaciology ◽

10.3189/2013jog13j064 ◽

2013 ◽

Vol 59 (218) ◽

pp. 1179-1188 ◽

Cited By ~ 23

Author(s):

Amber A. Leeson ◽

Andrew Shepherd ◽

Aud V. Sundal ◽

A. Malin Johansson ◽

Nick Selmes ◽

...

Keyword(s):

Satellite Imagery ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Automated Classification ◽

Temporal Sampling ◽

Supraglacial Lakes ◽

Modis Imagery ◽

Single Dataset ◽

Average Size

AbstractSupraglacial lakes (SGLs) affect the dynamics of the Greenland ice sheet by storing runoff and draining episodically. We investigate the evolution of SGLs as reported in three datasets, each based on automated classification of satellite imagery. Although the datasets span the period 2001–10, there are differences in temporal sampling, and only the years 2005–07 are common. By subsampling the most populous dataset, we recommend a sampling frequency of one image per 6.5 days in order to minimize uncertainty associated with poor temporal sampling. When compared with manual classification of satellite imagery, all three datasets are found to omit a sizeable (29, 48 and 41 %) fraction of lakes and are estimated to document the average size of SGLs to within 0.78, 0.48 and 0.95 km2. We combine the datasets using a hierarchical scheme, producing a single, optimized, dataset. This combined record reports up to 67% more lakes than a single dataset. During 2005–07, the rate of SGL growth tends to follow the rate at which runoff increases in each year. In 2007, lakes drain earlier than in 2005 and 2006 and remain absent despite continued runoff. This suggests that lakes continue to act as open surface–bed conduits following drainage.

Download Full-text

Characterizing englacial drainage in the ablation zone of the Greenland ice sheet

Journal of Glaciology ◽

10.3189/002214308786570854 ◽

2008 ◽

Vol 54 (187) ◽

pp. 567-578 ◽

Cited By ~ 80

Author(s):

Ginny A. Catania ◽

Thomas A. Neumann ◽

Stephen F. Price

Keyword(s):

Simulation Model ◽

Strong Correlation ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Surface Velocity ◽

Ablation Zone ◽

Moderate Correlation ◽

Supraglacial Lakes ◽

Infill Material ◽

Englacial Drainage

AbstractRapid, local drainage of surface meltwater to the base of the Greenland ice sheet is thought to result in surface velocity variations as far inland as the equilibrium zone (Zwally and others, 2002). Ice-penetrating radar surveys throughout this region allow us to characterize englacial drainage features that appear as vertically stacked diffraction hyperbolae in common-offset profiles. These data are used with a radar-simulation model, which allows for variations in geometry, penetration depth and infill material, to understand the characteristics of these hyperbolae and the likelihood that they are produced by moulins. We find only a moderate correlation between the locations of these possible moulins and supraglacial lakes, indicating that many lakes drain over the surface of the ice sheet, or do not contain sufficient water to reach the bed through moulin formation. We find a strong correlation between moulin location in the ablation region and elevated along-flow tension (due to flow over rough bedrock), which generates surface crevassing and provides an entry point for meltwater. Although theory suggests that moulins may form anywhere on the ice sheet given sufficient meltwater input, our data suggest that they are far more common in the ablation zone than near, or inland from, the equilibrium line.

Download Full-text

The trough-system algorithm and its application to spatial modeling of Greenland subglacial topography

Annals of Glaciology ◽

10.3189/2014aog67a001 ◽

2014 ◽

Vol 55 (67) ◽

pp. 115-126 ◽

Cited By ~ 2

Author(s):

Ute C. Herzfeld ◽

Brian W. McDonald ◽

Bruce F. Wallin ◽

Phillip A. Chen ◽

Helmut Mayer ◽

...

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Algebraic Topology ◽

Dynamic Models ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Ice Dynamics ◽

Subglacial Topography ◽

Radar Measurements ◽

Elevation Model

AbstractDynamic ice-sheet models are used to assess the contribution of mass loss from the Greenland ice sheet to sea-level rise. Mass transfer from ice sheet to ocean is in a large part through outlet glaciers. Bed topography plays an important role in ice dynamics, since the acceleration from the slow-moving inland ice to an ice stream is in many cases caused by the existence of a subglacial trough or trough system. Problems are that most subglacial troughs are features of a scale not resolved in most ice-sheet models and that radar measurements of subglacial topography do not always reach the bottoms of narrow troughs. The trough-system algorithm introduced here employs mathematical morphology and algebraic topology to correctly represent subscale features in a topographic generalization, so the effects of troughs on ice flow are retained in ice-dynamic models. The algorithm is applied to derive a spatial elevation model of Greenland subglacial topography, integrating recently collected radar measurements (CReSIS data) of the Jakobshavn Isbræ, Helheim, Kangerdlussuaq and Petermann glacier regions. The resultant JakHelKanPet digital elevation model has been applied in dynamic ice-sheet modeling and sea-level-rise assessment.

Download Full-text

Wintertime storage of water in buried supraglacial lakes across the Greenland Ice Sheet

The Cryosphere Discussions ◽

10.5194/tcd-8-3999-2014 ◽

2014 ◽

Vol 8 (4) ◽

pp. 3999-4031 ◽

Cited By ~ 2

Author(s):

L. S. Koenig ◽

D. J. Lampkin ◽

L. N. Montgomery ◽

S. L. Hamilton ◽

J. B. Turrin ◽

...

Keyword(s):

Mass Loss ◽

Total Mass ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Subsurface Water ◽

Blue Color ◽

Total Mass Loss ◽

Supraglacial Lakes ◽

Hydrologic System ◽

Surface Melt

Abstract. Surface melt over the Greenland Ice Sheet (GrIS) is increasing and estimated to account for half or more of the total mass loss. Little, however, is known about the hydrologic pathways that route surface melt within the ice sheet. In this study, we present over-winter storage of water in buried supraglacial lakes as one hydrologic pathway for surface melt, referred to as buried lakes. Airborne radar echograms are used to detect the buried lakes that are distributed extensively around the margin of the GrIS. The subsurface water can persist through multiple winters and is, on average, ~4.2 + 0.4 m below the surface. The few buried lakes that are visible at the surface of the GrIS have a~unique visible signature associated with a darker blue color where subsurface water is located. The volume of retained water in the buried lakes is likely insignificant compared to the total mass loss from the GrIS but the water will have important implications locally for the development of the englacial hydrologic network, ice temperature profiles and glacial dynamics. The buried lakes represent a small but year-round source of meltwater in the GrIS hydrologic system.

Download Full-text

Use of Remote-Sensing Data in Modelling Run-Off from the Greenland Ice Sheet

Annals of Glaciology ◽

10.3189/s0260305500000641 ◽

1987 ◽

Vol 9 ◽

pp. 215-217

Author(s):

H.H. Thomsen ◽

R.J. Braithwaite

Keyword(s):

Drainage Basin ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Remote Sensing Data ◽

Landsat Data ◽

Local Surface ◽

Drainage Patterns ◽

Lack Of Information ◽

Run Off ◽

Subglacial Topography

Download Full-text

The 4DGreenland project: Greenland hydrology assessment from remote sensing

10.5194/egusphere-egu21-10728 ◽

2021 ◽

Author(s):

Louise Sandberg Sørensen ◽

Keyword(s):

European Space Agency ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Regional Warming ◽

Supraglacial Lakes ◽

Space Agency ◽

Subglacial Lakes ◽

Global Sea Level ◽

Project Objectives ◽

Response To Temperature

The high latitudes of the Northern Hemisphere have&#160;experienced the largest regional warming over the last decades.&#160;On the Greenland ice sheet, rapid changes are observed in response to temperature increase, with the amount of liquid water at the surface particularly increasing. Understanding Greenland&#8217;s ice sheet hydrology is essential to assess&#160; its contribution to global sea-level rise in a future warming climate.With the objective of maximizing the use of Earth Observation (EO) data, the European Space Agency (ESA) has funded the 2-year project 4DGreenland (https://4dgreenland.eo4cryo.dk/) to assess and quantify the hydrology of the Greenland ice sheet. The project is focused on dynamic variations in the hydrological components of the ice sheet, and on quantifying the water fluxes between reservoirs including surface melt, supraglacial lakes and rivers, and subglacial melt and lakes. Efforts will focus on a thorough analysis of various components of the hydrological network in selected test regions and their impact on ice sheet flow. 4DGreenland started in September 2020. Here, we will present the project objectives, methods, and show initial results obtained within the project such as a comparison of supraglacial lake depths from optical imagery and ICESat-2 altimetry data, estimation of basal melt water production, and identification and mapping of surface meltwater presence and subglacial lakes from EO data.&#160;

Download Full-text