scholarly journals A fully-coupled 3D model of a large Greenlandic outlet glacier with evolving subglacial hydrology, frontal plume melting and calving

2021 ◽  
pp. 1-17
Author(s):  
Samuel J. Cook ◽  
Poul Christoffersen ◽  
Joe Todd
Keyword(s):  
Distributed System ◽  
3D Model ◽  
Drainage System ◽  
Ice Flow ◽  
Outlet Glacier ◽  
Dynamic Memory ◽  
Tidewater Glaciers ◽  
West Greenland ◽  
Tidewater Glacier ◽  
Fully Coupled

Abstract We present the first fully coupled 3D full-Stokes model of a tidewater glacier, incorporating ice flow, subglacial hydrology, plume-induced frontal melting and calving. We apply the model to Store Glacier (Sermeq Kujalleq) in west Greenland to simulate a year of high melt (2012) and one of low melt (2017). In terms of modelled hydrology, we find perennial channels extending 5 km inland from the terminus and up to 41 and 29 km inland in summer 2012 and 2017, respectively. We also report a hydrodynamic feedback that suppresses channel growth under thicker ice inland and allows water to be stored in the distributed system. At the terminus, we find hydrodynamic feedbacks exert a major control on calving through their impact on velocity. We show that 2012 marked a year in which Store Glacier developed a fully channelised drainage system, unlike 2017, where it remained only partially developed. This contrast in modelled behaviour indicates that tidewater glaciers can experience a strong hydrological, as well as oceanic, control, which is consistent with observations showing glaciers switching between types of behaviour. The fully coupled nature of the model allows us to demonstrate the likely lack of any hydrological or ice-dynamic memory at Store Glacier.

scholarly journals A fully-coupled 3D model of a large Greenlandic outlet glacier with evolving subglacial hydrology, frontal plume melting and calving

2021 ◽  
Author(s):  
Samuel Cook ◽  
Poul Christoffersen ◽  
Joe Todd
Keyword(s):  
Distributed System ◽  
3D Model ◽  
Drainage System ◽  
Ice Flow ◽  
Outlet Glacier ◽  
Dynamic Memory ◽  
Tidewater Glaciers ◽  
West Greenland ◽  
Tidewater Glacier ◽  
Fully Coupled

We present the first fully coupled 3D full-Stokes model of a tidewater glacier, incorporating ice flow, subglacial hydrology, plume-induced frontal melting and calving. We apply the model to Store Glacier (Sermeq Kujalleq) in west Greenland to simulate a year of high melt (2012) and one of low melt (2017). In terms of modelled hydrology, we find perennial channels extending 5 km inland fromthe terminus and up to 41 km and 29 km inland in summer 2012 and 2017, respectively. We also report a hydrodynamic feedback that suppresses channel growth under thicker ice inland and allows water to be stored in the distributed system. At the terminus, we find hydrodynamic feedbacks exert a major control on calving through their impact on velocity. We show that 2012 marked a year inwhich Store Glacier developed a fully channelised drainage system, unlike 2017, where it remained only partially developed. This contrast in modelled behaviour indicates that tidewater glaciers can experience a strong hydrological, as well as oceanic, control, which is consistent with observations showing glaciers switching between seemingly dominant types. The fully coupled nature of the model allows us to demonstrate the likely lack of any hydrological or ice-dynamic memory at Store.

scholarly journals Rapidly-changing subglacial hydrology pathways at a tidewater glacier revealed through simultaneous observations of water pressure, supraglacial lakes, meltwater plumes and surface velocities

2017 ◽  
Author(s):  
Penelope How ◽  
Douglas I. Benn ◽  
Nicholas R. J. Hulton ◽  
Bryn Hubbard ◽  
Adrian Luckman ◽  
...  
Keyword(s):  
Water Pressure ◽  
Drainage System ◽  
Ice Flow ◽  
Tidewater Glaciers ◽  
Glacier Tongue ◽  
The North ◽  
Supraglacial Lakes ◽  
Tidewater Glacier ◽  
Lake Drainage ◽  
Subglacial Meltwater

Abstract. Subglacial hydrological processes at tidewater glaciers remain poorly understood due to the difficulty in obtaining direct measurements and lack of empirical verification for modelling approaches. Here, we investigate the subglacial hydrology of Kronebreen, a fast-flowing tidewater glacier in Svalbard during the 2014 melt season. We combine observations of water pressure, supraglacial lake drainage, surface velocities and plume activity with modelled runoff and water routing to develop a conceptual model that thoroughly encapsulates subglacial drainage at a tidewater glacier. Simultaneous measurements suggest that an early-season episode of subglacial flushing took place during our observation period, and a stable efficient drainage system effectively transported this water through the north region of the glacier tongue. Drainage pathways through the central/southern region of the glacier tongue were disrupted throughout the following melt season. Periodic plume activity at the terminus seems to be a signal for modulated subglacial pulsing i.e. an internally-driven storage and release of subglacial meltwater. This storage is a key control on ice flow in the 2014 melt season. Evidence from this work, and previous studies, strongly suggests that long-term changes in ice flow at Kronebreen are controlled by the location of efficient/inefficient drainage and the position of regions where water is stored and evacuated from.

A 3D full-Stokes model of Store Glacier, Greenland, with coupling of ice flow, subglacial hydrology, submarine melting and calving

2020 ◽  
Author(s):  
Samuel Cook ◽  
Poul Christoffersen ◽  
Joe Todd ◽  
Donald Slater ◽  
Nolwenn Chauché ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Water Pressure ◽  
Drainage System ◽  
Greenland Ice Sheet ◽  
Pressure System ◽  
Ice Flow ◽  
Tidewater Glaciers ◽  
Iceberg Calving ◽  
Subglacial Drainage

<p>Tidewater glaciers are complex systems, which present numerous modelling challenges with regards to integrating a multitude of environmental processes spanning different timescales. At the same time, an accurate representation of these systems in models is critical to being able to effectively predict the evolution of the Greenland Ice Sheet and the resulting sea-level rise. In this study, we present results from numerical simulations of Store Glacier in West Greenland that couple ice flow modelled by Elmer/Ice with subglacial hydrology modelled by GlaDS and submarine melting represented with a simple plume model forced by hydrographic observations. The simulations capture the seasonal evolution of the subglacial drainage system and the glacier’s response, and also include the influence of plume-induced ice front melting on calving and buttressing from ice melange present in winter and spring.</p><p>Through running the model for a 6-year period from 2012 to 2017, covering both high- and low-melt years, we find inputs of surface meltwater to the subglacial system establishes channelised subglacial drainage with channels >1 m<sup>2</sup> extending 30-60 km inland depending on the amount of supraglacial runoff evacuated subglacially. The growth of channels is, however, not sufficiently fast to accommodate all inputs of meltwater from the surface, which means that basal water pressures are generally higher in warmer summers compared to cooler summers and lowest in winter months. As a result, the simulated flow of Store Glacier is such that velocities peak in warmer summers, though we suggest that higher surface melt levels may lead to sufficient channelisation for a widespread low-water-pressure system to evolve, which would reduce summer velocities. The results indicate that Greenland’s contribution to sea-level rise is sensitive to the evolution of the subglacial drainage system and especially the ability of channels to grow and accommodate surface meltwater effectively. We also posit that the pattern of plume melting encourages further calving by creating an indented calving front with ‘headlands’ that are laterally unsupported and therefore more vulnerable to collapse. We validate our simulations with a three-week record of iceberg calving events gathered using a terrestrial radar interferometer installed near the calving terminus of Store Glacier.</p>

scholarly journals Basal melting beneath a fast-flowing temperate tidewater glacier

2013 ◽  
Vol 54 (63) ◽  
pp. 265-271 ◽  
Author(s):  
D.J. Alexander ◽  
T.R.H. Davies ◽  
J. Shulmeister
Keyword(s):  
Mass Balance ◽  
Published Data ◽  
Glacier Mass Balance ◽  
Glacier Surface ◽  
Ice Flow ◽  
Tidewater Glaciers ◽  
Tidewater Glacier ◽  
Order Of Magnitude ◽  
Basal Melting

AbstractThe role of melting at the base of temperate tidewater glaciers is rarely discussed, and its potential importance for total glacier mass balance and subglacial dynamics is often overlooked. We use Columbia Glacier, Alaska, USA, as an example of a temperate tidewater glacier to estimate the spatial distribution of basal melt due to friction both before and during the glacier’s well-documented retreat since the early 1980s. Published data on glacier surface and bed profiles, ice-flow velocities and surface melt were collated and used as input data for a two-dimensional basal melt model. We estimate that before the retreat of Columbia Glacier (pre-1980s), mean basal melt amounted to 61 mm a–1, increasing to 129 mma–1 during retreat (post-1980s). According to our calculations, basal melt accounts for 3% and 5% of total glacier melt for the pre-retreat and syn-retreat (i.e. during retreat) glacier profiles, respectively. These calculations of basal melt are an order of magnitude greater than those typically reported in polar glacier settings. Basal melting in temperate tidewater settings may be a non-negligible process affecting glacier mass balance and subglacial dynamics.

scholarly journals The Cordilleran Ice Sheet in Northern British Colombia

2007 ◽  
Vol 45 (3) ◽  
pp. 355-363 ◽  
Author(s):  
June M. Ryder ◽  
Denny Maynard
Keyword(s):  
Early Phase ◽  
Ice Sheet ◽  
Drainage System ◽  
Ice Flow ◽  
Outlet Glacier ◽  
Radiocarbon Dates ◽  
Coast Mountains ◽  
British Colombia ◽  
Late Wisconsinan ◽  
Cordilleran Ice Sheet

ABSTRACT Dates from lavas associated with tills and erratics indicate that ice-sheet glaciations occurred between 4 and 0.6 Ma BP. The few radiocarbon dates that are available suggest that the chronology of the Late Wisconsinan (Fraser Glaciation) ice sheet of northern British Columbia was similar to that of the southern part of the province. During what may have been a long, early phase of this glaciation, Glacial Lake Stikine was dammed by advancing valley glaciers in the Coast Mountains, and alpine glaciers developed on the intermontane plateau. At the climax of Fraser Glaciation, ice-flow patterns were dominated by outflow from a névé centred over the northern Skeena Mountains. Déglaciation occurred partly by frontal retreat of ice tongues and partly by downwasting of stagnant ice. Recessional moraines mark one or more resurgences or stillstands of the ice margin. During déglaciation, Stikine River valley was occupied by an active outlet glacier and a major subglacial drainage system.

scholarly journals A ten-year record of supraglacial lake evolution and rapid drainage in West Greenland using an automated processing algorithm for multispectral imagery

2013 ◽  
Vol 7 (4) ◽  
pp. 3543-3565 ◽  
Author(s):  
B. F. Morriss ◽  
R. L. Hawley ◽  
J. W. Chipman ◽  
L. C. Andrews ◽  
G. A. Catania ◽  
...  
Keyword(s):  
Surface Velocity ◽  
Lake Area ◽  
Ice Flow ◽  
Outlet Glacier ◽  
West Greenland ◽  
Subglacial Environment ◽  
Supraglacial Lakes ◽  
Automated Method ◽  
Modis Imagery ◽  
Glacier Flow

Abstract. The rapid drainage of supraglacial lakes introduces large pulses of meltwater to the subglacial environment and creates moulins, surface-to-bed conduits for future melt. Introduction of water to the subglacial system has been shown to affect ice flow, and modeling suggests that variability in water supply and delivery to the subsurface play an important role in the development of the subglacial hydrologic system and its ability to enhance or mitigate ice flow. We developed a fully automated method for tracking meltwater and rapid drainages in 78 large, perennial lakes along an outlet glacier flow band in West Greenland from 2002 to 2011 using ETM+ and MODIS imagery. Results indicate interannual variability in maximum coverage and spatial evolution of total lake area. We identify 238 rapid drainage events, occurring most often at low and middle elevations during periods of net filling or peak lake coverage. We observe a general progression of both lake filling and draining from lower to higher elevations but note that the timing of filling onset, peak coverage, and dissipation are also variable. While lake coverage is sensitive to air temperature, warm years exhibit greater variability in both coverage evolution and rapid drainage. Mid elevation drainages in 2011 coincide with large surface velocity increases at nearby GPS sites, though the relationships between iceshed-scale dynamics and meltwater input are still unclear.

scholarly journals Rapidly changing subglacial hydrological pathways at a tidewater glacier revealed through simultaneous observations of water pressure, supraglacial lakes, meltwater plumes and surface velocities

2017 ◽  
Vol 11 (6) ◽  
pp. 2691-2710 ◽  
Author(s):  
Penelope How ◽  
Douglas I. Benn ◽  
Nicholas R. J. Hulton ◽  
Bryn Hubbard ◽  
Adrian Luckman ◽  
...  
Keyword(s):  
Water Pressure ◽  
Drainage System ◽  
Northern Region ◽  
Ice Flow ◽  
Glacier Tongue ◽  
Run Off ◽  
Tidewater Glacier ◽  
Borehole Water ◽  
Lake Drainage ◽  
Subglacial Meltwater

Abstract. Subglacial hydrological processes at tidewater glaciers remain poorly understood due to the difficulty in obtaining direct measurements and lack of empirical verification for modelling approaches. Here, we investigate the subglacial hydrology of Kronebreen, a fast-flowing tidewater glacier in Svalbard during the 2014 melt season. We combine observations of borehole water pressure, supraglacial lake drainage, surface velocities and plume activity with modelled run-off and water routing to develop a conceptual model that thoroughly encapsulates subglacial drainage at a tidewater glacier. Simultaneous measurements suggest that an early-season episode of subglacial flushing took place during our observation period, and a stable efficient drainage system effectively transported subglacial water through the northern region of the glacier tongue. Drainage pathways through the central and southern regions of the glacier tongue were disrupted throughout the following melt season. Periodic plume activity at the terminus appears to be a signal for modulated subglacial pulsing, i.e. an internally driven storage and release of subglacial meltwater that operates independently of marine influences. This storage is a key control on ice flow in the 2014 melt season. Evidence from this work and previous studies strongly suggests that long-term changes in ice flow at Kronebreen are controlled by the location of efficient/inefficient drainage and the position of regions where water is stored and released.

scholarly journals A ten-year record of supraglacial lake evolution and rapid drainage in West Greenland using an automated processing algorithm for multispectral imagery

2013 ◽  
Vol 7 (6) ◽  
pp. 1869-1877 ◽  
Author(s):  
B. F. Morriss ◽  
R. L. Hawley ◽  
J. W. Chipman ◽  
L. C. Andrews ◽  
G. A. Catania ◽  
...  
Keyword(s):  
Surface Velocity ◽  
Lake Area ◽  
Ice Flow ◽  
Outlet Glacier ◽  
West Greenland ◽  
Subglacial Environment ◽  
Supraglacial Lakes ◽  
Automated Method ◽  
Modis Imagery ◽  
Glacier Flow

Abstract. The rapid drainage of supraglacial lakes introduces large pulses of meltwater to the subglacial environment and creates moulins, surface-to-bed conduits for future melt. Introduction of water to the subglacial system has been shown to affect ice flow, and modeling suggests that variability in water supply and delivery to the subsurface play an important role in the development of the subglacial hydrologic system and its ability to enhance or mitigate ice flow. We developed a fully automated method for tracking meltwater and rapid drainages in large (> 0.125 km2) perennial lakes and applied it to a 10 yr time series of ETM+ and MODIS imagery of an outlet glacier flow band in West Greenland. Results indicate interannual variability in maximum coverage and spatial evolution of total lake area. We identify 238 rapid drainage events, occurring most often at low (< 900 m) and middle (900–1200 m) elevations during periods of net filling or peak lake coverage. We observe a general progression of both lake filling and draining from lower to higher elevations but note that the timing of filling onset, peak coverage, and dissipation are also variable. Lake coverage is sensitive to air temperature, and warm years exhibit greater variability in both coverage evolution and rapid drainage. Mid-elevation drainages in 2011 coincide with large surface velocity increases at nearby GPS sites, though the relationships between ice-shed-scale dynamics and meltwater input are still unclear.

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