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Subglacial Controls on the Short Term Dynamics at the Margin of the Greenland Ice Sheet

Applicant Lüthi Martin Peter
Number 127197
Funding scheme Project funding
Research institution Versuchsanstalt für Wasserbau, Hydrologie und Glaziologie ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Hydrology, Limnology, Glaciology
Start/End 01.02.2010 - 31.01.2014
Approved amount 449'414.00
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All Disciplines (3)

Discipline
Hydrology, Limnology, Glaciology
Climatology. Atmospherical Chemistry, Aeronomy
Geophysics

Keywords (12)

borehole; geophysics; stability; sliding; glacial hydraulics; ice deformation; numerical modeling; Glacier; Basal processes; Greenland; Ice Sheet; Dynamics

Lay Summary (English)

Lead
Lay summary
The Greenland Ice Sheet is losing mass at high and accelerating rates through increased surface melt, peripheral thinning and accelerated flow of outlet glaciers. While a consistent explanation of the unprecedented, almost simultaneous acceleration of several large outlet glaciers is emerging, the situation is less clear for the observed mass loss of the slower moving marginal areas. Ice dynamics of these temperate-based, slow-moving areas is highly susceptible to timing and amount of melt water discharge to the base of the ice sheet, leading to big and widespread flow acceleration in summerRouting of surface melt water to the base of the ice sheet affects the local subglacial water pressure, leads to short term variations in ice-bed coupling and ice flow velocity, and thus affects mass transport and ice sheet geometry in the ablation area. Since the number of melt days and the area affected by surface melt in summer have increased substantially over the last decade, concerns have arisen about the feedback of faster mass transport from the ice sheet's interior to low elevations, more meltwater production, and therefore increasingly rapid mass loss from the ice sheet periphery.The aim of this project is a better understanding of the processes responsible for peripheral thinning and seasonal flow velocity variations of the marginal areas of the Greenland Ice Sheet. In a coordinated international and interdisciplinary effort we will collect a unique body of in situ measurements along a flow line in the ablation area downstream of Swiss Camp. We will instrument boreholes to the bedrock to obtain information on processes at the ice-bedrock interface, the thermal structure, internal deformation and layering within the ice body. These data sets will be complemented by high time-resolution measurements of surface motion, climate parameters, and seismicity. To investigate the short term dynamic response of the ice body to changes in the subglacial hydraulic system we will monitor the diurnal cycle, and additionally disturb the subglacial water pressure by routing water pulses of increasing magnitude into the boreholes.To interpret the collected data sets we will use models of surface melt and glacial hydraulics, and a 3D thermo-mechanically coupled ice dynamics model.With an inverse modeling approach we will attempt to quantify the dependence of basal motion on stress state and water pressure. Such parametrizations are key requisites for realistic and high resolution ice sheet models. Measured quantities, such as ice temperatures and internal layering structures, will provide benchmarks for high resolution dynamic models of the GrIS.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Name Institute

Collaboration

Group / person Country
Types of collaboration
Dartmouth College, Hanover NH United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
NASA Goddard SFC, Greenbelt MD United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
Los Alamos National Laboratories, Los Alamos, NM United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
University of Texas, Austin TX United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
- Exchange of personnel

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
IASC Arctic Science Summit Week Talk given at a conference Influence of Melt Water Supply on the Dynamics of the Greenland Ice Sheet 13.04.2013 Krakow, Poland, Poland Lüthi Martin Peter;
IASC Network on Arctic Glaciology Annual Meeting Talk given at a conference Caterpillar-like motion of the Greenland Ice Sheet 26.02.2013 Obergurgl, Austria, Austria Lüthi Martin Peter;
AGU Fall Meeting / General Assembly Talk given at a conference Caterpillar-like ice flow of the Greenland Ice Sheet: observations of basal control on ice motion 03.12.2012 San Francisco, United States of America Lüthi Martin Peter; Funk Martin; Ryser Claudia;
Swiss Geoscience Meeting Poster Caterpillar-like flow of the Greenland Ice Sheet: observations of basal control on ice motion. 17.11.2012 Bern, Switzerland Ryser Claudia; Lüthi Martin Peter;
IGS conference: Glaciers and ice sheets in a warming climate Talk given at a conference Short term dynamics of the Greenland Ice Sheet observed with sensors in deep boreholes. 24.06.2012 Fairbanks, AK, USA, United States of America Lüthi Martin Peter;
Alpine Glaciology Meeting Talk given at a conference Subglacial controls of the short term flow dynamics at the margins of the Greenland Ice Sheet 02.02.2012 Zurich, Switzerland Ryser Claudia; Lüthi Martin Peter; Funk Martin;
IASC Network on Arctic Glaciology Annual Meeting Talk given at a conference Subglacial controls on the short term flow dynamics at the margins of the Greenland Ice Sheet. 09.01.2012 Zieleniec, Poland Lüthi Martin Peter;
AGU Fall Meeting / General Assembly Talk given at a conference Subglacial Controls of the Short Term Dynamics at the Margins of the Greenland Ice Sheet: Interaction between subglacial water pressure and ice deformation 06.12.2011 San Francisco, United States of America Funk Martin; Lüthi Martin Peter; Ryser Claudia;
Swiss Geoscience Meeting Talk given at a conference Subglacial controls of the short term dynamics at the margins of the Greenland ice sheet: Interaction between subglacial water pressure and ice deformation 12.11.2011 Zürich, Switzerland Ryser Claudia; Lüthi Martin Peter;


Self-organised

Title Date Place
Alpine Glaciology Meeting 02.02.2012 Zürich, Switzerland

Communication with the public

Communication Title Media Place Year
Media relations: print media, online media Phasenversetzte Eisbewegungen Horizonte Italian-speaking Switzerland Western Switzerland German-speaking Switzerland 2014
Talks/events/exhibitions Das Ende der Gletscher in Sicht? German-speaking Switzerland 2013
Media relations: print media, online media Die neue Arktis Sonntagszeitung German-speaking Switzerland 2012
Talks/events/exhibitions Lange Nacht der Museen German-speaking Switzerland 2012
Talks/events/exhibitions Quer durchs Groenlandeis German-speaking Switzerland 2012
Media relations: print media, online media Unter dem Eisschild ETH Globe International German-speaking Switzerland 2012
Media relations: print media, online media Auf Grönlands schmelzendem Eis Horizonte (SNF) Italian-speaking Switzerland Western Switzerland German-speaking Switzerland 2011

Associated projects

Number Title Start Funding scheme
156098 Understanding long-term outlet glacier calving dynamics with a combined high-resolution field,- remote-sensing- and modeling approach. 01.03.2015 Project funding
133759 Renewal of the portable instrument pool at the Institute of Geophysics and Swiss Seismological Service: The mid-period and strong-motion component 01.12.2010 R'EQUIP
197015 Comprehensive Observations of Episodic Basal, Englacial and Lateral Influences on Ice Stream Dynamics 01.03.2021 Project funding
129898 Extension: Understanding the causes and future direction of the present rapid thinning of Jakobshavn Isbræ, Greenland 01.04.2010 Project funding
113503 Understanding the causes and future direction of the present rapid thinning of Jakobshavn Isbrae, Greenland 01.04.2007 Project funding

Abstract

The Greenland Ice Sheet (GrIS) is currently losing mass at a rate of 100-200Gt/a through increased surface melt, peripheral thinningand accelerated flow of outlet glaciers, thus contributing 0.3-0.6 mm/a to global sea level rise. While a consistentexplanation of the unprecedented, almost simultaneous acceleration of severallarge outlet glaciers is emerging, the situation is less clear for theobserved mass loss of the slower moving marginal areas. Ice dynamics of thesetemperate-based, slow-moving areas is highly susceptible to timing and amountof melt water discharge to the base of the ice sheet, leading to big andwidespread flow acceleration in summer.Routing of surface melt water to the base of the ice sheet affects the localsubglacial water pressure, leads to short term variations in ice-bed couplingand ice flow velocity, and thus affects mass transport and ice sheet geometryin the ablation area. Since the number of melt days and the area affected bysurface melt in summer have increased substantially over the last decade,concerns have arisen about the feedback of faster mass transport from the icesheet's interior to low elevations, more meltwater production, and thereforeincreasingly rapid mass loss from the ice sheet periphery.The aim of this project is a better understanding of the processes responsiblefor peripheral thinning and seasonal flow velocity variations of the marginalareas of the GrIS. In a coordinated international and interdisciplinaryeffort we will collect a unique body of \emph{in situ} measurements along aflow line in the ablation area downstream of Swiss Camp (West Greenland,indicated in Fig.~1). We will instrument boreholes to the bedrock to obtaininformation on processes at the ice-bedrock interface, the thermal structure,internal deformation and layering within the ice body. These data sets willbe complemented by high time-resolution measurements of surface motion,climate parameters, and seismicity. To investigate the short term dynamicresponse of the ice body to changes in the subglacial hydraulic system, wewill monitor diurnal cycles, and in addition disturb the subglacial waterpressure by routing water pulses of increasing magnitude into the boreholes.To interpret the collected data sets we will use models of surface melt andglacial hydraulics, and a 3D thermo-mechanically coupled ice dynamics model.With an inverse modeling approach we will attempt to quantify the dependenceof basal motion on stress state and water pressure. Such parametrizations arekey requisites for realistic and high resolution ice sheet models. Measuredquantities, such as ice temperatures and internal layering structures, willprovide benchmarks for high resolution dynamic models of the GrIS.This project is a joint effort with research partners from the USA who haveapplied for funding from the US National Science Foundation: Ginny Catania(University of Texas, Austin, TX), Robert Hawley (Dartmouth College, Hanover,NH) and Thomas Newmann (University of Vermont, Burlington, VT).
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