Investigating meltwater flow beneath the Greenland Ice Sheet using a multi-tracer approach

Lead Research Organisation: University of Edinburgh
Department Name: Sch of Geosciences

Abstract

The Greenland Ice Sheet is the main reservoir of ice in the northern hemisphere capable of affecting sea level in the 21st Century. Measurements of the elevation of the ice sheet surface from aircraft now provide a much better picture of the whether the ice sheet is graining or losing mass. However, until there is a better understanding of how ice flows from the ice sheet interior to the ocean, models that aim to predict the response of the Greenland Ice Sheet to climate change and the impact on sea level are unlikely to produce accurate estimates. One of the least poorly understood aspects of ice flow is how meltwater lubrication at the ice sheet sole might affect the rate of ice discharge to the ocean. Recent research has shown that the input of surface meltwater to the ice sheet bed in summer causes considerable ice speed up. Exactly how meltwater flows at the bed (does it flow in discrete channels or does it spread out and flow in a more diffuse manner?) is crucial to understanding how the ice sheet might respond to increased melt inputs in a warming climate. Currently, little is known about basal meltwater routing because the vast amounts of meltwater prevent the use of traditional tracing techniques (e.g. dye tracing). This project aims to apply novel tracing methods which will survive large scale dilution, and which can be injected to holes (moulins) on the glacier surface and detected when the water emerges at the ice sheet front. Some of these techniques have been using widely in oceanography to trace currents across ocean basins. Our tracer experiments will provide new information regarding characteristics of meltwater flow paths and their temporal/spatial variations at the bed of the ice sheet and provide detailed measurements (e.g. pressure) of along-flow path characteristics. Comparison of our tracer results (e.g. water flow speeds, pressure conditions in channels) with ice velocity data from the same glacier will help identify linkages between meltwater routing and ice flow mechanisms, and will generate a unique dataset for future numerical modelling studies aimed at quantifying the future contribution of the Greenland Ice Sheet to global sea level rise.level rise.

Publications

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Hawkings JR (2017) Ice sheets as a missing source of silica to the polar oceans. in Nature communications

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Linhoff B (2017) Utility of 222Rn as a passive tracer of subglacial distributed system drainage in Earth and Planetary Science Letters

 
Title Science advisor for the documentary film 'Aquarela' 
Description A film by Aconite Productions and iconic Russian director Victor Kossakovsky about the power, beauty and potentially destructive nature of water in all its forms - with the inevitable links to climate change and environmental warnings. I acted as a scientific (and location) advisor for the glacier and iceberg content of the documentary filmed in Greenland, I am in the credits as a Science Advisor and was invited to the film premier (attending the UK premiere in Glasgow). 
Type Of Art Film/Video/Animation 
Year Produced 2018 
Impact The film premiered at the Venice International film festival. In the UK, it premiered at the Glasgow film festival in Feb 2019. 
URL https://www.scottishfield.co.uk/culture/whatson/enjoy-the-wonders-of-nature-in-the-winter/
 
Description This information is covered by the return from the main Grant Holder (P.I. Wadham) at Bristol University.
Exploitation Route This information is covered by the return from the main Grant Holder (P.I. Wadham) at Bristol University.
Sectors Aerospace, Defence and Marine,Education,Environment

 
Description Feedback to the Chief Scientific Adviser Rural Affairs and Environment for The Scottish Government
Geographic Reach Multiple continents/international 
Policy Influence Type Gave evidence to a government review
 
Title Greenland ice motion data 
Description The database includes ice velocity data collected as part of this NERC grant and is stored at the Polar Data Centre as Tedstone, A. & Nienow, P. "Ice motion measurements, south-west Greenland Ice Sheet" v2 (2018) Polar Data Centre, Natural Environment Research Council, UK. doi:10.5285/1f69fba3-4c62-47ad-8119-08cfeec05e46 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
Impact The data is being used by other researchers including citation in: Koziol et al, The Cryosphere, 11, 2783-2797, 2017. Incorporating modelled subglacial hydrology into inversions for basal drag. 
URL http://doi.org/ch3p
 
Title Ice motion measurements, south-west Greenland Ice Sheet 
Description From May 2009 to May 2013, seven dual-frequency GPS receivers were deployed along a 120 km-long transect in the south-west of the Greenland Ice Sheet. Two additional dual-frequency GPS receivers were deployed perpendicular to longitudinal ice flow at ~14 km inland: one 5 km distant from June 2011 to May 2013, and another 2.5 km distance from May 2012 to May 2013. Each receiver recorded position observations every 10 seconds or 30 seconds (depending on configuration), enabling resolution of horizontal and vertical ice motion. Sites were powered by solar panels and operated 24 hours a day during summer but shut down in the autumn. Absolute ice displacements at each site were obtained for each summer and winter period in the absence of continuous measurements. Position measurements were kinematically corrected relative to an off-ice base station using TRACK (Chen, 1999). Daily velocities were then obtained by differencing across 24-hour periods, whilst continuous velocities were obtained through application of a sliding 6-hour differencing window. At each GPS site we also measured (1) the near-surface air temperature every 15 minutes year-round, (2) net seasonal ablation using ablation stakes, and (3) at several selected sites melt rates using sonic ranging sensors. This version 1 of the dataset has been succeeded by a new version with ice motion records at 1-day resolution rather than 2-day resolution. In other respects the dataset has not changed. 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
 
Title Ice motion measurements, south-west Greenland Ice Sheet (version 2) 
Description From May 2009 to May 2013, seven dual-frequency GPS receivers were deployed along a 120 km-long transect in the south-west of the Greenland Ice Sheet. Two additional dual-frequency GPS receivers were deployed perpendicular to longitudinal ice flow at ~14 km inland: one 5 km distant from June 2011 to May 2013, and another 2.5 km distance from May 2012 to May 2013. Each receiver recorded position observations every 10 seconds or 30 seconds (depending on configuration), enabling resolution of horizontal and vertical ice motion. Sites were powered by solar panels and operated 24 hours a day during summer but shut down in the autumn. Absolute ice displacements at each site were obtained for each summer and winter period in the absence of continuous measurements. Position measurements were kinematically corrected relative to an off-ice base station using TRACK (Chen, 1999). Daily velocities were then obtained by differencing across 24-hour periods, whilst continuous velocities were obtained through application of a sliding 6-hour differencing window. At each GPS site we also measured (1) the near-surface air temperature every 15 minutes year-round, (2) net seasonal ablation using ablation stakes, and (3) at several selected sites melt rates using sonic ranging sensors. This version 2 of the dataset updates the previously 2-day temporal resolution of the ice motion records to 1-day resolution. In other respects the dataset has not changed. 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
 
Title Proglacial discharge measurements, Leverett Glacier, south-west Greenland (2009-2012) 
Description Measurements of water discharge, suspended sediment concentration and electrical conductivity during the melt seasons of 2009, 2010, 2011 and 2012 in the proglacial river draining from the tongue of Leverett Glacier, a land-terminating glacier in the south-west of the Greenland Ice Sheet. The measurements were made in a stable bedrock section approximately 2 km downstream from the glacier terminus. Data loggers recorded measurements every 15 minutes from approximately May to August each year. Water depth (stage) was converted to discharge (Q) using season-specific ratings curves derived from repeat dye-dilution injections undertaken across the stage values. Suspended sediment concentration (SSC) was obtained by calibrating turbidity sensor readings with sediment samples taken in-situ and then filtered, dried and weighed. Electrical conductivity (EC) was recorded using a water conductivity probe; the data were filtered for bad values and corrected for temperature, but no smoothing was applied. These version 2 files are presented as CSV lists, with some summary metadata included as comments at the start of each file; they essentially contain the same data as the previous version files. 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
 
Description Boat of Garten 'Boat talks' - 'The stability of the Greenland Ice Sheet' 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact I was invited to give a talk to the series of talks at Boat of Garten entitled 'Boat talks' - 'The stability of the Greenland Ice Sheet'
Year(s) Of Engagement Activity 2018
URL https://www.eventbrite.co.uk/e/boat-talks-the-stability-of-the-greenland-ice-sheet-with-professor-pe...
 
Description Midlothian Science Festival talk at IKEA - 'The Greenland Ice Sheet in a warming world'. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact About 30 members of the public attended my talk, 'The Greenland Ice Sheet in a warming world' at IKEA as part of the Midlothian Science Festival.
Year(s) Of Engagement Activity 2018
URL https://midlothiansciencefestival.com/event/climate-change-greenlands-ice-sheet/
 
Description Royal Society of Edinburgh - 'Winter Wonders' public event - talk and discussion. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Royal Society of Edinburgh - 'Winter Wonders' public event - talk and discussion. Invited talk with Prof David Sugden whom spoke about Antartica, I spoke about the Greenland Ice Sheet and we discussed and answered questions from the floor.
Year(s) Of Engagement Activity 2018
URL https://www.scottishfield.co.uk/culture/whatson/enjoy-the-wonders-of-nature-in-the-winter/
 
Description Science advisor to "Aquarela", a cinematic climate science documentary 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact I contributed expert glacial knowledge to the film/documentary 'Aquarela' on water, ice and climate change - I am acknowledged in the credits and attended the UK premier as a guest
Year(s) Of Engagement Activity 2019
URL https://www.theguardian.com/film/2019/dec/11/aquarela-review-victor-kossakovsky-climate-crisis-docum...
 
Description Talk at Kingussie High School - 'Climate change, ice-sheets and satellites' 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact Invited talk at Kingussie High School to their S4 and S5 Geography Higher class - 'Climate change, ice-sheets and satellites'
Year(s) Of Engagement Activity 2019
 
Description Talk at a science festival 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Evening talk at IKEA, Edinburgh as part of the Midlothian Science Festival entitled 'Science in Extreme Conditions'. Talk focussed on investigations of Greenland Ice Sheet stability, especially with respect to the importance of collecting hard won field based data sets to support the science.
Year(s) Of Engagement Activity 2017
 
Description Talk to the Probus Club of Lomond, Drymen - 'The stability of the Greenland Ice Sheet' 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Invited to give a talk to the Probus Club of Lomond in Drymen, Scotland - talk title 'The stability of the Greenland Ice Sheet'
Year(s) Of Engagement Activity 2018