Basal Properties of the Greenland Ice Sheet (BPoG)

Lead Research Organisation: University of Bristol
Department Name: Geographical Sciences

Abstract

The single most important boundary condition for modelling ice sheet evolution is bed topography, from which - in conjunction with surface elevations - ice thickness can be determined. This importance is demonstrated by the facts that ice motion due to deformation is very sensitive to ice thickness-the thicker the ice the more it deforms-and that the point at which the ice sheet is contact with the ocean is also very sensitive to thickness and bed profile. Small changes in ice thickness and basal stickiness (friction) at this contact point can result in large change in ice discharge.

Advances in our knowledge of ice thickness and bedrock topography in Greenland have been made since the last comprehensive study was published over ten years ago. The most recent bed data set, published in 2013, possesses more complete coverage of the ice sheet interior and margins and was sufficient to resolve a huge ancient canyon, carved by a river tens of thousands of years ago, and now buried beneath the several kilometres of ice. The canyon extends for more than 750 km, and is possibly the longest in the world yet has only just been discovered. Close to the ice sheet margins, however, gaps in observations are still prevalent due to the steep relief and warm ice in these areas. This is particularly true for the numerous outlet glaciers that control ice discharge into the ocean. Outlet glaciers are where ice is flowing fastest, where the greatest ice mass losses have been observed and where models are most sensitive to small changes, or errors, in bed geometry. Furthermore, the topography of the seafloor (the bathymetry) in the fjords that the glaciers flow into is, currently, poorly known. Uncertainties of hundreds of metres in bathymetry exist while numerical modelling studies have shown that the bathymetry has a strong influence on the interaction of the ocean with the glaciers. These big errors in the bathymetry mean that the models will have difficulty simulating the behaviour of this interaction because the errors will feed into the results. It is the problem of "garbage in, garbage out". The models are limited by the quality of the data that are used to drive them. This project aims to address all these limitations by producing the "next generation" bed elevation data set for Greenland and the coastal area including bathymetry. It will also provide key information on the properties of the ice/bed interface: in particular whether there is water at the bed or not. The result of this work will be data sets that will greatly advance our understanding of the sensitivity of the ice sheet to changes in atmospheric and oceanic forcing.

Planned Impact

There are three broad categories of user groups who will benefit from the results and activities of the project in addition to scientists working directly on ice sheets and sea level rise. These are i) the climate change policy community including NGOs, ii) mineral exploration companies and iii) the general public, (including schools).


i) Climate change policy community.
We have direct links with the several organizations who have benefited from previous related research and who will benefit from this work. The list below is not meant to be exhaustive but to illustrate the type of beneficiary in this category with an indication of how they might benefit:
UK Met Office & DECC: coordinating the AVOID programme (a DECC/DEFRA funded project, http://www.avoid.uk.net/) Public Interest Research Centre (http://www.pirc.info/) provides climate policy documents for the public and UNFCC.
UN Environment Programme: provides information about climate change and sea level rise to general public and educational establishments. Past experience indicates that this category of end user has greatly benefited from a strong interaction and involvement with the experts doing the work.

ii) The oil and gas industry is surveying the shelf seas west and east of Greenland for exploration and possible exploitation of hydrocarbons, while mining companies are looking to exploit various mineral resources in Greenland (see e.g. Greenland Minerals and Energy Ltd; http://www.ggg.gl/). Both these sectors would benefit from improved knowledge of fjord bathymetry, marginal bed topography and the vulnerability of marine terminating margins to climate change.


iii) The general public. Arctic research has huge potential for capturing the public imagination and engaging students at both primary and secondary level in issues related to climate change, environmental policy, glaciology and polar processes. Because of the profound societal impacts of sea level rise, the vulnerability of the Arctic to climate change, and the dramatic impacts of climate change already occurring in the Arctic and Greenland specifically, the general public are an important beneficiary of this work. This includes those witnessing the changes such as the Greenlandic inhabitants.

JLB and MJS currently undertake talks to local schools and also to a Geography teacher training programme run by the Princes Teaching Institute. JLB was until recently head of undergraduate admissions for Geography at UoB and, in this capacity, developed a number of widening participation activities which he is still involved with. The PI and Co-Is have a long record of working with the media. Britain's only dedicated Polar Museum is located in the Scott Polar Research Institute, University of Cambridge, while the media and outreach activities associated with the Lake Ellsworth project (http://www.ellsworth.org.uk/) were widely reported and followed including social media outlets.

Publications

10 25 50
 
Description We have identified difference in the distribution of water at the bed of the ice sheet compared to previous assessments. We have also identified differences in the magnitude and spatial pattern of geothermal heatflux across Greenland.
Exploitation Route Our findings are being used by ice sheet modellers to improve their representation of basal processes and basal topography
Sectors Environment

URL https://bpog.blogs.ilrt.org/
 
Description The basal topography data developed by the project have been used by British Antarctic Survey to create a Greenland Basal Topography hard-copy map as part of its BAS Thematic map series (ISBN: Folded 978-0-85665-216-5, Flat 978-0-85665-216-5). https://www.bas.ac.uk/data/our-data/maps/thematic-maps/greenland-basal-topography/
First Year Of Impact 2017
Sector Environment
Impact Types Societal

 
Description NERC standard grant award
Amount £479,642 (GBP)
Funding ID NE/M000869/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 10/2014 
End 10/2017
 
Title IceBridge BedMachine Greenland, Version 3 
Description This dataset contains a bed topography/bathymetric map of Greenland based on mass conservation, multi-beam data, and other techniques. The data set also includes surface elevation, ice thickness and an ice/ocean/land mask. Version 3 includes ocean bathymetry all around Greenland based on data from NASA's Ocean Melting Greenland (OMG) and other campaigns of bathymetry measurements. The subglacial bed topography has also been updated by including more ice thickness data and constraining the ice thickness at the ice/ocean interface based on bathymetry data when available. 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
Impact Greenland's bed topography is a primary control on ice flow, grounding line migration, calving dynamics and subglacial drainage. Moreover, fjord bathymetry regulates the penetration of warm Atlantic Water (AW) that rapidly melts and undercuts Greenland's marine-terminating glaciers. This dataset presents a new compilation of Greenland bed topography that assimilates seafloor bathymetry and ice thickness data through a mass conservation (MC) approach. A new 150-m horizontal resolution bed topography/bathymetric map of Greenland is constructed with seamless transitions at the ice/ocean interface, yielding major improvements over previous datasets, particularly in the marine-terminating sectors of northwest and southeast Greenland. The map reveals the total sea level potential of the Greenland Ice Sheet is 7.42+/-0.05 m, which is 7 cm greater than previous estimates. Furthermore, it explains recent calving front response of numerous outlet glaciers and reveals new pathways by which AW can access glaciers with marine-based basins, thereby highlighting sectors of Greenland that are most vulnerable to future oceanic forcing. 
URL https://nsidc.org/data/idbmg4
 
Title Subglacial bed roughness of Greenland, provided using two independent metrics 
Description These two files (.csv) provide independent methods of quantifying subglacial roughness in Greenland, both calculated from radio-echo sounding (or ice penetrating radar) data collected by the Operation Ice Bridge programme using CReSIS instrumentation. 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
Impact Roughness here, and in the wider literature, is defined as the variation in bed elevation (in the vertical) at the ice-bed interface, over a given length-scale. These two metrics calculate/quantify this variation in different ways: one shows topographic-scale roughness, calculated from the variation in along-track topography (bed elevation measurements derived from the radar pulse); and the other shows scattering-derived roughness, calculated from quantifying characteristics of each bed-echo (the return from the radar pulse at the ice-bed interface). 
URL https://data.bas.ac.uk/full-record.php?id=GB/NERC/BAS/PDC/01060
 
Title Synthetic channel mesh routine 
Description The code provided enables the creation of points with assigned elevations to populate channels where only the centreline has been prior mapped. This is achieved by creating points normal to the centreline of a channel up to its banks, the extent of which is constrained by a land classification mask. The long profile elevation trend of the channel is derived from elevations close to or at the head and mouth of the channel, including also any point observations within the channel. Where the centreline itself has only a known elevation at the head and mouth of its length, the long profile elevation trend is simply linear. The cross-profile is constructed as a second order polynomial, using elevations at either edge (using the nearest observed elevations) and the centreline elevation. The meshing procedure is described in Williams et al., 2017. 
Type Of Material Data analysis technique 
Year Produced 2017 
Provided To Others? Yes  
Impact Used in the following publication: Williams, C. N., Cornford, S. L., Jordan, T. M., Dowdeswell, J. A., Siegert, M. J., Clark, C. D., Swift, D. A., Sole, A., Fenty, I., and Bamber, J. L.: Generating synthetic fjord bathymetry for coastal Greenland, The Cryosphere, 11, 363-380, https://doi.org/10.5194/tc-11-363-2017, 2017. 
URL https://github.com/Chris35Wills/synthetic_channel_mesh
 
Description Collaboration with John Paden (University of Kansas) 
Organisation University of Kansas
Country United States 
Sector Academic/University 
PI Contribution Analysis and interpretation of data acquired by Univ Kansas
Collaborator Contribution Provision of data, expert advice and assistance with analysis and interpretation of IPR data
Impact The collaboration has resulted in the following papers: - Jordan, T.M., Bamber, J.L., Williams, C.N., Paden, J.D., Siegert, M.J., Huybrechts, P., Gagliardini, O. and Gillet-Chaulet, F., 2016. An ice-sheet-wide framework for englacial attenuation from ice-penetrating radar data. The Cryosphere, 10(4), p.1547 - Jordan, T. M ., Cooper, M. A., Schroeder, D. M., Williams, C. N., Paden, J.D., Siegert, M. J., & Bamber, J. L. (2017). Self-affine subglacial roughness:consequences for radar scattering and basal water discrimination in northern Greenland. Cryosphere, 11(3), 1247-1264. DOI: 10.5194/tc-11-1247-2017
Start Year 2014
 
Description Collaboration with Mathieu Morlighem (UCI) 
Organisation University of California, Irvine
Country United States 
Sector Academic/University 
PI Contribution Provision of methods and analyses towards a joint product and publication
Collaborator Contribution Provision of methods and analyses towards a joint product and publication
Impact The collaboration has resulted in the following paper: - Morlighem, M., Williams, C. N., Rignot, E., An, L., Arndt, J. E., Bamber, J. L et al. (2017). BedMachine v3: Complete bed topography and ocean bathymetry mapping of Greenland from multibeam echo sounding combined with mass conservation, Geophysical Research Letters, 44, 11,051-11,061. https://doi.org/10.1002/2017GL074954
Start Year 2016
 
Description Collaboration with Olivier Gagliardini (Université Grenoble Alpes) 
Organisation University of Grenoble
Country France 
Sector Academic/University 
PI Contribution Provision of input data for modelling
Collaborator Contribution Incorporation of our datasets in their numerical simulations
Impact The collaboration has resulted in the following paper: - Jordan, T.M., Bamber, J.L., Williams, C.N., Paden, J.D., Siegert, M.J., Huybrechts, P., Gagliardini, O. and Gillet-Chaulet, F., 2016. An ice-sheet-wide framework for englacial attenuation from ice-penetrating radar data. The Cryosphere, 10(4), p.1547
Start Year 2012
 
Description Collaboration with Steve Price (LANL) 
Organisation Los Alamos National Laboratory
Country United States 
Sector Public 
PI Contribution Provision of input data for modelling
Collaborator Contribution Incorporation of our data sets in their numerical simulations and provision of model output fields for our analysis
Impact The collaboration has not produced any formal outputs
Start Year 2012
 
Title Chris35Wills/Synthetic_Channel_Mesh: Synthetic Channel Meshing Routine 
Description The code provided here enables the construction of synthetic channel geometry following Williams et al., 2017. This was developed as part of the BPOG (Basal Properties of Greenland) project. An implementation of the code was used to construct fjord geometry and define elevations within fjords surrounding Greenland currently void of observational data for the new Greenland bed topography dataset - BedMachine v3. For more information, please visit the following links: Formal description - Williams et al., 2017 The BPOG blog BedMachine dataset 
Type Of Technology Software 
Year Produced 2017 
Open Source License? Yes  
 
Description Press release (Greenland Basal Topography BedMachine v3) 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Press release to accompany publication of the Greenland Basal Topography BedMachine v3, and subsequent dissemination of hard-copy maps to interested individuals
Year(s) Of Engagement Activity 2017
URL https://www.bas.ac.uk/media-post/new-map-reveals-landscape-beneath-greenlands-ice-sheet/