Airborne geophysical investigations of basal conditions at flow transitions of outlet glaciers on the Greenland Ice Sheet

Lead Research Organisation: University of Cambridge
Department Name: Scott Polar Research Institute


The 1.7 million km2 Greenland Ice Sheet is divided into a series of major drainage basins, each typically about 50-100,000 km2 in area. Most of these basins drain into the marine waters of fjord systems via relatively narrow and heavily crevassed outlet glaciers that dissect the mountains fringing the island. Over the past few years it has become clear that the Ice Sheet is losing mass and has become a significant contributor to global sea-level rise. This is related to, first, the doubling in speed of several outlet glaciers, increasing ice flux to the sea and, secondly, a major increase in the area affected by summer melting and runoff from the ice-sheet surface. Both of these changes have taken place in the past decade and have been linked with warmer air and water temperatures over and around Greenland. A major question for both scientists and policymakers is how the Greenland Ice Sheet will continue to react to the temperature rises that are predicted for the coming century by a suite of climate models, particularly in the context that the Arctic is likely to warm at a greater rate than the global average due to the continuing loss of its surrounding sea-ice cover and the changes in ocean albedo and, therefore, energy balance that will result. We will acquire geophysical data from a series of ten outlet glaciers of the Greenland Ice Sheet using airborne ice-penetrating radar, laser altimeter, gravimeter, and magnetometer and GPS instruments. These glacier systems have been selected because: (a) they are major drainage basins within the ice sheet which provide a high ice flux to the sea; and (b) they represent different sub-environments within the Greenland Ice Sheet and its related climate and ocean setting. We will focus our investigations on three key areas of each outlet glacier: first, the heavily crevassed fast-flowing outlet glaciers themselves, that flow in narrow channels through Greenland's fringing mountains; secondly, an upper transition zone between the ice-sheet interior and these narrow outlet glaciers; and thirdly, the grounding zone marking the transition of fast-flowing outlet glaciers to floating ice tongues that are present at the head of many Greenland fjords. Our scientific objectives are: 1. To determine ice surface elevation and subglacial bed elevation, including measurement beneath areas of heavy crevassing in fast-flowing outlet glaciers. 2. To characterize the substrate beneath the ice, in particular whether it is crystalline bedrock or deformable sediments. 3. To establish the distribution of subglacial melting and characterize the subglacial hydrological system where water is present. 4. To identify the transition zones between inland ice, outlet glaciers and the grounding zone and reveal basal character changes associated with them. 5. To describe the three-dimensional nature of internal ice layering within transition zone from inland ice to outlet glacier to measure the distribution of accumulation, strain, and basal melting. This information will make a fundamental contribution to the computer modelling of ice sheets, and how Greenland in particular may respond in future to changes in air and ocean temperate over the coming decades. This because these models require information, known as boundary conditions, on the shape of the bed and also the processes that are going on there in order to make useful predictions. To date, we know little about, for example, the distribution of water beneath these outlet glaciers. The changing amount of ice lost from the ice sheet by surface melting and iceberg production is important, in turn, for predictions on the future contributions of Greenland to sea-level rise in a warming Arctic. This is of significance beyond the academic community. In the UK and elsewhere, governments at national and regional level are requiring information about rates of sea-level rise and the remediation measures, such as sea defences, that are needed.


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Description Two field seasons of airborne radio-echo sounding of the Greenland Ice Sheet took place in 2011 and 2012. Both seasons were highly successful with new bed topographic and related data obtained from West Greenland, East Greenland and North Greenland sectors of the ice sheet. A number of fast-flowing outlet glaciers, for example, Rink, Store, Humboldt and Daugaard Jensen glaciers, were sounded.

The data from these campaigns has been reduced and analysed and the findings are being worked up as papers. One paper has appeared in The Cryosphere, updating the geometry of the Greenland Ice Sheet. A second paper, published recently in Science, incorporates our radar observations of ice thickness and bed elevation in North Greenland in the mapping of a huge subglacial canyon. A third paper, in Geophysical Research Letters, outlines the discovery of the first subglacial lakes beneath the NW sector of the Greenland Ice Sheet. Ice thickness and bedrock elevation data from the Humboldt Glacier area of North Greenland has been incorporated in a further contribution on the dynamics of this major basin of the ice sheet which has appeared in the Journal of Glaciology..

The radar data are also being used in numerical modelling of major drainage basins of the Greenland Ice Sheet, where basal properties including hydrology are included by Co-I Christofferen and Bougamont.
Exploitation Route Incorporation of data in talks to non-specialist audiences, for example schools visiting the Polar Museum of the Scott Polar Research Institute. Presentations at international scientific conferences.
Sectors Environment

Description The findings of this project have been used, for example, to inform an invited talk by Prof. Dowdeswell at the World Economic Forum in Davos, Switzerland, in January 2014. Aspects of the work were also used in a talk in Parliament to an all party group of MPs in December 2013 and in a 2015 discussion of a House of Lords Select Committee. In these examples, the effects of climate change on the cryosphere were projected to political leaders, and in the case of Davos, to other international leaders of commerce and industry as well. In addition, displays on the science linked to this grant, on airborne radar measurements of ice thickness in particular, have been projected to diverse audiences through the Polar Museum at the Scott Polar Research Institute, which receives about 45,000 visitors per year.
First Year Of Impact 2013
Sector Education,Environment,Government, Democracy and Justice,Culture, Heritage, Museums and Collections
Impact Types Economic

Description Expert panels and talk at Nobel Dialogues Day, preceding the Nobel Prizes Ceremony in Stockholm, December 2018 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact About 100 people listened to the Nobel Dialogues presentations which were also streamed internationally. Dowdeswell talked about the role of the Arctic and Antarctic in global environmental change.
Year(s) Of Engagement Activity 2018
Description Ideas Lab presentation at World Economic Forum, Davos, on Adapting to Climate Change - Predicting glacier and ice sheet change 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Policymakers/politicians
Results and Impact Discussion of climate change issues as they affect the cryosphere, and, through that, humankind

Followup by several participants
Year(s) Of Engagement Activity 2014
Description Seminar and Q & A session as part of Cambridge Advanced Leadership Programme 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Wide-ranging discussion of how environmental change affects the cryosphere and how that, in turn, affects humankind through, for example, sea-level rise

Followup from several industrial participants
Year(s) Of Engagement Activity 2011,2012,2013,2014
Description Talks to groups visiting the Polar Museum of the Scott Polar Research Institute 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact Talks to at least three schools and general public visits to the Institute's museum each year
Year(s) Of Engagement Activity 2014,2015,2016