Greenland in a warmer climate: What controls the advance & retreat of the NE Greenland Ice Stream

Over the past decade the Greenland ice sheet has thinned at an accelerating rate and is currently the largest single contributor to global sea-level rise. Understanding the likely rate and magnitude of future change matters because accurate projections of sea-level rise are necessary if governments are to plan for the future in a warming world and develop sustainable coastal defence strategies.

A significant portion of Greenland's contribution to sea-level rise has been associated with the speed-up and melting of an increased number of fast-flowing outlet glaciers. Rapid thinning of these glaciers has coincided with increases in air and ocean temperatures, suggesting that they are sensitive and responsive to these parameters. However, although various mechanisms related to atmospheric and oceanic forcing have been proposed to explain the recent thinning, there exist large uncertainties in the relative importance of and interplay between each of these and the ice sheet response to them over longer timescales. Without this crucial information output from the current generation of ice sheet models has limitations and there is potential for significant errors in sea-level rise projections.

This research will directly address this critical gap in our understanding by reconstructing the past behaviour of the Northeast Greenland Ice Stream (NEGIS) over the past 10,000 years. NEGIS is of particular interest because recent studies show that this cold, High Arctic region of the ice sheet has started to undergo sustained thinning after more than 25 years of relative stability. This has raised concerns that rapid inland retreat is already underway and could lead to drawdown of the NEGIS catchment. Complete collapse of its drainage basin would raise sea-level by ~1.4 m (equivalent to the combined Pine Island-Thwaites catchment in Antarctica) posing a major hazard for coastal populations. NEGIS provides an unparalleled opportunity to investigate the response of an ice stream to past change (oceanic and atmospheric warming), because there is evidence that it underwent dramatic retreat (and then advance) during the Holocene Thermal Maximum (a period of increased air temperatures analogous to that predicted for late 21st century).

To achieve this we have assembled an experienced team who will generate a detailed record of changes in NEGIS geometry, and the contemporaneous atmospheric, oceanic and relative sea level changes. We will reconstruct ice stream configuration (thickness, extent) from marine and terrestrial data, and produce high-resolution records of oceanic and atmospheric temperatures and relative sea level. Using a state-of-the-art ice sheet model (BISICLES), these data will be used to test the sensitivity of the ice stream to different forcing mechanisms at 100-1000 year timescales. Our chosen timescale will allow us to differentiate short term 'noise' from long term trends, something that has been recognised as a potential issue, which is not possible from investigations of contemporary margin fluctuations derived from a few decades of instrumental records. Ultimately our project will deliver significant improvements in our understanding of the sensitivity of the ice sheet to various forcing mechanisms that will help to underpin sea-level rise projections, shape policy on coastal defence and protect future generations.

The project has significant added value in that we will work within a funded European programme 'Greenland Ice Sheet/Ocean Interaction and Fram Strait Fluxes' and has confirmed funded logistical support through the Alfred Wegener Institute, Germany and a 50 day cruise on the RV Polarstern (2016) to this remote area.

Who will benefit?
1. Think Big Science day: The Think Big programme is part of Durham University's Supported Progression Programme for talented students studying in the North East and Cumbria who have the potential to study at university and who will benefit from additional help and support to reach their full potential. Through offering a Think Big science day on 'Ice Sheets and Climate Change' we would aim to inspire and attract Pre 16 school children from all across the northeast region to come and learn about ice sheets and the challenges of climate change, and to encourage them to join our Supported Progression Programme.
2. DynamIce interactive WWW site: Ice sheet models provide the key to predicting the future behaviour of our cryosphere in a warming world, but perhaps more importantly, they provide a spectacular visual means with which to engage the public. Ice sheet models are dynamic, colourful and informative. As part of this project we propose to design and build a user friendly, interactive, animated model that will enable the public to explore the response of an ice sheet to different climatic forcings.
3. Academic community: The numerical modelling community will benefit particularly from increased understanding of ocean-ice interactions and a benchmark dataset for testing numerical models of marine-based ice sheet outlet glaciers and ice shelves over centennial to millennial timescales.

How will they benefit?
1. Think Big Science day: The Think Big science day will provide 100 places for local children and teachers from local/regional secondary schools. We will offer children the chance to spend a day in the Geography Department with interactive laboratory sessions, guest lectures by the project team ('Climate Change + Ice' and 'Adventures in the Arctic') and a mini field trip
2. DynamIce interactive WWW site: DynamIce will be self-guiding and demonstrate the relationships between increasing ocean and air temperatures, ice sheet response and sea-level, but also illustrate concepts of non-linear response behaviour in the earth system. It would be trialled on the Think Big Science Day to get feedback on its ease of use and impact before being made more widely available through outreach programmes embedded within bodies such as the Geographical Association, the Royal Geographical Society, and the Quaternary Research Association. An improved understanding of numerical models and their associated uncertainties forms a critical part of the public debate on climate change and we hope that DynamIce will inform this debate.
3. Academic community: Our field data, providing the first well-constrained data on long-term ice-ocean-atmosphere coupling will help constrain and validate the next generation of ice sheet numerical models.

What will be done?
1. Think Big Science day: The Supported Progression team will implement the planning and development of the day in partnership with local schools.
2. DynamIce interactive WWW site: The project team will use a design and imaging team to develop Dynam-Ice.
3. Academic community: Our results will be communicated though conferences, workshops, and papers and our data added to the NERC National Geoscience Data Centre.