THINNING HISTORY OF THE FOUNDATION-THIEL TROUGH ICE STREAM: A KEY CONTROL ON DEGLACIATION OF THE WEST ANTARCTIC ICE SHEET, WEDDELL SEA EMBAYMENT
Lead Research Organisation:
British Antarctic Survey
Department Name: Science Programmes
Abstract
The Antarctic ice sheet is the largest on earth and any instability is likely to dominate global sea level change. We therefore require models of the ice sheet to make more reliable and robust predictions of future change. One problem in meeting this challenge is the lack of past data on deglaciation with which to initialize and calibrate the models. This problem has been particularly acute in the Weddell Sea embayment and in particular its eastern part where the Foundation - Thiel Trough has been a principal drainage route for the West Antarctic Ice Sheet (WAIS), and its southern extension may be a potential location for future instability. We propose here an integrated field and modelling study that will exploit the opportunity of several emerging field datasets from a range of different disciplines, collect fresh data from a crucial location, and investigate past and future deglaciation using sophisticated ice sheet models. To understand the history of ice thinning and retreat along the trough we will adopt a dipstick approach to survey the Foundation Ice Stream, an upstream extension of the ice stream that occupied the trough during the last ice age. We will determine the thinning history of this Foundation-Thiel Trough Ice Stream from geomorphology and exposure age dating: techniques that have been used effectively to provide insight into ice sheet history in other regions of Antarctica. We will apply a 3D model - incorporating significant recent theoretical advances - to the whole of the WAIS in order to understand the forcing mechanisms for the ice stream history we measure. We will go on to use this model to predict the likely future stability of the WAIS in terms of both long-term trajectory and any response to climate change scenarios, and in particular whether it will retreat further along the Foundation-Thiel Trough.
People |
ORCID iD |
Richard Hindmarsh (Principal Investigator) |
Publications
Arthern R
(2015)
Flow speed within the Antarctic ice sheet and its controls inferred from satellite observations
in Journal of Geophysical Research: Earth Surface
Bertler N
(2018)
The Ross Sea Dipole - temperature, snow accumulation and sea ice variability in the Ross Sea region, Antarctica, over the past 2700 years
in Climate of the Past
Bradley S
(2015)
Low post-glacial rebound rates in the Weddell Sea due to Late Holocene ice-sheet readvance
in Earth and Planetary Science Letters
Drouet A
(2013)
Grounding line transient response in marine ice sheet models
in The Cryosphere
Fretwell P
(2013)
Bedmap2: improved ice bed, surface and thickness datasets for Antarctica
in The Cryosphere
Hindmarsh R
(2018)
Past Glacial Environments
Hindmarsh, R.C.A.
(2020)
Radars and Ice Cores Reveal Styles of Retreat of Greenland and Antarctic Ice Sheets
in ECO SI
Kingslake J
(2016)
Ice-flow reorganization in West Antarctica 2.5 kyr ago dated using radar-derived englacial flow velocities
in Geophysical Research Letters
Lee JE
(2020)
An 83,000 year old ice core from Roosevelt Island, Ross Sea, Antarctica
in Climate of the Past
Description | We have investigated through modelling likely and physically realistic changes in geometry of the West Antarctic Ice-Sheet in the past few thousand years, based upon geological and geophysical evidence. Our results show that (a) at the Last Glacial Maximum (LGM) the ice-sheet may have advanced as far as the continental shelf break, but it did not have enough time to thicken; and (ii) since the LGM, the ice-sheet may have retreated farther back than the present-day grounding line and subsequently readvanced, over the past 4000 years. |
Exploitation Route | They can be used with data from other locations to build up a region-by-region description of the retreat history of the ice-sheet. |
Sectors | Environment |
Title | Effect of glacio-isostatic movement on depth of ice at the grounding-line |
Description | The grounding-line (GL) of a marine ice-sheet is the location where the ice has thinned with flow to reach the flotation thickness. Therefore, the GL indicates where an ice-shelf commences. Ice flux across the GL increases with the thickness of the ice, and recent theoretical work indicates that flux is proportional to the thickness to a power between four and five. These considerations led to the idea that a GL on a reverse slope (sloping inwards) is dynamically unstable, i.e. sensitive to the operation of feedbacks, since a retreat of the GL would lead to greater ice flux and further retreat. In contrast, an advance would lead to lower ice flux and further advance. An early discovery in glacial geology was the association of uplift of the earth surface with the retreat of large ice-sheets, owing to the unloading. For marine ice-sheets, such uplift means a further source of change in the ice-thickness at the grounding-line. Our discovery was that such shallowing can turn the unstable retreat of a marine ice-sheet into an unstable advance. This was used to explain some anomalous measurements of uplift from Antarctica, undertaken by recently installed continuous GPS stations. The anomalous results are either very slow rates of uplift, or in one case, downwards motion. The cause of these was attributed to reloading by ice, due to plausibly unstable GL readvance in the Weddell Sea sector of the the West Antarctic ice-sheet over the past 4000 years. |
Type Of Material | Improvements to research infrastructure |
Provided To Others? | No |
Impact | Publication of two papers (i)"Thomas, I.D., M.A. King, M.J. Bentley, P.L. Whitehouse, N.T. Penna, S.D.P. Williams, R.E.M. Riva, D.A. Lavallee, P.J. Clarke, E.C. King, R.C.A. Hindmarsh, H. Koivula, (2011), "Widespread low rates of Antarctic glacial isostatic adjustment revealed by GPS observations", Geophys. Res. Lett.,38, L22302, doi:10.1029/2011GL049277" (ii) "Bradley, S.L., R.C.A. Hindmarsh, P.L. Whitehouse, M.J. Bentley and M.A. King, (2015), Low post-glacial rebound rates in the Weddell Sea due to Late Holocene ice-sheet readvance, Earth Planet. Sci. Lett., 413, 79-89, doi:10.1016/j.epsl.2014.12.039" |
Title | Modelling ice-sheet grounding-line migration |
Description | In the 1970s several papers were published pointing out that if ice-flux across the grounding-line (the origin of the floating ice-shelf) increased with ice thickness, then grounding-lines situated on locations where the bed deepened up-glacier (has a 'reverse slope'), the situation was potentially unstable. For example, a small retreat of the grounding line would increase ice-flux, causing the ice-sheet to lose volume and induce further retreat of the grounding line. In contrast, a small advance would reduce ice-flux, allowing the ice-sheet to gain volume and result in more advance. These ideas had to wait until 2007 before they were given a rigorous mathematical footing by Schoof. Schoof gave a formula for flux as a function of thickness, which allowed the testing of numerical models. Two model intercomparisons have been carried out, both lead-authored by Frank Pattyn, with DOI's 10.5194/tc-6-573-2012 and 10.3189/2013JoG12J129. Richard Hindmarsh participated in these intercomparisons. We now have greatly increased confidence in the ability of numerical models to accurately compute grounding-line migration. |
Type Of Material | Improvements to research infrastructure |
Year Produced | 2012 |
Provided To Others? | Yes |
Impact | Greatly increased confidence in the numerical simulations of grounding line motion. |
Title | Questions about ice dynamics formulated on the basis of newly acquired data |
Description | The large group of earth scientists involved in investigating the palaeo-Antarctic Ice-Sheet (p-AIS) and palaeo-British-Irish Ice-Sheet (p-BIIS) has quite naturally led them to think about ice dynamical explanations for their observations. Nearly all of their conjectures and questions are well thought-through, which ultimately create questions for ice dynamicists and modellers to answer. We are improving and amending models to focus on these questions. |
Type Of Material | Computer model/algorithm |
Year Produced | 2015 |
Provided To Others? | Yes |
Impact | There are several different groups working on the p-AIS and p-BIIS, all aiming to make use of the new data. These groups talk with each other, but are all interested in different aspects of the behaviour of the ice-sheet. |
Title | Velocity profiles - Adelaide, Berkner, Fletcher, Roosevelt |
Description | Vertical velocity data from within a few kilometres of four ice divides sitting within ice rises. |
Type Of Material | Database/Collection of data |
Year Produced | 2014 |
Provided To Others? | Yes |
Impact | Provides data that can be used to invert for (i) ice rheology; and (ii) the formation date of the ice-rise. |
Title | Velocity profiles from ice-rises. - Korff, Henry, Skytrain, Fowler, Fletcher |
Description | Vertical velocity profiles can be measured with two accurately co-located radar surveys separated by a suitable period of time - in these cases, one year. |
Type Of Material | Database/Collection of data |
Provided To Others? | No |
Impact | These velocity profiles can be used with radar surveys of sub-surface structure to date the formation time of the ice-rises. The ice-rises are about 100 km by 30 km in horizontal dimension, up to 600 m thick. |
Description | Durham LGM Antarctica |
Organisation | Durham University |
Department | Department of Geography |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | BAS have organised the data gathering, geophysical surveying of ice-rises by radar-techniques. We can use these data to date the retreat of the main Antarctic grounding line. These ice-rises are located within the Ronne Ice Shelf. |
Collaborator Contribution | The project is ongoing - Durham have committed to using the data to model the behaviour of the Antarctic ice-sheet since the Last Glacial Maximum. |
Impact | BAS have completed the geophysical surveys. The data are due to be shared; once this occurs, Durham will use the data, in conjunction with other data they have acquired and models, to constrain the behaviour of the West Antarctic ice-sheet in the Weddell Sea area. BAS will contribute by collaborating on the organisation of the modelling studies. |
Start Year | 2013 |
Description | Newcastle GIA |
Organisation | University of Newcastle |
Country | Australia |
Sector | Academic/University |
PI Contribution | (i) BAS provided the solar and wind-driven power stations to support year-round continuous rock-based GPS measurements of isostatic uplift. (ii) BAS used the data in models to illuminate the complexity of the retreat history. |
Collaborator Contribution | Newcastle and Durham gathered and analysed the GPS data, using them to estimate uplift rates. |
Impact | (i) A data paper by Thomas et al, published in Geophysical Research Letters in 2011 - it's DOI number is 10.1029/2011GL049277. The paper was multi-disciplinary, involving (a) the construction and installation by BAS teams of continuous GPS stations in Antarctica; and (b) the analysis of these data by Newcastle and Durham using dedicated software to produce uplift rates. (ii) The use of these data to show that low uplift rates in the Weddell Sea area could be explained by readvance of part of the West Antarctic ice-sheet over the past 4000 years. The work was published in Earth and Planetary Science Letters in 2015, with DOI 10.1016/j.epsl.2014.12.039. The work was multi-disciplinary, involving mathematical modelling, solid-earth geophysics and glaciology. This work was a collaboration between BAS, Durham and Newcastle - a Newcastle collaborator Matt King has now moved to Tasmania. |
Start Year | 2011 |
Title | BASISM - the BAS Ice Sheet Model |
Description | BASISM has been developed over the past fifteen years, and has achieved successes in formal model intercomparison projects (MIPs), as well as being used to settle some long-standing problems. |
Type Of Technology | Software |
Year Produced | 2013 |
Impact | This software (and its brethren) have been used in MIPs to validate theoretical advances in grounding-line motion/stability and ice-stream formation. |
Description | Celebrating Charlie Raymond's 80th Birthday |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | Charlie Raymond was a highly successful glaciologist who influenced a great number and variety of scientists. My field work post-2000 CE was organised around his ideas regarding ice flow near ice divides; these ideas are called the 'Raymond Effect' which lead to anticlines called 'Raymond Arches', which are detected by ice-penetrating radar. The event attracted a wide variety of scientists. |
Year(s) Of Engagement Activity | 2019 |
Description | Modelling panel for BRITICE, for groups both internal and external to the main BRITICE project |
Form Of Engagement Activity | A formal working group, expert panel or dialogue |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Postgraduate students |
Results and Impact | The new data acquired by BRITICE from the North, Norwegian and Celtic Seas shows very clearly that the British-Irish Ice Sheet (BIIS) was a marine ice-sheet. The stability of such ice sheets is a major concern, since Antarctica is a marine ice-sheet and its observed retreat threatens to raise global sea-level by between 0.5m and 2m by 2100 CE. The quantity of new data points means the the BIIS is the most well-described marine ice-sheet, and already these data are illuminating issues of marine ice-sheet stability. |
Year(s) Of Engagement Activity | 2014,2015,2016,2017,2018 |
Description | Workshop on "Ice-Rises"; Tromsö 2014 |
Form Of Engagement Activity | A formal working group, expert panel or dialogue |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | The workshop was on the subject of "Ice Rises" - these are islands of grounded ice, surrounded by open sea or ice shelves, situated on the continental shelf ringing the main Antarctic ice-sheets. Ice-rises can be used for and in many applications. The workshop was 'networking' for interested workers from many disciplines. The organisers of the workshop were Kenichi Matsuoka (NPI Tromsö) and Richard Hindmarsh (BAS). A review paper Matsuoka et al. 2015 appeared - its DOI number is 10.1016/j.earscirev.2015.09.004 |
Year(s) Of Engagement Activity | 2014 |