Understanding marine ice stream retreat using numerical modelling and geophysical data

Lead Research Organisation: NERC British Antarctic Survey
Department Name: Science Programmes

Abstract

Currently there is major uncertainty surrounding the contributions of the Greenland and Antarctic ice sheets to future sea level rise. The majority of the ice discharged by these ice sheets into the surrounding oceans is by drainage of fast flowing 'marine ice streams' which have their bases below present sea level and which flow at speeds of a few hundred metres to several kilometres per year. Recent satellite observations show that some of these marine ice streams are experiencing rapid change in the form of thinning and retreat of their margins. These ice streams are a major focus for current glaciological research, but up until now this research has mostly concentrated on either theoretical studies of ice stream retreat and/or observations of modern ice streams. Such studies typically only provide a snapshot of an ice stream's life-cycle, limited to the last few decades. Current attempts to determine what controls the retreat of these ice streams remain inconclusive. This problem is compounded by the fact that existing large-scale ice sheet models, used for future sea level predictions in the 'Intergovernmental Panel on Climate Change' 2007 report, are not able to incorporate such rapid changes in ice streams. Understanding the controls of ice stream retreat and predicting their future behaviour will be crucial, if the scientific community intends to quantify future sea level rise with any degree of certainty. This study aims to determine the controlling factors on marine ice stream retreat by combining numerical modelling with marine-geophysical observations of ice stream retreat. We will use observations from three well documented palaeo-ice streams in Antarctica (i.e. ancient ice streams recorded by geological and geophysical evidence) that underwent contrasting styles and rates of retreat following the last glacial maximum and ranging from rapid through episodic to slow. The numerical model that we will use is specifically developed to allow us to simulate ice stream retreat. The marine geophysical and geological observations will provide the physical setting for the numerical model and, crucially, the retreat history of the different ice streams for comparison to the model simulations. To our knowledge, a robust comparison and validation of a numerical marine ice stream model using such data has never before been attempted. The inter-disciplinary approach taken in this project provides the urgently needed link between observational records of ice stream retreat and numerical modelling. It will advance our understanding of the factors that control such retreat and also provide crucial insights for developing ice sheet models, and thus contribute to improving the ability of the scientific community to predict future sea level rise.
 
Description The key findings of our project are that 1) ice sheet retreat from the Antarctic continental shelf since the last ice age was time transgressive, and 2) ice-stream retreat can halt temporarily during long phases of climate warming. Marine-based ice streams are the fast flowing arteries of ice sheets, draining approximately 90% of the ice that reaches the sea. They flow through large bathymetric troughs carved into the continental shelf towards the ocean, thereby reaching velocities of hundreds to thousands of metres in a year. The unpredictable nature of ice streams makes forecasting ice-sheet retreat and resulting sea-level rise extremely difficult. Satellite imagery from the last 20 years has enhanced our knowledge of ice sheet dynamical behaviour and has shown that many ice streams are getting thinner and retreating in response to oceanic and atmospheric warming. Radiocarbon dates on fossil biogenic material in marine sediment cores recovered from palaeo-ice stream troughs on the continental shelf around Antarctica have provided minimum ages for grounded ice retreat since the last ice age. Our new compilation and re-analysis of deglaciation ages (Livingstone et al. 2012, Earth Science Reviews) has revealed that the ice-sheet retreat was time transgressive and that individual ice stream systems exhibit different retreat histories. This variability allowed us to classify the Antarctic palaeo-ice streams into discrete retreat styles and to investigate the controls on grounding-line retreat. Our analysis highlighted the important impact of internal factors on ice stream dynamics, such as bed characteristics and slope, and drainage basin size. Whilst grounding-line retreat may be triggered, and to some extent paced, by external forcing (i.e. atmospheric and oceanic temperatures, sea level rise), the individual characteristics of each ice stream did modulate the precise timing and rate of retreat through time. We used a computer model to simulate the retreat history of the well studied Marguerite Trough palaeo-ice stream in West Antarctica (Jamieson et al. 2012, Nature Geoscience). Our research demonstrated that the physical shape of the trough, i.e. the landscape below the ice, is a crucial factor in controlling ice-sheet stability. The width of the trough can have a major effect on ice flow, and determines how fast retreat, and therefore sea-level rise, can happen. Although climatic and oceanic changes are important drivers of ice loss, our study showed that during an overall phase of retreat an ice stream can appear almost stable when in fact the opposite is the case. A series of simulations revealed that ice dragged on the sides of the trough more where it was narrow, causing retreat to slow and in places temporarily stop for decades to centuries before retreat continued. Many modern ice streams are found in troughs with beds below sea level that deepen inland. Current theory suggests that ice loss can increase rapidly in deeper water, but our new findings show that 'bottlenecks' in the troughs can cause retreat to slow down. These bottlenecks occur in the same place where pauses or slowdowns in past ice retreat have occurred.
Exploitation Route The direct beneficiaries of our research are ice-sheet modellers who can use our data to validate and improve their models used to predict future ice-sheet melting and resulting global sea-level rise.
Sectors Environment,Other

URL https://www.dur.ac.uk/geography/research/research_projects/?mode=project&id=479
 
Description Our research will help ice-sheet modellers to validate and improve their computer models and thus improve predictions of future sea-level rise in response to polar ice-sheet melting. Beneficiaries: Scientists investigating marine-based ice-stream dynamics and ice-sheet modellers will benefit from our research. These academic beneficiaries will be able to provide much more improved forecasts of future sea-level rise in response to climate change that will allow governments and policy makers to take appropriate counter-measures. Therefore, environment, economy and the wider community will benefit as well.
First Year Of Impact 2012
Sector Environment
 
Title One-dimensional numerical model of ice-stream flow with robust grounding-line dynamics 
Description The model is a one-dimensional numerical flow-line model that is specifically designed for tracking grounding-line motion, thereby including a buttressing ice shelf and sub-ice shelf oceanic melting. The model is used for reconstructing ice-stream retreat, can be compared to and constrained by geological data and can be used for evaluating the influence of different driving mechanisms forcing grounding-line retreat. 
Type Of Material Computer model/algorithm 
Year Produced 2012 
Provided To Others? Yes  
Impact The model was designed for reconstructing the retreat of the Marguerite Trough palaeo-ice stream (western Antarctic Peninsula shelf) after the Last Glacial Maximum. It successfully reconstructed the history of retreat of this ice stream as reconstructed from palaeo-geological data and highlighted the various importance of different controlling factors on ice-stream flow and grounding-line retreat (Jamieson et al. 2012, Nature. Geosci.; Jamieson et al. 2014, J. Geophys. Res. Earth Surf.). The model was described and its details provided to the community in the supplementary information of the corresponding publications (Jamieson et al. 2012, Nature. Geosci.; Jamieson et al. 2014, J. Geophys. Res. Earth Surf.). It is now used for modelling the retreat of palaeo-ice streams elsewhere (e.g. in Greenland). 
 
Description Collaboration on the integration of palaeo-data into models for developing, testing and improving numerical ice-stream models and understanding the role of climate drivers in forcing ice-sheet retreat 
Organisation Durham University
Country United Kingdom 
Sector Academic/University 
PI Contribution I helped with the compilation and interpretation of marine geological and marine geophysical data constraining ice-stream retreat from the Antarctic continental shelf following the Last Glacial Maximum, the compilation of data on drivers (e.g. oceanic and atmospheric warming, sea-level rise) and boundary conditions (e.g. shelf bathymetry) for ice-sheet retreat, the interpretation of the results from modelling ice-stream retreat and the publication of the palaeo-data compilations and modelling studies.
Collaborator Contribution The colleagues from the universities of Durham, Zurich, Sheffield and Cambridge led or assisted with the collection, compilation and interpretation of palaeo data about ice-stream retreat from the Antarctic continental shelf following the Last Glacial Maximum, the compilation of data on drivers (e.g. oceanic and atmospheric warming, sea-level rise) and boundary conditions (e.g. shelf bathymetry) for ice-sheet retreat, the development of numerical ice-stream models, the interpretation of the modelling results and the publication of the palaeo-data compilations and modelling studies.
Impact Hillenbrand, C.-D., Melles, M., Kuhn, G., Smith, J., Livingstone, S.J., Ó Cofaigh, C., Stokes, C., Vieli, A., Jamieson, S., Graham, A.G.C., Larter, R.D., (2012) The last ice-sheet advance and retreat across the Antarctic continental shelf: Current knowledge and uncertainties. In: XXXII SCAR and Open Science Conference; multi-disciplinary (marine geology, glaciological modelling) Hillenbrand, C.-D., Livingstone, S.J., Ó Cofaigh, C., Stokes, C.R., Vieli, A., Jamieson, S.R.R., Smith, J.A., Kuhn, G., Melles, M., Graham, A.G.C., Larter, R.D. (2012): The last ice-sheet advance and retreat across the Antarctic continental shelf: Synchrony or diachrony? http://fallmeeting.agu.org/2012/eposters/eposter/c53a-0831/; multi-disciplinary (marine geology, glaciological modelling) Livingstone, S.J., Ó Cofaigh, C., Stokes, C.R., Hillenbrand, C.-D., Vieli, A., Jamieson, S.S.R. (2012): Antarctic palaeo-ice streams. - Earth-Science Reviews, 111: 90-128; multi-disciplinary (marine geology, marine geophysics) Livingstone, S.J., Ó Cofaigh, C., Stokes, C.R., Hillenbrand, C.-D., Vieli, A., Jamieson, S.S.R. (2013): Glacial Geomorphology of Marguerite Bay Palaeo-Ice Stream, western Antarctic Peninsula. - Journal of Maps, 9: 558-572; multi-disciplinary (marine geology, marine geophysics) Jamieson, S.S.R., Vieli, A., Livingstone, S.J., Ó Cofaigh, C., Stokes, C.R., Hillenbrand, C.-D., Dowdeswell, J.A. (2012): Ice stream grounding-line stability on a reverse bed slope. - Nature Geoscience, 5: 799-802; multi-disciplinary (marine geology, marine geophysics, glaciological modelling) Jamieson, S.S.R., Vieli, A., Ó Cofaigh, C., Stokes, C.R., Livingstone, S.J., Hillenbrand, C.-D. (2014): Understanding controls on rapid ice-stream retreat during the last deglaciation of Marguerite Bay, Antarctica, using a numerical model. - Journal of Geophysical Research, 119: 1-17; multi-disciplinary (marine geology, marine geophysics, glaciological modelling)
Start Year 2009
 
Description Collaboration on the integration of palaeo-data into models for developing, testing and improving numerical ice-stream models and understanding the role of climate drivers in forcing ice-sheet retreat 
Organisation University of Cambridge
Country United Kingdom 
Sector Academic/University 
PI Contribution I helped with the compilation and interpretation of marine geological and marine geophysical data constraining ice-stream retreat from the Antarctic continental shelf following the Last Glacial Maximum, the compilation of data on drivers (e.g. oceanic and atmospheric warming, sea-level rise) and boundary conditions (e.g. shelf bathymetry) for ice-sheet retreat, the interpretation of the results from modelling ice-stream retreat and the publication of the palaeo-data compilations and modelling studies.
Collaborator Contribution The colleagues from the universities of Durham, Zurich, Sheffield and Cambridge led or assisted with the collection, compilation and interpretation of palaeo data about ice-stream retreat from the Antarctic continental shelf following the Last Glacial Maximum, the compilation of data on drivers (e.g. oceanic and atmospheric warming, sea-level rise) and boundary conditions (e.g. shelf bathymetry) for ice-sheet retreat, the development of numerical ice-stream models, the interpretation of the modelling results and the publication of the palaeo-data compilations and modelling studies.
Impact Hillenbrand, C.-D., Melles, M., Kuhn, G., Smith, J., Livingstone, S.J., Ó Cofaigh, C., Stokes, C., Vieli, A., Jamieson, S., Graham, A.G.C., Larter, R.D., (2012) The last ice-sheet advance and retreat across the Antarctic continental shelf: Current knowledge and uncertainties. In: XXXII SCAR and Open Science Conference; multi-disciplinary (marine geology, glaciological modelling) Hillenbrand, C.-D., Livingstone, S.J., Ó Cofaigh, C., Stokes, C.R., Vieli, A., Jamieson, S.R.R., Smith, J.A., Kuhn, G., Melles, M., Graham, A.G.C., Larter, R.D. (2012): The last ice-sheet advance and retreat across the Antarctic continental shelf: Synchrony or diachrony? http://fallmeeting.agu.org/2012/eposters/eposter/c53a-0831/; multi-disciplinary (marine geology, glaciological modelling) Livingstone, S.J., Ó Cofaigh, C., Stokes, C.R., Hillenbrand, C.-D., Vieli, A., Jamieson, S.S.R. (2012): Antarctic palaeo-ice streams. - Earth-Science Reviews, 111: 90-128; multi-disciplinary (marine geology, marine geophysics) Livingstone, S.J., Ó Cofaigh, C., Stokes, C.R., Hillenbrand, C.-D., Vieli, A., Jamieson, S.S.R. (2013): Glacial Geomorphology of Marguerite Bay Palaeo-Ice Stream, western Antarctic Peninsula. - Journal of Maps, 9: 558-572; multi-disciplinary (marine geology, marine geophysics) Jamieson, S.S.R., Vieli, A., Livingstone, S.J., Ó Cofaigh, C., Stokes, C.R., Hillenbrand, C.-D., Dowdeswell, J.A. (2012): Ice stream grounding-line stability on a reverse bed slope. - Nature Geoscience, 5: 799-802; multi-disciplinary (marine geology, marine geophysics, glaciological modelling) Jamieson, S.S.R., Vieli, A., Ó Cofaigh, C., Stokes, C.R., Livingstone, S.J., Hillenbrand, C.-D. (2014): Understanding controls on rapid ice-stream retreat during the last deglaciation of Marguerite Bay, Antarctica, using a numerical model. - Journal of Geophysical Research, 119: 1-17; multi-disciplinary (marine geology, marine geophysics, glaciological modelling)
Start Year 2009
 
Description Collaboration on the integration of palaeo-data into models for developing, testing and improving numerical ice-stream models and understanding the role of climate drivers in forcing ice-sheet retreat 
Organisation University of Sheffield
Country United Kingdom 
Sector Academic/University 
PI Contribution I helped with the compilation and interpretation of marine geological and marine geophysical data constraining ice-stream retreat from the Antarctic continental shelf following the Last Glacial Maximum, the compilation of data on drivers (e.g. oceanic and atmospheric warming, sea-level rise) and boundary conditions (e.g. shelf bathymetry) for ice-sheet retreat, the interpretation of the results from modelling ice-stream retreat and the publication of the palaeo-data compilations and modelling studies.
Collaborator Contribution The colleagues from the universities of Durham, Zurich, Sheffield and Cambridge led or assisted with the collection, compilation and interpretation of palaeo data about ice-stream retreat from the Antarctic continental shelf following the Last Glacial Maximum, the compilation of data on drivers (e.g. oceanic and atmospheric warming, sea-level rise) and boundary conditions (e.g. shelf bathymetry) for ice-sheet retreat, the development of numerical ice-stream models, the interpretation of the modelling results and the publication of the palaeo-data compilations and modelling studies.
Impact Hillenbrand, C.-D., Melles, M., Kuhn, G., Smith, J., Livingstone, S.J., Ó Cofaigh, C., Stokes, C., Vieli, A., Jamieson, S., Graham, A.G.C., Larter, R.D., (2012) The last ice-sheet advance and retreat across the Antarctic continental shelf: Current knowledge and uncertainties. In: XXXII SCAR and Open Science Conference; multi-disciplinary (marine geology, glaciological modelling) Hillenbrand, C.-D., Livingstone, S.J., Ó Cofaigh, C., Stokes, C.R., Vieli, A., Jamieson, S.R.R., Smith, J.A., Kuhn, G., Melles, M., Graham, A.G.C., Larter, R.D. (2012): The last ice-sheet advance and retreat across the Antarctic continental shelf: Synchrony or diachrony? http://fallmeeting.agu.org/2012/eposters/eposter/c53a-0831/; multi-disciplinary (marine geology, glaciological modelling) Livingstone, S.J., Ó Cofaigh, C., Stokes, C.R., Hillenbrand, C.-D., Vieli, A., Jamieson, S.S.R. (2012): Antarctic palaeo-ice streams. - Earth-Science Reviews, 111: 90-128; multi-disciplinary (marine geology, marine geophysics) Livingstone, S.J., Ó Cofaigh, C., Stokes, C.R., Hillenbrand, C.-D., Vieli, A., Jamieson, S.S.R. (2013): Glacial Geomorphology of Marguerite Bay Palaeo-Ice Stream, western Antarctic Peninsula. - Journal of Maps, 9: 558-572; multi-disciplinary (marine geology, marine geophysics) Jamieson, S.S.R., Vieli, A., Livingstone, S.J., Ó Cofaigh, C., Stokes, C.R., Hillenbrand, C.-D., Dowdeswell, J.A. (2012): Ice stream grounding-line stability on a reverse bed slope. - Nature Geoscience, 5: 799-802; multi-disciplinary (marine geology, marine geophysics, glaciological modelling) Jamieson, S.S.R., Vieli, A., Ó Cofaigh, C., Stokes, C.R., Livingstone, S.J., Hillenbrand, C.-D. (2014): Understanding controls on rapid ice-stream retreat during the last deglaciation of Marguerite Bay, Antarctica, using a numerical model. - Journal of Geophysical Research, 119: 1-17; multi-disciplinary (marine geology, marine geophysics, glaciological modelling)
Start Year 2009
 
Description Collaboration on the integration of palaeo-data into models for developing, testing and improving numerical ice-stream models and understanding the role of climate drivers in forcing ice-sheet retreat 
Organisation University of Zurich
Country Switzerland 
Sector Academic/University 
PI Contribution I helped with the compilation and interpretation of marine geological and marine geophysical data constraining ice-stream retreat from the Antarctic continental shelf following the Last Glacial Maximum, the compilation of data on drivers (e.g. oceanic and atmospheric warming, sea-level rise) and boundary conditions (e.g. shelf bathymetry) for ice-sheet retreat, the interpretation of the results from modelling ice-stream retreat and the publication of the palaeo-data compilations and modelling studies.
Collaborator Contribution The colleagues from the universities of Durham, Zurich, Sheffield and Cambridge led or assisted with the collection, compilation and interpretation of palaeo data about ice-stream retreat from the Antarctic continental shelf following the Last Glacial Maximum, the compilation of data on drivers (e.g. oceanic and atmospheric warming, sea-level rise) and boundary conditions (e.g. shelf bathymetry) for ice-sheet retreat, the development of numerical ice-stream models, the interpretation of the modelling results and the publication of the palaeo-data compilations and modelling studies.
Impact Hillenbrand, C.-D., Melles, M., Kuhn, G., Smith, J., Livingstone, S.J., Ó Cofaigh, C., Stokes, C., Vieli, A., Jamieson, S., Graham, A.G.C., Larter, R.D., (2012) The last ice-sheet advance and retreat across the Antarctic continental shelf: Current knowledge and uncertainties. In: XXXII SCAR and Open Science Conference; multi-disciplinary (marine geology, glaciological modelling) Hillenbrand, C.-D., Livingstone, S.J., Ó Cofaigh, C., Stokes, C.R., Vieli, A., Jamieson, S.R.R., Smith, J.A., Kuhn, G., Melles, M., Graham, A.G.C., Larter, R.D. (2012): The last ice-sheet advance and retreat across the Antarctic continental shelf: Synchrony or diachrony? http://fallmeeting.agu.org/2012/eposters/eposter/c53a-0831/; multi-disciplinary (marine geology, glaciological modelling) Livingstone, S.J., Ó Cofaigh, C., Stokes, C.R., Hillenbrand, C.-D., Vieli, A., Jamieson, S.S.R. (2012): Antarctic palaeo-ice streams. - Earth-Science Reviews, 111: 90-128; multi-disciplinary (marine geology, marine geophysics) Livingstone, S.J., Ó Cofaigh, C., Stokes, C.R., Hillenbrand, C.-D., Vieli, A., Jamieson, S.S.R. (2013): Glacial Geomorphology of Marguerite Bay Palaeo-Ice Stream, western Antarctic Peninsula. - Journal of Maps, 9: 558-572; multi-disciplinary (marine geology, marine geophysics) Jamieson, S.S.R., Vieli, A., Livingstone, S.J., Ó Cofaigh, C., Stokes, C.R., Hillenbrand, C.-D., Dowdeswell, J.A. (2012): Ice stream grounding-line stability on a reverse bed slope. - Nature Geoscience, 5: 799-802; multi-disciplinary (marine geology, marine geophysics, glaciological modelling) Jamieson, S.S.R., Vieli, A., Ó Cofaigh, C., Stokes, C.R., Livingstone, S.J., Hillenbrand, C.-D. (2014): Understanding controls on rapid ice-stream retreat during the last deglaciation of Marguerite Bay, Antarctica, using a numerical model. - Journal of Geophysical Research, 119: 1-17; multi-disciplinary (marine geology, marine geophysics, glaciological modelling)
Start Year 2009