How important are ice streams in accelerating ice sheet deglaciation?
Lead Research Organisation:
Durham University
Department Name: Geography
Abstract
It is widely accepted that the Earth's climate is warming and that glaciers are losing mass and increasing sea level. Small glaciers are particularly susceptible but only represent a fraction of the Earth's freshwater stored as ice. In contrast, the huge ice sheets in Greenland and Antarctica store several 10s of metres of equivalent sea level and recent studies suggest that they, too, are losing mass and that this appears to be accelerating.
Ice sheets transfer ice to the oceans via numerous fast flowing glaciers called 'ice streams'. It has been discovered that ice streams can speed up, slow down, and even stop altogether; as well as switch their position. These changes can occur relatively rapidly (over a few years) but it is not clear whether they are part of a long-term trend of ice sheet shrinkage (over centuries to millennia) or simply reflect their natural variability. Another possibility is that the recent acceleration and thinning is the beginning or 'pre-cursor' of an episode of widespread mass loss but the question remains: how important are ice streams in accelerating ice sheet deglaciation, e.g. beyond that which might be excepted from climate forcing alone?
In order to assess the significance of these short-term changes, we need to understand how ice streams operate over time-scales longer than current measurements allow and we also need to view ice streams as an integrated pattern of drainage within the ice sheet that evolves over several millennia. This can be achieved through investigation of past ice stream behaviour. Past-ice streams can be identified because, compared to slow-flowing ice, their rapid flow creates distinctive glacial landforms on the now-exposed ice sheet bed. We can locate these ice stream 'footprints' on past ice sheet beds very easily (e.g. in the UK or North America) and then use dating techniques (e.g. radiocarbon dating) and other evidence related to ice sheet flow patterns to estimate when and for how long they existed. This approach has been taken by scientists and has increased our understanding of their behaviour over long time-scales but studies have tended to focus on just one ice stream or specific regions. What we really want is information on the activity of lots of ice streams from across an entire ice sheet and, ideally, from as long a time-span as possible i.e. from a complete deglaciation, when the ice sheet shrinks from its maximum extent and disappears altogether.
This aim of this project, therefore, is to produce a ground-breaking dataset that reconstructs the spatial and temporal activity of every ice stream in the North American Laurentide Ice Sheet (which was similar in size to Antarctica) from its maximum extent around 21,000 yrs ago to its near-disappearance around 5,000 yrs ago. We will map all the flow patterns on the ice sheet bed, including ice streams, and date these using an existing database of ~4,000 radiocarbon dates (and other published dates). A recent pilot study shows that we can date the duration of individual ice streams to within 250-500 yrs. This will allow us to see how an entire drainage network of ice streams evolves during deglaciation and whether their combined activity caused major episodes of significant mass loss. It will also reveal the extent to which ice stream activity is linked to abrupt climate and sea level changes in the past, e.g. abrupt warming or cooling and rapid changes in sea level. Taken together, this will provide a firm context with which to model and predict the future response and likely magnitude of changes in modern-day ice sheets, e.g. for the next IPCC Report.
Ice sheets transfer ice to the oceans via numerous fast flowing glaciers called 'ice streams'. It has been discovered that ice streams can speed up, slow down, and even stop altogether; as well as switch their position. These changes can occur relatively rapidly (over a few years) but it is not clear whether they are part of a long-term trend of ice sheet shrinkage (over centuries to millennia) or simply reflect their natural variability. Another possibility is that the recent acceleration and thinning is the beginning or 'pre-cursor' of an episode of widespread mass loss but the question remains: how important are ice streams in accelerating ice sheet deglaciation, e.g. beyond that which might be excepted from climate forcing alone?
In order to assess the significance of these short-term changes, we need to understand how ice streams operate over time-scales longer than current measurements allow and we also need to view ice streams as an integrated pattern of drainage within the ice sheet that evolves over several millennia. This can be achieved through investigation of past ice stream behaviour. Past-ice streams can be identified because, compared to slow-flowing ice, their rapid flow creates distinctive glacial landforms on the now-exposed ice sheet bed. We can locate these ice stream 'footprints' on past ice sheet beds very easily (e.g. in the UK or North America) and then use dating techniques (e.g. radiocarbon dating) and other evidence related to ice sheet flow patterns to estimate when and for how long they existed. This approach has been taken by scientists and has increased our understanding of their behaviour over long time-scales but studies have tended to focus on just one ice stream or specific regions. What we really want is information on the activity of lots of ice streams from across an entire ice sheet and, ideally, from as long a time-span as possible i.e. from a complete deglaciation, when the ice sheet shrinks from its maximum extent and disappears altogether.
This aim of this project, therefore, is to produce a ground-breaking dataset that reconstructs the spatial and temporal activity of every ice stream in the North American Laurentide Ice Sheet (which was similar in size to Antarctica) from its maximum extent around 21,000 yrs ago to its near-disappearance around 5,000 yrs ago. We will map all the flow patterns on the ice sheet bed, including ice streams, and date these using an existing database of ~4,000 radiocarbon dates (and other published dates). A recent pilot study shows that we can date the duration of individual ice streams to within 250-500 yrs. This will allow us to see how an entire drainage network of ice streams evolves during deglaciation and whether their combined activity caused major episodes of significant mass loss. It will also reveal the extent to which ice stream activity is linked to abrupt climate and sea level changes in the past, e.g. abrupt warming or cooling and rapid changes in sea level. Taken together, this will provide a firm context with which to model and predict the future response and likely magnitude of changes in modern-day ice sheets, e.g. for the next IPCC Report.
Planned Impact
Policymakers and International Scientific Panels/Groups: our project targets current limitations identified in the 4th IPCC report concerning our ability to accurately predict sea level contributions from ice sheets. We will discover whether dynamic changes in ice streams led to rapid acceleration(s) in mass loss and the likely magnitude and time-scales over which these episodes occurred, thereby improving IPCC predictions of future sea level change (see LoS from Tony Payne, lead author of 5th IPCC report: 'Sea Level Change'). IPCC draws consensus from scientific papers but we will also target policymakers through contributions such as NERC Planet Earth, NERC Science Days, and invitations to local MPs, e.g. Stokes has previously been invited to present results of his research at the House of Commons. Our project will also contribute to several international working groups. It is central to the INQUA project 'Meltwater Routing and Ocean-Cryopshere-Atmosphere response' (MOCA), led by Project Partner Tarasov, which aims 'to establish a constrained regional meltwater and iceberg discharge chronology for the northern hemisphere'. MOCA is also linked to the 'Paleo Model Intercomparison Project' (PMIP II), and we will contribute to their aim of developing improved palaeo-environmental datasets. Ice sheet modellers will also benefit from our dataset, which can be used to test/validate models of ice stream/ice sheet behaviour. Our regional analyses of marine-based ice streams is also relevant to the Marine Ice Sheet Intercomparison Project (MISMIP), which is focused on evaluating agreement between marine-ice sheet models and 'real' ice sheet behavior (see LoS from Hindmarsh/Payne). In other disciplines, palaeo-oceanographers will benefit from new knowledge of the likely magnitude and timing of iceberg discharge events and meltwater pulses from ice streams; and palaeo-climatologists will benefit from a new understanding of the links between ice sheet dynamics, palaeo-climate and palaeo-oceanography (e.g. see LoS from Anders Carlson).
Teachers, educators, schoolchildren: this group will benefit from our involvement in the Climate Change for Schools Project (CCSP), which aims to put climate change at the heart of the national curriculum and make schools 'beacons' for positive action in their local communities. Following consultation with Project Manager Dr Krista McKinzey (see LoS) as to how we can best contribute, we propose to run 5 x 1 day workshops for secondary school teachers. The purpose of these will be to disseminate scientific knowledge on glaciers and climate change and devise new resources/schemes of work on this topic for the curriculum. The project website will have pages specifically designed for different educational groups (primary, secondary, tertiary), including resources for teachers to download with suggested activities. We also plan to continue existing activities in secondary/tertiary education where Stokes has given talks in schools and at education conferences (e.g. Philip Allan AS/A2 Physics Conference; British Association Science Festival, South African Science Festival) and written articles (e.g. 'Physics Review' A-level magazine).
General Public: the behaviour of large polar ice sheets has the potential to engender a wider public interest. Following consultation with the Director for Science Communication at the award-winning 'Life' Science Centre, Newcastle (see LoS from Ian Simmons), we propose to improve understanding and raise awareness of these issues through a series of 'Meet the Scientist' days. We will hold an exhibit on 'Glaciers and Climate Change' and provide computer portals for exercises and mapping of glacier change, and take-away resources/fact-sheets, etc. As with previous outputs that have been covered in a variety of national and international media (e.g. the Co-I's recent appearance on national television), newsworthy results will be disseminated through University press releases.
Teachers, educators, schoolchildren: this group will benefit from our involvement in the Climate Change for Schools Project (CCSP), which aims to put climate change at the heart of the national curriculum and make schools 'beacons' for positive action in their local communities. Following consultation with Project Manager Dr Krista McKinzey (see LoS) as to how we can best contribute, we propose to run 5 x 1 day workshops for secondary school teachers. The purpose of these will be to disseminate scientific knowledge on glaciers and climate change and devise new resources/schemes of work on this topic for the curriculum. The project website will have pages specifically designed for different educational groups (primary, secondary, tertiary), including resources for teachers to download with suggested activities. We also plan to continue existing activities in secondary/tertiary education where Stokes has given talks in schools and at education conferences (e.g. Philip Allan AS/A2 Physics Conference; British Association Science Festival, South African Science Festival) and written articles (e.g. 'Physics Review' A-level magazine).
General Public: the behaviour of large polar ice sheets has the potential to engender a wider public interest. Following consultation with the Director for Science Communication at the award-winning 'Life' Science Centre, Newcastle (see LoS from Ian Simmons), we propose to improve understanding and raise awareness of these issues through a series of 'Meet the Scientist' days. We will hold an exhibit on 'Glaciers and Climate Change' and provide computer portals for exercises and mapping of glacier change, and take-away resources/fact-sheets, etc. As with previous outputs that have been covered in a variety of national and international media (e.g. the Co-I's recent appearance on national television), newsworthy results will be disseminated through University press releases.
Publications
Dalton A
(2022)
Evolution of the Laurentide and Innuitian ice sheets prior to the Last Glacial Maximum (115 ka to 25 ka)
in Earth-Science Reviews
Dalton A
(2020)
An updated radiocarbon-based ice margin chronology for the last deglaciation of the North American Ice Sheet Complex
in Quaternary Science Reviews
Dulfer H
(2023)
Glacial geomorphology of the northwest Laurentide Ice Sheet on the northern Interior Plains and western Canadian Shield, Canada
in Journal of Maps
Margold M
(2015)
Ice streams in the Laurentide Ice Sheet: Identification, characteristics and comparison to modern ice sheets
in Earth-Science Reviews
Margold M
(2018)
Reconciling records of ice streaming and ice margin retreat to produce a palaeogeographic reconstruction of the deglaciation of the Laurentide Ice Sheet
in Quaternary Science Reviews
Margold M
(2014)
Ice streams in the Laurentide Ice Sheet: a new mapping inventory
in Journal of Maps
Siegert M
(2019)
Major Ice Sheet Change in the Weddell Sea Sector of West Antarctica Over the Last 5,000 Years
in Reviews of Geophysics
Stokes C
(2017)
Geomorphology under ice streams: Moving from form to process
in Earth Surface Processes and Landforms
Stokes C
(2017)
Deglaciation of the Laurentide Ice Sheet from the Last Glacial Maximum
in Cuadernos de Investigación Geográfica
STOKES C
(2016)
Ribbed bedforms on palaeo-ice stream beds resemble regular patterns of basal shear stress ('traction ribs') inferred from modern ice streams
in Journal of Glaciology
Description | Will the vast ice streams draining the Greenland and Antarctic ice sheets enter into a runaway acceleration in a warming climate? If so, a worst-case scenario for rapid sea level rise could occur. We have assembled the available evidence from the retreat of the Laurentide Ice Sheet in North America that took place between 22,000 and 7,000 years ago, and show that during deglaciation the number of ice streams and their total discharge decreased (Stokes et al., 2016: Nature). This suggests that ice stream activity decreases along with the size of the ice sheet itself, and that ice streams do not contribute to a runaway ice sheet demise, as has been suggested. Using these data, we have also produced a new reconstruction of the ice sheet, showing the activity of the ice streams as it deglaciated (Margold et al., 2018). The results, however, are specific to the retreat of the Laurentide Ice Sheet and it is unknown whether they can be directly translated to moder ice sheet dynamics. We have also developed the first comprehensive inventory of ice streams in the Laurentide Ice sheet (Margold et al., 2015: Journal of Maps) and written a major review paper on their characteristics and compared them to modern ice streams (Margold et al., 2015: Earth-Science Reviews) and discovered some new landforms (traction ribs) on the bed of the former Laurentide Ice Sheet (Stokes et al., 2016). |
Exploitation Route | It is anticipated that our findings will be iof use to a range of scientific communities such as glaciologists, glacial geomorphologists, climatologists, oceanographers. Once the project is complete, our findings should help to constrain predictions of modern-day ice sheets in Greenland and Antarctica. |
Sectors | Environment |
Description | Some of the findings from the project were used to develop teacher resources for key stage 3 on the topic of 'glaciers and climate change'. This was a formal part of the pathways to impact document. |
First Year Of Impact | 2013 |
Sector | Education |
Impact Types | Cultural Societal |
Title | Data for: Reconciling records of ice streaming and ice margin retreat to produce a palaeogeographic reconstruction of the deglaciation of the Laurentide Ice Sheet |
Description | The attached Excel spreadsheet provides additional information for individual ice streams covered in the manuscript 'Reconciling records of ice streaming and ice margin retreat to produce a palaeogeographic reconstruction of the deglaciation of the Laurentide Ice Sheet' |
Type Of Material | Database/Collection of data |
Year Produced | 2018 |
Provided To Others? | Yes |
URL | https://data.mendeley.com/datasets/ngctzcr586/1 |
Title | Laurentide ice streams database |
Description | We have produced a new database of all of the ice streams in the former Laurentide Ice Sheet |
Type Of Material | Database/Collection of data |
Year Produced | 2015 |
Provided To Others? | Yes |
Impact | Too early to say, but the paper has started to get cited and the data are being used by other groups. |
URL | http://www.tandfonline.com/doi/full/10.1080/17445647.2014.912036 |
Description | AGU JA Conference (Montreal) |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | Stokes, C.R., Margold, M. (2015): The Geomorphology of Ice Stream Beds: Recent Progress and Future Challenges. AGU Joint Assembly, Montreal, Canada, 3-7 May, 2015. Talk Stokes, C.R., Margold, M. (2015): 'Traction ribs' on the palaeo-ice stream tracks of the Interior Plains, North America. AGU Joint Assembly, Montreal, Canada, 3-7 May, 2015. Poster |
Year(s) Of Engagement Activity | 2015 |
Description | Development of Teachers Resources for Key Stage 3 on Glaciers and Climate Change |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | Yes |
Geographic Reach | National |
Primary Audience | Schools |
Results and Impact | Together with teachers, we developed five lesson plans for use in Key Stage 3. It is anticipated that the lessons will change thinking and behaviour in relation to climate change. |
Year(s) Of Engagement Activity | 2013 |
URL | https://www.dur.ac.uk/geography/ice_sheets_and_sea_level_outreach/ |
Description | EGU Conference (Vienna) |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | Margold, M., Stokes, C.R., Clark, C.D. (2015): Ice Stream Dynamics during Deglaciation of the Laurentide Ice Sheet. EGU General Assembly 2015, Vienna, Austria, 13-17 April, 2015. Talk. Margold, M., Stokes, C.R. (2015): 'Traction ribs' on the palaeo-ice stream tracks of the Interior Plains, North America. EGU General Assembly 2015, Vienna, Austria, 13-17 April, 2015. Poster. |
Year(s) Of Engagement Activity | 2015 |
Description | Invited seminar at the Department of Geography, VUB Brussels, Belgium |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Professional Practitioners |
Results and Impact | 20-30 people listened to a research seminar on the results of this NERC project |
Year(s) Of Engagement Activity | 2016 |
Description | Invited seminar at the Institute of Geophysics of the Czech Academy of Sciences, Prague, Czech Republic |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Professional Practitioners |
Results and Impact | 20-30 academics, research students and undergraduates listened to a talk on the results of this NERC project |
Year(s) Of Engagement Activity | 2016 |
Description | Invited talk at EGU Conference, Vienna (2016) |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | Invited conference talk at major international conference |
Year(s) Of Engagement Activity | 2016 |
Description | Invited visiting researcher seminar, University of Tromso, Norway |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Professional Practitioners |
Results and Impact | 30 people listened to my seminar on ice stream dynamics |
Year(s) Of Engagement Activity | 2016 |
Description | Media article in The Conversation |
Form Of Engagement Activity | A magazine, newsletter or online publication |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Public/other audiences |
Results and Impact | This was an article for 'The Conversation' website which described the results of our Nature paper (Stokes et al., 2016) in an accessible way. It has been read almost 5,000 times. Link below. https://theconversation.com/how-ice-sheets-collapse-a-lesson-from-the-past-54587 |
Year(s) Of Engagement Activity | 2016 |
URL | https://theconversation.com/how-ice-sheets-collapse-a-lesson-from-the-past-54587 |
Description | Past Gateways Conference (Potsdam, Germany) |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | Margold, M., Stokes, C.R., Clark, C.D. (2015): Ice Stream Dynamics during Deglaciation of the Laurentide Ice Sheet. PAST Gateways meeting 2015, Potsdam, 18-22 May, 2015. Talk. |
Year(s) Of Engagement Activity | 2015 |
Description | Public Lecture on Antarctic Ice Sheet Dynamics (Durham University UK) |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Public/other audiences |
Results and Impact | Public lecture on Antarctica. |
Year(s) Of Engagement Activity | 2016 |
Description | Public lecture (glaciers and climate change) |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Public/other audiences |
Results and Impact | Talk sparked questions and discussion afterwards Schools visit have arisen Invitations for further public lectures |
Year(s) Of Engagement Activity | Pre-2006,2006,2007,2009,2014,2015 |
URL | https://www.dur.ac.uk/geography/ice_sheets_and_sea_level_outreach/ |
Description | Quaternary conference (Newfoundland) |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | We presented two talks from our project: Margold, M., Stokes, C.R. (2015): 'Traction ribs' on the palaeo-ice stream tracks of the Interior Plains. CANQUA meeting 2015, 16-19 August, 2015. Talk. Stokes, C.R., Margold, M., Clark, C.D., Tarasov, T. (2015): Ice Stream Dynamics during Deglaciation of the Laurentide Ice Sheet. CANQUA meeting 2015, 16-19 August, 2015. Talk. |
Year(s) Of Engagement Activity | 2015 |
Description | Talk to North Eastern Geological Society |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Public/other audiences |
Results and Impact | Raising awareness of ice sheets and global climate change and sea level change |
Year(s) Of Engagement Activity | 2018 |