Abstract:
Uncertainties in future sea level projections are dominated by our limited understanding of the dynamical processes that control instabilities of marine ice sheets. A valuable case to examine these processes is the last deglaciation of the British-Irish Ice Sheet. The Minch Ice Stream, which drained a large proportion of ice from the northwest sector of the British-Irish Ice Sheet during the last deglaciation, is well constrained, with abundant empirical data which could be used to inform, validate and analyse numerical ice sheet simulations. We use BISICLES, a higher-order ice sheet model, to examine the dynamical processes that controlled the retreat of the Minch Ice Stream. We simulate retreat from the shelf edge under constant "warm" surface mass balance and subshelf melt, to isolate the role of internal ice dynamics from external forcings. The model simulates a slowdown of retreat as the ice stream becomes laterally confined at a "pinning-point" between mainland Scotland and the Isle of Lewis. At this stage, the presence of ice shelves became a major control on deglaciation, providing buttressing to upstream ice. Subsequently, the presence of a reverse slope inside the Minch Strait produces an acceleration in retreat, leading to a "collapsed" state, even when the climate returns to the initial "cold" conditions. Our simulations demonstrate the importance of the Marine Ice Sheet Instability and ice shelf buttressing during the deglaciation of parts of the British-Irish Ice Sheet. Thus, geological data could be used to constrain these processes in ice sheet models used for projecting the future of our contemporary ice sheets.
Funding was provided by the Natural Environment Research Council (NERC) SPHERES Doctoral Training Partnership (NE/L002574/1) with CASE support from the British Geological Survey.
Keywords:
BISICLES, British-Irish Ice Sheet, Ice Shelf Buttressing, Marine Ice Sheet Instability, Minch Palaeo Ice Stream
Gandy, N. (2018). Simulated retreat of the Minch Ice Stream, northwest Scotland, during the last glacial cycle (Version None) [Data set]. Polar Data Centre, Natural Environment Research Council, UK Research & Innovation. https://doi.org/10.5285/5f5bad08-c968-4840-8bb0-1388ce70d42e
| Access Constraints: | No restrictions apply. |
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| Use Constraints: | This data is governed by the NERC data policy http://www.nerc.ac.uk/research/sites/data/policy/ and supplied under Open Government Licence v.3 http://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/ |
| Creation Date: | 2018-09-14 |
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| Dataset Progress: | Complete |
| Dataset Language: | English |
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| Parameters: |
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| Personnel: | |
| Name | UK PDC |
| Role(s) | Metadata Author |
| Organisation | British Antarctic Survey |
| Name | Niall Gandy |
| Role(s) | Technical Contact, Investigator |
| Organisation | University of Leeds |
| Parent Dataset: | N/A |
| Reference: | Gandy, N., Gregoire, L. J., Ely, J. C., Clark, C. D., Hodgson, D. M., Lee, V., Bradwell, T., and Ivanovic, R. F.: Marine Ice Sheet Instability and Ice Shelf Buttressing Influenced Deglaciation of the Minch Ice Stream, Northwest Scotland, The Cryosphere Discuss., https://doi.org/10.5194/tc-2018-116, in review, 2018. | |
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| Lineage: | ||
| Spatial Coverage: | |
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| Latitude | |
| Southernmost | 50 |
| Northernmost | 60 |
| Longitude | |
| Westernmost | -19 |
| Easternmost | 0 |
| Altitude | |
| Min Altitude | N/A |
| Max Altitude | N/A |
| Depth | |
| Min Depth | N/A |
| Max Depth | N/A |
| Location: | |
| Location | United Kingdom |
| Detailed Location | Scotland |
| Location | Ireland |
| Detailed Location | N/A |
| Source(s): |
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| Data Collection: | The data was produced through a series of experiments using the BISICLES ice sheet model. See referenced publication for the full methodology. Instrumentation: The BISICLES ice sheet model, using the branch available at; https://anag-repo.lbl.gov/svn/BISICLES/public/branches/smb/ Resolution: 4km x 4km resolution for the entire domain, 500 m x 500 m resolution at the ice sheet margin in the Minch Palaeo Ice Stream catchment. See referenced publication for details of domain resolution set-up. |
| Data Storage: | The data comprises of the results of 11 experiments. See referenced publication for details of experiment set up. Experiments results are divided as follows; RETREAT = 160 output files (50 yr timestep), totalling 2.4GB RETREAT_NOSHELF = 160 output files (50 yr timestep), totalling 2.4GB READVANCE_0800yr = 119 output files (50 yr timestep), totalling 1.8GB READVANCE_1600yr = 119 output files (50 yr timestep), totalling 1.8GB READVANCE_2400yr = 119 output files (50 yr timestep), totalling 1.8GB READVANCE_3200yr = 119 output files (50 yr timestep), totalling 1.8GB READVANCE_4000yr = 119 output files (50 yr timestep), totalling 1.8GB READVANCE_4800yr = 119 output files (50 yr timestep), totalling 1.8GB READVANCE_5600yr = 119 output files (50 yr timestep), totalling 1.8GB READVANCE_6400yr = 119 output files (50 yr timestep), totalling 1.8GB READVANCE_7200yr = 119 output files (50 yr timestep), totalling 1.8GB Each timestep file from these experiments follows the following naming convention; "plot.scot_500m.l1l2.0lev.[time].2d.nc"; Where [time] is the timestep in the experiment, 0050, 0100 etc. Each output file is in netCDF4 format, and contains the following variables; Thickness_500 - The thickness of ice (m) for the Minch catchment xVel_500 = x Velocity (m/y) for the Minch catchment yVel_500 = y Velocity (m/y) for the Minch catchment zVel_500 = z Velocity (m/y) for the Minch catchment Vel_500 = Velocity (m/y) for the Minch catchment Z_base_500 = Ice Sheet bed elevation (m) for the Minch catchment Z_bottom_500 = Ice Sheet base elevation (m) for the Minch catchment Thickness_4 = The thickness of ice (m) for the entire domain xVel_4 = x Velocity (m/y) for the entire domain yVel_4 = y Velocity (m/y) for the entire domain zVel_4 = z Velocity (m/y) for the entire domain Vel_4 = Velocity (m/y) for the entire domain Z_base_4 = Ice Sheet bed elevation (m) for the entire domain Z_bottom_4 = Ice Sheet base elevation (m) for the entire domain Input data is also provided to run the experiments, totalling 33MB. This includes; A bed friction file "scot_beta.2d.hdf5", A surface mass balance file "smb.2d.hdf5", And an inputs file, "inputs.biis_4km_run_crev.l1l2". The inputs file already points to the relevant variables of the bed friction and surface mass balance files. Projection: The domain coverage is ~50-60N, 19-0W. More precisely, the domain is projected in the "ETRS 1989 LAEA" projection; Projection = Lambert Azimuth Equal Area False Easting = 4321000.0 False Northing = 3210000.0 Central Meridian = 10.0 Latitude of Origin = 52.0 Linear Unit = 1.0 Meter In this projection the arrays have the following extent; Top = 4244753.01141 Bottom = 2662091.01568 Left = 3686091.01568 Right = 3220753.01141 |
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