Airborne geophysical investigation targets basal boundary conditions for the Institute and Moller ice streams, West Antarctica

  • Rippin, David (Principal investigator)
  • Bingham, Robert (Co-investigator)
  • Corr, Hugh F. J. (Co-investigator)
  • Ferraccioli, F (Co-investigator)
  • Jordan, Tom (Co-investigator)
  • Le Brocq, Anne (Co-investigator)
  • Ross, Neil (Co-investigator)
  • Siegert, Martin J. (Co-investigator)

Project: Research project (funded) › Research

Project Details

Description

We hypothesise that the Institute and Möller ice streams are underlain by weak marine sediments, which were deposited at a time when the West Antarctic Ice Sheet was less extensive than today, and which can affect ice flow variability in a manner similar to that observed across the Siple Coast. While reconnaissance geophysical data collected 30 years ago allow this hypothesis to be built, to test it thoroughly requires a dedicated modern airborne geophysical campaign of the ice streams’ catchments, involving radio-echo sounding of ice-sheet thickness and englacial/basal conditions, and magnetic and gravity data collection relating to the underlying geology. Results will reveal the geophysical characteristics of the ice sheet base and their spatial variability, which we can use to identify material properties of the bed and, from this, test the hypothesis. Using these geophysical data as inputs, numerical modelling will be used to assess the region’s flow regime both now and in the past. The project outcomes include a vastly improved
understanding of the Institute/Möller region’s basal boundary conditions, the quantification of ice flow processes in this poorly understood sector of West Antarctica and an assessment of their sensitivity to external drivers, such as climate and ocean warming, sealevel rise and neighbouring glaciological changes.

Layman's description

The Institute and Möller ice streams (IIS/MIS) drain about 20% of the West Antarctic Ice Sheet (WAIS) to the Ronne Ice Shelf, yet our knowledge of their current form and flow history is severely restricted compared with other fast flowing regions in West Antarctica. Data relating to the ice thickness and the ice-sheet bed is limited to reconnaissance transects acquired in the 1970s. Bingham and Siegert (2007) inspected these data, and showed the remarkably smooth and flat bed was similar to the Siple Coast ice streams that drain to the Ross Ice Shelf. As the Siple Coast region is thought to be underlain by marine sediments, deposited when the ice sheet size was smaller than today, Bingham and Siegert (2007) concluded a similar, probably simultaneous, history for the Institute/Möller region. The implications of this finding are significant for future changes in West Antarctica. Bingham and Siegert's (2007) analysis allows us to hypothesise substantial former ice-shelf loss and grounding line retreat in two of the three major drainage outlets of West Antarctica. An extensive airborne geophysical survey of the Institute and Möller ice streams is therefore clearly warranted, to test this hypothesis and better understand the risk of future change. The survey will also allow a better depiction of bed topography and geological boundary conditions in West Antarctica, which will allow us to better quantify the flow and form of the entire WAIS through numerical modelling.

The project's objectives are as follows. 1. To undertake an airborne geophysical survey of the Institute and Möller ice streams of West Antarctica. 2. To quantify bed topography and measure bed roughness from radar data. 3. To map englacial structures (layering and crevasses). 4. To determine power reflection coefficients, forming an appreciation of basal water distribution. 5. To analyse magnetic and gravity anomalies to derive geological boundary conditions for ice flow. 6. To employ numerical modelling to quantify modern and ancient ice flow processes. 7. To use numerical modelling to predict the risk of former changes reoccurring.

This project will result in the following deliverables:
1. The quantification of subglacial topography (and bed roughness) in a hitherto poorly known region of West Antarctica. This information will be made available to the BEDMAP II database, and will make a fundamental contribution as an ice sheet modelling boundary condition. We will analyse these data to determine landscape evolution and ice sheet history.
2. The classification of subglacial thermal conditions and locations of subglacial lakes. This will allow us to comprehend how ice stream flow and subglacial lake/hydrology evolution is both interrelated and affected by subglacial geology and thermal conditions.
3. The measurement of the englacial structure in the WAIS. We will analyse this information to calculate the flow history of the ice sheet and to delineate the margins of the IIS and MIS both now and in the recent past.
4. The definition of crustal structure and subglacial geology of the IIS and MIS catchments of the WAIS.

The glacial history of the WAIS is of direct relevance to assessments of the present day risk of collapse and sea level rise. We aim to report our results directly to the international scientific community by linking to the Scientific Committee on Antarctic Research's (SCAR) scientific research programme entitled Antarctic Climate Evolution (ACE), which integrates geology and geophy sical datasets, forming hypotheses concerning past changes, which can be tested through modelling. The ACE link also allows us to disseminate results to the IPCC through SCAR's observer status in that organisation. We will also make results available to the SCAR programme named Subglacial Antarctic Lake Environments (SALE) and will contribute the new magnetic dataset to the international Antarctic Digital Magnetic Anomaly Project.

Key findings

We identify a large subglacial basin upstream of the grounding line of Institute and Moller Ice Streams. Here, there is also a steep reverse bed slope, declining approximately 400 m over 40 km. The floor of the basin is smooth and flat, with little small-scale topography to delay retreat. This indicates that it has previously been covered with marine sediment and was deglaciated prior to inundation by the Antarctic Ice Sheet. Well-defined fjords, calved by glaciers lie upstream of the basin. To date, evidence suggests that this sector of West Antarctica has been stable, but our data suggests that the region could be near to a physical threshold of substantial change.
AcronymIIS/MIS
StatusFinished
Effective start/end date1/10/10 → 31/03/13

Funding

  • NATURAL ENVIRONMENT RESEARCH COUNCIL: £15,440.00
View all 6 research outputs