ISTAR-D - The contribution to sea-level rise of the Amundsen Sea sector of Antarctica

This proposal will resolve the differences between satellite altimeter, SAR and gravity estimates of the mass imbalance of the Amundsen sector ice streams, through exploiting surface observations of accumulation, density and solid Earth motion made on the ISAR-D traverses in 2012/3 and 2013/4 of the Pine Island basin, and the wider BAS logistics from 2013 to 2016. In particular, it will:The objectives of this proposal are:

1. Determine, at deep cores at some 10 sites along an 850 km traverse throughout the Pine Island Basin, the inter-annual, decadal, and ~ 50-year average accumulation.

2. Determine, using shallow access holes at some 50 sites along the traverse, the annual fluctuations of accumulation and near surface density over the past ~ 15-years.

3. Interpolate along the traverse the spatial variation in accumulation using surface-dragged accumulation radar measurements, and the annual fluctuations of accumulation and near surface density, using airborne radar measurements.

4. Determine the motion of the solid Earth, and millennial-scale ice sheet elevation history, at 3 nunatak sites in the interior of the Pine Island Basin.

5. Evaluate the accuracy of accumulation and densification forecast models using the inter-decadal, fluctuation measurements, and more sophisticated densification models, and use the combination to best estimate the fluctuations of accumulation and density over the past ~ 20-years in the Amundsen Sea sector and beyond.

6. Use a West Antarctic ice history model, based on exposure dates, with other observations, to best estimate the solid Earth motion of the Amundsen sea-sector, and use the measurements of crustal motion to test this.

7. Determine the contributions of accumulation and density fluctuations, and solid Earth motion, to altimetric and gravity satellite estimates of the mass balance of the Amundsen sector, and reassess the SAR-based estimates of mass balance in the light of the new accumulation and measurements. 8. Best estimate the mass balance, and its change in time, of the Amundsen sector basins.

These objectives answer directly to the objectives of the ISTAR-D Announcement of Opportunity, in that they will result in the determination of the spatial and temporal variability of the regions mass imbalance, and, inter alia, quantify the uncertainties associated with the satellite estimates. More widely, they answer to an identified priority of the NERC Polar Strategy, "Ice sheets and Sea Level Rise", and to challenges of the NERC Climate and Earth System Science themes.