NSFGEO-NERC: Collaborative Research: How important are sea-level feedbacks in stabilizing marine-based ice streams?

The purpose of the proposed research is to investigate the importance of sea-level feedbacks (SLF) in stabilizing marine-based ice sheets during their retreat. The proposed investigation will combine new late Pleistocene/Holocene relative sea-level constraints to be collected from raised shorelines, existing

offshore marine cores, and isolation basins from across northwestern Scotland to refine the glacial isostatic adjustment (GIA) models for the British Isles. The proposal will also investigate SLF feedbacks at a more local level and at the scale of a Late Pleistocene ice stream that once flowed through the Minch of northwestern Scotland. Specifically, we will test three hypotheses: 1.) SLF did not provide a stabilizing influence for the Minch Ice Stream during its retreat following the Last Glacial Maximum, 2.) along indented ice-sheet margins, SLF are governed not by the local ice front but by the regional GIA signal, and 3.) the influence of SLF in stabilizing marine ice streams is a function of the rheology of the Earth beneath it.

One of the largest uncertainties related to future projections of sea-level rise is the influence of ice sheets. Model projections differ by as much as 2 m over the next 100-years depending on how existing ice sheets behave with respect to ongoing sea-level rise and warming. Our understanding of the feedbacks between ice sheet behavior and sea-level changes at the scale of extant ice streams of concern (e.g.

Thwaites Glacier in Antarctica, Jakobshavn Isbrae in Greenland) is limited to numerical models that have rarely been tested against real-world examples at decadal to century time-scales. The retreat of ice streams following the Last Glacial Maximum provides an excellent test ground for the factors controlling the behavior of ice streams during their retreat.

The data generated as part of this project will not only examine ice-sheet behavior but also contribute to GIA models used to predict future sea-level changes and past studies of climate, paleogeography, and archeology. It will also provide some of the first absolute ages on raised shorelines across northwestern Scotland.