By Michelle Tigchelaar (University of Washington)
Fri Oct 20, 2017 10:30am - 11:30am Central Time
Host: Pedro Di Nezio
Abstract: Antarctic ice-sheet instabilities could become a major driver for future global sea level rise. However, the rate at which Antarctic ice-sheet mass loss will occur is a matter of intense debate and subject to large uncertainties. To further constrain the response of the Antarctic ice sheet to environmental change, it is necessary to study its sensitivity to past changes in greenhouse gas concentrations and orbital parameters. So far, long-term Antarctic simulations have used proxy-based parameterizations of climatic drivers, presuming that external forcings are applied in synchrony with each other. Here for the first time we have used a transient, three-dimensional climate simulation over the last eight glacial cycles to drive an Antarctic ice sheet model. We show that the evolution of the Antarctic ice sheet was mostly driven by CO2 and sea level forcing with a period of about 100,000 years, synchronizing both hemispheres. However, high surface melt and ice-shelf calving rates during precessionally-driven periods of austral summer insolation maxima cause a decoupling of bipolar ice-sheet variations during the warmest interglacials. Sensitivity runs with individual climatic drivers indicate that they add nonlinearly, implying that the full spectrum of climate forcing needs to be considered when evaluating the sensitivity of the Antarctic ice sheet to past and future climate change.