FIELD EVIDENCE, MODELING RESULTS, AND NEW INVESTIGATIVE STRATEGIES SHED LIGHT ON THE TIMING AND AMPLITUDE OF SEA LEVEL CHANGE DURING PAST WARM CLIMATES

Oscillations of sea level, whether rapid or gradual, influence the degree and style of shorline formation including reef framework construction, destruction, and preservation. Using insight from modern shoreline systems, members of the PLIOMAX project have mapped mid-Pliocene, MIS11, and MIS5e shorelines at numerous localities around the world and modeled the effects of subsequent glacial isostatic adjustment (GIA) on their current position. For both MIS5e and MIS11 we conclude that an ice sheet stability threshold was crossed in the last few kyr of each interglacial resulting in the catastrophic collapse of polar ice sheets with a rise in eustatic sea level to ~8m or more above present. We further show that dynamic topography, supported by convectively maintained stresses generated by viscous flow in the mantle and associated buoyancy variations in the lithosphere, plays a significant role in the post-depositional displacement of Pliocene and even much younger Pleistocene shorelines. We will discuss how we are using predicted global patterns of GIA and dynamic topography to guide field efforts aimed at extracting the eustatic component of sea level change during past warm climates. We also discuss how our field data is helping, in turn, to constrain uncertainties in models of both GIA and the long-term convective evolution of the Earth (uncertainties in mantle viscosity, for instance).