A full coupled ice-sheet -- sea-level model: relative sea level simulations over the last glacial cycle

Abstract:

Relative sea-level variations during the late Pleistocene can only be reconstructed with the knowledge of ice-sheet history. On the other hand, the knowledge of regional and global relative sea-level variations is necessary to learn about the changes in ice volume. Overcoming this problem of circularity demands a fully coupled system where ice sheets and sea level vary consistently in space and time and dynamically affect each other. Here we present results for the last glacial cycle from the coupling of a set of 3-D ice-sheet-shelf models to a global sea-level model based on the solution of the gravitationally self-consistent sea-level equation. The sea-level model incorporates all the glacial isostatic adjustment feedbacks for a Maxwell viscoelastic and rotating Earth model with variable coastlines. Ice volume is computed with four 3-D ice-sheet-shelf models for North America, Eurasia, Greenland and Antarctica. With an inverse approach, ice volume and temperature are derived from a benthic δ¹⁸O stacked record. The derived surface-air temperature anomaly is applied on the present-day climatology to simulate glacial-interglacial changes in temperature and hence ice volume. The ice-sheet thickness variations are forwarded to the sea-level model to compute the bedrock deformation, the change in sea-surface height and thus the relative sea-level change. The latter is coupled back to the ice-sheet models. Due to rotational effects, local isostatic depression and growth or collapse of the forebulge, RSL differences can reach up to 100 m between different locations over the globe. Additionally, ice-sheet model parameters have been varied such that we come up with a suite of different modelling results of ice volume and accompanying global RSL over the last glacial cycle. Subsequently, we will present a first-order comparison of our results with RSL reconstructions derived from geological and archaeological paleo sea-level indicators over the globe.