EARLY HOLOCENE GLOBAL DEGLACIAL HISTORY

According to the latest SROCC report, the global rate of sea level rise in 2100 will be 10-20 mm/yr under RCP8.5 and associated extreme events will become more common. Past relative sea-level (RSL) change can be a major source of knowledge to understand future sea-level rise and the threat that this accelerated RSL rise poses to low-lying areas around the world. Even though we have some understanding about past RSL changes, we have certain critical gaps in the Early Holocene (EH) RSL history. The EH deglacial history is essential for the sea-level community to understand because of the similarities in climatic conditions with the present. The Laurentide Ice Sheet, the Greenland Ice Sheet and the Antarctic Ice Sheet are believed to have contributed to the RSL rise during the 10-7 ka time period, but the contributions of each of these ice sheets are not well quantified. So, a better understanding of the rates and sources of RSL change between 10-7 ka can help in stronger predictions of future sea level rise. In fact, this is considered as one of the remaining outstanding questions regarding eustatic sea level by Khan et al. (2019). In this project, a global RSL database spanning 10-7 ka is being prepared, by applying a more stringent set of criteria than commonly used, to form the basis for estimating RSL change rates using a statistical analysis approach that will capture and account for inherent uncertainties in the data. Only 95 sea-level index points (SLIPs) are included in this global database at present. To be included, a RSL indicator has to be between 10-7 ka in age (the central age of the calibrated ¹⁴C age distribution), from a reasonably stable area (unaffected by any recent tectonic activity and/or glacial isostatic adjustment), an in situ SLIP with a well-defined vertical and horizontal resolution. RSL proxy data have inbuilt noise in both temporal and spatial axes. We use a Bayesian statistical analysis approach to estimate RSL rates from the RSL proxy data collated in the database, which takes into account these uncertainties. One of the goals of this project is to use the RSL database in understanding the contributions of the different ice masses that were disintegrating during EH using the sea-level fingerprinting method.

Khan, N.S., Horton, B.P., Engelhart, S., Rovere, A., Vacchi, M., Ashe, E.L., Törnqvist, T.E., Dutton, A., Hijma, M.P., and Shennan, I., 2019, Inception of a global atlas of sea levels since the Last Glacial Maximum: Quaternary Science Reviews, v. 220, p. 359-371.