Parameters controlling mid-Holocene highstand in Glacial Isostatic Adjustment modelling

Holocene relative sea-level (RSL) records from regions distal from ice sheets (far-field) are commonly characterized by a mid-Holocene highstand, when RSL reached higher than present levels. The magnitude and timing of the mid-Holocene highstand varies spatially due to hydro-isostatic processes including ocean syphoning and continental levering. While there are open questions regarding the timing, magnitude and source of ice-equivalent sea level in the middle to late Holocene.

Here, we compare Glacial Isostatic Adjustment (GIA) model predictions to a standardized database of sea-level index points (SLIPs) from Southeast Asia where we have near-complete Holocene records. The database has more than 130 SLIPs that span the time period from ~9.5 ka BP to present. We investigate the sensitivity of mid-Holocene RSL predictions to GIA parameters, including the lateral lithospheric thickness variation, mantle viscosity (both 1D and 3D), and deglaciation history from different ice sheets (e.g., Laurentide, Fennoscandia, Antarctica).

We compute gravitationally self-consistent RSL histories for the GIA model with time dependent coastlines and rotational feedback using the Coupled Laplace-Finite Element Method. The preliminary results show that the timing of the highstand is mainly controlled by the deglaciation history (ice-equivalent sea level), while the magnitude is dominated by Earth parameters (e.g., lithospheric thickness, mantle viscosity). We further investigate whether there is meltwater input during middle to late Holocene and whether the RSL records from Southeast Asia can reveal the meltwater source, like Antarctica.