Rapid early Holocene sea-level rise in Prydz Bay, East Antarctica

Stephen J Roberts,Wim Vyverman,Elie Verleyen,Gijs De Cort,Dominic A Hodgson,Koen Sabbe,Philip O'Brien,Sonja Berg,Pippa L Whitehouse,Ines Tavernier

doi:10.1016/j.gloplacha.2015.12.020

Stephen J Roberts, Wim Vyverman + Show 8 more

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https://doi.org/10.1016/j.gloplacha.2015.12.020

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Abstract

Prydz Bay is one of the largest embayments on the East Antarctic coast and it is the discharge point for approximately 16% of the East Antarctic Ice Sheet. Geological constraints on the regional ice sheet history include evidence of past relative sea-level change at three sites; the Vestfold Hills, Rauer Islands and Larsemann Hills. In this paper we compile updated regional relative sea-level data from these sites. We compare these with a suite of relative sea-level predictions derived from glacial isostatic adjustment models and discuss the significance of departures between the models and the field evidence. The compiled geological data extend the relative sea-level curve for this region to 11,258calyr BP and include new constraints based on abandoned penguin colonies, new isolation basin data in the Vestfold Hills, validation of a submarine relative sea-level constraint in the Rauer Islands and recalibrated radiocarbon ages at all sites dating from 12,728calyr BP. The field data show rapid increases in rates of relative sea level rise of 12–48mm/yr between 10,473 (or 9678) and 9411calyr BP in the Vestfold Hills and of 8.8mm/yr between 8882 and 8563calyr BP in the Larsemann Hills. The relative sea-level high stands of ≥8.8m from 9411 to after 7564calyr BP (Vestfold Hills) and ≥8m at 8563 and 7066calyr BP (Larsemann Hills) are over-predicted by some of the glacial isostatic adjustment models considered here, suggesting that assumptions relating to the magnitude and timing of regional ice loss since the Last Glacial Maximum may need revising. In the Vestfold Hills and Rauer Islands the final deglacial sea-level rise was almost exactly cancelled out by local rebound between 9411 and 5967calyr BP and this was followed by a near exponential decay in relative sea-level. In the Larsemann Hills the sea-level data suggest that the rate of ice retreat in this region was not uniform throughout the Holocene. Swath bathymetric surveys of the benthic seafloor topography show the presence of multiple offshore basins. These are a priority for further study as those that remained free of grounded ice should provide precise constraints on relative sea-level rise and ice sheet history during the most rapid phases of the last major deglaciation.

Highlights

The Antarctic Ice Sheet represents the largest potential source of future sea-level rise but the rate at which this reservoir will be depleted is not quantifiable (Church et al, 2013)
Reconstructions of RSL are critical for constraining regional ice-loading histories, and the gravitational signal associated with the ongoing solid Earth response to past ice load changes, a process known as Glacial Isostatic Adjustment (GIA)
The regional RSL data compilations are compared with published model predictions of RSL associated with four deglacial models for Antarctica, each of which has previously been used to predict RSL change in Prydz Bay

Summary

Introduction

The Antarctic Ice Sheet represents the largest potential source of future sea-level rise but the rate at which this reservoir will be depleted is not quantifiable (Church et al, 2013). Uncertainties remain with regard to the timing and magnitude of the ice sheet response to potential future climate scenarios, and the ‘likely’ magnitude of sea-level rise during the century due to dynamic ice discharge from Antarctica is considered by the IPCC to lie in the range of -20 to + 185 mm (Church et al, 2013). D.A. Hodgson et al / Global and Planetary Change 139 (2016) 128–140 relative vertical displacement between the sea surface and the land over a period of time. Hodgson et al / Global and Planetary Change 139 (2016) 128–140 relative vertical displacement between the sea surface and the land over a period of time It is influenced by changes in ocean volume (eustatic changes in sea level) and deformation of the geoid and solid Earth (isostatic changes) caused by changes in the mass of overlying ice and ocean loads (Farrell and Clark, 1976). Knowledge of the GIA signal is necessary for improving the accuracy of satellite gravity based estimates of ice mass change because it enables the separation of ice mass change from total mass change via the subtraction of the GIA signal

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