Rapid relative sea-level fall, 8–6 ka, in the Windmill Islands, East Antarctica

Abstract

Records of relative sea-level (RSL) change shed light on mechanisms that control ice-sheet evolution and are used to improve estimates of current mass loss. Despite being the largest potential contributor to future sea-level change there are relatively few records of RSL from the margin of the East Antarctic Ice Sheet. We provide new geological data that define the timing of deglaciation and the pattern and rates of subsequent RSL change in the Windmill Islands in Wilkes Land, East Antarctica. Our new data constrain deglaciation by 10.0–9.5 ka. Combining our new data with previously unused sea-level indicators from penguin remains redefines understanding of RSL changes after deglaciation. A high-stand at c. 8.0 ka was followed by rapid sea-level fall with RSL dropping to <15 m at 6.0 ka at a rate of ∼10 m ka⁻¹, more than double that inferred previously. A reinterpretation of an existing marine core provides circumstantial evidence that RSL fell below 5 m ASL at c. 3.6–2.8 ka which would be coincident with a previously inferred retreat-readvance of the ice margin at this time. Overall, the timing of the Holocene sea-level high stand in the Windmill Islands is similar to other sites around East Antarctica. However, the greater magnitude of this high stand and the rapid fall during the period 8 - 6 ka suggests that interactions between the ice sheet and solid Earth in this sector of East Antarctica may be influenced by relatively lower mantle viscosities.