Abstract
This paper defines the spatial trend in sea-level around Australia at 3 timescales, namely at the time of the maximum of the last interglacial around 125000 yr BP, during the Holocene maximum between 5-6000 yr BP and over the last 20 years. Last interglacial elevations range from -2m around the Great Barrier Reef to +32m in northeast Tasmania. Trend surface analysis shows that over 77% of the noise in these sea-level elevations can be accounted for by a pattern evidencing tectonic uplift towards the southern edge of the continent. Assuming a eustatic sea-level at this time of +4 to 6m, most of the east coast of New South Wales and the west coast of Western Australia can be considered tectonically stable, while the southern edge of the continent has risen by at least 5m and the north-northeast corner has downwarped by at least 2m. The spatial pattern of the Holocene maximum tentatively supports the continuation of this tectonic deformation. Sea-level at this time reached 1.6m and 2.4m above present high tide limits around the northern and southeastern coastlines of Australia respectively. This Holocene pattern is weak because much of the data is dominated by local variations reflecting differential loading of the continental shelf by water during the Holocene transgression. The Holocene trend surface does not support geophysical modelling implying a southern latitudinal downwarping of the crust produced by the melting of the Antarctic ice sheet and the loading of the ocean crust with meltwater. However the spatial pattern of modern trends appears to contain a remnant Holocene signal fitting this isostatic model rather than the long term pattern of tectonic flexure since the last interglacial. Sea-level is presently rising at a rate of 1.75mm yr-1 in northern Australia compared to only 0.75mm yr-1 in Tasmania. These results imply that isostatic factors, as well as previously identified climatic variables, may be controlling present-day variations in the rate of change of sea-levels around the Australian continent.
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Publication Details
This article was originally published as Bryant, EA, Last interglacial and Holocene trends in sea-level maxima around Australia: Implications for modern rates, Marine Geology, 108(2), 1992, 209-217. The original article is available here.