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Ocean Beach, Tasmania: A swell-dominated shoreline reaches climate-induced recessional tipping point?

Citation

Sharples, C and Walford, H and Watson, C and Ellison, JC and Hua, Q and Bowden, N and Bowman, D, Ocean Beach, Tasmania: A swell-dominated shoreline reaches climate-induced recessional tipping point?, Marine Geology, 419 Article 106081. ISSN 0025-3227 (2020) [Refereed Article]


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DOI: doi:10.1016/j.margeo.2019.106081

Abstract

Global sea-level rise since the Nineteenth Century is expected to eventually cause recession of many shores, however most swell-exposed sandy beaches have not yet shown such response. This study analysed a 70-year air photo and beach profile record for swell-dominated Ocean Beach (western Tasmania) to show an abrupt change of long-term shoreline position variability circa 1980, from episodic erosion and accretion since at least 1947 to persistent recession with no recovery up to the present. Dating of back-dune peats exposed in the dune scarp showed that recent shoreline recession exceeds any in the last 1800 years. Investigation of potential causes identified recent-onset sea-level rise (SLR) on a tectonically-stable coast and increasing winds driving increased wave-setup as drivers with sufficient explanatory power to account for the observed changes, although data limitations and residual uncertainties mean additional contributing factors such as interdecadal wave direction changes cannot be ruled out. We hypothesise that Ocean Beach has experienced earlier recession in response to SLR and other climate change effects than many other beaches owing to exposure to a very high-energy stormdominated wave climate, littoral drift efficiently delivering eroded sand to a large-capacity active sand sink, and low variability in swell-wave directions and inter-annual sea-levels. We hypothesise that sea-level rise with higher onshore wind speeds generating increased wave setup at Ocean Beach since before the 1980s has increased upper beach erosion event frequency until the formerly stable or gaining sand budget reversed to deficit. A major storm or storm cluster abruptly tipped the beach into its current recessional mode when its sand budget was close to deficit. Factors causing an early shoreline response to sea-level rise at this site are applicable more widely as potential indicators of beaches likely to respond earlier than others to climate-induced changes including not only SLR but also wind climate changes.

Item Details

Item Type:Refereed Article
Keywords:beach processes, sea level change, Australia and New Zealand, spatial analysis, erosion, recession, coastal erosion, sea-level rise, Tasmania
Research Division:Earth Sciences
Research Group:Physical Geography and Environmental Geoscience
Research Field:Physical Geography and Environmental Geoscience not elsewhere classified
Objective Division:Environment
Objective Group:Ecosystem Assessment and Management
Objective Field:Ecosystem Assessment and Management of Coastal and Estuarine Environments
UTAS Author:Sharples, C (Mr Chris Sharples)
UTAS Author:Walford, H (Ms Hannah Walford)
UTAS Author:Watson, C (Dr Christopher Watson)
UTAS Author:Ellison, JC (Associate Professor Joanna Ellison)
UTAS Author:Bowden, N (Mr Nicholas Bowden)
UTAS Author:Bowman, D (Professor David Bowman)
ID Code:135859
Year Published:2020
Deposited By:Geography and Spatial Science
Deposited On:2019-11-19
Last Modified:2019-11-20
Downloads:0

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