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

Sharples, C; Walford, Hannah; Watson, Christopher; Ellison, JC; Hua, Quan; Bowden, Nicholas; Bowman, David M. J. S.

doi:10.1016/j.margeo.2019.106081

Cited by 12 publications

(7 citation statements)

References 39 publications

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“…Our results suggest that the shift toward accelerated erosion of wave‐dominated coastlines is also well underway. These results are consistent with those from a study of Ocean Beach, Tasmania, where an abrupt shift from episodic shoreline erosion and accretion to persistent shoreline recession during the past 70 yr is attributed to accelerated sea‐level rise and increasing wind driven wave influence (Sharples et al., 2020). This implies a global mechanism.…”

Section: Cause(s) Of the Reversal In Coastal Barrier Evolutionsupporting

confidence: 91%

Unprecedented Historical Erosion of US Gulf Coast: A Consequence of Accelerated Sea‐Level Rise?

Anderson,

Wallace,

Rodriguez

et al. 2023

Earth's Future

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Most of the US Gulf Coast is composed of barrier islands, peninsulas, chenier plains, and mainland beaches that are the main line of defense for wetlands, estuaries, and urban and industrial centers from rising sea level and severe storms. These wave‐dominated shorelines are currently experiencing widespread erosion. Using newly acquired and existing results from 13 sites spanning south Florida to south Texas, we compare shoreline migration rates during the late Holocene (∼−4000 to 1850 CE) with historical changes since the mid‐19th century. The records show an overall trend of seaward growth during the late Holocene followed by landward migration or a decrease in the rate of growth during historical time. Diminishing offshore sand supply, human alteration of rivers and coastal sand transport, and severe storms have contributed to this change in shoreline trajectory, but their influence has been mostly limited in extent. The most likely cause of this reversal from coastal stability and growth to widespread shoreline retreat is the dramatic historical increase in the rate of sea‐level rise over the past century.

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Section: Cause(s) Of the Reversal In Coastal Barrier Evolutionsupporting

confidence: 91%

Unprecedented Historical Erosion of US Gulf Coast: A Consequence of Accelerated Sea‐Level Rise?

Anderson,

Wallace,

Rodriguez

et al. 2023

Earth's Future

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“…It is likely that the older deposits at Sandy Cape, like the Ainslie dunes and those on Prime Seal Island, are the remains of a longitudinal linear dune field that once extended across the continental shelf, which was much wider during the last glacial period (Lambeck and Chappell, 2001); the dunes’ ultimate origin may have been the coast several kilometres to the west. In contrast, beach-backing dunes to the south at Ocean Beach near Strahan are of Late Holocene age (Sharples et al, 2020).…”

Section: Coastal Dunes and Relict Longitudinal Dunesmentioning

confidence: 99%

Late Pleistocene and Early Holocene aeolian deposits of Tasmania and their climatic implications

McIntosh¹,

Neudorf

Lian

et al. 2020

Quat. res.

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Late Pleistocene and Early Holocene aeolian deposits in Tasmania are extensive in the present subhumid climate zone but also occur in areas receiving >1000 mm of rain annually. Thermoluminescence, optically stimulated luminescence, and radiocarbon ages indicate that most of the deposits formed during periods of cold climate. Some dunes are remnants of longitudinal desert dunes sourced from now-inundated continental shelves which were previously semi-arid. Others formed near source, often in the form of lunettes east of seasonally-dry lagoons in the previously semi-arid Midlands and southeast of Tasmania, or as accumulations close to floodplains of major rivers, or as sandsheets in exposed areas. Burning of vegetation by the Aboriginal population after 40 ka is likely to have influenced sediment supply. A key site for determining climate variability in southern Tasmania is Maynes Junction which records three periods of aeolian deposition (at ca. 90, 32 and 20 ka), interspersed with periods of hillslope instability. Whether wind speeds were higher than at present during the last glacial period is uncertain, but shells in the Mary Ann Bay sandsheet near Hobart and particle size analysis of the Ainslie dunes in northeast Tasmania suggest stronger winds during the last glacial period than at present.

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“…All sandy shorelines and estuaries have such a tipping point, although the shoreline response may lag the sea-level trend (Mariotti and Hein, 2022). Sharples et al (2020) recently identified this tipping point for a wave-dominated beach on the western coast of Tasmania through a comparison of historical air photos and a range of climate and sea-level datasets. Beaches with positive sediment budgets can absorb a certain level of sea-level rise and either continue to prograde or remain stable.…”

Section: Projected Sea-level Rise -A Future Tipping Pointmentioning

confidence: 99%

Holocene estuary infill leads to coastal barrier initiation from fluvial sand supply in southeastern Australia

Oliver,

Owers,

Tamura

et al. 2023

The Holocene

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A morphodynamic approach to coastal evolution involves recognition of internal thresholds, feedbacks and boundary conditions and should underpin coastal management. The Holocene evolution of the Bega River estuary and Tathra Beach coastal barrier was examined integrating existing sediment cores and radiocarbon dating, airborne terrestrial and marine Lidar and OSL dating. Sediment coring reveals the Bega River estuary began infilling with fluvial sand once sea levels stabilised at or near their present elevation. Radiocarbon dating suggests a prograding fluvial delta reached the coast approximately 4000–2250 years BP. Barrier deposition commenced ~3200 years ago coinciding with the arrival of fluvial sand at the coast. Shoreline progradation of the Tathra barrier occurred at 0.15 m/year from ~3200 years to present forming a sequence of ~17 foredune ridges which were each active for an average of ~190 years. In the past ~500 years, a sand spit has restricted the entrance of the Bega River estuary to the northern end of the embayment. The infill of the Bega River estuary over the Holocene represents an internal morphodynamic threshold or tipping point, which then enabled coastal barrier deposition as fluvial sand reached the coast. The coastal system approaches another threshold as the Tathra embayment infills, and sediment may be transported northward out of the embayment. At Tathra Beach, the positive sediment budget which resulted in barrier progradation is approximately 0.55 m3/m/year. This signal is masked on the yearly to decadal scale by fluctuations in beach volume an order of magnitude greater (5–20 m3/m/year depending on the timeframe examined). Thus longer-term datasets of beach change or reconstructions from the geological record are needed to underpin management decisions which will impact shorelines decades or centuries into the future.

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

Cited by 12 publications

References 39 publications

Unprecedented Historical Erosion of US Gulf Coast: A Consequence of Accelerated Sea‐Level Rise?

Unprecedented Historical Erosion of US Gulf Coast: A Consequence of Accelerated Sea‐Level Rise?

Late Pleistocene and Early Holocene aeolian deposits of Tasmania and their climatic implications

Holocene estuary infill leads to coastal barrier initiation from fluvial sand supply in southeastern Australia

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