Abstract
On the east Australian coast, climate change is expressed as a slowly rising sea level. Analysis of records, dating back over two centuries, also shows oscillating multidecadal ‘storm’ and ‘drought’ dominated climate periods that are distinct from long-term climate change. Climate variability, as expressed by these distinct multidecadal periods, is generally associated with phases of the Interdecadal Pacific Oscillation Index (IPO). Two centuries of climate and coastline response are examined for the central east coast of Australia, between Fraser Island and Coffs Harbour. The long record has been compiled by analysing a wide range of indicators and observations, including: historical accounts, storm records, sea level trends, assessment of storm erosion faces, and coastal movement in relation to fixed monuments, surveys, and maps. Periods of suppressed sea level, beach accretion, and drought were found to be associated with strongly positive IPO. Periods of higher sea level, increased storminess, and beach erosion were associated with strongly negative IPO. Understanding the behaviour of climate variability over different timescales has the potential to improve the understanding of, and responses to, climate change. This will be important in the sustainable management of geomorphic and ecological systems.
Highlights
Climatic and geomorphic evidence indicates that the east Australian coastline observed by the firstEuropeans settlers 200 years ago was experiencing a relatively stable climatic period, when the sea level was slightly below that in the present
Periods of higher sea level, increased storminess, and beach erosion have been shown to be associated with strongly negative Interdecadal Pacific Oscillation (IPO)
In the most recent positive IPO phase, with characteristically low storm activity, erosion is observed in the southern sections of ocean compartments and on the western shorelines of barrier islands
Summary
Europeans settlers 200 years ago was experiencing a relatively stable climatic period, when the sea level was slightly below that in the present. Consistent findings of slowly receding shorelines and erosion of Holocene dunes suggest that the coast was influenced by slowly rising sea levels from the early 1800s to present day [1]. Simulation from HadCM3 [2] shows a trend of global sea level rise from 1820. The east coast sea level rise follows, but has been below the global mean, due to the non-uniform distribution of thermal expansion resulting in different regional rates of sea level rise [3]. The IPO index oscillates irregularly as positive and negative phases over several decades, resulting in major climate shifts [4,5,6,7]. References [8,9] relate oceanic ecosystem production and salmon catches in the North Pacific Ocean to decadal phases of IPO
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