AIMS Research - Climate History

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Climate and environmental histories from coral

Instrumental records of climate and environmental change on the tropical coral reefs only cover a relatively short time period.

Long-lived massive coral skeletons contain historical records in the form of annual density bands. These allow dating and examination of climate and environmental changes over the past several centuries, contributing to the global jigsaw puzzle of past climate variability. They provide evidence that can be used to evaluate the nature and significance of current climate changes due to the enhanced Greenhouse effect.

At AIMS, specialised equipment is used to remove ~50-70mm diameter cores from old coral colonies, which can be several metres in size.

A concrete plug is placed in the resulting hole and the living coral tissue around the edges grows back over the top. Slices, ~7mm thick, are taken from the core using specialised sawing equipment. An x-ray of the coral slice then reveals the annual density banding pattern.

Divers

Measurement and analyses of coral growth characteristics provide insights into coral responses to climatic change and environmental stresses on corals over the past several centuries. Analysis of the geochemical composition of the coral skeleton can also provide ‘proxies’ for water temperature, salinity and sediment extending back several centuries.

Coral fluorescent banding

When placed under ultraviolet light, slices of corals from near shore water show bright luminescent lines that are directly related to the occurrence and intensity of freshwater flood and rainfall events on the GBR.

This has allowed scientists to reconstruct freshwater flow into the GBR and Queensland rainfall as far back as 1631AD, tripling the length of instrumental records for the region.

These reconstructions show that although there has been no overall trend towards wetter or drier conditions in northeast Australia, there has been an increase in extreme events, in line with projections for the consequences of continued global warming in the region.

AIMS has the most extensive collection of long coral cores in the world. The longest core from a living coral in the collection has been dated back to 1300AD.

Corals can be well-preserved after death and AIMS also has eight old whole coral colonies dredged up during the marina development at Nelly Bay on Magnetic Island that contain information over a 100-200 year period. These colonies, which lived and died ~6,000 years ago, a period known as the mid-Holocene, provide a window on the more distant past.

This collection is now being expanded to Western Australia to develop marine climate histories for the whole of tropical marine Australia.

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March 18, 2008