Cosmogenic Climate Archives of the Southern Hemisphere (CcASH) 

Revealing climate secrets of the past with isotopes.

Atmospheric cosmic ray shower, as illustrated over Uluru.

Cosmogenic Climate Archives of the Southern Hemisphere (CcASH) is an ANSTO initiative aimed at enhancing our understanding of past climate variability and environmental conditions in Australasia and Antarctica.

Understanding Earth's past climate system will lead to better predictions of future change in our region. The study of global climate change recorded in corals, speleothems, tree-rings, glacial deposits, ocean and lake sediments and Antarctic ice cores reveals a complex scale of variations ranging from major Glacial Cycles (100,000 years), millennial (1,000 years) timescales and even decadal changes - i.e., El Nino (radiocarbon techniques are useful for items up to 50,000 years old. Coal, for instance, is millions of years old).

Global patterns of climate change are inferred principally from Northern Hemisphere records and modelling approaches. For the major glaciations this seems to be reliable. However, data is now emerging that, on shorter timescales, Earth's climate change behaviour, particularly since the Last Glacial Maximum (about 25,000 years ago) to the beginning of the warmer interglacial period of today, things are not simple, or global.

Within the CcASH task there are three major themes of research activity with specific sub tasks. They are: Glacial and Sedimentary Systems which looks at continental glacial cycles in the Southern Hemisphere and Antarctica using in-situ cosmogenic exposure age dating, Atmospheric and Oceanic Radiocarbon Systems, which examines atmospheric transport, ocean circulation and environmental changes using radiocarbon in tree-rings, corals and speleothems to improve our understanding of abrupt climate change, and Ice Sheets and Micro-carbon Studies, which looks at the source histories of carbonaceous greenhouse gases in the atmosphere and from air bubbles in polar ice sheets by analysing radiocarbon signatures.

ANSTO facilities

CcASH uses ANSTO's ANTARES and STAR AMS Facilities, supported by a comprehensive suite of geochemical sample preparation laboratories, to perform routine measurements of ¹⁴C, ¹⁰Be, ²⁶Al, ¹²⁹I, ²³⁶U, and Pu isotopes.

The project team has established strong partnerships with New Zealand, Australian, and international universities, and government agencies. They also provide access to ANSTO's capabilities in application of isotopes related to paleoclimate studies and environmental management.

The project offers a framework for interaction of research scientists and students in these fields to exchange their multi-disciplinary expertise. Within the next five years the project will include U-series and ICP-MCMS capabilities.