Reconstruction of past temperature history from Australian borehole temperature data : evidence of climate change

Abstract

Paleoclimate records are an important resource to help distinguish between natural variability and anthropogenic effects on the earth’s climate and thus facilitate better future climate projections. A dearth of paleotemperature records limits knowledge of past climate during the late Pleistocene in the Southern Hemisphere compared to the Northern Hemisphere, which emphasize the need to develop more paleoclimate records from the Southern Hemisphere. This is particularly evident in Australia where temperature proxy records are often clustered and limited to a few sites, which means they do not provide representative cover of the diverse climates across the continent. Borehole temperature data retain the signal of past changes in land surface temperatures and have been used successfully in other parts of the world. Boreholes are often drilled for exploration of geothermal, mineral, gas and water resources and have the potential to provide centennial scale paleotemperature histories. Thus paleotemperature reconstructions from borehole records can be used as supplement of existing climate proxy data and increase the spatial density of historical climate records in Australia. This study reconstructed 61 new paleotemperature histories, ranging in duration from the last 500 to the last 50,000 years, using borehole temperature-depth profiles from eastern mainland Australia and Tasmania. In addition, it investigated fundamental issues with application of the technique such as the variability of paleotemperature reconstructions between boreholes, the quality and quantity of boreholes required for precise paleotemperature reconstruction and the use of past temperature records to correct heat flow measurements. Analysis shows the degree of variability of the reconstructed past temperature changes between boreholes are primarily linked to spatial scale. Variability was lower at the local rather than at the regional or national scale. Climatic factors were identified as a source of the magnitude of variability between boreholes. Non-climatic factors including topography, lithology and land use did not appear to strongly influence the magnitude of variability. Vertical heat flow measurement in shallow boreholes (

Date of Award	2018
Original language	English
Awarding Institution	University of Canberra
Supervisor	Duanne White (Supervisor) & Fiona Dyer (Supervisor)