Late Holocene temperature variability in Tasmania inferred from borehole temperature data

Asadusjjaman Suman,Fiona Dyer,Duanne White

doi:10.5194/cp-13-559-2017

Abstract

Abstract. Thirty-six borehole temperature–depth profiles were analysed to reconstruct the ground surface temperature history (GSTH) of eastern Tasmania for the past 5 centuries. We used the singular value decomposition method to invert borehole temperatures to produce temperature histories. The quality of borehole data was classified as high or low based on model misfit. The quality of the borehole data was not dependent on topography or land use. Analysis reveals that three to five high-quality borehole temperature–depth profiles were adequate to reconstruct robust paleotemperature records from any area. Average GSTH reconstructed from Tasmanian boreholes shows temperature increases about 1.2 ± 0.2 °C during the past 5 centuries. Reconstructed temperatures were consistent with meteorological records and other proxy records from Tasmania during their period of overlap. Temperature changes were greatest around the north-east coast and decreased towards the centre of Tasmania. The extension of the East Australian Current (EAC) further south and its strengthening around the north-east coast of Tasmania over the past century was considered a prime driver of warmer temperatures observed in north-east Tasmania.

Highlights

Reconstructions of past temperatures are essential for understanding the trajectory of future environmental change, especially as regards distinguishing between natural variability and anthropogenic effects on the earth’s climate
Using a borehole network from eastern Tasmania, this study investigates the quality of borehole data and the minimum number of boreholes required to reconstruct plausible past temperature records
Detailed analysis reveals that not all borehole temperature–depth data are suitable for inversion to reconstruct ground surface temperature history (GSTH)

Summary

Introduction

Reconstructions of past temperatures are essential for understanding the trajectory of future environmental change, especially as regards distinguishing between natural variability and anthropogenic effects on the earth’s climate (Hulme et al, 1999; St. Jacques et al, 2010; Soltwedel et al, 2015). There is progress in hemispheric (Beltrami and Bourlon, 2004; Neukom and Gergis, 2011) and global (Huang et al, 2000) average temperature estimation over the last millennia, but there are still significant uncertainties in understanding regional responses to global anthropogenic effect (Mann et al, 2009).

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Discussion

Conclusion