Reconstructing terrestrial temperatures in the Australian sub-tropics and tropics: A chironomid based transfer function approach

Abstract

This paper presents chironomid-based transfer functions for temperature reconstructions intended for use in the Australian tropics and sub-tropics. Temperature was the primary independent control of chironomid assemblages. Two transfer functions were created to infer mean annual (MAT) and mean summer temperature as represented by February temperatures (MFT) as it was not reasonable to automatically assume that chironomid populations in the tropics are controlled by summer temperatures. Weighted average partial least square (WA-PLS) models were the most robust. For MAT they produced a coefficient of determination (r2jack) of 0.83, a maximum bias of 1.74 °C and a root mean squared error of prediction (RMSEP) of 2.35 °C while for MFT an r2jack of 0.76, maximum bias of 2.43 °C, and RMSEP of 2.43 °C was achieved. Based on the statistics we recommend that the MAT model is used for chironomid work in tropical regions.Though chironomid head capsule counts were low, we tentatively applied the MAT function to published Holocene chironomid data from Lake Barrine, northeast Queensland. The results suggest only minor temperature change through the last 9000 years. Based on other proxies, this appears to result in realistic temperature reconstructions. Consequently we highlight that sub-fossil chironomids have the potential to provide high quality temperature records for the Australian tropics.