Synopsis 

The timing and impacts of extreme climate change in the past and future remain highly uncertain – even to this day. Geological, chemical and biological records (often referred to as ‘natural archives’) can inform on large-scale and sometimes irreversible (centennial to millennial in duration) shifts in the climate system that took place in the past. However, chronological uncertainties preclude high-precision correlation of records of palaeoenvironmental change.

A major focus has been on the late Pleistocene (11,650 to 50,000 years ago; henceforth 11.65-50ka) where contrasting Greenland and Antarctic temperature trends show millennial-scale warming (Greenland interstadial) events in the north. This event led to cooling in the south (WAIS, 2015); thought to have been driven by imbalances in the rate of formation of North Atlantic and Antarctic Deep Water (the ‘bipolar seesaw’) (Broecker, 1998; WAIS, 2015).

However, until now multi-centennial uncertainties in the phasing of climate trends in ice core sequences and a poorly defined radiocarbon (14C) calibration curve (Reimer et al., 2013) have precluded the high-precision alignment of terrestrial, ice, marine and palaeofaunal records. While past changes in atmospheric 14C offer the potential to undertake high-precision correlation between terrestrial and marine records. No contiguous record of global atmospheric radiocarbon concentration is currently available across the full timescale (Turney et al., 2016). 

Aims 

We have uncovered an extensive (250 trees) collection of subfossil Huon pine in Tasmania. These trees were collected from river gravels up to several metres' in-depth nearly 20 years ago, but these have not been studied. These trees offer considerable potential for providing detailed (annually-resolved) multi-centennial records of atmospheric 14C.

Unfortunately, there’s no current age control on any of these trees. Previous field expeditions have demonstrated that subfossil Huon pines from river gravels may be only a few centuries old or up to 40,000 years old. To provide rangefinder ages on these archived trees, we have set up a project to radiocarbon date all 250 trees.

Success in the project: “Unearthing Australia’s Climate History: Sampling & Radiocarbon Dating Subfossil Tasmanian Huon Trees” will allow us to target the trees of late Pleistocene age and undertake more detailed (continuous) 14C measurements for high-precision alignment of terrestrial, marine and ice records.

For this honours project, you’ll be required to visit Tasmania to systematically sample all the archived trees and prepare them for 14C dating at UNSW. In addition, you’ll also be required to spend two weeks at a radiocarbon dating facility. No previous experience is required but a passion for using the past to understand the Earth system is crucial.

Student Benefits

Through this project, you’ll learn how to:

  • Design and carry out experiments
  • Analyse and interpret data
  • How to write a scientific paper  

You’ll also be integrated into the Centre of Excellence for Australian Biodiversity and Heritage, which has funding available for training and career development.