Paleoclimate and paleoecology of Tasmania, Australia

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Earth's climate varies enormously in time and space. We know that, on the scale of thousands to tens of thousands of years, the Earth has gone through major changes in climate from Ice Ages to warm interglacial periods (between Ice Ages). How the Earth switches from one to the other is of great interest. Until recently, it was thought that the Northern Hemisphere (NH) is the main player in climate change during this transition, but it now seems that the Southern Hemisphere (SH) leads the NH out of an Ice Age. The bias to the NH being the important hemisphere in driving climate change has now tipped, resulting in increased research in the SH. How do climate events that occur in the SH compare with those in the NH? Are events synchronous or not? Are they of the same duration and magnitude? A major focus of this research is to address questions relating to climate linkages between the hemispheres in the past. And, going further back in time, how warm was the previous interglacial period (about 125,000-135,000 years ago) compared to today's interglacial? To address these questions, we will analyze cores of lake sediment from Tasmania, which is located near the important climate boundary of the Roaring Forties (high westerly winds). One of the lakes we will work on, L. Selina, is a rarity for the SH in having a continuous sediment record for more than one complete glacial/interglacial cycle (more than 135,000 years). We will apply a mathematical model, which estimates summer warmth from the kinds and abundances of midge flies (chironomids), to fossil midges from sediments that date as far back as 135,000+ years ago, in order to obtain quantitative estimates of summer temperatures thousands of years ago. The temperature curves that we produce can then be compared with others throughout the world. In addition, we will examine fossil pollen to determine how past vegetation may have been affected by changes in summer warmth. Finally, fire is known to be a major influence on present vegetation, so we will examine charcoal preserved in lake sediments, along with the pollen and midges, to gain a comprehensive picture of how these factors have interacted to structure past vegetation.