LAST GLACIAL ATMOSPHERIC DUST AND CLIMATE CHANGE IN EUROPE

Understanding causes of global climatic change is one of the most important scientific challenges we face. Past climate reconstruction from sediment and ice archives indicate that climate can change dramatically over short timescales, of the order of decades to millennia. These changes have great potential to disrupt the sustainable development of society, making understanding the causes of these events a critical line of research.

Atmospheric, wind-blown mineral dust is one of the key components of the climate system and also shows abrupt past changes, with dramatic pulses potentially linked to global climate change. Despite this, understanding of the significance of dust in climate change is poorly known; as recently stated in the latest Intergovernmental Panel on Climate Change (IPCC) 2013 global assessment. Atmospheric dust changes the absorption of incoming solar radiation, affects cloud formation, and impacts oceanic productivity, in turn changing atmospheric carbon dioxide, but crucially, it also responds to changes in climate such as reductions in precipitation. As such, there is a complex dust-climate feedback loop operating in the climate system but currently the triggers of changes in this are poorly known. Our proposal seeks to directly address this gap through the first systematic continental-wide analysis of the largest archive of past wind-blown dust deposits available: the Eurasian loess belt. Loess is comprised of deposited atmospheric dust and analysis of loess sequences can shed light both on past climate change but also past dust activity.

The deposits from the Quaternary Ice Age period (starting 2.6 million yrs ago) are particularly extensive and this period is also characterized by dramatic changes in climate. Constraining the accumulation of these loess deposits can shed light on how much dust there was in the atmosphere, while knowledge of the sources of this dust can demonstrate the causes of this dust emission. Large changes in dust accumulation seen in multiple loess records across Eurasia would demonstrate wide-scale pulses of atmospheric dust, while concurrent dust source changes would allow constraint of the environmental triggers of this atmospheric loading. Comparison to past climate records from the same sequences would allow the relative timing of the pulses of dust and abrupt climate change to be characterized, allowing determination of the initial causes of change in the climate-dust feedback. However, until now this level of analysis has not been possible as it requires detailed, robust and precise independently dated age models for loess deposits, as well as simultaneously highly resolved geochemical analysis of dust source changes. Here we will utilize new advances in equipment and technique that allow this for the first time for loess deposits covering the last 250,000 yrs. We will employ new state of the art joint chemical and age dating analysis at unprecedented sampling interval across Eurasian loess deposits for the first time. This will be backed up with targeted radiocarbon dating and zircon U-Pb provenance analysis to develop detailed and accurate independent age models that we will use to determine dust accumulation rates and compare to the paired dust source data. We will also use X-ray fluorescence, SEM, grain-size analysis and mineral magnetic analysis to construct past climate records from the same sequences. This gives us the unique opportunity to constrain abrupt, short-term changes in the past dust-climate feedback system in unprecedented detail across a wide area. Importantly, this analysis allows constraint of the triggers for these changes in the cycle, allowing constraint of how dust impacts and is affected by large-scale abrupt climate change. We will also monitor current dust sources in the loess areas across Eurasia, comparing this to past activity. This will significantly increase our understanding of one of the least well-known aspects of climate. We will also incorporate our data and information on causality into climate models for simulation of the role of dust in climate change, leading to improvements in prediction and better mitigation of the effects of future change. It will also help in constraining where dust may be emitted under different climate scenarios, allowing planning for impacts on climate, society and human health.