Bushfire-generated alluvial fans in southeast Australia – a Holocene record of changing bushfire activity and climate change (Dr Philip Marren)
Funded by the Australian Institute of Nuclear Sciences and Engineering (AINSE, 2014); University of Chester QR Award.
Post-bushfire debris flows are a common occurrence in many mountainous landscapes. Alluvial fans in northeast Victoria, Australia, provide a record of repeated bushfire activity extending back over 10,000 years. Radiocarbon dating of debris flow deposits provides a record of shifting bushfire frequencies, relating to major changes in climate over the Holocene.
Investigating the spatial expression of millennial-scale Holocene climate changes (sub-arctic and Balkan Peninsula)(Dr Graham Wilson, Dr Mick Frogley (Sussex), Dan Fower, Prof. Melanie Leng (NIGL; Nottingham), Dr Phil Hughes (Manchester)
There is increasing evidence of global climate instability during the Holocene, characterised by several abrupt climate changes, commonly associated with a drop in high-latitude temperatures coincident with tropical aridity. Palaeoclimate records from the North Atlantic region reveal that these millennial scale events have quasi-periodicities of c.2,500 yrs and c.1,500 yrs. The impact of these abrupt climate changes on human civilisations is significant. Whatever the overall cause of these abrupt events, there is firm evidence for periodic changes in the strength of the Atlantic Meridional Overturning Circulation (AMOC) during the Holocene. Given that changes in the strength of the AMOC have been shown to influence regional and even global climate during the last glacial phase, it follows that such changes in the Holocene, albeit of smaller magnitude, may have the potential to influence climate over a wider area. The range of influence and relative impacts of Holocene rapid climate events are poorly understood, however. These research projects are concerned with assessing the temporal and spatial range of influence of Holocene millennial-scale climate oscillations on terrestrial ecosystems. This is being achieved through targeted multi-proxy (diatoms and isotope geochemistry) investigations of lake sediment sequences from sub-arctic N Finland and from the mountain lakes of Montenegro. Both regions have experienced historically low population densities, and thus minimal human impact on terrestrial ecosystems. The lakes in both regions are environmentally sensitive, with subtle changes in climate expected to result in marked changes in lake physio-chemistry.Terrestrial and lake hydrological response to millennial-scale climate oscillations during the penultimate glacial in southern Europe Dr Graham Wilson, Dr Mick Frogley (Sussex), Dr Tim Jones, Dr Phil Hughes (Manchester), Prof. Melanie Leng (NIGL; Nottingham)
There is growing evidence that millennial-scale climate oscillations are a pervasive feature of glacial intervals. During the last glaciation (Marine Isotope Stage (MIS) 2–4), incursions of cold water into the North Atlantic appeared to coincide with abrupt reductions in southern European tree populations, suggesting down-stream impacts on continental hydroclimate. Ice-rafting into the North Atlantic during the penultimate glacial (MIS 6) is thought to be less extensive than at times during MIS 2–4, perhaps resulting in more subdued climate oscillations. Published pollen data from Lake Ioannina in NW Greece suggest pronounced oscillations in southern Europe tree population extent during early MIS 6, followed by much-reduced tree populations and subdued oscillations throughout late MIS 6. Previous studies of the diatom and isotope records from the same sequence during the MIS 7/6, 6/5e and 2/1 transitions, and from MIS 5e and 1 demonstrate the sensitivity of these proxies to changes in regional climate. Therefore, this research applies a combined diatom and stable isotope approach to further explore the influence of millennial-scale oscillations on southern Europe hydroclimate during MIS 6.Application of stable carbon isotope and geochemical datasets for Holocene sea-level reconstruction in NW Europe (Dr Graham Wilson).
Bulk organic stable carbon isotope (δ13C), element geochemistry (organic carbon to total nitrogen (Corg/Ntot) and total organic carbon (TOC)) analysis is a developing technique in palaeosea-level research. The uptake of this technique in Northern Europe is limited compared to North America, where the common existence of isotopically distinctive C3 and C4 vegetated coastal marshes permits their distinction in the sediment record, along with associated reference water levels. In Northern Europe, the reduced range in δ13C values between organic matter sources in C3 estuaries can make the identification of elevation-dependent environments in the Holocene sediment record challenging and this is compounded by the potential for post-depositional alteration in bulk δ13C values. The application of regional δ13C, C/N and TOC datasets representing the range of physiographic conditions commonly encountered in coastal wetland Holocene sediment sequences is a promising development. This approach opens up the potential of using absolute values of sediment geochemistry to infer depositional environments and associated reference water levels. This research further explores the application of contemporary bulk organic δ13C, C/N and TOC to reconstruct Holocene relative sea-level. This is being achieved by increasing the range of modern analogues for δ13C, C/N and TOC values in Holocene coastal deposits, and utilizing statistical techniques to objectively identify reference water levels based on sediment geochemistry.
https://www1.chester.ac.uk/research/global-environmental-change-and-hazard-management/environment-and-climate-change