Palaeoenvironmental Reconstruction and Modelling

Introduction

This research group has 12 academic and research staff and 25 postgraduate research students. Our research focus is the understanding of the global environment through study of the behaviour at the macroscale of specific environmental systems over timescales ranging from centuries to millions of years. The strategy is to contribute a disciplinary perspective on spatial and temporal scales that have been under-represented in the past. A major benefit of this strategy is that it has allowed us to explore innovative interdisciplinary approaches, especially with geophysicists, atmospheric modellers and archaeologists. The common thread to our activities has been (a) the development of numerical and conceptual models designed to bridge the gap between theory and geographical reality, (b) the need to obtain novel and improved empirical data with which to constrain the models and (c) the employment of GIS techniques as a way of facilitating and representing complex models.

Over the past few years this group has: 1) developed high-resolution ice sheet models as a way of bridging the gap between glaciological theory and glacial geomorphology; 2) explored new approaches to the landscape evolution of passive continental margins; 3) used geomorphological approaches to argue for the long-term stability of the East Antarctic Ice Sheet; 4) pioneered the use of fine-grained volcanic ashes as a means of establishing high-resolution Holocene chronologies in north-west Europe; 5) developed the use of freshwater diatoms in reconstructing human-induced and natural environmental change in the sub-tropics, and 6) identified the role of soils in influencing landscape and environmental change. Working with GIS colleagues, the group has explored new approaches in the modelling of ice sheets, snow cover and snow avalanches. One recent development includes the establishment of a cosmogenic isotope analysis capability, in conjunction with the Scottish Universities Environmental Research Centre (SUERC), for applications in Quaternary dating, quantifying long-term rates of denudation and the investigation of specific geomorphic processes. Members of the group are also involved in a multi-disciplinary international initiative to study the interactions of humans and landscapes in the North Atlantic region, a project funded from the UK, USA and Scandinavia, and involving participants from ten countries.

Our work has been supported by numerous research grants from NERC (including awards under the Joint Research Equipment Initiative and the Joint Infrastructure Fund), charitable trusts, the Department of the Environment and the ODA. We have a large laboratory suite within which there are laboratories dedicated to palaeoenvironmental research (pollen and diatom and grain size analysis) and sample preparation for the key geochronological techniques of tephrochronology, radiocarbon dating and cosmogenic ²⁶Al, ¹⁰Be, ³He, ²¹Ne and ³⁶Cl. A separate large laboratory is used for soil and sediment analysis, including an atomic absorption spectrophotometer and a cold storage facility for organic samples. Other facilities include a microscopy room and a digital image capture microscope.

Particular Research Strengths

Geomorphology

Macrogeomorphology: The aim is to model the long-term interactions between tectonics and denudation in the evolution of passive continental margins. In particular, through collaborative projects, we have used apatite fission track analysis and cosmogenic isotope analysis to assess rates and timing of denudation over a range of timescales up to tens of millions of years. This work has included projects based in southern Africa and Antarctica.

Applications of Cosmogenic Isotope Analysis: We have been using measurements of the isotopes produced within surface exposed minerals and rocks through the effects of cosmic radiation to quantify rates of surface processes and date landforms and deposits. Projects include the measurement of cosmogenic ³He and ²¹Ne from Antarctic samples using the new MAP 215-50 noble gas mass spectrometer based at SUERC, and the development of glacial chronologies in Patagonia, Scotland and Pakistan using ¹⁰Be and ²⁶Al.

Glacial geomorphology: The aim is to develop an integrated view of the role of glaciers as geomorphic agents. At a macroscale, we have developed ice sheet models and glacial systems which can simulate the evolution of an existing or former ice sheet during the course of a glacial cycle and whose output is at a sufficiently high resolution to be compared with geomorphological evidence on the ground. At an intermediate scale, we are using tephrochronology and ice-radar survey, together with modelling, to study the response of Icelandic glaciers to climate change. At the smallest scale, we are exploring the use of tephras to study contemporary glacier flow in Iceland. Published highlights include ice sheet models of Greenland, Scotland, Patagonia and Antarctica demonstrating how topography and changing climate influences ice sheet behaviour; geomorphological evidence (including discovery of the world’s oldest ice at 8 million years) arguing for the stability of the East Antarctic Ice Sheet; evidence that Icelandic glaciers existed and fluctuated right through the Holocene rather than disappearing in the mid-Holocene as previously believed.

Tropical Soils and Soil-Plant Community Interactions: Researchers work closely with botanists and ecologists from the Royal Botanic Gardens at Edinburgh and Kew and the Natural History Museum, London, and soil scientists from the Scottish Agricultural College and have close links with counterparts in Brazil, central America and southern Africa. The aim has been to assess the spatial and temporal influence of soil properties on biotic features of the landscape and upon changes in the environment. Recent research has included the soil-plant relationship component of the Maraca Island Rain Forest Project in Amazonia, work on forest – savanna boundaries, research into savanna soils, particularly in the Brazilian cerrado, and fire and nutrient budgets in Zimbabwe.

Palaeoenvironmental Reconstruction and Modelling

Tephrochonology: The group has pioneered the use of fine-grained Icelandic tephras as a means of improving both the resolution of tephrochronology and the geographical coverage of the technique in the study of Holocene environmental change. This has involved refining and testing analytical procedures and assumptions through work in Iceland and the Atlantic region. Published highlights include: a development of a tephrochronology for Britain with 8 tephra layers spanning 1510 AD - 7000 BP and supported by over 200 ¹⁴C dates; development of laboratory procedures and standards for the analysis of fine-grained layers; the application of the technique within environmental archaeology; refining the volcanic history of Iceland and determining the geochemistry, dispersal volumes and chronology of key silicic tephras; the creation of a tephrochronological database accessible ll on the Web. Research is in collaboration with the Science Institute, University of Iceland and Institute of Archaeology, Iceland. Further developments are taking place in central Mexico where a regional tephrochronology is being developed through stratigraphic studies, mapping, geochemical analysis and ¹⁴C dating. This tephrochronology is being used for temporal control in diatom-based palaeoenvironmental reconstructions. In Patagonia, (Chile) a tephrochronology has been developed to constrain studies of glacial fluctuations and pollen and diatom-based palaeoecologies.

Lake sediments: Our study of lake, marsh and estuarine sediments provides a means of reconstructing environmental change over a range of timescales and has provided a key to understanding the nature and impacts of climatic change. The work is inherently multi-disciplinary. Research is currently focused in Mexico, South America and the UK. In Mexico and Belize, there have been two strands: exploring the relationships between climate change and human impact on lake basins and in providing basic data on climatic change for a region which is expected to have undergone significant changes with movements in the atmospheric circulation associated with the growth and decline of the Laurentide ice sheet. The study of diatom assemblages is a key element in environmental reconstruction and is being further developed in collaboration with the Royal Botanic Garden, Edinburgh and the University of Newcastle. A recent development is the increasing integration of palaeoecological and tephrochronological studies with joint projects in Mexico involving the study of short-term high resolution environmental changes in Mexico using laminated sediment sequences and studies of the mineral magnetic properties of lake sediments in collaboration with the Department of Geology and Geophysics at Edinburgh.