School of Geography - Faculty of Environment

PROJECTS & WORK IN PROGRESS

NERC small grant (NE/H011773/1): Long-term forest dynamics in Peruvian Amazonia. Start date: 1st July 2010; ends 30th June 2011 (Principle Investigator).

Reconstructing late Pleistocene and Holocene lake level changes at Ioannina, northwest Greece (co-investigator; applied 31 March 2009, awarded 15 May 2009): NERC/NIGL stable isotope allocation, grant in kind.

Application of automated image analysis to establish the pattern and timing of deforestation in Medieval Iceland.
Earth and Biosphere Institute, University of Leeds; seed money competition; awarded April 2009.

The potential of Amazonian rainforest trees to preserve century-scale records of environmental change.
British Ecological Society, Small Ecological Project; awarded June 2008.

Previous Projects

The penultimate climatic cycle in Northern Europe: a new, high resolution record from the Eifel region of Germany. Visiting research fellow in the geology department of the University of Mainz, July-September 2007.

Intense volcanic activity affected the Eifel region of western Germany during the Pleistocene leaving numerous crater or maar lakes in which sediments could accumulate. The lake sediments represent windows onto various different time intervals, beginning when volcanism ceased and ending when the basins became full. They provide extremely high resolution records since the sediment accumulation rates are high and the lakes are often deep, at least early in their history, enabling annually laminated (varved) sequences to form.

Detailed pollen records of the last climatic cycle, including the Eemian (MIS 5e), and Holsteinian (thought to be equivalent to MIS 11) from the Eifel region have been published recently (Sirrocko et al. 2007). Sequences spanning the two intervening interglacial complexes, equivalent to MIS 7 and 9, have not yet been identified in the Eifel region. There is good reason to think that they should be represented here and, if they are, the records ought to be as detailed as those of MIS 5 and 11 since the depositional environments available were probably the same. Terrestrial sedimentary records of MIS 7 and 9 are still extremely rare. There are a number in southern Europe (Wijmstra and Smit, 1976; Follieri et al. 1988; Tzedakis et al. 1993; Reille et al. 2000; Roucoux et al. submitted) and a number of marine pollen records spanning this interval from the Portuguese margin (Roucoux et al. 2006; Desprat et al. 2006) but none in northern Europe that can be securely correlated with MIS 7 or 9. This is due partly to the lack of continuous sequences, with secure stratigraphic control, and partly to the uncertainties inherent in radiometric dating material on which terrestrial chronologies of this interval must rely.

A core obtained from Walsdorfer Maar is thought to be a possible contender for a record spanning this missing part of the last half-million years. My work in Mainz, on the detailed palynology of this sequence, contributed to efforts aimed at establishing the stratigraphic position of this temperate interval. Preliminary palynological analyses reveal an interval of temperate woodland that is dissimilar to both the Eemian (MIS 5e and the Holsteinian (MIS 9 or, as some think, MIS 11) below cold stage sediments and below a phonolitic tephra layer dated to c. 150 ka.

The penultimate climatic cycle (c. 250 to 135 ka) is an interesting interval as it includes examples of apparent de-coupling between climatic forcing and response. For example, insolation changes of the highest amplitude of the last 600,000 years are accompanied by relatively subdued changes in global ice volume; large remnant ice (possibly the result of a small glacial termination) persist during the interglacial intervals despite high insolation values. Knowledge of the nature of the vegetation through this interval in the Eifel region would be of value as it is at a critical latitude for climate forcing via vegetation-controlled albedo-temperature feedback. A record from Eifel would contribute one point on the map (not much, but a start!) showing the time at which the taiga-tundra transition took place there, which may help us to understand what kept the interglacials of MIS 7 cool.

The penultimate climatic cycle in southern Europe

Response of vegetation to climate variability on orbital and millennial frequencies during the penultimate climate cycle in NW Greece. NERC standard three-year grant, 2003-2006. Principle Investigator Prof. P.C. Tzedakis.

The aim of this project is to improve our understanding of the sensitivity of vegetation to climate forcing under different combinations of environmental boundary conditions. The penultimate climatic cycle includes climatic states and events that are not yet well understood, experiencing combinations of carbon dioxide levels, ice volume and insolation that are not consistent with our understanding of the climate system. The nature and extent of vegetation changes in NW Greece during this interval, 130-245 thousand years ago (ka), are being determined by pollen analysis of a long lake sediment sequence, I-284, from Lake Pamvotis, Ioannina, northwest Greece. I-284 is one of very few sequences in Europe to provide a continuous, high resolution record of multiple glacial-interglacial cycles. For reasons of geography and topography, the record is sensitive to climatic change, influenced by North Atlantic oceanographic events, and the status of the site as a glacial refugium for thermophilous trees ensures a vegetation response characterized by a negligible time lag. Comparison of the resulting proxy vegetation record with marine and ice core records and with orbital parameters is enabling us to explore vegetation responses on a range of time scales. Specific research questions include: 1) Which factors control the extent of interglacial forest development in NW Greece? Insolation, global ice volume, and atmospheric carbon dioxide concentrations have all been suggested as potential drivers of terrestrial vegetation change. 2) Did refugial temperate tree populations persist in NW Greece through the penultimate glaciation? Is there a correspondence between ice volume and the size of temperate tree populations? In view of the fact that the extent of glaciation was greater during the penultimate glaciation than during the last cold stage, we might expect refugial populations to have been smaller.

Response of vegetation to climate variability on orbital and millennial frequencies during the penultimate climate cycle in NW Greece. NERC standard three-year grant, 2003-2006. Principle Investigator Prof. P.C. Tzedakis.

The aim of this project is to improve our understanding of the sensitivity of vegetation to climate forcing under different combinations of environmental boundary conditions. The penultimate climatic cycle includes climatic states and events that are not yet well understood, experiencing combinations of carbon dioxide levels, ice volume and insolation that are not consistent with our understanding of the climate system. The nature and extent of vegetation changes in NW Greece during this interval, 130-245 thousand years ago (ka), are being determined by pollen analysis of a long lake sediment sequence, I-284, from Lake Pamvotis, Ioannina, northwest Greece. I-284 is one of very few sequences in Europe to provide a continuous, high resolution record of multiple glacial-interglacial cycles. For reasons of geography and topography, the record is sensitive to climatic change, influenced by North Atlantic oceanographic events, and the status of the site as a glacial refugium for thermophilous trees ensures a vegetation response characterized by a negligible time lag. Comparison of the resulting proxy vegetation record with marine and ice core records and with orbital parameters is enabling us to explore vegetation responses on a range of time scales. Specific research questions include: 1) Which factors control the extent of interglacial forest development in NW Greece? Insolation, global ice volume, and atmospheric carbon dioxide concentrations have all been suggested as potential drivers of terrestrial vegetation change. 2) Did refugial temperate tree populations persist in NW Greece through the penultimate glaciation? Is there a correspondence between ice volume and the size of temperate tree populations? In view of the fact that the extent of glaciation was greater during the penultimate glaciation than during the last cold stage, we might expect refugial populations to have been smaller.

Land-ocean correlation over multiple glacial-interglacial cycles, NERC small grant 2002-2003, Principle Investigator Prof. P.C. Tzedakis, School of Geography, University of Leeds.

In collaboration with the Godwin Laboratory, in Cambridge, working under the auspices of EU-funded project Pole-Ocean-Pole, we have produced a marine pollen record spanning the interval 180 to 420 ka. This constitutes the highest resolution vegetation record for this period in Europe, and the first for Iberia, and shows that the vegetation of southern Europe was responding to environmental oscillations so far only identified in Antarctic ice cores. It reveals that the duration of forested phases varied from one warm stage to the next and that these phases do not coincide precisely with phases of low ice volume. The implication of this is that presently we cannot predict when the current warm stage, of which 10,000 years has so far elapsed, will end (Tzedakis; Roucoux etal. 2006). We also demonstrate that abrupt climatic oscillations occurred within these warm stages, and correlation with Antarctic ice core data suggests that these were coeval with variations in greenhouse gas concentrations.

Vegetation response to the millennial scale climatic oscillation of the last cold stage NERC-funded PhD 1996-2000: supervisor Prof. Sir N.J. Shackleton, Godwin Laboratory, University of Cambridge.

During my PhD I produced a high resolution pollen record for the last glaciation, which established that forest cover in Portugal responded immediately to the abrupt shifts in climatic and oceanographic conditions in the North Atlantic (Roucoux et al. 2001; Roucoux et al. 2005). These large and rapid switches in temperatures are famously recorded in the Greenland ice cores (Dansgaard et al. 1993) and registered in North Atlantic sediments as periodic southward penetrations of icebergs (Thomson et al. 1999). Rapid warming events in the North Atlantic were accompanied immediately by woodland expansion in Iberia, and cold events were accompanied by tree population collapse (Roucoux et al. 2001; Roucoux et al. 2005). This discovery lent weight to the earlier assumption that rapid oscillations recorded in terrestrial pollen records elsewhere in southern Europe were synchronous with North Atlantic climatic oscillations and therefore that the climate of southern Europe was dominated by the behaviour of the North Atlantic.

Grants

• Contributions to conference expenses from Quaternary Research Association and university sources (<£1,000)
• Previously held a NERC PhD studentship and postdoctoral research position.
• Awarded Special Payment by University of Leeds, August 2004, for exceeding expectations.