Palaeoclimatology

Introduction

Global climate change is one of the most high profile areas of scientific endeavour in modern times. The emission of anthropogenic CO2 will cause global scale climate changes, but the relationship and sensitivity of climate to CO2 remains uncertain (IPCC AR5)

A key tool in the determination of climate sensitivity and the dynamics behind climate change is the study of Earth’s history as recorded in sediments. Geological records contain information on the climate at the time of deposition, and climate models constrained by palaeodata may be more helpful in forming models to predict future climate.

In their 1986 paper, Brassell et al. introduced the technique of molecular stratigraphy that still forms the basis of our palaeoclimatology work in the OGU; that is the use of organic biomarkers, fossilised in the sedimentary record, to reconstruct the palaeoenviroment and palaeoclimate.

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What biomarkers tell us

We use a wide variety of organic geochemical proxies to interrogate the Earth’s climate history, such as the Uk37 proxy which reflects sea surface temperature (SST) based on the relative distribution of unsaturated alkenones from haptophyte algae, or the TEX86 palaeothermometer, which records SSTs from the relative distribution of archaeal membrane lipids known as glycerol dialkyl glycerol tetraethers, or GDGTs.

Our state-of-the art compound specific stable isotope techniques (GC/C/IRMS) are also used to provide novel insight into past climates; for example, the carbon isotopic compositions of the same alkenones used to reconstruct SSTs can be used to reconstruct atmospheric pCO2, and the carbon isotopic compositions of n-alkanes can be used to study past changes in vegetation.

We also use higher plant biomarker hydrogen isotopic compositions to examine a range of questions related to past hydrological change, a topic of much interest due to its impact on human welfare.

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Topics we currently study

There has been, and continues to be, a diverse range of projects within the group developing records of past climate and environments throughout geological time, ranging from fairly modern (the past 10,000 years) to deep time (150 million years ago and more). For example, we are currently involved in a multi-disciplinary study undertaking the reconstruction of Eocene climate during the Descent into the Icehouse in collaboration with the University of Southampton and Cardiff University, as well at the University of Bristol’s School of Geographical Sciences.

As an example of a study in deeper time, we are using compound specific deuterium isotopes of higher plant biomarkers to reconstruct novel records of the hydrological cycle at the Paleocene Eocene Thermal Maximum (PETM), a transient and catastrophic event of rapid global warming occurring around 55 million years ago. Other projects include investigating changes in carbon dioxide concentration and nutrient cycling across Ocean Anoxic Event 1a (~120Ma) using compound specific carbon isotopes and biogeochemical models.

Interdisciplinary and collaborative

The sediments we analyse are sourced from a diverse range of localities and projects, often involving close work with collaborators: e.g. ocean drill core sediments from the Integrated Ocean Drilling Program (IODP), lake core sediments from the International Continental Drilling Program (ICDP), Tanzania Drilling Program (TDP) sediments in collaboration with Cardiff University, or outcrop sediments from localities such as New Zealand or the USA.

In fact, practically all of the palaeoclimate reconstruction studies contribute to much larger research efforts involving collaborations with other established research groups developing complementary multi-proxy climate records. Along these lines, we actively collaborate with other scientists across the University of Bristol as part of the Cabot Institute.

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Further reading

Pancost, R.D., Taylor, K.W.R., Inglis, G., Kennedy, E., Handley, L., Hollis, C., Crouch, E., Pross, J., Huber, M., Schouten, S., Pearson, P., Morgans, E and Raine, I (2013) Early Paleogene evolution of terrestrial climate in the SW Pacific, Southern New Zealand. Geochemistry, Geophysics, Geosystems. 14. 5413-5329

Hollis, C., Taylor, K.W.R., Handley, L., Pancost, R.D., Huber, M., Creech, J., Hines, B., Crouch, E., Morgans, E., Crampton, J., Gibbs, S., Pearson, P. and Zachos, J (2012) Early Paleogene temperature history of the Southwest Pacific Ocean: reconciling proxies and models. Earth and Planetary Science Letters. 349. 53-66

Handley, L., Pearson, P.N., McMillan, I.K. andPancost, R.D. (2008) Large terrestrial and marine carbon and hydrogen isotope excursions in a new Paleocene/Eocene boundary section from Tanzania. Earth and Planetary Science Letters 275, 17-25.

Naafs and Pancost, 2014

Badger et al.. 2014

Martinez-Boti et al..2015

Picture of an algal bloom of the coast of France
Our state-of-the art compound specific stable isotope techniques are used to provide novel insight into past climates.
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