Icehouse tropical climates and plankton evolution

The Earth today has major ice caps on Antarctica and Greenland, but this was not always the case. The planned research focuses on climate change during a time period known as the Oligocene (34 to 24 million years ago). This interval of time is of particular interest as it began with a big shift in climate. Before 34 million years ago, the climate was warm - so warm that there was no permanent ice on Antarctica and palm trees stretched as far north as the Arctic Circle. However, this warm period ended abruptly at 34 million years ago when a large ice sheet developed on Antarctica. Once the Antarctic ice cap was established, it waxed and waned many times between periods with relatively little ice and periods with very expansive ice sheets. My previous work has shown that like a flickering switch, the climate was balanced on the cusp between glaciated and greenhouse states, making the Oligocene particularly exciting to research if we want to understand a world somewhat warmer than the modern. However the Oligocene climate remains something of a mystery because, until now, there have been no good records to document climate changes in the tropics. The tropics are vital because it is heat differences between the tropics and poles that ultimately drives the circulation of the atmosphere and oceans. Unfortunately tropical Oligocene sediments are fairly scarce and most previously acquired records are incomplete or do not have sufficiently well-preserved microfossils for the kind of analyses that are required to reveal the climate. Many questions still need to be addressed, such as; What were conditions in the tropics like while the poles were undergoing these dramatic climate swings? Did the climate cool gradually before each phase of ice build up, and warm before the ice caps waned? How did the Earth's biota respond to the big shifts in climate? These questions can be addressed by analysing the geochemical composition of microfossils from marine sediments. I work with tiny microscopic fossils called foraminifera. These are single-celled organisms that commonly build a skeleton made from calcium carbonate. Over time the shells of dead foraminifera accumulate in marine sediments and yield a long and valuable fossil record, which palaeontologists can exploit to gain information on oceans and climate of the past. One of the most marvellous things about these tiny organisms is that the chemistry of their shells reflects the water in which they grew and other features of their environment. Analysis of fossil shells can be employed to reconstruct many aspects of the climate, such as the temperature of the sea surface and global ice volume. In the past few years I have set about to systematically identify and acquire all the best tropical samples that have very abundant and well preserved foraminifera, making them ideal for chemical analyses and to study the oceans of the Oligocene. More collecting is also required, in areas such as Puerto Rico and East Africa. A detailed study of foraminifer chemistry will build an accurate picture of how the Oligocene climate changed and will lead to a greater understanding of climatic events and oceanographic processes. Studying intervals of dramatic climate change, allow a greater understanding of the oceans and climate system. Knowledge of the climate is particularly important to society in light of current increases in atmospheric carbon dioxide which is predicted to cause rapid and profound global warming. Climatic modelling experiments have suggested that the climate shift from a warm to cool Earth during the Oligocene may have been related to a reduction in atmospheric carbon dioxide levels (in a way, the reverse process of what is predicted for the future). These records will provide the data to test and refine climate models and may provide information useful for predicting the future climate response of abrupt warming, from the ice sheets to the tropics.