Sub-annual climate variability during the last deglaciation: New views from coralline biogeochemistry

If we travelled back in time some 18 000 years, we would hardly recognise our planet. Many parts of the Northern Hemisphere that are densely populated today were frozen wastes: glaciers covered the cities of New York and Berlin, and the ground where London and Paris would become established was permanently frozen. Not long after however, this ice began to melt. The oceans were flooded with fresh water, causing sea level to rise and changing the pattern of ocean circulation. The question that we want to answer in this proposal, is what effect did this change in the pattern of circulation have on Earth's climate? The problem is that direct measurements of our climate (for example, temperature) extend back no further than the past few hundred years, so such information must instead be reconstructed from so-called proxies, or 'substitutes'. Corals are particularly useful proxies, because they can be accurately dated and their chemical composition reflects a number of important environmental parameters, such as the temperature of the water in which they grew. Here, we propose to obtain records of the variation in the chemical composition of coral skeletons from Tahiti that are between 20 000 and 10 000 years old. What is unique, is that we will use new laser technology that enables us to obtain records at extremely high resolution (a few days to a few months). This means that we will be able to capture the short-term events that can influence the transition from glacial to warmer conditions on Earth.