During one of my rests as I struggled up a peak in the Pyrenees last summer, I found myself thinking of the pioneer explorers of these mountains. Many gruesome tales exist about these early mountaineers. Take the case of Pierre Barrau, whose body emerged from the ice in 1941, 117 years after he fell down a crevasse on the Maladeta glacier. Now I'm no great mountaineer and yet there I was happily trotting across the Maladeta glacier. However, my expedition was much tamer than Pierre Barrau's, thanks to the Pyreneen glaciers shrinking by as much as a half in the last century.
Global warming partially explains why the glaciers have shrunk but it isn't the whole story. Other pieces of evidence suggest that Europe suffered some pretty harsh winters a few hundred years ago; people frequently held 'frost fairs' on the river Thames and ships records tell of many devastating winter storms. These are examples of the climate's natural cycles of cooling and warming. The unfortunate Pierre Barrau lived in a particularly cold time period, sometimes known as the 'little ice age.' My research involves searching for and identifying these climate cycles, both in the present, and at a time when the dinosaurs were roaming around, millions of years ago.
Since the dinosaurs weren't the most diligent of weather recorders I have to look for another source to find out what the weather was like all that time ago. This is not an easy task. I have turned to the rock record and have collected rocks from the walls of a quarry in the Sahara. These rocks are special because of the way they were created.
Imagine you can travel back in time. Step into your time capsule, set the dial to the Sahara, 90 million years ago, and make sure you remember your diving gear.
You are now under about 200m of seawater, a rain of particles falls around you and settles. In years to come these particles will compress into a hard rock. Most of the particles are dead microscopic organisms that lived in the surface waters of the ocean. They are a type of algae called coccolithophores, and are made up from many intricate calcite plates. Coccolithophores are so small that around 10,000 could sit on the tip of a pencil. There is little else to see in these murky depths so lets get back to our capsule.
Those coccolithophores that you saw earlier have a very useful property; they respond to changes in climate. When ocean surface waters are warm some species thrive, meanwhile if surface waters cool a different set of species becomes predominant. Since ocean surface temperature is strongly related to air temperature, it is possible to use these coccolithophores as a fossilised thermometer.
My rock slices from the quarry consist of millions of wafer thin layers, sometimes less than a millimetre thick. Each layer represents a season of accumulation at the ocean floor. From analysing the coccolithophores layer by layer, I am building up a picture of the climate cycles acting at that time. But are these cycles the same as those we experience today, or did the dinosaurs live under different climate controls?
To answer this question I am taking a closer look at some muds from the Cariaco basin, off the coast of Venezuela. These slimy muds were laid down much more recently; within the last 10,000 years. Most importantly they are a good modern day comparison to the quarry 90 million years ago, since the Cariaco basin is a similar depth, size and latitude. By looking at the changes in coccolithophores in these muds I can compare recent climate cycles to ancient ones.
So why look at climate cycles at all? Climate and what controls it is an incredibly complicated system and there is still plenty we don't understand. Climate cycles give some indication of what is driving the climate at any one time. My work may help to piece together a little bit more of the climatic puzzle which has such a bearing on the world today. But I'm just curious as to whether the dinosaurs ever held frost fairs too!
Copyright Kate Ravilious