Unlocking the Secrets in Mud: From Fossil Molecules to Ancient Climates

Kate intro pic2

This blog post comes from Kate Newton, a 2nd year PhD student in the Earth Sciences department at the University of Birmingham. Here she tells us a bit about what her research is all about.

Earth’s climate is changing. Temperatures are increasing, ice is melting and sea levels are on the rise….

Climate change today is real, it is human caused, and it is serious. But, actually, Earth’s climate has always changed. Over hundreds, thousands, millions of years. It’s been a lot warmer before and it’s been a lot colder. And that’s what my research is about – the study of ancient climate change.

Now this isn’t meant to downplay the seriousness of current climate change, not at all. But what if we could use these past changes to help us? I mean, what if we could build a time machine and go back, and see how climate has changed before? And how different environments responded under the same conditions we’re creating today? Surely then we’d have a better idea of what we’re in for and how serious it could be?

Well, that’s what my research is trying to do! I’m not exactly building a time machine, but I have the next best thing… ancient deep sea mud!

I study lipid biomarkers – fossilised fat molecules which are the remains of ancient organisms preserved within deep sea mud. These generally come from phytoplankton, teeny tiny creatures at the bottom of the food chain, which live in the surface of the oceans, soaking up the sun’s energy and CO2 as they photosynthesise. When the phytoplankton die, they fall to the bottom of the sea, along with other organisms or particles washed or blown in from land, and gradually build up on the sea floor over time.

biomarker process2
Tiny phytoplankton which live in the oceans fall to the sea floor when they die and accumulate over millions of years. We can then take these sediment samples to the lab, extract the lipid biomarkers and see what climate clues are in there.

Sitting at the bottom of the sea, the phytoplankton will eventually start to degrade. However, these lipid components, such as fatty acids, are the most resistant and can persist within the sediments for many millions of years. The great thing about these lipid molecules is that they capture a signal of what the environmental conditions were like when the organisms were alive, through their structure, abundance and isotopic ratio. So if the climate changes over time, so will our biomarkers. So if we can study them in the lab, it means that, like a detective, we can piece together these different clues and create a picture of changing environments through time as we dig down through the sea floor – temperatures, CO2, ocean currents, ice melt… These secrets have all been recorded, we just have unlock them!

We can take the signals we get from biomarkers and put them together with other pieces of evidence we can find on the sea floor. The type, abundance and geochemistry of different microfossils will also give us lots of information about the environment, as will the other material that’s in there, such as the amount of mud, silt or sand, or even plant-waxes blown or washed in from the surrounding land. When we put all this data together, we can start to see how climate and environments have changed over hundreds, thousands or even millions of years, right up to the present day. We can compare different regions and types of environments, and even build up a global picture.

foram image
Microfossils, like this foraminifera, are also useful tools for reconstructing Earth’s climate. These tiny creatures are smaller than a grain of sand and have lived in the ocean’s surface for millions of years.

Understanding how climate has changed naturally over these long time periods is vital for us to really understand what’s driving our climate today. We can start to see what the main forcings and feedbacks in the climate system are, and even look back at past warm periods, when global climate became much hotter that it is today. These can serve as potential analogues for our future planet, and help us answer the questions of the ‘sensitivity’ of the climate – what happens when we inject more CO2 into the atmosphere? We can also understand how what humans are doing to the climate today compares to that seen in the geological record: climate change forced by natural processes alone. And that shows us just how serious it is; because the rate of change happening today is significantly faster than the planet would experience naturally, which means many environments simply don’t have the time to adapt or evolve.

I hope that through my work we can gain a better understand of how climate and environments have changed before, ranging from the Antarctic regions over the past few thousand years, to the tropical oceans many millions of years ago.

In the short video below I explain my research in 2 minutes, filmed at the Open University as part of the ‘Engaging with end-users’ training course in March 2017:

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