The relationship between the ocean and the Earth’s climate is complex, and is still full of unknowns. The chemical composition of samples collected in the oceans hold countless clues about the causes of geologic transitions, which enable scientists to create a picture of past, ongoing and even future processes of planetary change.

“We know today that the ocean and climate can change quite rapidly but it can be hard to put those changes into a historic perspective,” says Dr Laura Robinson, who is embarking on a five-year project to collect new data on the chemistry and circulation of the Atlantic Ocean over the last 40,000 years.  “I’m really interested in finding out how and why the ocean changes and how those changes affect global climate; when things change; how fast they can change, and why.”

A six-week cruise will see Dr Robinson and a team of researchers collect samples of deep-sea coral skeleton, from the surface to depths of 5,000 meters beneath the Atlantic Ocean.  The samples will be collected from a research ship equipped with specialised equipment including remotely operated vehicles; robots that operate deep below the sea-surface. In this project, the focus will be directed towards using corals to examine the unknowns of the past: “What’s really exciting and new about looking at deep-sea corals is that by analysing their chemistry using high precision chemical tracers, you can find out exactly how old they are and then find out something about the chemistry of the ocean in the past. That level of precision is hard to achieve with other archives of the past.”

By creating a comprehensive transect that stretches right across the Atlantic from east to west, the team will chart the areas where corals live today and where they have lived in the past.  The samples will be analysed in state-of-the-art isotope labs, and in a suite of new geochemistry labs Dr Robinson is specifically setting up for this research at the University of Bristol’s School of Earth Sciences. 

First the specimens will be dated using the radioactive decay of uranium which is included in the coral skeleton, a technique that can date samples ranging back as far as nearly half a million years. Once the age of each sample is known, additional analyses will be made to examine the oceanic conditions in the past. Just as the concentric circles in a cross-section of a tree indicate the tree’s age, dissection and chemical analysis of a coral skeleton can reveal the environmental conditions in which it grew.  For example, they will measure how much radio carbon is present in each coral sample. Radiocarbon decays away at a rate of half being lost every 5,500 years, allowing researchers to use radiocarbon as a tracer of the rates of ocean processes. Since radiocarbon enters the ocean from the surface atmosphere the quantity of radio carbon in coral samples is indicative of the circulation rate and carbon cycling in the deep ocean at any given time.

Interpreting the data will involve the expertise of marine biologists, geophysicists, mathematical and climate modellers, as well as geologists, to provide a comprehensive picture of the history of the Atlantic.  It is a project of great significance and almost limitless scope; the archive of samples that Dr Robinson’s team collects will open up opportunities for research way beyond the project’s initial five-year span. 

It is an increasingly urgent and timely endeavour through which Dr Robinson hopes to learn more about the ocean before the damage wreaked by activities such as deep-sea fish trawling plunders the ocean of its beauty and all that it might yield for science: “Using geochemical tools and looking at corals is endlessly fascinating from a biological and geological perspective because some of the novel things you can learn.  It would be a tragedy to destroy all of our deep sea ecosystems before we’ve even looked at them.”

Key facts:

Please contact Aliya Mughal for further information.