Understanding climate changeThe National Oceanography Centre, Southampton brings together scientists and engineers from the Natural Environment Research Council and the University of Southampton in a collaborative environment on the city’s waterfront.  The centre is a multidisciplinary hub of expertise, housing oceanographers, geologists, ecologists and physicists, delivering the technologies needed to carry out world-leading research that answers pressing questions about our planet.

Increasingly, studies have focused on understanding the ocean’s relationship with the climate, in terms of global warming. Three key areas of research which feed into UK and global policy on climate change are featured here, demonstrating the range and depth of exploration needed to gain a clearer picture of what is happening to our climate.

Studying sea levels and climate change

Eelco Rohling is Professor of Ocean and Climate Change at the University of Southampton’s School of Ocean and Earth Science. He is a palaeoceanographer, and is studying sea-level change in relation to climate.

Large, long-term sea-level rises are inevitably associated with sustained global warming, but predicting more accurately when, and by how much, sea level will rise, is very difficult. One successful outcome from the research conducted over the last 16 years has been the development of a new method to reconstruct sea-level changes in 100-year time steps, going back over the last 500,000 years. 

Prof Rohling explains: “By looking back at previous natural fluctuations, we can match this against current conditions, and make more realistic assessments of the risks ahead of us. Some of our figures are being used to inform extreme scenarios for flood protection plans for strategic centres like London, Manhattan, Rotterdam and Seattle, where major defences will be needed to protect lives and assets from sea-level rise.”

The 2007 Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) projected a rise in sea level of up to 70cm by 2100.  However, Prof Rohling’s research indicates that this estimate may be too low, because we need to account for the long-term melt-water releases from the world’s major ice sheets. 

Prof Rohling comments: “Our project shows that the last time the Earth was as warm as it is predicted to be at the end of this century, sea levels rose by 1-2 metres every 100 years. Those rates reflect the sum total of both fast and slow-acting processes. The steadily increasing rates of sea-level rise seen over recent decades are dominated by fast processes of ocean warming and glacier reduction. Once the slow processes of ice-sheet reduction become dominant, it will be too late.”

Prof Rohling argues that even if CO2 emissions were stabilised now, those processes would lead to high rates of rise over many centuries until the global sea level reaches 15-25m above where the coastline sits today.

The period of his study covers five complete ice-ages, with global sea level changes between 10m above and 130m below current levels.  Evidence comes from sediment found in the Red Sea, which reveals the chemical make-up of the tiny sea creatures present through these periods. The study also compares sea level rises with temperatures and CO2concentrations, using Antarctic ice samples. When the temperature cools, ice caps expand and the seal level drops - when things heat up, as with global warming, the ice retreats and sea levels rise.

“Modern CO2 emissions are largely man-made, but the greenhouse gas properties of CO2remain the same: higher sea levels are the delayed reaction to an increasingly warm climate,” states Prof Rohling. “Long-term research such as this can point to issues that may not affect the man-in-the-street now, but they will be important to his grandchildren.”

How marine animals and plants capture carbon

The oceans are the largest carbon reservoir on earth. They ‘sink’ CO2, absorbing it from the atmosphere and drawing it down into the ocean – taking up more even than the rain forests. They hold about a third of the CO2 emitted, but, since the industrial revolution, the amount and rate of CO2 being pumped into the atmosphere is increasing at a rate unprecedented in human existence. So one of the key questions about climate change, is: ”How much more carbon can the oceans take?”

Dr Debora Iglesias-Rodriguez has been studying ocean biochemistry and ecosystems for 15 years, and is leading a project at the National Oceanography Centre, Southampton to look at the effect of ‘ocean acidification’ on marine organisms. As CO2 dissolves in water, it forms carbonic acid, making seawater more acidic. This study is beginning to show what effects the changing chemistry of the sea is having on marine life, and how this may impact on all of us. Creatures such as coccolithophores (chalk-producing phytoplankton) and sea urchin larvae (echinoderms) use the carbon to make chalky skeletons and shells. When they die, part of the chalk accumulates on the ocean floor sediment, and so this carbon is captured and held. 

Dr Iglesias-Rodriguez says: “If the oceans are becoming increasingly acidic, can these organisms adapt fast enough to keep up, and does the acidity affect their health?”

Not only is this a key issue for those wishing to understand the effects of climate change on marine life, but there is a knock-on effect in the food chain. For example, sea urchin larvae, as well as many other echinoderm and fish larvae, require the production of skeletons within their first 48 hours of life, and an increasingly acidified ocean could cause a decline in adult populations. Although the impact of ocean acidification on food availability is difficult to predict, given that fisheries provide up to 20% of protein in Southeast Asian countries, western coastal Africa and western and northern Europe, understanding the effects of ocean acidification on fisheries is a priority.

There are some interesting outcomes from the research, which involves a combination of laboratory-based testing and field observations. Dr Iglesias-Rodriguez continues: “Our work contradicts previous findings and shows, for the first time, that calcification by phytoplankton vary depending on species. Some of these microscopic organisms, which are major players in the Earth’s cycling of carbon, are responding to climate change by increasing the size of their calcium carbonate plates.”

However, not all species of coccolithophores, and not all marine life, responds in this way. Corals, for example, are highly susceptible to increased acidification, and so the research at Southampton continues to feed into the climate change debate.

RAPID Programme - global scale research and the future:

Professor Meric Srokosz is science co-ordinator of the NERC RAPID climate change programme at the National Oceanography Centre, Southampton. This is a project, exploring the North Atlantic circulation by making a decade of observations - between 2004 and 2014 - integrating the study of the oceans and their effect on climate. The project is tracking changes to the circulation, and using these to develop improved models, which will forecast future change.

Since 2004, one particular observation is that the ‘natural’ patterns of the North Atlantic circulation are much more variable than previously thought.

Prof Srokosz comments: “Oceanography is a relatively new science, which really didn’t exist before the 1950s in terms of sustained instrumental measurements. Meteorologists have been making measurements for centuries and have a wealth of data, and if we combine this with the study of the ocean, then we can be more confident in our predictions of climate change in the future. In recent years, oceanography using satellites has made a huge contribution to our understanding of ocean currents, enabling us to model them more accurately.”

The RAPID programme is looking at the movement of heat by the ocean currents, and how global warming is working to redistribute heat and cold in the ocean. How would an increase in the Atlantic Ocean’s warmth affect the UK?  Obtaining data which is robust on a short timeframe – such as the 10- year span of RAPID – is extremely challenging, but this is the sort of timeframe that governments tend to focus on. In response, the programme is working with the Meteorological Office Hadley Centre which advises the Government on climate change issues, and is funded through the Department for Environment, Food and Rural Affairs (Defra), the Department of Energy and Climate Change (DECC) and the Ministry of Defence (MOD).