Atmospheric Sciences

GeoTalk: Talking about ‘ocean burps’ with James Rae

GeoTalk: Talking about ‘ocean burps’ with James Rae

Trying to understand the reasons behind the global warming of our climate is a never ending quest for scientists across the geosciences. Scientists often rely on deciphering past change to help us understand, and perhaps predict, what might happen in the future. Many will be familiar with the common saying ‘the past is the key to the future’. This is exactly what James Rae, a research fellow at the Earth & Environmental Sciences Department at the Universty of St. Andrews and this year’s recipient of the Biogeosciences Division Outstanding Young Scientists Award, has been focusing his efforts on. James’ research interest lies in understanding past climate change and he was recognised by the Biogeosciences Division after the publication of his research into ocean ‘burps’ – he and his colleagues found that changes in ocean circulation in the North Pacific caused a massive ‘burp’ of CO2 to be released from the deep ocean into the atmosphere, helping to warm the planet sufficiently to trigger the end of the ice age.

Before we get stuck into the details of your work, could you introduce yourself and tell us a little more about yourself and your career?

My name’s James Rae and I’m a geoscientist at the University of St Andrews. I actually grew up just down the road – in Edinburgh – but only just moved back to Scotland last year, after studies in Oxford, Bristol, and California. The locals tell me that the transition from LA to St Andrews shouldn’t be too tough – apparently St Andrews is “one of the sunniest places in the whole of Scotland”!

I got into geosciences through a love of the outdoors and outdoor sports – mountain biking, surfing, snowboarding, climbing – and though most of my work is now in a super clean lab, I still try to get out in the Scottish Highlands whenever possible.

My career to date has focussed on using geochemistry to reconstruct past environmental change. This means I make measurements of the chemistry of things like shells, fossils, rocks, and ice, which often reflect aspects of the environment they formed in. So by making a series of these measurements on fossil shells back through time we can see how the environment changed in the past. My specialty is using boron in tiny fossil shells, called foraminifera, to reconstruct past CO2 change.

So, ocean ‘burps’? During EGU 2015, you received the Biogeosciences Division Outstanding Young Scientists Award for your study of this unusual phenomenon. Can you tell us more about those?

One of the most interesting things about the ice ages of the last few million years is that they seem to be punctuated with really dramatic rapid climate change. The most recent examples of this are at the end of the last ice age – between about 20 and 10 thousand years ago – where we see intervals of rapid CO2 rise recorded in ice cores. The only place where you can quickly get enough carbon to drive these CO2 changes is the deep ocean. During ice ages we think CO2 gets hidden away beneath the waves, at water depths of 2000 – 5000m, and because the Pacific is so big it’s likely that a lot of this CO2 is stored down there. Other scientists had suggested that this CO2 remerged at the end of the last ice age in the ocean round Antarctica. However my research shows that it could also “burp” out in the North Pacific.

Schematic of how James use boron isotope measurements in foraminifera to reconstruct pH and CO2. Credit: James Rae

Schematic of how James use boron isotope measurements in foraminifera to reconstruct pH and CO2. Credit: James Rae

And how exactly did the release of CO2 in these ‘burps’ affect the climate of the ice age?

Our Pacific “burp” happens right at the beginning of the end of the last ice age – it coincides with the first CO2 rise that heralds the start of the deglaciation. It’s possible that the warming associated with the CO2 “burp” helped push the earth out of it’s ice age, though we need to do more work to test this. But even aside from the CO2, the change in circulation that drove this event had a big influence on local climate. Although most of the Northern Hemisphere is really cold at this time the North Pacific is actually quite warm, which I think is a result of this unusual circulation state.

So, the Northern Hemisphere was very cold at this time; can you describe a little more what the Earth might have looked at during this time and how the local climate of the North Pacific might have been different?

At the end of the last ice age massive ice sheets still covered much of North America and Northern Europe. Over St Andrews the ice was around a kilometre thick. Then, at the beginning of the last deglaciation, in an interval called Heinrich Stadial 1, the ice sheets round the North Atlantic start collapsing. This flooded the North Atlantic Ocean with fresh water and reduced the Atlantic overturning circulation that currently provides heat to this region. As a result much of the Northern Hemisphere got colder. However the climate in the North Pacific does something very different. Likely in response to the big cooling in the North Atlantic, there was a large change in the position of major rain belts, like the Westerly storm track and East Asian Monsoon, and we think this acted to make the North Pacific more salty. This led to a more vigorous overturning circulation in the Pacific, a regional warming, and a burp of CO2 release from the deep sea.

What is the next step, if you like, in order to better understand ocean ‘burps’?

At the moment our key evidence for the North Pacific burp comes from a single sediment core. To test the idea we really need to make more measurements from other cores in this region. Our main evidence for ocean CO2 change also currently comes from records from the deep ocean. One of my PhD students is currently making new records to test how much CO2 made it up from the deep to the surface ocean, and from there to the atmosphere. Finally, with collaborators in Switzerland and the US we’re also testing the physical driving mechanisms of this circulation change using state of the art climate models.

(L) An ocean cruise on which the sediment cores used in the study are collected. (R) Benthic foraminifera - James uses these to make measurements of the chemistry of these to reconstruct past climate change. Credit: James Rae

(L) An ocean cruise on which the sediment cores used in the study are collected. (R) Benthic foraminifera – James uses these to make measurements of the chemistry of these to reconstruct past climate change. Credit: James Rae

You’ve enjoyed success as a researcher, not least your 2015 EGU Award. As an early career researcher, do you have any words of advice for masters and PhD students who are hoping to pursue a career as a scientist in the Earth sciences?

Do what you really enjoy. This feeds in to everything else you do; it means you’ll work hard and carefully in lab, find the reading interesting, and be able to present your work effectively to your colleagues. We do science because we love it, so it’s really important to find topics within your field that you love working on. I think it’s also helpful to find skills to be a specialist in and be known for, but then to try to apply these broadly to big picture questions in geosciences.

The EGU Network blogs are looking for guest contributions

Are you a budding science writer, or want to try your hand at science communication? You might just be the person for our EGU network bloggers! A number of our network blogs would like to give their pages a bit of a boost and are seeking guest bloggers to contribute new, informative and engaging posts on an ad hoc basis.

If you’ve recently been thinking about trying your hand at blogging, but aren’t sure if it’s for you or simply have a great story or research that you’d like to see ‘in print’, why not give guest blogging a try? Read on to find out which blogs are looking for contributions.

Four Degrees

4degreesWritten by Flo Bullough and Marion Ferrat , Four Degrees, looks at environmental geoscience issues from a science for policy perspective. Environmental geochemistry, climate change, policy and sustainability are brought together in this blog and explored at the interface between science and society.

Flo and Marion are looking for guest contributions, but would also be happy to welcome a more regular blogger to their team. So if you are interested in geoscience and policy and are looking for the opportunity to get into some regular science writing, fill out this form and Flo and Marion will be in touch soon!

Geology for Global Development (GfGD)

GfGDGfGD is a UK-based organisation, working to support young geologists to make an effective contribution to international development. The network blog is a place for the organisation to share articles, discussions, photographs and news about the role of geology within sustainable development and the fight against global poverty

Blog editor, and founder of the organisation, Joel Gill, has his hands full running the blog, the organisation and completing his PhD. As a result, the blog is particularly looking for guest contributions which explore the principles of international development and how the earth sciences can make a difference. Take a look at the blog for some inspiration and pitch your ideas to Joel using this form.

Geology Jenga

JengaA broad range of topics find their way into the posts of Geology Jenga, with authors Dan Schillereff and Laura Roberts Artal writing about all things science communication, their careers as budding academics, as well as the science behind geophysics and geomorphology.

However, since finishing their PhDs, the demands of their 9 to 5 jobs mean that Dan and Laura have less time to write and would welcome guest contributions on any of the topics above. If you’d like to contribute to the blog, why not get in touch with them using this form?


GeoSphereThe term geosphere is an all-encompassing word that incorporates just about every aspect of the earth sciences. This means that topics ranging from geophysics to geochemistry to geobiology are part of the geosphere. The blog Geosphere honours its namesake by covering any and every topic in the geosciences. However, with blog author, Matt Herod’s research interests in geochemistry and hydrogeology you’ll likely find more posts on these topics.

Matt aims to make science clear for anyone that should stumble upon the geosciences and enhance awareness of the geosphere. If these goals resonate with you, then you writing for the Geosphere blog might just be the thing for you. Why not get in touch with Matt using this form?

Polluting the Internet

PollutingWill Morgan, an atmospheric sciences researcher from the University of Manchester, blogs at Polluting the Internet. Focusing on tiny particles suspended in our atmosphere, called aerosols, which can build up and pollute our skies. In the blog, Will explores current research in aerosol science, as well as his fieldwork exploits in pursuit of these tiny particles.

If this is your area of research too and you’d like to contribute a guest blog post on the subject, why not give it a go! You can get in touch with Will by filling out this form.

Green Tea and Velociraptors

GreenWhilst swamped by the writing of the thesis, Jon welcomes guest contributions to his blog too. Covering the subject of palaeontology as well as regularly writing about science communication and the open science movement, the blog has a diverse readership and offers a great platform for anyone how has something to say about these topics. Get in touch with Jon using this form.

The network blogs cover a range of topics in the Earth, planetary and space sciences, with the aim to foster a diverse community of geoscientist bloggers. If you’d like to submit a guest blog post, please fill out the forms available above. For general guest blogging guidelines, please refer to the submit a post page on the EGU official blog GeoLog.

Imaggeo on Mondays: The warming

Imaggeo on Mondays: The warming

Events of meteorological significance, such as thunderstorms, hurricanes, cyclones, jet streams and global-scale circulations can be described by a general term: atmospheric dynamics. When it comes to it, atmospheric dynamics deals with nothing more than air, which, in truth, is very difficult to directly observe, (with the exception of clouds and precipitation). This makes the study of atmospheric dynamics problematic!

So how is it that we know so much about weather systems and atmospheric dynamics? Scientists are able to observe changes in the temperature, pressure, density (or thermodynamic state to use the technical term), and the general state of the air, as well as changes in its motion, including its direction and speed (ie the winds). But even if the observations can be made, visualising the dynamic events still remains a problem.

That is where rendering – the process by which an image can be generated from 2D or 3D data – comes in. From simple line plots over two-dimensional contours, to three-dimensional visualization and even animations, every type of rendering has its own place and utility in atmospheric science research.

Stratospheric Sudden Warmings (SSWs) are prime examples of global scale atmospheric events that cannot be observed directly, as neither clouds, nor precipitation, nor any other visible structures are involved. SSWs are events where the stratospheric polar vortex –a persistent large-scale cyclone which circles the poles – breaks down within a few days, and strong anomalies can be measured in many variables, such as temperature, wind, and its height position relative to sea level and adjusted for the effects of gravity.

Today’s Imaggeo on Mondays image is a rendering of the SSWs and its associated height anomalies on February 23, 1979, (taken from the European Centre for Medium-Range Weather Forecasts ERA-Interim reanalysis dataset). From the image, Martin Jucker, a researcher at New York University, was able to show that the 1979 event spanned the entire polar and subpolar regions and throughout the stratosphere.

“Not seen in this picture (as it is a temporal snapshot) is the influence such SSWs can have even on the state of the atmosphere at surface levels. Indeed, there can be implications throughout the atmospheric column all the way to the surface, with the jet streams being perturbed and prolonged periods of unusual weather observed in mid- to high latitudes,” explains Martin.

This is a great example of how three-dimensional renderings can give intuitive understanding of the internal structure of important global scale atmospheric events. They can help appreciate the spatial extent of the anomalies generated throughout the atmosphere. Phenomena which are not visible without the help of computer visualisation techniques can be categorised and even defined!


By Martin Jucker, researcher at New York University and Laura Roberts, EGU Communications Officer.

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at

GeoTalk: Deciphering the mysteries of the Mediterranean Sea with Katrin Schroeder

GeoTalk: Deciphering the mysteries of the Mediterranean Sea with Katrin Schroeder

Geotalk is a regular feature highlighting early career researchers and their work. Following the EGU General Assembly, we spoke to Katrin Schroeder, the winner of a 2015 Arne Richter Award for Outstanding Young Scientists.

First, could you introduce yourself and tell us a little more about your career path so far

Meet Katrin!

Meet Katrin! Credit: Katrin Schroeder

I am a physical oceanographer with a background in environmental science. I did my studies at the University of Venice(Italy) and in collaboration with the Institute for Marine Sciences of the Italian National Research Council (CNR-ISMAR). I started off working on biogeochemical cycles in coastal waters and then moved to the larger scale and to the physics of ocean dynamics in the open sea, trying also to combine physical and biogeochemical oceanography. In 2006 I started to work at CNR ISMAR in La Spezia, on the shore of the Ligurian Sea, in a beautiful office with sea view, reminding me every morning how lucky I was to have my job. I finally got a permanent position at CNR ISMAR in Venice in 2011. This period was characterized by intense learning, participation to workshops, summer schools and conferences, prolonged visits at the National Oceanography Centre in Southampton, writing my PhD thesis and papers, and participating in oceanographic cruises of the Mediterranean Sea, 1-2 months per year. I slowed down this rhythm recently, but just a bit, after the birth of my first son (now 3 years old), and my two twin boys (now 1 year old). I am looking forward to go back out to sea again soon.

What sparked your interest in oceanography?

At the beginning it was more or less by chance that I started to work on the Mediterranean Sea, and became a physical oceanographer, since after several applications to various marine and environmental institutes in 2004 I got my first fellowship at the Unit for Marine Research (ENEA in La Spezia). After my first oceanographic cruise, in 2005, in the Western Mediterranean Sea, I knew that that was “my” job. At that time there was no internet on research vessels and offshore the mobile phones served only to help you to wake up in time for your next shift in the middle of the night (these vessels operate 24/24 hours): you were completely in another dimension for days or weeks, without any contact with the “outside world”, working hard and in close contact with a limited number of persons. For me, that was great. What I really love in my job as a sea-going physical oceanographer is the alternation between “thinking” phases (in the office, in front of a pc) and “operating” phases (the cruise, the pre and post activities).

Much of your research focuses on the Mediterranean Sea, what makes it such an ideal candidate for oceanographic studies?

The Mediterranean has a number of valuable advantages (besides, CNR ISMAR being on its door steps). It is in many ways a miniature ocean and a natural laboratory for climatic studies: it has deep water formation varying on interannual time scales and a well-defined overturning circulation, and there are distinct surface, intermediate and deep water masses circulating between the western and the eastern basin. What makes the Mediterranean particularly useful for climate change studies is that its time scale is much shorter than for the global ocean, with a turnover time of roughly 60 years compared with more than 500 years for the global ocean. Changes can happen faster, on the time scale of a human lifetime.

During EGU 2015, you received the Arne Richter Award for Outstanding Young Scientists for your work on experimental oceanography, where you have contributed original ideas on the understanding of the formation and spreading of Mediterranean deep waters. Could you tell us a bit more about your research in this area?

In the deep layers of the Western Mediterranean an almost constant trend towards higher salinity and temperature has been observed since the ‘50s. More recent observations evidenced an acceleration of this tendency. An alteration of the water mass vertical distribution, associated with an abrupt temperature and salinity increase has been observed. In particular, since March 2005 large volumes of new bottom water has formed in the northwestern Mediterranean Sea. Remarkably this new bottom water is warmer and saltier than the old deep waters so it has become an easily recognized water mass when temperature and salinity profiles are made through the water column. Since its formation, this new bottom water has spread out into the western Mediterranean so that now it forms a bottom layer of warm salty water up to 1000 m thick throughout the western Mediterranean basin. The new bottom water has provided a natural tracer release experiment for understanding how bottom water fills the basin. The processes of deep water formation, the filling of the western Mediterranean with the new deep waters formed in the north, and the mixing between old and new deep waters are keys to understand how the Mediterranean is changing under changing climate conditions. An important open issue is how the old and new deep waters mix, on what time scale and by what processes, and in particular to quantify the role of turbulent mixing in the overall diffuse upwelling, the returning branch of the vertical thermohaline circulation.

The possible impacts these changes could have on a global scale are still an open issue.


Mediterranean thermohaline circulation (modified by Loic Houpert from Tsimplis et al., 2006): AW=Atlantic Water, LIW=Levantine Intermediate Water, WMDW=Western Mediterranean Deep Water, EMDW=Eastern Mediterranean Deep Water. Credit: Katrin Schroeder

With my team we observed the anomaly thanks to repeated oceanographic cruises in the Western Mediterranean. We started to publish about the deep water formation event in the north-western Mediterranean in 2006 (Schroeder et al., 2006, GRL). The event was extraordinary for its large volume of warmer and thermohaline properties of the deep water produced during the severe winter of 2004/2005. I have explored the causes of this event, tracing its origin back to the Eastern Mediterranean, from where increased amounts of heat and salt were imported to the Western Mediterranean and I have examined with new observations the spreading of the new water as a transient tracer through the western Mediterranean.

How does bottom water form, exactly and how is it different to other water in Mediterranean?

Bottom water forms in some specific regions worldwide, and few of them are also located in the Mediterranean Sea. Deep waters are “formed” (or we should rather say “transformed” from surface and intermediate water masses) where the air temperatures are cold and where the salinity of the surface waters are relatively high. The combinations of salinity and cold temperatures make the water denser and cause it to sink to the bottom. Its formation may occur either in the open ocean by deep convection or on the continental shelves by a process called dense shelf water cascading. In the Mediterranean both phenomena are present: in the Gulf of Lion (north-western Mediterranean Sea), in the Adriatic Sea and in the Aegean Sea. This sites maintain the Mediterranean thermohaline circulation in motion and, ventilating the deep layers, provide fresh oxygen to the deep water ecosystems. The Mediterranean also hosts a surface water mass, which comes directly from the Atlantic Ocean and circulates through the whole basin, gradually increasing its density because of the strong evaporation that takes place in the region. In the Mediterranean intermediate water masses are also formed, with processes that are similar to the bottom water formation, but in different locations and with density characteristics that do not allow these water masses to sink to the very bottom.

Earlier, you mentioned that the Mediterranean is useful for climate change studies due to having a much quicker turnover than the larger oceans. Can you describe an example of just how the study of the Mediterranean has been useful in this way?

The most important example is the in depth investigation of the process of deep water formation, which is an essential component of the global ocean conveyor belt, and sustains the present climatic state. The process happens mostly at high latitudes, but also in the north-western Mediterranean Sea on much smaller scales. Observations of the processes involved in open-ocean deep convection began with the now classical Mediterranean Ocean Convection (MEDOC) experiment in the Gulf of Lion [MEDOC Group, 1970]. With respect to high latitude sites, the Mediterranean site had the advantages of being less expensive to investigate, given an easier access with oceanographic vessels, due to its closeness to the coast and oceanographic institutes, of offering to milder winter conditions (season during which the dense water formation takes place) facilitating operations at sea. It is also very likely that studies about process related to ocean acidification and carbon sequestration as a consequence of dense water formation will be more feasible in the Mediterranean Sea.

What advice do you have for early career scientists on how achieve a good work/life balance?

Well, this is strongly dependent on the specific conditions you have in your life and it depends on your priorities: I have strong support from my family, I have the possibility to have a kindergarten close to our home with an affordable fee (this is the most important thing I must say!), and I have made the choice to let the household behind ….and I do not iron!

Finally, could you tell us a bit about your future research plans?

Staying very general, I am starting to follow a path of a higher interdisciplinary in oceanographic disciplines, trying to enforce the dialogue between us, physical oceanographers, and biological, microbiological and chemical oceanographers, as well as with climatologists and meteorologists.


Schroeder K., Gasparini G.P., Tangherlini M., Astraldi M.: Deep and Intermediate Water in the Western Mediterranean under the influence of the Eastern Mediterranean Transient. Geophys. Res. Lett. 33, doi: 10.1028/2006GL02712


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