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GeoTalk: Eleanor Frajka-Williams, the 2017 Ocean Sciences Division Outstanding Early Career Scientists Awardee

GeoTalk: Eleanor Frajka-Williams, the 2017 Ocean Sciences Division Outstanding Early Career Scientists Awardee

Geotalk is a regular feature highlighting early career researchers and their work. Following the EGU General Assembly, we spoke to Eleanor Frajka-Williams, the 2017 Ocean Sciences Division Outstanding Early Career Scientists awardee. In her work, Eleanor uses real-world measurements – from ships, satellites, sea gliders and moorings – to understand how the world’s oceans work. In today’s interview we talk to her a little more about why the oceans are so fundamental to our planet’s health and some of the lesson’s she’s picked up while her career has developed.

Thank you for talking to us today! Could you introduce yourself and tell us a little more about your career path so far?

Thanks – and it’s great to be able to talk to EGU.  I’m an associate professor of physical oceanography at the University of Southampton.  I started at the University in 2012 after a couple of years as a research fellow at the National Oceanography Centre.  I originally studied applied math at university, but discovered oceanography through an undergraduate research placement and it seemed like a great way to apply math and physics to understanding the natural world.

Your research focuses on the world’s oceans, what attracted you to study the processes which govern them?

I liked the idea of studying something that was important and intense, but which we couldn’t actually see with the naked eye—because except for the sea surface, everything else is hidden.  But by collecting observations—the right set of observations—we can piece together a picture of what is happening, and maybe think about teasing apart cause and effect.  Add to that the chance to use underwater gliders, piloted remotely by satellite communications, and what’s not to like?

Deep in the bowls of the world’s oceans, huge masses of water move: cold, salty water sinks, while warmer water rises. Your work focuses on understanding how and why this happens. Can you tell us a little more about these processes?

The ocean is typically stratified, meaning that light waters overly dense waters.  The global ocean overturning circulation describes how the ocean circulation moves through the warm equatorial regions, towards the northern North Atlantic where waters are progressively cooled and transformed, to the point where they sink.  These deep waters then move south and are upwelled either around Antarctica or in distributed mixing regions around the ocean basins.

While this circulation pattern is sometimes called the ‘great ocean conveyor’, suggesting that there is a single pathway moving at a consistent speed, it’s really a set of interconnected processes including the sinking, upwelling and also interplay with the ocean gyres (wind-driven ocean currents) and between the atmosphere and ocean.

One of the most dramatic of these processes—deep ocean convection—occurs in the northern North Atlantic when cold dry winds originating over the Canadian arctic cool the surface of the ocean to the point where the waters become as dense as, or denser than, the water 1000 m deep.  During this turbulent sinking, carbon and heat are stored in the deep ocean where they may stay for centuries.

And these ocean processes also have an effect on climate too?

We expect that they do.  On long timescales (paleo-timescales), we have extensive evidence that changes in the global overturning circulation coincided with rapid changes in global temperatures.  In some cases, the shutdown of the global overturning circulation resulted from a large input of freshwater (about 100,000 km3) being dumped over the northern North Atlantic from the ice sheet melting over Canada.  This freshwater would then float on the surface of the ocean, and because it’s so buoyant, could reduce or even prevent deep convection and through it, the overturning.

In the present-day climate, we have seen mini-versions of this happening.  In the 1960s, the ‘Great Salinity Anomaly’, which should really be called the ‘Great Freshwater Anomaly’ saw the input of about 20,000 km3 of freshwater to the northern North Atlantic.  Deep convection was suppressed for several years.  Unfortunately, we don’t have any observations of what the overturning was doing at the time though the deep western boundary current (considered to be the southward flowing limb of the overturning) was still active.

It’s still a tricky problem to try to sort out, because there are limited observations and a lot of moving parts to the problem (the sinking, the southward and northward flow, and the role of the gyres or atmosphere).

If freshwater is the culprit, for a reduced overturning, we will need to keep a close eye on Greenland, which is a major reservoir of freshwater in the region.  It has been melting more quickly and some new evidence suggests that it could begin to influence (slow down) the overturning in the next 10 years.

It wasn’t just your scientific work which led to you being named OS Division Outstanding Early Career Scientists, but also your work to promote and support budding scientists. What are the most valuable lessons you’ve learnt transitioning between being a fledgling researcher to an associate professor?

Being able to support young scientists is one of the most rewarding things about my job.  It is refreshing and inspiring to work with people starting to make discoveries of their own.

Some of the lessons I’ve learned are that work-life balance is an ongoing endeavour, and it’s rare to always be ‘in balance’, but aiming for a healthy average is a good start.

I’ve also discovered that with each promotion (or each life transition, e.g. starting a family), time becomes less abundant.  So, I’ve added strategies for efficiency along the way—and of course, with more experience, tasks that took forever the first time, take a lot less time now.  And every now and then, I find it can be useful to ‘drop the ball’ and ignore those pressing administrative or other duties, and just do a bit of science.  It helps to remember what I got into it for.

Interview by Laura Roberts Artal, EGU Communications Officer

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.

oceans

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.

References

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

Imaggeo on Mondays: Fly away, weather balloon

Some aspects of Earth Science are truly interdisciplinary and this week’s Imaggeo on Mondays photograph is testament to that. The maiden voyage of the research cruise SA Agulhas II offered the perfect opportunity to combine oceanographic research, as well as climate science studies. Raissa Philibert, a biogeochemistry PhD student, took this picture of the daily release of a weather balloon by meteorologists from the South African Weather Services.

Fly away, weather balloon! Credit: Raissa Philibert (distributed via imaggeo.egu.eu)

Fly away, weather balloon! Credit: Raissa Philibert (distributed via imaggeo.egu.eu)

The highlights of Raissa trip aboard the ship include

“the multidisciplinary aspects of the cruise. It was fascinating talking to people doing such different things. Being on the first scientific cruise aboard the vessel was also extremely exciting as well as going to the southern ocean in winter as this provides such rare datasets.”

This cruise was an excellent opportunity for scientists ranging from physical oceanographers, biogeochemists, meteorologists, ornithologists and zoologists to collect data. The two main scientific programmes aboard the cruise aimed to understand 1) the seasonal changes in the carbon cycle of the Southern Ocean, and 2) gain a better understanding of the modifications in water composition caused by the meeting and mixing of the Indian and Atlantic Oceans in the Agulhas Cape region in South Africa.

Understanding both of these processes is important because they impact on the global thermohaline circulation (THC), which is strongly related to global climate change. Think of the THC as a giant conveyor belt of water within the Earth’s oceans: warm surface currents, rush from equatorial regions towards the poles, encouraged by the wind. They cool and become denser during the time it takes them to make the journey northwards and eventually sink into the deep oceans at high latitudes. They then find their way towards ocean basins and eventually rise up (upwell if you prefer the more technical terms), predominantly, in the Southern Ocean. En route, these huge water masses transport energy (in the form of heat), as well as solids, dissolved substances and gases and distribute these across the planets Oceans. So you can see why understanding the THC is crucial to researchers wanting to better understand climate change.

This map shows the pattern of thermohaline circulation. This collection of currents is responsible for the large-scale exchange of water masses in the ocean, including providing oxygen to the deep ocean. The entire circulation pattern takes ~2000 years. Credit: Nasa Earth Observatory.

This map shows the pattern of thermohaline circulation. This collection of currents is responsible for the large-scale exchange of water masses in the ocean, including providing oxygen to the deep ocean. The entire circulation pattern takes ~2000 years. Credit: Nasa Earth Observatory.

The THCs also plays a large part in the carbon cycle in the oceans. Microscopic organisms called phytoplankton drive the main biological processes through which the ocean takes up carbon. They photosynthesise like plants which mean that they use carbon dioxide and water along with other nutrients to make their organic matter and grow. After some time, the phytoplankton die and their organic matter sinks. Part of this organic matter and carbon will remain stored in the deep ocean under various forms until it is brought back up thousands of years later by the THC. Through this cycle, phytoplankton play a major role in controlling the amount of carbon dioxide in the atmosphere and hence, also the Earth’s climate.

 

By Laura Roberts, EGU Communications Officer, and Raissa Philibert, PhD Student.

If you pre-register for the 2015 General Assembly (Vienna, 12 – 17 April), you can take part in our annual photo competition! From 1 February up until 1 March, every participant pre-registered for the General Assembly can submit up three original photos and one moving image related to the Earth, planetary, and space sciences in competition for free registration to next year’s General Assembly!  These can include fantastic field photos, a stunning shot of your favourite thin section, what you’ve captured out on holiday or under the electron microscope – if it’s geoscientific, it fits the bill. Find out more about how to take part at http://imaggeo.egu.eu/photo-contest/information/.

Geosciences Column: Shifting the O in H2O

Wherever you are in the world’s oceans, you can identify particular bodies of water (provided you have the right equipment) by how salty they are. You can get a feel for how productive that part of the ocean is by measuring a few chemical components in the water column. And, year on year, you will see a recurring pattern in how things like temperature, salinity and oxygen content vary with depth. This last property – the oxygen content – is vital for life in the oceans, but recent decades have seen shifts in the amount available.

There is always more oxygen at the surface than there is at depth. When waves break they mix an abundance of tiny air bubbles into the water, providing oceans with their oxygen supply, which is mixed into the deep through large-scale ocean circulation and storms over winter. At the surface, algae make the most of the abundant light to photosynthesise, beginning the base of the marine food web and adding a little more oxygen to the water in the process. These microscopic plants are eaten by animal plankton (zooplankton), which are, in turn, eaten by other plankton, crustaceans, fish, and a plethora of other predators – none of which contribute to the ocean’s oxygen. Instead, they, and a multitude of microbes, slowly use up more and more of the supply as they respire and there comes a point in the water column where there is no longer enough oxygen for these aerobic animals to survive – the oxygen minimum zone (OMZ).

The surface ocean, where oxygen begins its journey to the deep. (Credit: Anna Lourantou, distributed via imaggeo.egu.eu)

The surface ocean, where oxygen begins its journey to the deep. (Credit: Anna Lourantou, distributed via imaggeo.egu.eu)

What marks the boundary of this zone is dependant not on the properties of the water, but the life that lives there – it is the point when marine organisms experience hypoxic stress, usually an oxygen concentration in the range of 60–120 μmol kg−1. Below this, life in the marine environment is very different indeed. Anaerobic microbes thrive below the OMZ, making the most of life in an environment where there is very little oxygen in each litre of seawater.

The boundary between oxygen-rich water and the OMZ is known as the oxygen limiting zone (OLZ), and during the day many small swimming species take refuge here to avoid their predators. In the Eastern Pacific, you reach the OLZ when there’s 60 μmol kg−1 oxygen in the water, and the OMZ when there’s a mere 20 μmol kg−1.

Waves are key to mixing oxygen into the ocean. When they break at the surface they mix air bubbles into the water, taking oxygen from the atmosphere into the sea. (Credit: NOAA Okeanos Explorer Program)

Waves are key to mixing oxygen into the ocean. When they break at the surface they mix air bubbles into the water, taking oxygen from the atmosphere into the sea. (Credit: NOAA Okeanos Explorer Program)

The depth of the OMZ depends on temperature. Because warmer water is capable of containing less dissolved gas than cold, the OMZ is found at shallower depths in the tropics, and occurs at shallower depths in the summer than it does over winter. Winter weather allows more oxygen to be mixed into the deep ocean as storms break down the sea’s stratification, bringing nutrients to the surface and replenishing supplies closer to the sea floor. However, when there’s a lot of production at the surface (which draws down the oxygen) and the replenishment at depth is slow, large oxygen minimum zones persist from year to year.

Recently though, the upper boundaries of these zones have been shifting to shallower depths, resulting larger hypoxic regions in the ocean. Since the 1960s, the OLZ in the Gulf of Alaska, for example, has shifted some 100 metres shallower. Why?

The oceans are absorbing more heat in response to climate change. Because high temperatures reduce oxygen solubility, they reduce the amount of dissolved oxygen at the surface. The increase in surface heat also creates stronger stratification in the ocean, making it harder for oxygen to be mixed deep into the water column, and reducing dissolved oxygen at depth. Ocean circulation systems are also in a state of change, with systems like the Atlantic meridional overturning circulation in decline. Such changes in ocean circulation will also affect the amount of oxygen that’s mixed into the deep sea.

Atlantic meridional overturning circulation, better known as AMOC. Red arrows show warm water circulation in the upper 1100 m and blue arrows show the southward flow of cold, deep water. (Credit: Smeed et al., 2014)

Atlantic meridional overturning circulation, better known as AMOC. Red arrows show warm water circulation in the upper 1100 m and blue arrows show the southward flow of cold, deep water. (Credit: Smeed et al., 2014)

Working out whether this is part of a long-term trend is a difficult task, as records of deep ocean oxygen only stretch back to 70 years ago. Only a longer record of observations will help determine the trend, but for now we can be sure that shoaling oxygen minimum zones will change the amount of habitat available to species either side of the line between oxygen-rich and oxygen-poor.

By Sara Mynott, EGU Communications Officer

References:

Gilly, W. F., Beman, J. M., Litvin, S. Y., & Robison, B. H.: Oceanographic and biological effects of shoaling of the oxygen minimum zone. Annual Review of Marine Science, 5, 393-420, 2013

Smeed, D. A., McCarthy, G. D., Cunningham, S. A., Frajka-Williams, E., Rayner, D., Johns, W. E., Meinen, C. S., Baringer, M. O., Moat, B. I., Duchez, A., and Bryden, H. L.: Observed decline of the Atlantic meridional overturning circulation 2004–2012, Ocean Sci., 10, 29-38, 2014