Carbon on CUSTARD: Episode 1

cover pic by Sofia Alexiou, NOC

Dr Maribel García-Ibáñez & Mr Gareth Lee, University of East Anglia, UK


EPISODE 1: Why we measure carbon dissolved in the ocean

Atmospheric carbon dioxide (CO2) enters the ocean through three “pumps”: the solubility pump (or physical pump), the biological pump, and the carbonate pump. Continuous contact and interaction between the atmosphere and the ocean allows CO2 to be readily absorbed into the surface ocean. This is what is called the solubility pump or physical pump. The biological pump consists of the transformation in the ocean surface of dissolved CO2 into organic matter, whose deposition creates a flow of organic carbon to the deep ocean. Phytoplankton, the base of the oceanic food webs, absorb dissolved CO2 to synthesize organic matter. As it passes through the food web, the organic matter is transported to deeper layers of the oceans, being oxidized and decomposed. Part of this organic material reaches the seafloor, joining seabed sediments. The carbonate pump, on the contrary, releases CO2 in the ocean surface layer through the creation of calcium carbonate external structures by some marine organisms such as coccolithophores and foraminifera. This calcium carbonate precipitates during photosynthesis and sinks.

Schematic of the global carbon cycle. Numbers represent mass reservoirs in PgC (1 PgC = 1015 gC) and annual carbon exchange fluxes (in PgC·yr–1). Black numbers and arrows indicate mass reservoirs and exchange fluxes estimated for the time prior to the Industrial Era (~1750). Red arrows and numbers indicate annual anthropogenic fluxes averaged over the 2000–2009 time period. These fluxes are a perturbation of the carbon cycle during Industrial Era (post 1750). The red arrows parts of Net land flux and Net ocean flux are the uptake of anthropogenic CO2 by the ocean and by terrestrial ecosystems (carbon sinks). Red numbers in the reservoirs denote cumulative changes of anthropogenic carbon over the Industrial Period 1750–2011. By convention, a positive cumulative change means that a reservoir has gained carbon since 1750. Uncertainties are reported as 90% confidence intervals. Source: Ciais et al. (2013).

Understanding how CO2 behaves in the ocean, therefore, gives us information about how the ocean uptakes atmospheric CO2 and how it is the redistributed in the ocean. Human activities have increased atmospheric CO2 concentrations since the industrial revolution. These anthropogenic CO2 emissions occur on top of an active natural carbon cycle that circulates carbon between the atmosphere, ocean and land reservoirs. The ocean dominates the storage of CO2 due to its high solubility in seawater and its sequestration through water sinking away from the surface. In fact, the oceans have absorbed about 30% of the anthropogenic CO2 emitted to the atmosphere since the industrial revolution. But this anthropogenic CO2 is not evenly distributed throughout the oceans. While CO2 concentration in the surface layers of the ocean increases as CO2 increases in the atmosphere, its penetration into the deep ocean depends on the slow vertical mixing of the water column and the circulation of water. About half of the anthropogenic CO2 is found in the first 400 m of the water column. However, in some regions where vertical movements of water are relatively fast, such as the Southern Ocean, the time scale necessary for deep penetration of anthropogenic CO2 is of the order of decades instead of centuries.

During the CUSTARD cruise, we, the UEA CO2 team, are quantifying two variables of the carbon system in the water of the Southern Ocean to help in answering the question of how deep in the ocean the CO2 is stored and, therefore, for how long it is kept out of the atmosphere. Understanding how the ocean uptakes the atmospheric CO2, which processes are responsible for this uptake, and where in the water column the CO2 is stored will allow us to understand how the ocean will continue this task, favourable to us all, in the future.

Please see our next blog post ‘Carbon on CUSTARD- EPISODE 2’ to learn more about how we go about measuring dissolved carbon in the ocean.

Scientists measure Carbon on CUSTARD research expedition, here’s why

‘Marine Snow’ Trilogy: Episode 2

Dr Frédéric Le Moigne (CNRS, Marseille, France) and Dr Katsia Pabortsava (NOC, Southamtpon, UK)


EPISODE 2: What is the ocean’s biological carbon pump?

Currents and biological activity play a critical role in controlling the uptake of atmospheric carbon dioxide by the oceans. This affects marine life from microbes to large fishes everywhere in the ocean, including the remote waters around Antarctica. And this is where we currently are, in the Southern Ocean, aboard the RRS DISCOVERY trying to understand how and why this process works.

‘Marine Snow’ courtesy of Dr N Briggs, NOC

Dr Katsia Pabortsava (NOC, Southamtpon, UK) and I, Dr Frédéric Le Moigne (CNRS, Marseille, France), are investigating the important process of the oceanic carbon uptake, called the “biological carbon pump”. In essence, it represents the amount of carbon that marine particles transport from the surface ocean to depths greater than 1 km as they sink by gravity. We call these sinking particles “marine snow” because they often resemble flocs of snow, as shown in the picture on the right.

Marine snow forms mainly when phytoplankton and zooplankton die and due to the motion of water collide and stick to each other. Eventually marine snow sinks down into the deep ocean carrying along all the organic carbon that originated from photosynthetic plankton. This mechanism is essential for the ocean because it “pumps” carbon from the surface ocean and transfers it to the deep ocean for long periods of time. The deeper marine snow sinks, the longer carbon remains locked at depth and the longer it takes for it to get back to the atmosphere. The central question of our CUSTARD expedition is how deep does this carbon sink?

SAPS being deployed, photo by S Alexiou, NOC

There are multiple ways of collecting and studying marine snow particles. In ‘Marine Snow Episode 1’, Dr Nathan Briggs described various cameras that he uses to detect and describe marine snow. We, however, directly capture marine snow from the ocean to primarily investigate their chemical composition. We are most interested in how much organic carbon these particles contain as this will tell us how strong the biological carbon pump is. We collect sinking particles using 6 water pumps, called  Stand Alone Pumps or SAPS (as shown on the left). We attach the SAPS to the ship’s wire and send them to different depths to pump seawater at the same time. The SAPS usually filter around 1500 L of seawater during just one hour of pumping.

On this CUSTARD expedition, we are deploying SAPS every other day at the three main research sites in order to collect the crucial information on the amount of carbon sinking at various depths and how it may change as phytoplankton grow in the surface. So far, we have deployed the SAPS ten times and collected particles from approximately 50,000 liters of water! That’s equivalent to 71,428 bottles of mulled wine!

‘Marine Snow’ Trilogy: Episode 2 – What is the Ocean’s Biological Carbon Pump?

‘Marine Snow’ Trilogy: Episode 1

Dr Nathan Briggs, National Oceanography Centre, UK


EPISODE 1: What is “Marine Snow” and how does it help keep the earth cooler?

On land, plants use sunlight to take carbon dioxide from the air and convert it into organic matter as they go through photosynthesis. In the ocean, tiny, plant-like cells called “phytoplankton” do the same thing, taking carbon dioxide out of the water as they drift in the sunlit upper ocean. As long as this organic matter is “stored” in the phytoplankton, this means there is less carbon dioxide in the ocean. The upper ocean is closely connected with our atmosphere, thus carbon storage in phytoplankton leads to less carbon dioxide in the atmosphere as well.

So, does this mean that phytoplankton are like the trees of the ocean, locking up large amounts of carbon dioxide, keeping our planet cooler and our oceans less acidic?

Well, not exactly…

On land, trees can grow for centuries, storing more carbon each year, but in the ocean, tiny, single-celled phytoplankton do not. The organic matter in phytoplankton is usually consumed within days to weeks, either by the phytoplankton themselves or by the various, and tiny, “zooplankton” that eat them. When organic matter is consumed, its carbon is converted back to carbon dioxide, which makes its way back into the ocean (and atmosphere). Nevertheless, phytoplankton play an important role in carbon storage.

How? One important answer to this question has to do with the deep ocean… and “marine snow”.

Take a look at the photo below. Does it remind you of falling snow? This “marine snow” is in fact organic matter, originally produced by phytoplankton, which has aggregated into larger particles that sink slowly from the surface to the deep ocean. This marine snow is one of the reasons we have travelled 1000 km west of the southern tip of Chile. Specifically, we want to know how much marine snow is produced here and how deep it sinks before it is consumed. Here in the Southern Ocean, below the sunlit surface waters, currents drive some water back to the surface and other water deeper still, where it will remain out of contact with the surface for 100s to 1000s of years.

The image on the left is an example of the large clump of marine snow we are finding in the Southern Ocean during the CUSTARD research expedition. It will most likely be consumed within a few days. In that time, which current will it sink to? The upwards current? In this case, the carbon dioxide locked within it will be released back into the atmosphere. But if it is consumed within the downward current, the carbon dioxide it releases will be “stored” in the deep ocean, keeping it out of the atmosphere for centuries, and keeping the planet a little bit cooler (or reducing its warming) during that time.

The various research teams on board are trying to learn more about the formation, sinking, and consumption of marine snow in different ways.

My team’s role is to study marine snow in its “natural habitat” by lowering cameras into the water and counting the number, shapes and sizes marine snow particles that we see at different locations and different depths. We also look for the zooplankton that may eat the marine snow, or may eat phytoplankton and produce “fecal pellets” (plankton poo) that sink, adding to the marine snow. On the right is our “Red Camera Frame” being lowered into the water.

What have we found so far?

Two different research sites, with very different amounts and types of marine snow. At our southern site (60°S), where we took the marine snow picture above, we found lots of aggregates, they were big (some over centimeters across!), and we found them deep (well past 1000 m). This means they were either sinking fast or they were consumed less quickly than usual.

We also found some odd shapes. Many of the marine snow aggregates photographed with our “Underwater Vision Profiler” system, like the picture on the left, appeared to be “ring” or “donut” shaped! We are not sure whether these shapes are natural or caused by water flow around our camera, but either way these shapes might tell us something about how marine snow forms and interacts with ocean turbulence.

In our northern site (54°S) we have seen very few aggregates so far, but we have seen one smaller (less than 1 mm) aggregate with a half-millimeter zooplankton attached, presumably eating. We will continue to monitor marine snow at these sites over the next four weeks. Any changes in conditions, combined with the many other measurements on board, from turbulence to photosynthetic rates, may help us understand the cause of our southern “snowstorm”. And, who knows, we may also solve the mystery of the marine “snonuts”!

All photographs courtesy of Dr Nathan Briggs, NOC

#CUSTARDcruise 2019 #blog 4 – ‘Marine Snow’ Trilogy: Episode 1

‘Adopt-A-Float’: just in time for Christmas


Besides conducting research, as scientists we also feel as passionate about the legacy our work produces.  From new scientific discoveries and better understanding of the Earth System to informing governments’ policy on the environment, assisting development, encouraging people’s interest in the oceans, and educating & inspiring the next generation of young scientists. 

In this spirit, CUSTARD is delighted to partner with the ‘Adopt-A-Float’ Initiative, linked to the US Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) project that is deploying a fleet of ARGO floats in the remote waters around Antarctica.  Argo is an international programme, operational since 2000, that uses profiling floats to observe temperature, salinity, currents, and, recently, to provide information on the life and chemistry of the Earth’s oceans. The globally-spanning data they provide has revolutionised climate and oceanographic research. 

The Adopt-a-float initiative provides a unique opportunity for elementary and secondary school students to engage directly with scientists around the world by adopting and naming Argo-floats scheduled to be deployed in the Southern Ocean (SO) that they can later track online, and by looking at the data being sent back, to learn more about scientific research, the SO and climate change.

On the current CUSTARD research expedition we are deploying six Argo-floats, all of which have been adopted by schools through the ‘Adopt-a-Float’ initiative.  It has been great fun for us to decorate the floats with the students’ imaginative and creative chosen mascots; we hope they approve and enjoy our ‘artistic’ attempts.

CUSTARD wishes to give a big Shout Out and Thanks to all the students of the schools below who have adopted these floats. We wish you great scientific endeavours and hope to one day see you on board our ships as researchers.

 School NameFromSchool YearFloat NameArgo Float #
1North Monterey County Middle SchoolCastroville, California 7BULL PHOENIX18242
2James H. Eldredge SchoolEast Greenwich, Rhode Island 4THE BLOBINATORS18545
3Carmel Del Mar SchoolSan Diego, California 6DRAGON HEART18771
4Twin Oaks High SchoolSan Marcos, California10 – 12FRINGEHEAD18721
5Lincoln Akerman SchoolHampton Falls, New Hampshire 7 – 8LEGACY18098
6California State University – Monterey BaySeaside, CaliforniaCollegeOTTER POP18320

You can find out more about the Adopt-a-Float Initiative on the SOCCOM project website, including details for any teachers out there who  would like to have their students involved.

CUSTARD 2019, Blog # 3 – ‘Adopt-a-Float’: just in time for Christmas

SO Christmas: Why here? Why now?

Sofia Alexiou, NOC


“You’re going to be WHERE for Christmas?!” is the most common response I get from family and friends after I tell them I will be going on a sea-going research expedition in the Southern Ocean for 6 weeks over the holidays. Followed by “Whatever for?”  With 29 scientists, marine engineers and technicians on board the RRS Discovery, (and an equal amount of crew), it occurred to me that this is probably a common theme amongst us, and at some point we all must’ve had that awkward moment where we needed to explain why we go to the far end of the world to conduct our work.  Because a one-sentence response of “to do research” isn’t sufficient enough to satiate their curiosity, nor does any justice to the complexity of interdisciplinary science, carefully coordinated activities of 60 persons, shift patterns, myriad of methodologies and procedures, running of instruments and labs, operating scientific equipment, marine robots, large cranes and winches, all whilst moving about a vessel in 3 to 4m swells, sometimes 25 or even 40 knot winds, in the cold, 700 nautical miles from Antarctica.

Therefore, this post is dedicated to all of our loved ones who we miss during this special time of year, and who support us in our endeavours to understand the ocean and our planet, strive to progress in our fields of research, and for some of us, (ahem), for whom the call of the sea runs deep –  Thank You! And here is a bit of what we are up to, and why it is important.

Oct 2019 RRS Discovery docked outside NOC in Southampton loading equipment for Southern Ocean expeditions
photo by Adrian Martin, NOC

Why Here?

CUSTARD is mainly studying the seasonal growth of microscopic marine plants, called phytoplankton, whose annual growth equals that of all land plants worldwide combined. Without life in the sea, carbon dioxide concentrations in the atmosphere would be 50% higher.

For all the keen gardeners out there, you know how important the type and amounts of nutrients, pH, temperature and light conditions affect the health and growth of your garden. These same conditions determine the growth rate of phytoplankton in the ocean. When these plants go through the process of photosynthesis, absorbing carbon dioxide, and eventually die, the carbon held within them moves deeper into the ocean, some in the stomachs of crustaceans and fish that eat them, or by sinking as ‘marine snow’ to deeper parts of the ocean.

This movement of carbon into the deep sea is particularly important in the Southern Ocean since the region is effectively a ‘motorway junction’ for ocean currents. Which motorway the carbon enters determines how long it will remain ‘locked’ away in the ocean – If shallow, maybe just a year or less, but if deep, possibly for hundreds or thousands of years.

Why Now?

Simple – We come to the Southern Ocean during the holiday season because it is mid-summer here at the moment, when marine plants should be blooming – perfect timing for us to sample. Also, sea & weather conditions are more favourable this time of year in this notoriously rough part of the ocean.

Over the coming weeks, our blog will feature more in-depth stories directly from the research teams about their experiences at sea, the work they are conducting, the variety of equipment deployed, including large water samplers, marine snow catchers, moorings with intricate and novel sensors, ocean gliders, marine robots, the labs they are working in, that are kitted out with state of the art instruments used for analysis of nutrients, oxygen, carbon, trace metals, pictures of phytoplankton species, and more.

You can also follow the activities of the expedition and daily Christmas Advent Calendar on the Twitter feed on the right, #CUSTARDcruise

CUSTARD 2019, Blog # 2: SO Christmas: Why here? Why now?

Sailing South for Christmas

RRS Discovery docked in Punta Arenas port, Chile
photo credit: Sofia Alexiou, NOC

by Dr Adrian Martin, Principal Scientist (National Oceanography Centre, UK)


While many people may be thinking of stockings, Rudolph and Frosty at Christmas, the CUSTARD team is heading to the Southern Ocean to study how marine life helps keep carbon dioxide out of the atmosphere. Last year we deployed a mooring studded with sensors and two unmanned ‘glider’ submarines at 59oS 89oW, west of the tip of South America. These have given us the first insight into how the ecosystem of this remote environment changes throughout the year, including the harsh winter when you really do not want to be there in a boat. With the team now fully assembled in Punta Arenas, all are now busy unpacking and setting up the equipment that we will need on our return to the site.

This year we will be making much more intense use of the fantastic facilities and laboratories we have on board, to get a more detailed picture of what is happening to the local phytoplankton population and its fate, as its rapid growth leads to starvation as the nutrients run out. Over the next few weeks you will get to read about the many ways in which we study the ocean, from drifting floats to optics and the inevitable big bottles of water. For now though, it is a last chance to send a Christmas postcard before we sail.

Follow us on Twitter for daily CUSTARD Advent Calendar

King Penguins in Punta Arenas, RRS Discovery coming into port
photo credit: Katsia Pabortsava, NOC

CUSTARD sailing south for Christmas on RRS Discovery

The Southern Ocean in a changing climate: open-ocean physical and biogeochemical processes

The Southern Ocean in a changing climate: open-ocean physical and biogeochemical processes (OS1.12/BG4.13/CL4.28)

There will be a Southern Ocean session at the EGU General Assembly 2020 in Vienna (3–8 May 2020).

The Southern Ocean around the latitudes of the Antarctic Circumpolar Current is a key region for the vertical and lateral exchanges of heat, carbon and nutrients, with significant impacts on the climate system as a whole. The role of the Southern Ocean as a sink of anthropogenic carbon and heat, and as a source of natural carbon in present and future climate conditions remains uncertain. To reduce this uncertainty, understanding the physical and biogeochemical processes underlying the Southern Ocean internal variability and its response to external forcing is critical. Recent advances in observational capabilities, theoretical frameworks, and numerical models (e.g. CMIP6 simulations) are providing a deeper insight into the three-dimensional patterns of Southern Ocean change. This session will discuss the current state of knowledge and novel findings concerning the role of the Southern Ocean in past, present, and future climates. In particular, it will address physical, biological, and biogeochemical processes, including interior ocean mixing and transport pathways, the cycling of carbon and nutrients, as well as ocean-ice-atmosphere interactions, and their wider implications for lower latitudes and the global climate.

Highlight: Solicited speaker Michael Meredith will report on the outcomes of the Polar Regions chapter of the recent “IPCC Special Report on the Ocean and Cryosphere in a Changing Climate” during this session.

Abstarct submission: (deadline is 15 January 2020, 13:00 CET).

ECS travel support: (deadline is 1 December 2019).

Apply now: post-docs and PhD positions available at UEA

Two research positions and one PhD stipend are available at UEA to join the research group of Prof. Corinne Le Quéré, with the overall aim of better understanding the interactions between the carbon cycle and climate change. Prior experience in carbon cycle research is not essential to apply for these post. 

Post-doctoral research position in carbon cycle modelling. We seek a researcher with experience in computer modelling to develop the first “High-Resolution-High-Complexity” model of the marine carbon cycle, and use the model to understand recent variability in the carbon cycle and project future change, particularly in the Southern Ocean. Prior experience with carbon cycle research is not essential to apply for this post. Funding is secured for 2 years in a first instance, through the NERC SONATA project and the Royal Society. Closing date 3 October.

Post-doctoral research position in oxygen and carbon budget analysis. The post-holder will establish the first global oxygen budget, and provide strong constraints on how the land and ocean carbon reservoirs respond to climate variability and climate change. This work builds on the successful analysis of the global carbon budget, which helped to gain insights and keep track of how the carbon cycle evolves through time. Funding is secured for 30 months, through the European Project CCiCC (Climate-carbon interactions in the coming century) and the Royal Society. Closing date 4 October.

PhD on the impact of climate change and variability on ocean oxygen. Apply by 20 October. Start date is 1 January 2020.

Machine Learning Post-doc

Exciting post-doctoral opportunity to conduct research combining Machine Learning approaches with modelling of the marine carbon cycle and its interactions with climate change. The post-holder will develop and apply Machine Learning approaches to quantify the growth rates of different types of marine plankton as a function of environmental conditions, and use the model to explore the response of marine ecosystems to climate change and other environmental changes. This is an exciting opportunity to join the growing carbon cycle modelling team of Professor Corinne Le Quéré and to work in collaboration with international networks. You do not need prior knowledge of carbon cycle of climate change science to apply for this post. The post is available for 33 months from 1 July or as soon as possible. Application deadline is 6 June.

8th International Symposium on Gas Transfer at Water Surfaces

19 May – 22 May 2020, Plymouth Marine Laboratory, UK

Bringing together approximately 150 scientists from countries all over the world, this 5-yearly symposium covers all domains where atmosphere and water meet, which include but are not limited to, fresh water, estuarine, mountain, glacial, marine (coastal and open ocean) and polar regions.


Physicochemical and biogeochemical processes that govern atmosphere-water gas exchange and fluxes, which include turbulence, shear, breaking waves, bubbles and natural and anthropogenic surfactants.


The organisers welcome topics including field observations, laboratory and numerical studies, near-surface processes, biological effects including surfactants, the micro-layer, remote sensing, global scale processes and many more.


We are pleased to be able to offer reduced registration fees for students and those from developing countries to enable participation from across the field. In addition, some financial support is available for early career scientists and to help promote women in science.


Early bird registration closes 15th November

ABSTRACT deadline: 14 February 2020



For any queries contact: