Processes Influencing Carbon Cycling: Observations of the Lower limb of the Antarctic Overturning (PICCOLO)

Lead Research Organisation: Plymouth Marine Laboratory
Department Name: Plymouth Marine Lab


The vast, remote seas which surround the continent of Antarctica are collectively known as the Southern Ocean. This region with its severe environment of mountainous seas, winter darkness, strong winds, freezing temperatures and ice is unsurprisingly one of the least explored and under-observed parts of the global ocean. However, because of these extremes, it plays a large and still unquantified role in Earth's climate system. In this region, large amounts of heat and carbon dioxide are exchanged between the atmosphere and the ocean.

The physical mechanisms controlling these atmosphere-ocean exchanges are the subject of the NERC ORCHESTRA programme. We propose within PICCOLO to concentrate on the role that chemistry and biology play within those exchanges. In particular, PICCOLO will focus on understanding the mechanisms that transform the carbon contained in the seawater as it rises to the surface near Antarctica, interacts with the atmosphere, ice, phytoplankton and zooplankton inhabiting the near surface, before descending to the ocean depths.

PICCOLO will undertake an ocean research expedition to the region close to Antarctica, as computer models and satellite images show that these are areas crucial for carbon processes. Freezing seawater in these regions releases salt into the water below, making it denser and therefore causing it to sink. Strong winds cause the sea ice to be pushed away from the Antarctic coastline, leaving areas of open water called polynyas. Within the polynyas the water has enough light during the summer to allow phytoplankton to grow, as well as providing dense waters which sink to the deep, driving a giant ocean conveyor belt which has a large impact upon Earth's climate system.

The PICCOLO team will measure the key variables that control the biological and chemical processes in this region including iron, nutrients, phytoplankton and zooplankton. Crucially the team will study the controlling rate terms between different parts of this biological and chemical system. The PICCOLO team will make use of the latest technologies, including autonomous submarines, gliders and floats, to observe these processes in otherwise inaccessible and previously unstudied areas such as under the sea ice. Most ambitiously we will anchor a submarine to the seabed within a polynya and leave it over a winter season to collect data, recovering it the following spring. The PICCOLO team will put instruments on seals which will continuously take data as they dive up and down through the water, sending it back to scientists in real-time via satellite communication links.

This wealth of novel data will be analysed by the PICCOLO team, using state of the art computer models, to test our ideas about how the whole complex set of physical, chemical and biological processes affects carbon. Conceptually we will follow an imaginary parcel of water through the system looking at processes between the atmosphere and ocean, biological processes in the surface layer, exchanges between the upper and lower ocean and the final fate of the carbon.

The PICCOLO hypotheses address the following:

(i) Factors controlling the exchange of carbon dioxide between the ocean and atmosphere and the role of ultra-violet light in controlling the concentration of carbon dioxide in seawater;
(ii) The role of light, iron and nutrients in how carbon is processed by the plankton in the water;
(iii) The mediating processes governing the export of carbon from the upper ocean to depth;
(iv) The processes that take the carbon into the deep ocean on the next stage of its global journey.

Planned Impact

Here we summarise the non-academic communities who will benefit from this research project and how they will benefit. Please see the Pathways to Impact attachment for the activities we plan in PICCOLO in order to achieve this impact.

The main beneficiaries of data and knowledge from PICCOLO are:

i) Stakeholders and high level users of the Global Carbon Budget analysis will benefit through an improved product with PICCOLO biogeochemical observations being available for model evaluation and quantification of the ocean carbon sink via high-profile data synthesis products, such as the Global Ocean Data Analysis Project (GLODAP) and the Surface Ocean CO2 Atlas (

ii) The global earth system modelling community, and the users of such models such as governments, non-governmental organisations (NGOs), and the Intergovernmental Panel for Climate Change (IPCC), will benefit from the mechanistic understanding of carbon uptake processes in the Southern Ocean that PICCOLO will deliver, together with the roadmap for representing such processes in Earth system models. This will deliver a step-change in the quality of the projections undertaken by such models. The Hadley Centre at the UK Met Office will gain insight from PICCOLO, and we will work with them to assess the various NEMO-based models. The results of the project will aid the eventual parameterisation of carbon cycling processes for use in earth system models. The major results of PICCOLO will inform government policy with regard to the uncertainties in sea level rise predictions.

iii) Operational forecasters at global weather/climate services (such as the UK Met Office) and global navies will have free access to the near-real time (within hours of surfacing) temperature and salinity profiles from the Argo floats, gliders and seal tags, for assimilation into their operational forecast models. This will also benefit users of ocean reanalysis products that assimilate the PICCOLO profiles, since our targeted observational campaign location is a data desert.

iv) Those designing the global ocean (and climate) observing systems will benefit from PICCOLO. Our novel observational techniques will allow us to feed into the Southern Ocean Observing System (SOOS) design in order to design effective long-term measuring systems in the most useful locations. We will engage with the SOOS community through the Scientific Committee for Antarctic Research (SCAR).

v) The western and central Weddell Sea is very poorly sampled compared with the rest of this sector and the size of the krill stocks within it will be of interest to the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). The krill fishery in the Southwest Atlantic sector has expanded and there is a clear need for better understanding of the spatial scale of the exploited stocks. ICED (Integrating Climate and Ecosystem Dynamics) is an international multidisciplinary regional programme within the SCOR/Future Earth sponsored IMBER (Integrated Marine Biogeochemistry and Ecosystem Research) project, launched to develop integrated circumpolar analyses of Southern Ocean climate and ecosystem dynamics.

vi) PICCOLO will nurture and train early career scientists, giving them skills to equip them for a productive independent career and to meet national skills shortages.

vii) The general public and young people in particular will gain from PICCOLO outreach. We aim to interest more young people in science and in higher education, raise awareness of global change and polar processes, and attract more people to careers in scientific research. We will target deprived areas such as Great Yarmouth in Norfolk and Plymouth in Devon, where young people's aspirations and achievements are below the national average and where inspiration into education may make a difference.
Title Solar Simulator for photochemical experiments 
Description A custom Solar Simulator instrument was built, commissioned and tested at the Plymouth Marine Laboratory (PML). This instrument allows photochemical experiments to be carried out on environmental samples (e.g. investigating the photolysis of Dissolved Organic Matter and concomitant photoproduction of Inorganic Carbon). Compared to natural sunlight, this offers the advantage of constant spectral irradiance, characterized by chemical actinometry. This allows the user to derive quantum yields (product formed per unit irradiance) which can be directly applied to numerical models of aquatic biogeochemistry and climate modelling. 
Type Of Material Technology assay or reagent 
Year Produced 2019 
Provided To Others? No  
Impact The Solar Simulator instrument has allowed us to calculate the photochemical source of carbon dioxide in UK waters (manuscript in preparation) 
Description "Closer Look" film for BBC Countryfile 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Footage prepared with Countryfile team, covered local water based activities in the Southwest, well being and marine science.
Year(s) Of Engagement Activity 2020
Description Intreview for BBS Radio 4 "Inside Science" 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Provided a BBC Radio 4 interview on their programme "Inside Science" on the role of Antarctic krill in mixing the ocean through their swimming activities, 26.4.18
Year(s) Of Engagement Activity 2018
Description Participation in ASAID workshop 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Study participants or study members
Results and Impact ASAID data workshop looking at using a latent variable approach to look at large fieldwork datasets from Antarctic Circumnavigation Expedition, including N-osmolytes
Year(s) Of Engagement Activity 2019
Description Public talk for Kids and science stand as part of Plymouth Science Week. Title: How can seals and submarines help us explore the Antarctic ocean in winter? 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Event was part of British Science Week. I and a few PhD students ran a stand with a practical to engage the kids. We used cabbage water as a pH-sensitive dye to demonstrate how water (the oceans) can absorb carbon dioxide. I gave a public lecture aimed at kids (approx. 8-13 years old). I talked about the role of the Southern Ocean in taking up carbon dioxide, and how the PICCOLO project will try to understand this better using seals and submarines.

The intended purpose was to engage the kids and enthuse them about science. Approximately 280 seats were taken up for this free event. It sparked numerous questions and follow-up discussions with kids and their parents. I also had follow up interest via email. The PhD students gained experience by demonstrating and discussing science with young children.
Year(s) Of Engagement Activity 2018