(click to go to ...) General context   General Objectives     The Southern Ocean and oceanic CO2 pump   A natural laboratory in the Southern Ocean: the Kerguelen plateau       Objective 1   Objective 2   Objective 3 KEOPS in the national context International co-operations / KEOPS and the international research programs     References cited

KEOPS will improve the knowledge of biogeochemical cycles in the Southern Ocean. Mainly based on process studies it will contribute to a better understanding and prediction of the response of this large HNLC area to the global climatic change. Particularly KEOPS will study the effect of natural iron fertilisation of the ocean by the Kerguelen plateau, on the biological pump of CO2 and on the cycles of other chemical compounds relevant for climate. A multidisciplinary approach will be used, coupling physic and biogeochemistry. A strong link with the modellers will be also established. KEOPS will provide parameterisation for different kind of biogeochemical model. The project federates French teams and is largely open to foreign collaborations.

 

In the past century, the ocean has been a major sink for carbon dioxide (CO₂) mitigating the increase of CO₂ concentrations in the atmosphere. The uptake of anthropogenic CO₂ by the ocean is mainly due to the so-called physical pump (dissolution + general ocean circulation). In contrast, the biological pump (photosynthetic activity + organic carbon export) has been considered to play a minor role in sequestering the anthropogenic CO₂ in the ocean. Carbon is not a limiting factor for oceanic primary production and phytoplankton consumes and regenerates major nutrients in a constant ratio with dissolved inorganic carbon (Redfield ratio). The small variation of the concentrations of CO₂ in the atmosphere since 5000 BP up to the beginning of the industrial era support this assumption.

The observed global climate change induced by the increase in the concentration of greenhouse gases in the atmosphere may modify this paradigm. Three different mechanisms related to the intensity of the biological pump may be altered by the global climate change and may have a feedback effect (positive or negative) on the atmosphere/ocean flux of CO₂ and other greenhouse gases

- changes in the nutrient inventory (e.g. changes in dinitrogen fixation by the ocean).

- more efficient use of the major nutrients by oceanic phytoplankton (e.g. in HNLC areas).

- changes in the elemental composition of sinking biogenic material and/or changes in the carbonate/organic carbon ratio.

An increase in the sea surface temperature and the partial pressure of CO₂ and a change of the magnitude of the fluxes of major and minor nutrients to the ocean will be induced by global climate change. All these factors contribute to the control of phytoplankton growth and the specific composition of the phytoplankton community and the perturbation of these factors will modify the efficiency of the biological pump.

In addition to the carbon cycle and the related CO₂ biological pump, other biogeochemical cycles will be impacted (e.g. ; nitrogen, iron, sulphur…) with possible feedback effects on the global climate (for example sulphur cycle). The UV-visible radiation is also a climatic parameter which largely drives the biogeochemistry of the surface of the ocean. Changes of the distribution of aerosols and clouds and changes of stratospheric and tropospheric ozone concentrations will modify the intensity and the spectra of solar radiation reaching the sea surface. The visible and/or UV radiation drives important processes such as photosynthesis, photo-oxidation of dissolved organic matter and photo-dissolution of several important trace metals (e.g. Fe and Mn). Among all these processes, the light/mixing regime is one of the most studied because it controls primary production. However, it is not yet fully understood, especially in the Southern Ocean. Other light dependent processes mentioned above are still poorly understood and generally ignored in biogeochemical models. It is of primary importance to improve our knowledge in this field.

The prediction of the response of the biosphere to global climate change is a major challenge for oceanography. Global Ocean /Atmosphere Coupled Models are essential to achieve this goal. However, they require a good choice of the processes implemented in the model and a good parameterisation of these processes. Both can only be achieved by performing experimental studies in the laboratory or in the field.

 

The extensive work done under the umbrella of SO-JGOFS during the last decade has been recently synthesised  (Tréguer and Pondaven, 2002). The Southern Ocean plays a major role in the contemporary global carbon cycle. South of 50°S, the carbon sink, 0.47 GT C yr^-1, is about 20% of the global ocean sink (Takahashi et al. 2002). However the variability of the sink is large. For example at the inter annual scale, the pCO₂ measurements carried out during the OISO program in the region of interest for KEOPS, show a very contrasted situation between the year 1998 and 2000.

Figure 1 : left part: ship track during the OISO program. Central part: zonal and interranual variability of the air-sea flux of CO₂ observed during OISO. Right part: interranual variability of the pCO₂ in the surface water of the POOZ (region of interest for KEOPS). (N. Metzl)

Clearly a better understanding of the mechanisms that drive the uptake of CO₂ by micro-organisms (biological pump) is still required. The limitation of primary production by iron and or by silicic acid has been clearly demonstrated, during in situ fertilisation experiments (SOIREE, Boyd et al 2000) or natural observations (de baar, blain). However there remains large gaps about the interplay between the various processes and their parameterisation in biogeochemical model. 

There is yet a consensus that the carbon export out of the photic layer of the Southern Ocean is high, however the export flux of carbon deeper than 2000 meters is in the same order as in the rest of the ocean. So remineralisation of organic carbon should be high. Which pathway (sinking, subduction, bio-entrainement) is the most efficient for carbon export is still also an open question.

There is an urgent need for additional work on biogeochemical cycles in the Southern Ocean and specifically on the above unsolved questions.

During the glacial/interglacial transitions, the concentration of CO₂ in the atmosphere varied greatly. The responsible mechanisms are not yet completely elucidated, but there is evidence that the ocean was a corner stone of the story (Broecker, 1982) . The intensification of the biological pump for this period has been pointed out as a very likely scenario (Sigman and Boyle, 2000) . The iron hypothesis (Martin, 1990) (the increase of the input of iron to the ocean during the glacial period) is one of the possible explanations. This hypothesis has boosted research in iron biogeochemistry of the ocean during the last decade. Despite the significant progress made using various experimental approaches (see below), many questions are still open and debated. Such an increase of the iron flux to the ocean may also occur in the future due to global climate change or due to large scale iron fertilisation of the ocean. A better understanding of the possible responses to such a perturbation is fundamental.

Inputs of atmospheric iron to the ocean are occasional. Therefore this process is very difficult to study in situ in the actual context of oceanography (cruises are scheduled several years before they take place). Different approaches have been used to better understand iron biogeochemistry and to study interactions with other biogeochemical cycles: deliberated in situ iron fertilisation (Boyd et al., 2000; Coale et al., 1993; Smetacek, 2001) , natural iron fertilisation (Blain et al., 2001; de Baar et al., 1995) and numerous process studies (photochemistry, phytoplankton physiology, molecular biology…) carried out in the laboratory as well as in the field. This large effort has contributed to consider iron as an important nutrient in the ocean, and as an important controlling factor of primary production in oceanic systems. However, several important questions are still unresolved (e.g. Does iron fertilisation stimulate carbon export below the pycnocline?) and new questions arise (e.g. What controls iron concentrations in the ocean? Which feedback effects will follow large scale iron fertilisation?). In addition, iron speciation studies carried out during recent in situ experiments,  suggest that the various Fe pools after massive additions of FeSO₄, do not mimic the iron speciation created by natural inputs (from above or from below) to the ocean (Boyé et al. 2002).

Natural iron fertilised areas are privileged laboratories to investigate such  topics. The emerging international programs in marine biogeochemistry acknowledge the interest of such sites.

OCTET : (... & general strategy to advance our understanding of the southern ocean : process studies ).. investigator may study regions ‘downstream’from island (Kerguelen) to determine long term ecological response, as well as the net effect  on nutrient consumption and export  production, to a sustained iron supply.     http://www.msrc.sunysb.edu/octet/

SOLAS : …The long term fate of carbon sequestered by Fe-fertilisation could be investigated in areas subject to otherwise constant environmental conditions but strong natural gradients of Fe input. Plumes of iron rich waters ‘down stream’of islands located in the deep ocean could for example, be exploited as natural laboratories…  http://www.ifm.uni-kiel.de/ch/solas/main.html

The strategy comparing perturbed and reference sites is fruitful because the same processes can be studied in two contrasting strictly natural environments with different amounts and specific composition of biogenic and lithogenic material as well as different plankton assemblages.

 

 

Figure 2 : Monthly  SeaWiFS data  (pers. com. A. Jabaud LBCM Paris) demonstrating that the bloom occurs each year. A study area centred on 51°E, 73° W would be the best location. The intensity of the bloom is maximal in January beginning to decrease in February.

KEOPS will host the summer cruise of the program OISO (P.I. N. Metzl, LBCM Paris Fr). One of the aims of OISO is to observe the interannual variability of the sources and sinks of CO₂ in the Indian part of the Southern Ocean. In addition to under-way measurements as much as possible deep stations of the OISO program will be visited.  The detailed processes studies that will be carried out during KEOPS will contribute to a better understanding of this interannual variability. KEOPS  will benefit from the expertise of the “CO₂ team”of OISO which will be in charge of sampling and analysis of pCO₂ (air and water), total alkalinity and dissolved inorganic carbon.

KEOPS will also benefit from the results of the program CLIOKER (P.I. Y. Park MNHN paris Fr.). The current physical observations of CLIOKER at the Kerguelen plateau will provide information on the annual variability  of the physical variability.

The collaboration with scientists doing mainly atmospheric research is also an important point to be underlined.

As mention above, a collaboration is established with J. Sciare (LSCE) to collect aerosols at CROZET. In the case of DMS, a collaboration exits beetween S. Belviso and the ORE (Observatoire de Recherche et Environnement) : Etude du cycle du soufre en relation  avec le climat aux moyennes et hautes latitudes Sud. PI M. Legrand (LGGE Grenoble). For HCNM, there will be a close link between KEOPS and the program CAPOXY (capacité oxydante de l’atmosphère subpolaire) supported by  IPEV.

 

 

 

 

Foreign scientists of eight different countries have expressed their interest in the project KEOPS. They are summarised in the table below. They propose innovative work that fits well with the objectives of KEOPS. The proposed studies complete also nicely the expertise of the French participants. Most of the foreign contributors have already collaborated with other participants of KEOPS, especially in the Southern Ocean.

 

country	institut	name	Project	Previous collaboration with french participants	berths
Australia	ACRC	Trull T.	Export d13C and d15N	SAZ
		Bowie A.	Iron chemistry	IRONAGES
		Armand	phytoplankton
	CSIRO	Griffith B.	P-I curve, possibly CDOM	ANTARES 4, SAZ	4
Belgium	VUV	Savoye N.	Tracers of export	ANTARES, SAZ
		Cardinal D.	Tracers of export
		Dehairs F.	Tracers of export	ANTARES, SAZ
		Jacquet S	Tracers of export		1
Germany	IFMK	Croot P.	Iron (II) and iron ligands	IRONAGES	1
Greece	CNRM	Christaki U.	Mesoplankton bacteria	POMME	1
Netherlands	NIOZ	De Baar H.	Iron biogeochemistry	IRONAGES, ANT
		Gerringa L.	Iron photochemistry	IRONAGES
		Laan P.	Iron biogeochemistry	IRONAGES
		Timmermans K.	Iron phytoplankton	IRONAGES
		Kramer J.	Iron chemistry		3
		Hernl G.	Bacteria	ANTARES 4	1
New Zealand	NIWA	Boyd P.	Iron-light	SAZ	1
		Law C.	N2O, CH4, CO		1
United Kingdom	SOC	Pollard R.	Physics, ADCP	ANTARES 4	1
	UEA	Turner S.	Halocarbon, alkylnitrate	IRONAGES
		Liss P.	Halocarbon, alkylnitrate	IRONAGES
		Chuck A.	Halocarbon, alkylnitrate	IRONAGES	1
	UC	De la Rocha	30dSi
United State	UD	Hutchins D.	Iron phytoplankton	SAZ	1
	UD	Church T.	Polonium
	WHOI	Buesseler K.	Thorium

 

The Australian community brings an important contribution to KEOPS. In addition to the expertise of the different collaborators mentioned in the table above, we will deploy an Australian  mooring instrumented with sediment traps (Cooperation Franco Australienne). 

A collaboration is also established with Japan. Three different Japanese projects will take place in the Southern part of the Kerguelen plateau (2003-2006). Although these projects are not fully dedicated to biogeochemistry, they will provide useful information on the spatial variability of environmental conditions and biogeochemical processes in this area. In the case of iron, which is a critical parameter, but difficult to acquire, an intercomparison will be made with the Japanese team of S. Takeda. Samples from the Japanese cruise (2003) will be analysed in Brest and we will send samples collected during KEOPS to Japan. (Dr S. Takeda was the PI of the SEED project. A successful iron fertilisation experiment in the subarctic Pacific in 2001).

We have also proposed to organise a common synthesis phase of the different projects (France, Australia, Japan) in 2006. This will facilitate the exchange of data and the organisation of special sessions at international meetings. This will ensure a large dissemination and impact of our findings.

 

 

SOLAS : The general and specific objectives of KEOPS complement well the scientific plan of the international program SOLAS .

The specific questions that will be addressed in KEOPS are particularly relevant for :

>>focus 1, with special relevance for 1.3) Dimethylsulphide and Climate and 1.4) Iron and marine productivity

>>and also for focus 3) Air-sea flux of CO₂ and other long lived radiatively gases.

One of the promising approaches mentioned in the SOLAS document is to use the plume of iron-rich waters “down stream”of islands located in the deep ocean as natural laboratories. An effort has been made in KEOPS to include collaborators that are experts in atmospheric chemistry (aerosol, DMS, gases with oxidising capacity).

 

OCEANS: there is a recent initiative from IGBP and SCOR to create a new ten-year international research program called: Ocean biogeoChemistry and Ecosystems AnalySis, ‘OCEANS’. The background material presented to stimulate discussion at the Open Science Conference (   http://www.igbp.kva.se/obe/background.html) indicates that KEOPS can easily be placed under the umbrella of this program. A poster summarising the objectives and the strategies of KEOPS will be presented at the conference.

 

FP6 : The sixth program  for research of the European Community: It will be launched in November. Considering KEOPS, two different initiatives are important.

 

The network of excellence “ECCO” Ecosystems, biogeochemical cycles, and global change in the anthropocene ocean: (PIs P. Tréguer IUEM and L. Legendre LOV). KEOPS is relevant to the proposed “jointly executed research”:  Testing the biogeochemical iron fertilisation approach to carbon sequestration in the ocean.

 

The Integrated Project: “ACCESS”Antarctic Circumpolar Climate and Ecosystem Study. (PI V. Strass AWI, GE). The project aims to address the following questions:

-Which physical, biological and chemical processes in the Southern Ocean control the global and hence also european climate development.

-How sensitive are Southern Ocean processes and systems to climate change.

-Can large scale iron-fertlisation of the Southern Ocean provide a solution to the green house problem?

 

Two meetings are planned to refine both projects before the first call for proposal of the FP6. The KEOPS community will be present at the ECCO meeting (P.Treguer and B. quéguiner),  and at the ACCESS meeting (Bremerhaven, 21-23 Nov. ) S. Blain.

However, at the present day, it is not possible to say if both or one of the proposals will be relevant to the first call.