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section why

The Twilight Zone, located between the depths of ~ 100 m and 1000 m, is one of the least known environments on Earth: we mandatorily need to explore it as it provides essential services for our society and is pivotal to the ocean carbon cycle.

The Twilight Zone (TZ), being beyond the reach of sunlight, is critically undersampled and understudied during most ship-based oceanographic cruises while its depths elude satellite remote sensing. Yet the TZ plays an essential role in regulating the sequestration of carbon dioxide from the atmosphere for centuries or longer; in addition, the TZ hosts unique ecosystems and huge fish populations, which can potentially contribute to mitigating food insecurity; finally, the TZ is where global ocean deoxygenation occurs.

The ocean’s carbon-sequestration capacity is largely controlled by the Biological Carbon Pump (BCP). The BCP is driven by processes that control both the downward export (pump strength) of biogenic carbon photosynthesized in the well-lit Euphotic Zone (EZ, between surface and ~100m), as well as the remineralisation (pump efficiency) of part of this sinking carbon in the underlying TZ.

According to a recently formulated paradigm, the BCP is controlled by the cumulative and combined action of six different biologically- or physically-mediated pumps, namely: the Gravitational Pump, the Seasonal Migration Pump, the Diel Migration Pump, the Mixed Layer Pump, the Eddy Subduction Pump and the Large Scale Subduction Pump (not specifically addressed here).

REFINE proposes a framework for an integrated observational approach of five of these Biological Carbon Pumps in the World Ocean.

section when

REFINE is a five-year project associating interdependent phases

section how

REFINE aims to implement breakthrough in situ robotic process studies based on a new generation of highly instrumented jumboized profiling floats.

The successful BCG-Argo float technology provides a proven means for developing the new, more sophisticated robots required for conducting REFINE process studies. REFINE will rely on float developments initially conducted as part of the remOcean project to develop an improved, cutting-edge multi-process robot designed to address the various carbon pumps and associated carbon transformation within the TZ. This robot will integrate the latest technological developments combined with artificial-intelligence algorithms to measure and derive a wide suite of variables, proxies and fluxes.

The REFINE float will be a jumboized BGC-Argo float with enhanced capabilities: more available energy, onboard data processing, ice-avoidance capability, improved on-board data storage, increased flexibility for adaptive sampling. Basically, its scientific payload will rely on two complementary packages:

  • The standard BGC-Argo package including, alongside iridium communication: a Conductivity Temperature Depth (CTD) sensor, a fluorescence sensor, a backscattering sensor, a radiometer, an oxygen optode sensor, an optical nitrate sensor, a Deep-Sea DuraFET-based pH sensor.
  • The REFINE-specific sensor package including: a transmissiometer and a miniaturized underwater vision profiler (UVP).

Discover our Autonomous Profiling Float!
Click on each Pin to discover internal|external components.

Download a poster of the float in various languages

poster pdf arab
poster pdf Bulgarian
poster pdf in German
poster pdf English
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poster pdf Italian
poster pdf Japanese
poster pdf Norwegian
poster pdf Polski
poster pdf Spanish
poster pdf Chinese
section where

The breakthrough robotic process studies will initially be implemented in five key regions representative of the diversity of global oceanic biogeochemical conditions and their responses to climate change.

REFINE’s approach is to distribute the robotic process studies over a large latitudinal gradient to cover a broad scope of stratification, mixing, irradiance and nutrient conditions. As these environmental conditions are the main drivers of phytoplankton dynamics and composition, a wide range of TZ biogeochemical responses is expected. For REFINE, the five oceanic regions are located in three main latitudinal areas.

Polar areas schema

Polar areas

The Arctic Ocean is characterized by an extreme range of surface irradiance, which forces a distinctive response in phytoplankton, hence affecting energy transfer to higher trophic levels, and carbon sequestration in deep waters. The productive period is tightly linked to the seasonal dynamic of sea ice (coverage and thickness), with early summer phytoplankton blooms generally driven by increased diatom abundance at the edge of retreating sea ice, fostered by salinity stratification. REFINE site 1 is Baffin Bay.

Temperate and sub-polar areas schema

Temperate and sub-polar areas

Temperate and sub-polar areas are characterized by distinctive seasonal signals in phytoplankton dynamics, highly dependent on the seasonal cycle of the mixed layer. Following the winter “resetting” of nutrient concentrations in the upper layer, a spring bloom will develop, generally dominated by diatoms. Next will come a summer period characterized by low to moderate production conditions. This phenological sequence is accompanied by marked regional nutrient-driven differences. REFINE site 2 is the Labrador Sea, representing the North Atlantic subpolar gyre where the global ocean’s largest spring/summer blooms are found. REFINE site 5 is upstream of the Kerguelen Plateau, representing iron-limited areas associated with low phytoplankton biomass and a low-intensity spring bloom.

Low-latitude areas schema

Low-latitude areas

Low-latitude areas are generally characterized by permanently stratified conditions matched with fairly weak seasonality and the presence of deep chlorophyll maxima (DCM) largely associated with small phytoplankton. REFINE site 3 is the Guinea Dome, the quasi-permanent cyclonic doming structures in eastern subequatorial waters. These are high production hotspots thanks to sustained nutrient supply in sub-surface waters trapped by productive DCMs. REFINE site 4 is the South Atlantic Subtropical Gyre, representative of subtropical gyres that compose 60 % of the global ocean's surface. Here, in contrast to subequatorial waters, DCMs are less productive while the main contributors to export are very small particles.

section who

We are a team of experienced scientists and engineers hosting outstanding PhD students and post-docs. For more than 15 years now, we have been deeply involved in the development of autonomous platforms and innovative ways to conduct remote observations of oceanic biogeochemical processes. We are also very active in using these new ocean-scrutinizing approaches to develop and promote outreach in support of Ocean Literacy.

REFINE’s objectives (science and outreach) will be tightly linked and developed in sync with the United Nations Decade of Ocean Science for Sustainable Development. Moreover, REFINE will be implemented in close cooperation and interaction with JETZON (Joint Exploration of the Twilight Zone Ocean Network), an international coordinator and focal point for Twilight Zone studies.

REFINE an EU research project carried out by a synergistical multidisciplinary team

As the project gradually develops, we will be offering PhD and post-doc positions.
Stay tuned on our twitter|@ERC_REFINE to be informed.

section what's on

++ After remOcean, Hervé Claustre was awarded a 2nd ERC Research Advanced Grant. His new project REFINE (erc-refine.eu) focuses on the Ocean Carbon Pump with a particular emphasis on the Ocean Twilight Zone. ++