Specification report of common test protocols and intercomparison methodologies

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ABSTRACT

D1.2 Specification report of common test protocols and intercomparison methodologies
Project [[:Category:ENVRIplus|ENVRIplus]]
Deliverable nr D1.2
Submission date 2019-07-25
Type [[:Category:report|report]]

PDF | Zenodo

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The content of the present reports highlights a specific use case specified at the beginning of ENVRIplus project, the measurement of the pCO2 concentration from the air-sea interface to the bottom of the Ocean. 2The rationales of the relevancy of measuring pCO2 concentration in the sea-water is exposed as being an extremely important parameter for the global Carbon cycle monitoring, and in particular the contribution of the Inorganic Carbon. During the ENVRIplus project timeline, several initiatives have been carried-out by the task partners to (1) assess the use of commercially available sensors for pCO2measurements and (2) trying to refine a common approach for across-network collaborations.It appears that at the end of the exercise, no mature technology is suitable to cover all requirements needed for disparate networks, and that the Marine RIs have to start more cohesive synergies to achieve a common strategy for new sensors implementation.Nevertheless, Interesting discussions have started inside this task consortium, and future collaborations are engaged to converge towards a future continuum strategy from sea-surface to bottom for the innovative sensors implementation.

RATIONALES: the pCO2 Use case

The ocean absorbs about 25 % of anthropogenic carbon dioxide (CO2) emissions, moderating the rate and severity of climate change. Such massive input of CO2 generates sweeping changes in the chemistry of the carbon system, including an increase in dissolved inorganic carbon (CT) and bicarbonates (HCO3–) as well as a decrease in pH and in the concentration of carbonate (CO32–) ions. These changes are collectively referred to as “ocean acidification”. The pH of ocean surface water has decreased by 0.1 units since the beginning of the industrial era, corresponding to a 26 % increase in hydrogen ion concentration, and the total decrease by 2100 will range from 0.14 to 0.4 units. These changes are, however, quite variable regionally and with depth. Elucidating the biological, ecological, biogeochemical and societal consequences of ocean acidification therefore requires a fine resolution of ocean CO2 data in space and time. Thus, humankind is in urgent need of routine and sustained global information on the marine environment sufficient to meet society’s needs for describing, understanding and forecasting variability and long-term change. We do know, however, that significant marine CO2 sources and sinks exist in currently under sampled or even unsampled areas, which are undergoing rapid anthropogenically driven change and exhibit high vulnerability (e.g., increasingly ice-free Arctic Ocean, Southern Ocean, coastal seas). The situation at sea surface is monitored on long term time series in sparse places of the global ocean, by using repeated oceanographic cruises where ships are equipped with surface continuum pCO2sampling systems. The produced data can be directly compared to atmospheric measurements of the pCO2 concentration to assess the flux of inorganic carbon from atmosphere to ocean.It becomes consequently obvious that data on carbon fluxes in the ocean is drastically lacking pCO2measurements in the water column. This is a cross RIs topic involving EUROARGO, EMSO/EUROSITES and the glider community of GROOM together with the marine component of ICOS and projects like JERICO. Ideally, once adopted in EUROARGO and international ARGO, a pCO2 sensor will become a de facto standard in the marine domain. But the maturity of the sensor offer is not high enough to justify an integration in EUROARGO before a few years due to response time, energy consumption and calibration issues. That is why it is urgent that other RIs join their efforts with agreed methods and share of testing facilities, thus improving the sensing technologies to a level which could be mature enough for a global observation network such as the Argo program.

REVIEW OF THE EXISTING NETWORKS IN EUROPEAN MARINE DOMAIN

Surface Continuum

The surface measurements of pCO2 concentration are ensured during oceanographic cruises from ships. The equipment and possibilities offered by modern units benefit to RIs such as ICOS marine; allowing both

  • the under-surface sampling by using a continuous flow-through water pumping system connected to a bench water pCO2 analyzer
  • the above surface atmospheric sampling pumping the ambient air through gas inlets and analyzing the pCO2 concentration with standard equipment as found usually on terrestrial stations.

Some difficulties remain for this shipborne measurement, as the crews have to control continuously that the samples are not contaminated by the activity of the ship (gas outlets from the engine, contamination of the surface water layer close to the ship’s hull).These activities are organized in common with EUROFLEETS RI, which maintain a database of available technical means for these surface measurements (water/air inlets, possibility to install dedicated deck containers) and provides detailed ship position along with local meteorological measurements allowing to post process the data to eliminate the potentially contaminated ones.

Moorings and bottom stations

PCO2 concentration sensors are included on some long-term moorings across Europe, thus not being part of a standardized package for all of them.The EMSO ERIC associated with the former FIX03 network advocates for a standardization of the mooring systems and performs test cases for the adjunction of new sensors on their water column and bottom stations. This activity was monitored at European level inside the EUROSITES project now integrated in the EMSO ERIC.

Autonomous platforms (floats/gliders/others)

In order to complement the historical shipborne sampling of key oceanic parameters, the emergence of reliable autonomous platform technologies during the last three decades have allowed to push the measurements to a globalized scheme, enabling real-time monitoring of the ocean to be used by ocean forecaster communities and modelizers for the global change assessment.Autonomous Unmanned Vehicles, Gliders, Surface Wave Gliders, and Argo floats are now fully able to carry various sensors, potentially including the pCO2 concentration ones.The variability of spatial and temporal extension of each technology has induced the emergence of dedicated European Research Infrastructure or projects, with specific technological requirements for each of those:

  • High seas and deep measurements down to 6000 meters are ensured by the Argo Program, and its European component EUROARGO ERIC implementing the profiling float’s network for long term continuous sampling
  • The GROOM project has centralized the European effort to harmonize the use of Gliders, suitable for short term sampling of the upper layer of the ocean and concentrating on meso-scale processes
  • The JERICO project deals with the coastal sampling (Fix platform, Ferryboxes, etc), also implementing Gliders and exploring how surface autonomous vehicles such as Wave Gliders can be used on longer term deployments
  • Although usually dedicated to other scientific purpose (acoustics, seismology, etc.), AUVs are regularly deployed from oceanographic ships and are able to integrate additional sensors for short term campaigns. The available material is monitored by EUROFLEET RI which enables access for common collaboration between the different scientific communities

Towards a collaboration across the European Marine RIs

The harmonization effort across the marine domain European RIs sampling strategy can be balanced as compared to the atmospheric domain one to understand the technological difficulties inherent to the harsh marine environment.The Atmospheric domain RIs have managed to implement a common and global way to monitor the atmosphere essential variables defining standard instrumentation and minimal requirements for a sampling station settlement. Because the human presence is possible almost at every time on-site, ICOS, ACTRIS and IAGOS are able to deploy the same instruments even in such various environments as ground stations, planes, meteorological balloons or ships, ensuring the maintenance, the replacement of consumables, allowing cross-calibration campaigns without disturbing the time series.The Marine domain European RIs are facing much more difficulties because of inherent conditions to the Ocean sampling: continuous or regular human presence is not possible; sampling above surface, at the air-sea interface or into the water column until the bottom of ocean requires specific design of the instrumentation to face to issues such as corrosion, resistance to pressure, impossibility to replace the consumables, energy and sizing concerns. Although each single RI or project has defined some best practice procedures to harmonize the technological implementation of instrumentation on their own platforms, across RI collaborations have not really converged towards a global strategy to ensure a complete continuum from surface to bottom of the Ocean. Some of the specifications of each component of the marine domain sampling area are described in the following chapter.

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