GCOS Implementation Plan - WMO

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Implementation Plan for the Global Observing System for Climate in Support of the UNFCCC (2010 Update) • Reference station network. • Tropical moored buoy network. The main issue for the sub-surface temperature observing programme is fully sustaining the agreed global coverage and sampling density. See Actions O24-O28. ECV – Sub-surface Salinity Knowledge of the sub-surface salinity variability and change is essential in improving seasonal and interannual prediction and understanding the impact of changes in the hydrological cycle on ocean circulation. It can be observed with existing technology, but this ECV is not adequately sampled globally at present. The agreed programme will dramatically increase our knowledge of this ECV. Repeating XCTD observations from ships of opportunity are also feasible. The main issue for the sub-surface salinity observing programme is that none of the existing observing networks have the agreed global coverage and sampling density. Sub-surface salinity observing networks and systems include the previously described elements of the sub-surface system (Argo array; Full-depth repeat survey network; Reference Time Series mooring network; Tropical Moored Array network). The long-term stability and accuracy of salinity sensors remains an issue. See Actions O24-O28. ECV – Sub-surface Carbon The oceanic uptake of anthropogenic carbon is a key element of the planetary carbon budget. Over the last 250 years, the ocean has removed about 45% of the CO 2 that has been emitted into the atmosphere as a result of fossil fuel burning. Because the net ocean carbon uptake depends on biological as well as chemical activity, the uptake may change as oceanic conditions change (e.g., pH, currents, temperature, surface winds, and biological activity). At present, the community consensus is that the best strategy for monitoring the long-term ocean carbon uptake is via a global ocean carbon inventory network that measures both dissolved inorganic carbon and alkalinity. With present technology, a major improvement in our knowledge can be achieved with the agreed fulldepth repeat survey programme (see Figure 11), also benefiting from the air-sea exchange of CO 2 information obtained from the surface ocean pCO 2 network. This requires also strong commitments from the participating institutions and nations with fast submission of the data to the data centres in order to facilitate the large-scale synthesis. However, the first results from the repeat survey indicates that the level of variability is higher than originally expected, requiring a re-assessment of whether the original plan is adequate to fully characterise the decadal time change of the oceanic inventory of anthropogenic CO 2 . In addition, the proposed sampling network is inadequate to determine early responses of the oceanic carbon cycle to global climate change. Long-lived autonomous sensors for ocean carbon system components that can be deployed on moored or profiling observing elements are under development and will significantly increase our global observing capability. A more rapid repeat cycle for ocean survey sections will be needed for assessing the net carbon inventory change over intervals shorter than 10 years. See Actions O13, O15, O22 and O24. ECV – Sub-surface Oxygen Oxygen is an excellent tracer for ocean circulation and ocean biogeochemistry, but it is also essential for all higher life. Future projections indicate that the oceanic oxygen levels will decrease substantially, in part because of ocean warming and increased stratification, a process often referred to as ocean deoxygenation, but also because of increased nutrient loadings in nearshore environments that lead to eutrophication. In a business as usual scenario, the ocean is projected to 96
Implementation Plan for the Global Observing System for Climate in Support of the UNFCCC (2010 Update) lose nearly 20% of its oxygen. This could have dramatic consequences for marine biogeochemistry and marine life, as the ocean’s oxygen minimum zones will expand substantially, and large swaths of ocean will appear that have oxygen levels too low for fast swimming fish to survive. The classical method to measure oxygen (Winkler method) is a discrete method that provides highly accurate and precise oxygen measurements. In the recent years, autonomous sensors have made large progress and are now available for long-term deployments with sufficient accuracy and stability. Current networks and systems that contribute to the observation of sub-surface oxygen are: • Repeat survey network. • Reference station network. • Plus a few Argo floats that have been equipped with oxygen sensors. These networks are research and/or pilot programmes and require substantial up-scaling in order to adequately sample sub-surface oxygen variability. Particularly attractive is the possibility to link the recently developed sensors with autonomous platforms (e.g., Argo floats) to create a large-scale observing network. See Actions O5 and O24. Action O30 Action: Deploy a global pilot project of oxygen sensors on profiling floats. Who: Parties, in cooperation with the Argo Project and the Observations Coordination Group of JCOMM. Time-Frame: Continuous. Performance Indicator: Number of floats reporting oxygen. Annual Cost Implications: 1-10M US$ (10% in non-Annex-I Parties). ECV – Sub-surface Nutrients (phosphate, nitrate, silicates, silicic acid) Nutrient data are essential biogeochemical information, and provide essential links between physical climate variability and ecosystem variability, but are not adequately observed. They give an additional perspective on ocean mixing. Networks and systems that contribute to the observation of sub-surface nutrients are: • Repeat survey network. • Reference station network. These networks are research and/or pilot programmes and require technology development to attain reliable and accurate autonomous sensors and to deploy observing systems to sample better subsurface nutrient variability. Additional action: develop standards. See Actions O5, O22 and O24. ECV – Sub-surface Tracers 85 Ocean tracers are essential for identifying anthropogenic carbon uptake, storage, and transport in the ocean, as well as for understanding multi-year ocean ventilation, long-term mixing and ocean circulation and thereby, for providing essential validation information for climate change models. Ocean tracers are not adequately sampled at present. Present technology for most important tracers requires water samples and subsequent processing of these samples. 85 Such as oxygen and isotopes. 97
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FOREWORD This 2010 Update of the Im
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Implementation Plan for the Global
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GCOS Implementation Plan - WMO

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