GCOS Implementation Plan - WMO

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