Search

It is estimated that oceans absorb approximately a quarter of the total anthropogenic releases of carbon dioxide to the atmosphere each year. This is leading to acidification of the oceans, which has already been observed through direct measurements. These changes in the ocean carbon system are a cause for concern for the future health of marine ecosystems. A coordinated ocean acidification (OA) monitoring programme is needed that integrates physical, biogeochemical, and biological measurements to concurrently observe the variability and trends in ocean carbon chemistry and evaluate species and ecosystems response to these changes. This report arises from an OSPAR request to ICES for advice on this matter. It considers the approach and tools available to achieve coordinated monitoring of changes in the carbon system in the ICES marine area, i.e. the Northeast Atlantic and Baltic Sea. An objective is to measure long-term changes in pH, carbonate parameters, and saturation states (Ωaragonite and Ωcalcite) in support of assessment of risks to and impacts on marine ecosystems. Painstaking and sensitive methods are necessary to measure changes in the ocean carbonate system over a long period of time (decades) against a background of high natural variability. Information on this variability is detailed in this report. Monitoring needs to start with a research phase, which assesses the scale of short-term variability in different regions. Measurements need to cover a range of waters from estuaries and coastal waters, shelf seas and ocean-mode waters, and abyssal waters where sensitive ecosystems may be present. Emphasis should be placed on key areas at risk, for example high latitudes where ocean acidification will be most rapid, and areas identified as containing ecosystems and habitats that may be vulnerable, e.g. cold-water corals. In nearshore environments, increased production resulting from eutrophication has probably driven larger changes in acidity than CO2 uptake. Although the cause is different, data are equally required from these regions to assess potential ecosystem impact. Analytical methods to support coordinated monitoring are in place. Monitoring of at least two of the four carbonate system parameters (dissolved inorganic carbon (DIC), total alkalinity (TA), pCO2, and pH) alongside other parameters is sufficient to describe the carbon system. There are technological limitations to direct measurement of pH at present, which is likely to change in the next five years. DIC and TA are the most widely measured parameters in discrete samples. The parameter pCO2 is the most common measurement made underway. Widely accepted procedures are available, although further development of quality assurance tools (e.g. proficiency testing) is required. Monitoring is foreseen as a combination of low-frequency, repeat, ship-based surveys enabling collection of extended high quality datasets on horizontal and vertical scales, and high-frequency autonomous measurements for more limited parameter sets using instrumentation deployed on ships of opportunity and moorings. Monitoring of ocean acidification can build on existing activities summarized in this report, e.g. OSPAR eutrophication monitoring. This would be a cost-effective approach to monitoring, although a commitment to sustained funding is required. Data should be reported to the ICES data repository as the primary data centre for OSPAR and HELCOM, thus enabling linkages to other related datasets, e.g. nutrients and integrated ecosystem data. The global ocean carbon measurement community reports to the Carbon Dioxide Information Analysis Center (CDIAC), and it is imperative that monitoring data are also reported to this database. Dialogue between data centres to facilitate an efficient “Report-Once” system is necessary. Published Authors: Alberto V. Borges ● Carlos Borges ● Naomi Greenwood ● Susan E. Hartman David J. Hydes ● Caroline Kivimae ● Evin McGovern ● Klaus Nagel Solveig Olafsdottir ● David Pearce ● Elisabeth Sahlsten Carmen Rodriguez ● Pamela Walsham ● Lynda Webster Refereed Current 14.3 Inorganic carbon Best Practice Manual (incl. handbook, guide, cookbook etc)

Strategically positioned along the western margin of the North Atlantic, Irish shelf and offshore waters play a crucial role in the global thermohaline circulation and regional and global climate cycles. The main objective of this study was to investigate the biogeochemical characteristics of the main water masses in the region to generate information on how the marine environment is changing with time. Dissolved oxygen, nutrient and carbon data, collected across the Rockall Trough in February 2009 and 2010, proved useful as chemical tracers of water masses in the region and highlighted processes that could not have been identified using hydrographic data alone. Inorganic carbon data from 2009 and 2010 were compared with WOCE data collected across the Trough in the 1990s to assess the temporal evolution of anthropogenic carbon (Cant) in the region over 2 decades. Two methods were used to calculate Cant between surveys, CT-abio and extended multiple linear regression, both of which resulted in similar rates of increase in Cant through the water column, with subsequent decrease in pH and saturation state of calcium carbonate minerals. Between 1991 and 2010, pH in subsurface waters has decreased by 0.040±0.003 units and by 0.029±0.002 units in Labrador Sea Water. Net community production (NCP) was calculated along the western shelf edge between 49.8-55.4ºN. Generally maximum NCP was measured in surface waters over the 500-750m contours, decreasing in both offshore and shallower on-shelf surface waters. Where calculated, there was a net CO2 uptake from the atmosphere suggesting this region is a CO2 sink during the productive season. Due to its influence on the buffer capacity of the surface ocean, the distribution of total alkalinity (AT) in Irish coastal and shelf waters was investigated. The AT distribution in outer estuarine and coastal waters is more complex than along the western shelf and through the centre of the Irish Sea due to varying river inputs. Rivers with limestone bedrock catchments had relatively high AT concentrations which influence the buffer capacity, and hence rate of pH change, of the surrounding coastal waters. Results indicate that the algorithm produced by Lee et al. (2006) to calculate AT from temperature and salinity should not be used in Irish coastal waters due to variable but substantial riverine inputs of AT.