2016 SoE Marine Chapter - Pressures - Climate Change - Ocean acidification

Brief description

The Marine chapter of the 2016 State of the Environment (SoE) report incorporates multiple expert templates developed from streams of marine data. This metadata record describes the Expert Assessment "Pressures on the marine environment associated with climate change - ocean acidification". The full Expert Assessment, including figures and tables (where provided), is attached to this record. Where available, the Data Stream(s) used to generate this Expert Assessment are accessible through the "On-line Resources" section of this record. ---------------------------------------- DESCRIPTION OF THE PRESSURE The uptake of atmospheric CO2 by the ocean results in changes in seawater chemistry, including a decrease in pH and dissolved carbonate ion concentrations, know as ocean acidification. Since pre-industrial times the pH of waters around Australia are estimated to have decreased between 0.08 and 0.10, consistent with global estimates of pH change. Superimposed on the large-scale change is much more variability at seasonal and local scales where natural processes can amplify or offset ocean acidification in a range of environments (Mongin et al., 2016; Walbusser et al, 2014; Shaw et al., 2012). The detection of trends and state in most coastal, shelf and subsurface waters around Australia is limited by lack of data. The pH and dissolved carbonate ion concentration of ocean waters around Australia will continue to decrease at the ocean takes up atmospheric CO2 emissions. The rates of change are linked to different emission scenarios (Lenton et al., 2015). Ocean acidification will persist for many millennia, even if emissions are reduced (e.g. Frolicher and Joos, 2010). Seasonal undersaturation of aragonite in surface waters of the Southern Ocean is predicted to occur by 2030 with consequences for calcifying organisms like pteropods (McNeil and Matear, 2008; Hauri et al., 2015). Ocean acidification is expected to lead to widespread shifts in ecosystems and puts at risk regional economies reliant on healthy and sustainable marine ecosystems such as tourism and aquaculture. DATA STREAM(S) USED IN EXPERT ASSESSMENT Offshore data from around Australia as described in Lenton et al 2015. Details of the specific data sets used to generate this assessment have not been provided. ---------------------------------------- 2016 SOE ASSESSMENT SUMMARY [see attached Expert Assessment for full details] • 2016 • Assessment grade: Very high impact Assessment trend: Deteriorating Confidence grade: Adequate high quality evidence and high level of consensus Confidence trend: Adequate high quality evidence and high level of consensus Comparability: Grade and trend are somewhat comparable to the 2011 assessment • 2011 • Assessment grade: Very good Assessment trend: Deteriorating Confidence grade: Limited evidence or limited consensus Confidence trend: Limited evidence or limited consensus ---------------------------------------- CHANGES SINCE 2011 SOE ASSESSMENT More data are now available.

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Statement: QUALITY OF DATA USED IN THE ASSESSMENT Total dissolved CO2 and total alkalinity data and these data were obtained following procedures outlined in Dickson et al (2007). Certified reference materials (CRMs) from the Scripps Institution of Oceanography are analysed to determine the accuracy and precision of the measurements and are accurate to ± 2 micromol/kg for both parameters. Oceanic values of pCO2 were taken from an updated version of (Sasse et al., 2013) climatology that used a neural network to map values around Australia on a 1x1 degree grid each month for the year 2000.

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Purpose
To describe the pressures on the marine environment associated with climate change and ocean acidification for use in the Marine chapter of the 2016 State of the Environment report.