2021 State of the Environment Report Marine Chapter – Expert Assessment – Pressure – Climate Change – Ocean acidification

Researchers: Emma Flukes (Point of contact) ,  Lenton, Andrew (Author) ,  Tilbrook, Bronte (Author)

Brief description The Marine chapter of the 2021 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 - climate change - ocean acidification". ***A PDF of the full Expert Assessment, including figures and tables (where provided) is downloadable in the "On-line Resources" section of this record as "EXPERT ASSESSMENT 2021 - Ocean Acidification"*** ---------------------------------------- DESCRIPTION OF PRESSURE Ocean acidification describes changes in dissolved carbonate chemistry resulting from the ocean taking up about 25% of the annual carbon dioxide (CO2) emissions. The changes include decreases in seawater pH and a lowering of the saturation state of aragonite, a major mineral form used by marine organisms to produce shells and skeletal material. The changes are rapid with the pH change being ten-fold greater than at any time in the past 300 million years (Hönisch et al., 2012). Superimposed on the large-scale change is increased variability at seasonal and local scales, particularly in coastal regions (Mongin et al., 2016; Shaw et al., 2012). DATA STREAM(S) USED IN EXPERT ASSESSMENT Offshore data from around Australia as described in Lenton et al. 2016. Lenton, A., B. Tilbrook, R. Matear, T. Sasse and Y. Nojiri (2016) Historical reconstruction of Ocean Acidification in the Australian region, Biogeosciences, 13: 1753–1765. https://doi.org/10.5194/bg-13-1753-2016 ---------------------------------------- 2021 SOE ASSESSMENT SUMMARY [see attached Expert Assessment for full details] • 2021 • Assessment grade: Very high impact Assessment trend: Deteriorating Confidence grade: Somewhat adequate Confidence trend: Adequate Comparability: Comparable • 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 2016 SOE ASSESSMENT More data are now available.

Lineage Statement: QUALITY OF DATA USED IN THE ASSESSMENT Total dissolved CO2 and total alkalinity data were obtained following procedures outlined in Dickson et al., (2007). Certified reference materials (CRMs) from the Scripps Institution of Oceanography were analysed to determine a ± 2 micromol/kg accuracy and precision of the measurements 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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Notes Credit
Peer reviews of this assessment were provided by: Kim Currie (NIWA)

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