2016 SoE Marine Chapter - Pressures - Climate Change - Nutrient supply and cycling

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 - nutrient supply and cycling". 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 Macronutrient concentrations (e.g. nitrate and phosphate) in the surface ocean play an important role in controlling the ocean’s primary productivity. The oceans account for about half of the earth’s total primary productivity. Surface ocean waters around Australia typically have low macronutrient concentrations for nitrate and phosphate. The key physical processes supplying nutrients to the upper ocean are the seasonal deepening of the ocean surface mixed layer, the upwelling and vertical mixing associated with ocean eddies, and wind-driven coastal upwelling. In the Australian region, the first two processes dominate because conditions that cause wind-induced upwelling are confined to a few regions (e.g. Bonney upwelling off South Australia). As the ocean warms around Australia (Lenton et al, 2015) the upper ocean will become more stratified and the vertical supply of nutrients to the surface ocean could decline (Bopp et al, 2013) reducing primary productivity. However, increased eddy activity due to strengthening of the East Australian Current may compensate for a decline in the vertical nutrient supply in the Tasman Sea and cause an increase in primary productivity with climate change (Matear et al., 2013). DATA STREAM(S) USED IN EXPERT ASSESSMENT Offshore data from around Australia from the latest CARS compilation (CARS2009a v1.1, as of 12 July 2010). See http://www.marine.csiro.au/atlas/ ---------------------------------------- 2016 SOE ASSESSMENT SUMMARY [see attached Expert Assessment for full details] • 2016 • Assessment grade: High impact Assessment trend: Unclear Confidence grade: Evidence and consensus too low to make an assessment Confidence trend: Evidence and consensus too low to make an assessment Comparability: Grade and trend not comparable to the 2011 assessment • 2011 • Assessment grade: Very good Assessment trend: Stable Confidence grade: Limited evidence or limited consensus Confidence trend: Limited evidence or limited consensus ---------------------------------------- CHANGES SINCE 2011 SOE ASSESSMENT Unclear what data were used in the 2011 assessment; the 2016 assessment is based on the latest CARS compilations and so includes observations added to CARS 2011-2016.

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Statement: QUALITY OF DATA USED IN THE ASSESSMENT The CARS dissolved oxygen and nitrate data reflect a compilation of all ocean observations. To improve the robustness of the results we only show the annual mean values.

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