2021 State of the Environment Report Marine Chapter – Expert Assessment – Pressure – Ocean nutrients and dissolved oxygen

《2021年环境状况报告(SOE)》的海洋章节包含了从海洋数据流开发的多个专家模板。这一元数据记录描述了《海洋营养盐和溶解氧的压力》专家评估。<br/> *完整的专家评估PDF，包括图表(如果提供)，可在本记录的“在线资源”部分下载，名称为“专家评估2021--压力--海洋营养物质和溶解氧”*<br/> <br/> <br/> 压力说明<br/> 向上层海洋提供营养物质的重要物理过程(图1)是表层海洋混合层的季节性加深、与海洋涡旋相关的上升流和垂直混合以及由风驱动的上升流。在澳大利亚地区，前两个过程占主导地位，因为风引起的上升流仅限于少数几个小区域(例如南澳大利亚附近的邦妮上升流)。随着气候变暖，上层海洋将形成更强的垂直温度梯度，变得更加分层，减少向表层海洋垂直供应营养物质(Kwiatkowski等人，2020年)。气候变化预计还将改变风、加强边界流和增加涡旋活动及其垂直营养供应(例如，东澳大利亚洋流，Matear等人，2013年)。<br/> 氧气对海洋中的有氧生物来说是必不可少的。在表层海洋中，氧气水平很高，因为海气交换使氧气保持在接近饱和的水平。由于好氧呼吸作用，海洋内部的溶解氧浓度下降，中间水(300米至1000米)的浓度最低，远离这些水域与大气交换的区域(即南大洋，图2)。沿海地区的高耗氧量会将氧气降低到不再支持有氧生物体的水平，从而导致鱼类死亡(Hobbs和McDonald，2010)。氧在变暖的海洋中的溶解度降低，气候变化预计将导致低氧地区的扩大(Kwiatkowski等人，2020年)。<br/> 随着气候变化使海洋变暖，澳大利亚水域的海洋热浪预计将增加频率和强度(Hayashida等人，2020b)。<br/> 沿海海洋地区存在额外的压力，例如增加的营养物质输入(河流和河口)；这会减少氧气，有可能发生局部缺氧事件，并随着浮游植物水华的增加而增加营养物质。<br/> <br/> 数据流(S)在专家评估中的应用<br/> 数据来自CARS的硝酸盐、磷酸盐和氧气气候地图集(1996)。详情请访问：http://www.globcolour.info/products_description.html.<br/> <br/> <br/> 2021年国企评估总结[详见所附专家评估报告]<br/> <br/> ·2021年·<br/> 评估等级：高影响<br/> 评估趋势：不明朗<br/> 置信度：低<br/> 信心趋势：低迷<br/> 可比性：具有可比性(2016年分别评估氧气和营养素<br/> <br/> <br/> 2016年国企考核以来的变化<br/> 季节性气候基于最新版本的CARS，该版本引入了自2016年以来收集的额外观测数据。此外，之前对溶解氧、养分供应和循环进行了单独评估，但已将其合并为2021年的单一“生物地球化学”评估。

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 "Pressure of Ocean nutrients and dissolved oxygen". <br /> ***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 - Pressure – Ocean nutrients and dissolved oxygen"***<br /> <br /> ----------------------------------------<br /> <br /> DESCRIPTION OF PRESSURE<br /> The vital physical processes supplying nutrients to the upper ocean (Figure 1) are the seasonal deepening of the surface ocean mixed layer, the upwelling and vertical mixing associated with ocean eddies, and wind-driven upwelling. In the Australian region, the first two processes dominate because wind-induced upwelling is confined to a few small areas (e.g. Bonnie Upwelling off South Australia). As the climate warms, the upper ocean will develop a stronger vertical gradient in temperature, becoming more stratified, reducing the vertical supply of nutrients to the surface ocean (Kwiatkowski et al., 2020). Climate change is also projected to modify winds, and strengthen boundary currents and increased eddy activity their vertical nutrient supply (e.g. the East Australia Current, Matear et al., 2013).<br /> Oxygen is essential to living aerobic organisms in the ocean. In the surface ocean, oxygen levels are high because air-sea exchange keeps oxygen near saturation levels. Due to aerobic respiration, the dissolved oxygen concentrations in the ocean interior decline and are lowest in the intermediate water (300 m to 1000 m) away from regions these waters exchange with the atmosphere (i.e. the Southern Ocean, Figure 2). High oxygen consumption in coastal regions can lower oxygen to a level where it can no longer support aerobic organisms leading to fish kills (Hobbs and McDonald, 2010). Solubility of oxygen is reduced in a warming ocean, and climate change is projected to lead to the expansion of areas with low oxygen (Kwiatkowski et al., 2020).<br /> With climate change warming of the ocean, marine heatwaves in Australian waters are projected to increase in frequency and intensity (Hayashida et al., 2020b).<br /> Additional pressures exist in coastal ocean regions, such as increased nutrient input (rives and estuary); which reduces oxygen with the potential for local anoxic events and increases nutrients with the increase phytoplankton blooms.<br /> <br /> DATA STREAM(S) USED IN EXPERT ASSESSMENT<br /> Data come from the CARS climatological atlas of nitrate, phosphate and oxygen (1996). Details can be found at http://www.globcolour.info/products_description.html.<br /> <br /> ----------------------------------------<br /> <br /> 2021 SOE ASSESSMENT SUMMARY [see attached Expert Assessment for full details]<br /> <br /> • 2021 •<br /> Assessment grade: High impact<br /> Assessment trend: Unclear<br /> Confidence grade: Low<br /> Confidence trend: Low<br /> Comparability: Somewhat comparable (oxygen and nutrients assessed separately in 2016<br /> <br /> ----------------------------------------<br /> <br /> CHANGES SINCE 2016 SOE ASSESSMENT<br /> The seasonal climatologies are based on the latest version of CARS, which brings in additional observations collected since 2016. Additionally, dissolved oxygen and nutrient supply and cycling were previously assessed separately, but have been combined into a single ‘biogeochemistry’ assessment for 2021.