Marine sediments as archives of past climate and recent anthropogenic changes

海洋沉积物作为过去气候和近期人为变化的档案

• 批准号: RGPIN-2018-05607
• 负责人: Kienast, Stephanie
• 金额: $ 1.82万
• 依托单位: Dalhousie University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=713748
• 关键词: Marine; sediments; archives; past; climate

Dust aerosols play a direct role in Earth's energy balance by scattering as well as absorbing radiation. Mineral dust and its associated nutrients also fertilize ecosystems and thus influence climate indirectly via photosynthesis and carbon uptake. However, large gaps exist in our understanding of the global dust cycle, in part due to the severe lack of direct observations of dust deposition in present and past environments. Mineral dust and its effect on radiative forcing and future climate have been identified as critical areas of research by the Intergovernmental Panel on Climate Change (IPCC). The first objective of this proposal is to investigate how much dust was deposited where, at what time, and from which sources, and whether changes in dust deposition caused changes in phytoplankton productivity and carbon removal from the upper ocean-atmosphere system. We combine measurements of a novel radioisotope tracer (232Th) with other geochemical proxies in marine sediment cores to generate new paleo records of dust deposition and organic carbon fluxes in the global ocean. The results are compared to simulations of state-of-the-art coupled climate models, such as the Community Climate System Model (CCSM), which are used in climate change scenarios by the ICPP and provide time slice as well as transient targets for hindcasting studies of the dust cycle. Research related to this objective generates critical new knowledge on the dust and carbon cycles in the undisturbed atmosphere-ocean system of the past, which is a recognized pre-requisite for the accurate prediction of future climate conditions. In addition to recording past environmental conditions, marine sediments act increasingly as a sink for pollutants from human activities, especially in coastal areas. Using highly similar geochemical tools as above, the second objective of this research program is to investigate metal fluxes in coastal sediments near finfish aquaculture operations. Canadian aquaculture production has expanded fourfold since the 1990's, reaching ~187,000 tonnes worth $967 million in 2015. However, aquaculture related activities appear to cause increased accumulation of harmful metals, such Cu and Zn, in underlying sediments. We will analyze metal fluxes in coastal sites that are proximal and distal to finfish aquaculture operations and compare observed levels with baseline values (pre-Anthropocene, pre-industrial). We will test whether metal concentrations exceed Probable Effect Levels (PEL) identified by the Canadian Council of Ministers of the Environment. If so, we will investigate whether there is a risk of metal re-mobilization back into the water column. Research related to objective 2 generates new insight that will advance our understanding of environmental sustainability in coastal areas and contribute to sustainable resource extraction in Canada.

粉尘气溶胶通过散射和吸收辐射在地球的能量平衡中发挥着直接作用。矿尘及其相关营养物质也使生态系统变得肥沃，从而通过光合作用和碳吸收间接影响气候。然而，我们对全球灰尘循环的理解存在很大差距，部分原因是严重缺乏对当前和过去环境中灰尘沉积的直接观测。矿尘及其对辐射强迫和未来气候的影响已被政府间气候变化专门委员会（IPCC）确定为关键研究领域。该提案的第一个目标是调查在何处、何时、从哪些来源沉积了多少灰尘，以及灰尘沉积的变化是否导致浮游植物生产力和上层海洋大气系统碳去除的变化。我们将新型放射性同位素示踪剂 (232Th) 的测量与海洋沉积物岩心中的其他地球化学指标相结合，生成全球海洋中尘埃沉积和有机碳通量的新古记录。将结果与最先进的耦合气候模型的模拟进行比较，例如社区气候系统模型（CCSM），ICPP 在气候变化情景中使用该模型，并为沙尘循环的后报研究提供时间片和瞬态目标。与这一目标相关的研究产生了关于过去未受干扰的大气-海洋系统中的灰尘和碳循环的重要新知识，这是准确预测未来气候条件的公认先决条件。 除了记录过去的环境条件外，海洋沉积物越来越多地充当人类活动污染物的汇，特别是在沿海地区。使用与上述高度相似的地球化学工具，该研究计划的第二个目标是调查鱼类养殖作业附近沿海沉积物中的金属通量。自 1990 年代以来，加拿大水产养殖产量增长了四倍，2015 年达到约 187,000 吨，价值 9.67 亿加元。然而，水产养殖相关活动似乎导致底层沉积物中有害金属（例如铜和锌）的积累增加。我们将分析靠近和远离鱼类养殖作业的沿海地点的金属通量，并将观测到的水平与基线值（人类世前、工业化前）进行比较。我们将测试金属浓度是否超过加拿大环境部长理事会确定的可能影响水平 (PEL)。如果是这样，我们将调查是否存在金属重新回到水体中的风险。与目标 2 相关的研究产生了新的见解，将增进我们对沿海地区环境可持续性的理解，并为加拿大的可持续资源开采做出贡献。