Late Season Productivity, Carbon, and Nutrient Dynamics in a Changing Arctic

不断变化的北极的晚季生产力、碳和养分动态

• 批准号: 1504394
• 负责人: Laurie Juranek
• 金额: $ 115.91万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-01 至 2019-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1504394&HistoricalAwards=false
• 关键词: Late; Season; Productivity; Carbon; Nutrient

Satellite measurements have documented significant reductions in sea ice cover, thickness, and duration throughout the Arctic Ocean in recent decades. Because of the complex interactions and feedbacks among physical, biogeochemical and ecological processes in the Arctic, there is significant uncertainty regarding how these changes in sea ice will impact the marine biological pump, which fuels the rich bottom communities on Arctic ocean shelves and is key to the regional carbon cycle. While responses of the biological pump to increased light availability in spring are currently being pursued, a considerable gap in knowledge exists regarding biological processes in the late summer and early fall. Recent studies indicate a several-decade trend of intensifying wind forcing over the Alaskan margin along the Chukchi and Beaufort Seas in the late, ice-free season (September-November). These events could lead to mixing of nutrients into surface waters, fueling increased biological production and sequestering additional carbon into shelf bottom waters prior to the winter ice advance. However, the lack of direct, concurrent observations of primary and net community productivity rates, and nutrient and carbon distributions during this poorly-sampled time of year hinders efforts to assess the ecosystem implications of such changes. This project proposes to address the question of increasing biological production in the late season through intensive field sampling in two successive years.The investigators will use an innovative approach to better characterize how primary productivity (PP), net community productivity (NCP), and particulate and dissolved organic and inorganic carbon stocks (POC, DOC, DIC) are influenced by episodic nutrient inputs to the surface ocean in late summer and early fall. Over two field campaigns, they will collect high resolution surface measurements of dissolved gases, particulate and dissolved organic matter stocks and dissolved inorganic nutrients and carbon using a ship of opportunity (year 1) and dedicated research cruises (year 2). The use of geochemical rate tracers (oxygen/argon-based NCP and oxygen isotope-based PP; inventory changes of POC, DOC, nutrients, and DIC) offers a distinct advantage over incubation-based approaches by integrating processes on longer timescales (weekly to monthly). This approach is well-suited to capture the effects of episodic upwelling and subsequent ecosystem processing. On the dedicated regional research cruises in year 2 the investigators will also use a towed pumping sled to capture high-resolution vertical and cross-shelf observations. This towed sled will be equipped with standard CTD and optical sensors and interfaced to fast shipboard analyzers for measurement of nutrients and inorganic carbon (pCO2, DIC), as well as to automated samplers to collect water for oxygen/argon ratios, oxygen isotope, POC and DOC measurements. High-resolution chemical and biological distributions will be combined with ship-based ADCP measurements of water column velocities and continuity-based mass-balance calculations to constrain rates of NCP as well as the extent of vertical and lateral material fluxes. Outreach and education elements include a pilot program to engage pre-service secondary STEM teachers in educational planning and field work portions of the work. The program will provide field experience and on the job science training to teachers and result in short media outreach pieces and targeted curriculum addressing the three dimensions of science from the next generation science standards. The proposal will support one graduate student and several undergraduate students, who will participate in all aspects of the field and analytical work. The project will contribute to the early career development of a junior investigator.

卫星测量结果证明了近几十年来，整个北极海洋的海冰覆盖，厚度和持续时间的显着减少。由于北极的物理，生物地球化学和生态过程之间的复杂相互作用和反馈，因此海冰中的这些变化将如何影响海洋生物泵有很大的不确定性，这为北极海洋上的丰富底部群落燃料而言是该区域碳循环的关键。尽管目前正在追求生物泵对春季春季的光供应增加的反应，但在夏末和初秋，关于生物过程的知识存在很大的差距。最近的研究表明，在晚期无冰的季节（9月至11月），沿Chukchi和Beaufort海沿着阿拉斯加边缘上的风力强迫的风趋势。这些事件可能会导致养分混合到地表水中，从而在冬季冰上进步前加剧了生物产生的增加，并将额外的碳隔离到架子底水中。然而，在这一不足的一年中采样较差的时间里，缺乏直接的，同时观察到基本和净社区生产率，以及营养和碳分布，阻碍了评估此类变化的生态系统含义的努力。该项目建议通过连续两年的大量现场抽样来解决在季节后期增加生物产量的问题。研究人员将使用一种创新的方法来更好地表征主要生产力（PP），净社区生产力（NCP）以及颗粒物以及溶解的有机和无机碳库存（POC，DOC，DOC，DIC，DIC）的效果越来越多的效果效果，并溶解了有机和无机碳库存。在两次现场活动中，他们将使用机会船（1年级）和专门的研究巡游（第2年）收集溶解气体，颗粒和溶解有机物库存的高分辨率表面测量以及溶解的无机养分和碳。地球化学速率示踪剂（基于氧/氩的NCP和基于氧同位素的PP； POC，DOC，DOC，营养和DIC的库存变化）通过在较长的时间表上（每周到每月）整合过程来提供明显的优势。这种方法非常适合捕获情节上升流和随后的生态系统处理的影响。在第2年的专用区域研究巡游中，调查人员还将使用牵引式抽水雪橇来捕获高分辨率的垂直和跨架子观测。该牵引的雪橇将配备标准的CTD和光学传感器，并连接到快速船上分析仪，以测量养分和无机碳（PCO2，DIC），以及自动采样器，以收集用于氧气/氩气比率，氧气比率，氧气同位素，POC，POC和DOCUREMENT的水。高分辨率的化学和生物分布将与基于船舶的ADCP测量水柱速度的测量以及基于连续性的质量平衡计算，以限制NCP的速率以及垂直和侧向材料通量的程度。外展和教育元素包括一项试点计划，旨在让工作前的二级词干教师参与工作的教育计划和现场工作部分。该计划将为教师提供现场经验和工作科学培训，并提供简短的媒体外展作品，并针对性的课程针对下一代科学标准的科学三个维度。该提案将支持一名研究生和几名本科生，他们将参加该领域和分析工作的各个方面。该项目将有助于初级调查员的早期职业发展。