RAPID: Impacts of Increased Light Transmittance on Ocean Heating, Primary Productivity, and Carbon Cycling Across a Pacific Arctic Continental Shelf Gradient

RAPID：透光率增加对太平洋北极大陆架梯度的海洋加热、初级生产力和碳循环的影响

• 批准号: 2232855
• 负责人: Karen Frey
• 金额: $ 5.17万
• 依托单位: Clark University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-08-15 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2232855&HistoricalAwards=false
• 关键词: RAPID; Impacts; Increased; Light; Transmittance

Arctic sea ice is undergoing tremendous changes. There has been a pronounced decrease in summer sea ice cover, an overall thinning of the ice, and a lengthening of the summer melt season. Some of the greatest changes in sea ice cover across the pan-Arctic have been observed in the Chukchi and Beaufort Seas surrounding Alaska, where there has been substantial loss of perennial sea ice that persists year-round (including during summer). This Pacific Arctic sector is also among the most biologically productive marine ecosystems in the world and is an important region to monitor for the flow of carbon. Although sea ice is a dominant feature in these shallow marine environments at high-latitudes, we are only beginning to understand how changes in sea ice cover (through its influence on light, seawater temperature, salinity, and nutrient availability) will affect ecosystems in these regions. In particular, earlier ice-free conditions in the spring (as well as later ice-free conditions in the fall) have disrupted the timing of algae blooms and the livelihoods of marine mammals farther up the food chain. This research is focusing upon measurements of light transmittance through the ocean water column collected at science stations during the Synoptic Arctic Survey (SAS) cruise on the US Coast Guard Ship Healy. Measurements of light transmittance through the water column will further our understanding of how light impacts heat distribution, algae growth, and carbon flows throughout the region. In addition, this project is supporting an early-career researcher and the team is contributing material for numerous undergraduate courses and partnering with the Girls Inc. organization to involve middle and high school students in opportunities to learn about Arctic Ocean science.This research is establishing new measurements of light transmittance (320–780 nm) through the uppermost ~30–50 m of the ocean water column at observation points across a continental shelf gradient (over the Chukchi Shelf into the deep Arctic Ocean basin, with the return southward over the Chukchi Borderlands). These measurements are providing the baseline knowledge necessary to understand how light availability in the water column changes spatially (across a ~2000 km long continental shelf/latitudinal gradient) as well as temporally (across a seasonal gradient from early September through late October). Using these measurements, the team is testing the hypothesis that light transmittance increases with declines in sea ice cover and varies with light absorbing impurities in the water column. The seasonal timing and geographic location of the SAS cruise provide a rare opportunity to further assess the connections of late-open-water-season light transmittance to all three research focal areas of the SAS science and implementation plan: (1) physical drivers, (2) ecosystem responses, and (3) carbon cycling.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

北极海冰正在发生巨大变化。夏季海冰覆盖面积明显减少，冰层总体变薄，夏季融化季节延长。在阿拉斯加周围的楚科奇海和博福特海，观测到了泛北极海冰覆盖面积变化最大的一些地区，那里常年存在的海冰大量减少（包括夏季）。太平洋北极地区也是世界上生物生产力最高的海洋生态系统之一，是监测碳流动的重要区域。虽然海冰是高纬度浅海环境的主要特征，但我们才刚刚开始了解海冰覆盖的变化（通过其对光照，海水温度，盐度和营养物质的影响）将如何影响这些地区的生态系统。特别是，春季较早的无冰条件（以及秋季较晚的无冰条件）扰乱了藻类大量繁殖的时间和食物链上游海洋哺乳动物的生计。这项研究的重点是测量在美国海岸警卫队希利号上进行北极天气调查（SAS）巡航期间在科学站收集的海洋水柱的透光率。通过水柱的透光率测量将进一步了解光如何影响整个地区的热量分布，藻类生长和碳流动。此外，该项目正在支持一名早期职业研究人员，该团队正在为许多本科课程提供材料，并与Girls Inc.合作。这项研究是在跨越大陆架梯度的观测点（从楚科奇大陆架进入北冰洋盆地深处，向南返回楚科奇边界）建立对海洋水柱最上层~30-50米的透光率（320-780 nm）的新测量。这些测量提供了必要的基线知识，以了解水柱中的光可用性如何在空间上（跨越约2000公里长的大陆架/纬度梯度）以及时间上（从9月初到10月底的季节梯度）变化。利用这些测量结果，该团队正在测试一个假设，即透光率随着海冰覆盖的减少而增加，并随着水柱中的光吸收杂质而变化。SAS巡航的季节性时间和地理位置提供了一个难得的机会，以进一步评估开放水域后期透光率与SAS科学和实施计划的所有三个研究重点领域的联系：（1）物理驱动因素，（2）生态系统响应，以及（3）该奖项反映了NSF的法定使命，并通过使用基金会的智力价值进行评估，被认为值得支持和更广泛的影响审查标准。