Quantifying Processes Driving Interannual Variability in the Biological Carbon Pump in the Western Antarctic Peninsula

海洋表面的藻类通过光合作用将二氧化碳转化为有机碳。生物碳泵将这种有机碳从大气输送到深海，在那里它可以储存几十到几百年。每年运输的量与人类目前燃烧化石燃料排放的量相似。然而，目前我们无法预测这一重要过程将如何随着海洋变暖而改变。这些研究人员计划为南极半岛西部开发一个15年以上的垂直碳转移时间序列；一个高产的南极生态系统该地区也在迅速过渡到较暖的温度，导致海冰覆盖面积减少。这项工作将帮助研究人员更好地了解南极半岛西部的碳循环将如何应对气候变化。研究人员将开发海洋中任何地方碳通量的第一个大规模时间序列。这项研究还将支持一名研究生的教育和培训，并支持将南极研究的概念纳入为非科学专业学生和高级地球科学学生设计的两门本科课程。研究人员还将开发教育模块，向中小学生介绍一些重要的概念，如总初级生产力和净初级生产力、海洋和大气系统的反馈、相关性和因果关系之间的差异。这一建议的结果也将被纳入一本儿童读物《浮游生物做最奇怪的事情》，这本书的目标读者是5-7岁的孩子，旨在向他们介绍微观海洋生物令人难以置信的多样性和迷人的适应性。本研究旨在利用6年（2015-2020年）Palmer LTER项目收集的234个样本，5年的先前测量（2009-2010年，2012-2014年），以及即将到来的巡航（2021-2023年）来开发一个长达15年的WAP夏季粒子通量时间序列。238U-234不平衡方法利用粒子活性放射性同位素234相对于其母核素238U的活度变化来量化从海洋表面下沉的碳通量（在约一个月的时间尺度上）。该提案将资助为期9年（2015-2023年）的第234次邮轮分析，以及旨在调查驱动BCP年际变化过程的广泛分析。这些包括：1)物理模拟以量化平流和扩散在第234预算中的重要性，2)粒子通量的时间序列分析，以及3)Palmer LTER项目合作者测量的粒子通量与多种假定驱动因素（生物、化学、物理和气候指数）之间关系的统计建模。这种多方面的方法对于将测量与模型联系起来以及预测对气候变化的反应至关重要。它还将检验这样一种假设，即出口通量在WAP北部减少，在WAP南部增加，并在整个地区综合起来增加，这是由于海冰提前退缩和无冰区扩大。该项目还将研究碳输出与多种潜在控制因素之间的关系，包括初级生产力、藻类生物量和分类组成、生物氧饱和度、浮游动物生物量和分类组成、细菌产量、温度、冬季海冰范围、海冰退缩日期和气候模式。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Algae in the surface ocean convert carbon dioxide into organic carbon through photosynthesis. The biological carbon pump transports this organic carbon from the atmosphere to the deep ocean where it can be stored for tens to hundreds of years. Annually, the amount transported is similar to that humans are currently emitting by burning fossil fuels. However, at present we cannot predict how this important process will change with a warming ocean. These investigators plan to develop a 15+ year time-series of vertical carbon transfer for the Western Antarctic Peninsula; a highly productive Antarctic ecosystem. This region is also rapid transition to warmer temperatures leading to reduced sea ice coverage. This work will help researchers better understand how the carbon cycle in the Western Antarctic Peninsula will respond to climate change. The researchers will develop the first large-scale time-series of carbon flux anywhere in the ocean. This research will also support the education and training of a graduate student and support the integration of concepts in Antarctic research into two undergraduate courses designed for non-science majors and advanced earth science students. The researchers will also develop educational modules for introducing elementary and middle-school age students to important concepts such as gross and net primary productivity, feedbacks in the marine and atmospheric systems, and the differences between correlation and causation. Results from this proposal will also be incorporated into a children’s book, “Plankton do the Strangest Things”, that is targeted at 5-7 year olds and is designed to introduce them to the incredible diversity and fascinating adaptations of microscopic marine organisms. This research seeks to leverage 6 years (2015-2020) of 234Th samples collected on Palmer LTER program, 5 years of prior measurements (2009-2010, 2012-2014), and upcoming cruises (2021-2023) to develop a time-series of summertime particle flux in the WAP that stretches for 15 years. The 238U-234Th disequilibrium approach utilizes changes in the activity of the particle-active radio-isotope 234Th relative to its parent nuclide 238U to quantify the flux of sinking carbon out of the surface ocean (over a time-scale of ~one month). This proposal will fund 234Th analyses from nine years’ worth of cruises (2015-2023) and extensive analyses designed to investigate the processes driving inter-annual variability in the BCP. These include: 1) physical modeling to quantify the importance of advection and diffusion in the 234Th budget, 2) time-series analyses of particle flux, and 3) statistical modeling of the relationships between particle flux and multiple presumed drivers (biological, chemical, physical, and climate indices) measured by collaborators in the Palmer LTER program. This multi-faceted approach is critical for linking the measurements to models and for predicting responses to climate change. It will also test the hypothesis that export flux is decreasing in the northern WAP, increasing in the southern WAP, and increasing when integrated over the entire region as a result of earlier sea ice retreat and a larger ice-free zone. The project will also investigate relationships between carbon export and multiple potentially controlling factors including: primary productivity, algal biomass and taxonomic composition, biological oxygen saturation, zooplankton biomass and taxonomic composition, bacterial production, temperature, wintertime sea ice extent, date of sea ice retreat, and climate modes.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.