Free-Drifting Icebergs as Proliferating Dispersion Sites of Iron Enrichment, Organic Carbon Production and Export in the Southern Ocean

Abstract: Atmospheric warming has been associated with retreating glaciers, disintegrating ice shelves, and the increasing prevalence of icebergs in the Southern Ocean over the last decade. Our preliminary study of two icebergs in the NW Weddell Sea, an area of high iceberg concentration, showed significant delivery of terrestrial material accompanied by significant enhancement of phytoplankton and zooplankton/micronekton abundance, and primary production surrounding the icebergs. We hypothesize that nutrient enrichment by free-drifting icebergs will increase primary production and sedimentation of organic carbon, thus increasing the draw-down and sequestration of CO2 in the Southern Ocean and impacting the global carbon cycle. Our research addresses the following questions: 1) What is the relationship between the physical dynamics of free-drifting icebergs and the Fe and nutrient distributions of the surrounding water column? 2) What is the relationship between Fe and nutrient distributions associated with free-drifting icebergs and the organic carbon dynamics of the ice-attached and surrounding pelagic communities (microbes, zooplankton, micronekton)? 3) What is impact on the export flux of particulate organic carbon from the mixed layer? An interdisciplinary approach is proposed to examine iceberg structure and dynamics, biogeochemical processes, and carbon cycling that includes measurement of trace element, nutrient and radionuclide distributions; organic carbon dynamics mediated by microbial, ice-attached and zooplankton communities; and particulate organic carbon export fluxes. Results from this project will further our understanding of the relationship between climate change and carbon sequestration in the Southern Ocean. Our findings will be incorporated into the Antarctic Research division of the Ocean Exploration Center (OEC) as part of the SIOExplorer: Digital Library Project. The OEC allows users to access content, which is classified to one of four levels: entry (grade K-6), student (grade 6-12), college, and research. Graduate students, undergraduates, teachers, and volunteers are important participants in the proposed field and laboratory work. For the K-12 level, a professional writer of children's books will participate in cruises to produce an account of the expedition and a daily interactive website.

摘要：过去十年间，大气变暖与冰川消退、冰架崩解以及南大洋（Southern Ocean）中山浮冰愈发频发的现象密切相关。我们针对冰山高度聚集的威德尔海西北部（NW Weddell Sea）区域的两座冰山开展了初步研究，结果显示，冰山周边区域存在大量陆源物质输入，同时浮游植物、浮游动物/小型浮游生物（micronekton）的丰度显著提升，初级生产力亦随之增强。我们提出假说：自由漂流的冰山通过富集营养盐，将提升初级生产力与有机碳沉降，进而增强南大洋对二氧化碳的吸收与封存，并对全球碳循环产生影响。
本研究旨在解答以下三个核心问题：1）自由漂流冰山的物理动力学过程，与其周边水柱中铁元素与营养盐的分布存在何种关联？2）与自由漂流冰山相关的铁元素与营养盐分布，与附着于冰体及周边远洋群落（微生物、浮游动物、小型浮游生物）的有机碳动力学存在何种关联？3）其对混合层颗粒有机碳（particulate organic carbon）的输出通量产生何种影响？
本研究拟采用跨学科研究方法，对冰山结构与动力学过程、生物地球化学过程以及碳循环展开系统研究，具体研究内容包括：痕量元素、营养盐与放射性核素的分布测定；由微生物、冰附着群落与浮游动物群落介导的有机碳动力学研究；以及颗粒有机碳的输出通量测定。
本项目的研究成果将深化我们对气候变化与南大洋碳封存之间关联的认知。我们的研究发现将被纳入海洋探索中心（Ocean Exploration Center, OEC）的南极研究分部，作为SIOExplorer：数字图书馆项目的组成部分。该中心的内容分为四个分级：入门级（K-6年级）、学生级（6-12年级）、大学级以及科研级。研究生、本科生、教师与志愿者将成为本次野外与实验室工作的重要参与主体。针对K-12学段，将邀请儿童读物专业撰稿人随科考航次随行，记录科考历程并搭建每日互动式网站。