GEOTRACES: Multi-tracer investigation of the effect of climate change on nutrient and carbon cycles in the Arctic Ocean

Our sampling program took place from August 27, 2009 through September 12, 2009. It was part of Leg 3a of the 2009 CCGS Amundsen Expedition in the Arctic Ocean (ArcticNet 0903). Sampling started in the Mackenzie River delta and continued into the Beaufort Sea (Shelf, slope and deep Canada Basin). Various measurements (temperature, salinity, nutrients, alkalinity, pH, primary production, bacterial production) and sampling (seawater, marine particles) were conducted at 10 stations. Underway measurements (temperature, salinity, trace gases) and sampling (marine particles) were also conducted along the cruise track. Sampling tools on stations were the ship's CTD/rosette (ArcticNet), a Trace-Metal CTD/rosette system (UVic / UBC) and large volume in-situ pumps (UBC). We conducted measurements and collected samples to document a suite of key physical (temperature, salinity, ice cover, light penetration), chemical (nutrients, trace metals, trace gases, radioisotopes, stable isotopes) and biological (phytoplankton and microbial assemblages, primary and microbial productivity, trace metal phytoplankton quotas) parameters in relation to proximity to the Mackenzie River delta, seafloor bathymetry and ice cover to elucidate the processes influencing phytoplankton growth and carbon cycling in the Arctic Ocean. In particular, we collected samples to study the processes which supply and remove trace metals, nutrients and carbon to and from the upper ocean, and con ducted ship-board experiments to study how biological productivity is affected by various chemical and physical conditions. Through a combination of on-board measurements, experiments and subsequent laboratory analysis, our research program aims at: (i) documenting the pathways of addition, removal and cycling of key trace elements which act as biological micronutrients or tracers of carbon and nutrient cycles in the Arctic Ocean; (ii) elucidating the potential effects of changing ice cover and river discharge on productivity, carbon sequestration and trace gas emission in the Arctic Ocean; (iii) developing chemical tracers to establish a historical sedimentary record of Arctic Ocean productivity in relation to long term natural climate change.

本次采样工作于2009年8月27日至2009年9月12日开展，属于2009年北冰洋加拿大海岸警卫队“阿蒙森”号（CCGS Amundsen）科考航次第三分航次（Leg 3a），隶属于北极网络项目0903航次（ArcticNet 0903）。采样工作始于麦肯齐河三角洲（Mackenzie River delta），延伸至波弗特海（Beaufort Sea）的陆架、陆坡与加拿大海盆深部区域。研究团队在10个站位开展了多项测量（温度、盐度、营养盐、碱度、pH、初级生产力、细菌生产力）与采样（海水、海洋颗粒物）工作，同时沿航迹开展了走航测量（温度、盐度、痕量气体）与海洋颗粒物采样。站位采样使用的设备包括科考船搭载的温盐深/罗塞塔采水系统（CTD/rosette，ArcticNet）、痕量金属专用温盐深/罗塞塔采水系统（UVic / UBC）以及大体积原位泵（UBC）。本次测量与采样旨在记录一系列关键物理参数（温度、盐度、海冰覆盖、光穿透深度）、化学参数（营养盐、痕量金属、痕量气体、放射性同位素、稳定同位素）与生物参数（浮游植物与微生物群落、初级生产力与微生物生产力、浮游植物痕量金属配额），并结合其与麦肯齐河三角洲的距离、海底地形以及海冰覆盖的关联，阐明北冰洋内影响浮游植物生长与碳循环的过程。具体而言，研究团队采集样本以探究向真上层海洋输入与移除痕量金属、营养盐及碳的过程，并开展船基实验以探究不同化学与物理条件对生物生产力的影响。通过结合船载测量、实验与后续实验室分析，本研究计划的目标为：（i）记录北冰洋内作为生物微量营养元素或碳与营养盐循环示踪剂的关键痕量元素的添加、移除与循环路径；（ii）阐明海冰覆盖变化与径流量变化对北冰洋生产力、碳封存与痕量气体排放的潜在影响；（iii）开发化学示踪剂，以建立与长期自然气候变化相关的北冰洋生产力历史沉积记录。