Sea ice Trace Metals sampling during the SIPEX II voyage of the Aurora Australis, 2012

Antarctic sea ice is known to store key micronutrients, such as iron, as well as a suite of less studied trace metals in winter which are rapidly released in spring. This stimulates ice edge phytoplankton blooms which drive the biological removal of climatically-important gases like carbon dioxide. By linking the distribution of iron and other trace elements to the cycles of carbon, nitrogen and silicon in the sea ice zone in spring, this project will identify their biogeochemical roles in the seasonal ice zone and how this may change with predicted climate-driven perturbations.All sampling bottles and equipment were decontaminated using trace metal clean techniques. Care was taken at each site to select level ice with homogeneous snow thickness. At all the stations, the same sampling procedure has been used :Firstly, snow was collected using acid cleaned low density polyethylene (LDPE) shovels and transferred into acid-cleaned 3.8 l LDPE containers (Nalgene). Snow collected is analysed for temperature, salinity, nutrients, unfiltered and filtered metals. Snow thickness is recorded with a ruler.Ice cores were collected using a noncontaminating, electropolished, stainless steel sea ice corer (140 mm internal diameter, Lichtert Industry, Belgium) driven by an electric power drill. Ice cores were collected about 10 cm away from each other to minimise between-core heterogeneity.A first core is dedicated to the temperature, salinity and Chlorophyll a (Chla). To record temperature, a temperature probe (Testo, plus or minus 0.1 degrees C accuracy) was inserted in holes freshly drilled along the core every 5 to 10 cm, depending on its length. Bulk salinity was measured for melted ice sections and for brines using a YSI incorporated Model 30 conductivity meter. Chla is processed on board using a 10 AU fluorometer (turner Designs, Sunnyvale California). All those data, read from the screens instruments are directly inserted in the spreadsheet 'Notebook SIPEX-2' in the '4051 Lannuzel' folder. The total length of this core is cut in sections of 7 cm. The second core is dedicated to the POC/PON (Particulate Organic Carbon/ Particulate Organic Nitrogen), DOC (Dissolved Organic Carbon) and nutrients. Six sections of 7 cm are taken from this core. The six sections were chosen so that two top, two intermediate and two basal sections. Two cores are taken for the trace metal analysis. Those cores are directly triple bagged in plastic bags (the inner one is milli-Q washed) and frozen at -20 degrees C until analysis at the laboratory.Brine samples were collected by drainage from "sack holes". Brines and under ice seawater (~1 m deep) were collected in 1 l Nalgene LDPE bottles using an insulated peristaltic pump and acid cleaned C-flex tubing (Cole Palmer). All samples were then transported to the ship as quickly as possible to prevent further freezing. Those samples are used to analyse unfiltered and filtered metals, Chla, POC/PON, nutrients and DOC. Filtration for filtered metals is done on board using a peristaltic pump and a 0.2 micron cartridge filter.All the unfiltered and filtered metals collected are acidified (2 ppt HCl seastar) and stored at room temperature until analysis at the laboratory.Nutrients, DOC and filters for POC/PON are frozen at -20 degrees C until analysis. Chla filtrations and analysis are done on board.Auxiliary cores/brines/underlying seawater were also collected for Caitlin Gionfriddo ([e-mail], Uni. Melbourne) for total mercury (Hg) and methyl-Hg.Also included in this dataset are typed field notes.

众所周知，南极海冰在冬季会储存包括铁在内的关键微量营养元素，以及一系列尚未被充分研究的痕量金属，这些物质会在春季快速释放。此举会激发冰缘浮游植物水华 (phytoplankton blooms)，进而推动二氧化碳等对气候具有重要影响的气体的生物清除过程。本项目将春季海冰区中铁与其他痕量元素的分布，与碳、氮、硅的生物地球化学循环相结合，旨在明确这些物质在季节性海冰区中的生物地球化学作用，以及它们将如何随预测的气候扰动发生变化。所有采样瓶与设备均采用痕量金属洁净技术进行去污处理。每个采样点均选取雪厚均一的平整海冰。所有站位均采用统一采样流程：首先，使用经酸清洗的低密度聚乙烯 (low density polyethylene, LDPE) 铲收集积雪，并转移至经酸清洗的3.8升LDPE容器（Nalgene）中。所收集的积雪将被分析其温度、盐度、营养盐含量，以及未过滤与过滤后的金属浓度。积雪厚度通过直尺记录。海冰岩心采用无污染、电解抛光不锈钢海冰取芯器（内径140毫米，比利时Lichtert Industry公司生产）采集，取芯器由电动钻机驱动。冰芯采集间距约为10厘米，以最大程度降低岩心间的异质性。第一根冰芯用于测定温度、盐度与叶绿素a (Chlorophyll a, Chla)。为记录温度，沿冰芯每隔5至10厘米（取决于冰芯总长度）在新钻的孔中插入温度探头（Testo，精度±0.1℃）。对于融化的冰样与卤水，采用YSI公司Model 30型电导仪测定其总体盐度。叶绿素a浓度在船上通过10 AU荧光计（Turner Designs，美国加利福尼亚州森尼韦尔市）进行处理。所有从仪器显示屏读取的数据均直接录入"4051 Lannuzel"文件夹下的电子表格"Notebook SIPEX-2"中。该冰芯的总长度被切割为7厘米的分段。第二根冰芯用于测定颗粒有机碳/颗粒有机氮 (Particulate Organic Carbon/ Particulate Organic Nitrogen, POC/PON)、溶解有机碳 (Dissolved Organic Carbon, DOC) 与营养盐。从该冰芯中截取6段7厘米的样品，选取原则为表层、中层与底层样品各2段。另外采集两根冰芯用于痕量金属分析。这些冰芯直接用三重塑料袋封装（内层塑料袋经密理博纯水 (milli-Q) 清洗），并在-20℃下冷冻保存，直至实验室分析。卤水样品通过"袋状孔"引流采集。卤水与冰下海水（采集深度约1米）采用隔热蠕动泵与经酸清洗的C-flex管路（Cole Palmer公司生产）收集至1升Nalgene LDPE瓶中。所有样品需尽快转运至科考船，以防止再次结冰。这些样品将用于分析未过滤与过滤后的金属浓度、叶绿素a、颗粒有机碳/颗粒有机氮、营养盐与溶解有机碳。过滤金属样品的操作在船上通过蠕动泵与0.2微米筒式过滤器完成。所有采集的未过滤与过滤金属样品均采用2 ppt浓度的Seastar品牌盐酸进行酸化处理，并在室温下保存直至实验室分析。营养盐、溶解有机碳样品与用于颗粒有机碳/颗粒有机氮分析的滤膜均在-20℃下冷冻保存直至分析。叶绿素a的过滤与分析操作均在船上完成。此外还为凯特琳·金弗里多 (Caitlin Gionfriddo)（电子邮箱：[e-mail]，墨尔本大学）采集了辅助冰芯、卤水与下层海水样品，用于总汞 (total mercury, Hg) 与甲基汞 (methyl-Hg) 分析。本数据集还包含打印版野外记录。