Melt pond ice sampling for nutrients, oxygen isotope compositions, and salinity during expedition PS122/5 (MOSAiC Leg 5) to the Central Arctic in August-September 2020.

Nutrient concentrations (NO3-,NO2-,NH4+,PO43-,and Si(OH)4), water oxygen isotope compositions (delta 18 O), and salinity were measured for ice samples from melt pond, and water from melt pond and lead during MOSAiC Leg 5 (August and September 2020). Ice cores for the melt pond bottom ice and melt pond surface ice were collected using an ice corer (Mark II coring system, Kovacs Enterprises, Inc., Indianapolis, USA). Also, we sampled small pieces of the pond bottom ice dislodged and floated to the surface of the melt pond by poking with a ruler. After sampling ice samples, we immediately drilled holes on ice and measured ice temperatures with a needle-type temperature sensor (Testo 110 NTC, Brandt Instruments, Inc., USA). Ice cores were segmented at 10-cm intervals. Dislodged ice was cut into 0.25 m x 0.25 m size. All ice samples were placed into ice melting bags (Smart bags PA, AAK 5L, GL Sciences Inc., Japan) and melted in the dark at +4 degree C. For the discrete water sampling from the melt ponds and leads, first, we checked the vertical structure and depth of the meltwater layer from the same hole used for the RINKO Profiler (ASTD152, JFE Advantech, Japan) by attaching a conductivity sensor (Cond 315i, WTW GmbH, Germany) to a 2-m-long ruler and inserting the ruler into the lead water until the salinity measured with the Cond 315i increased at the meltwater-seawater interface. Water was pumped up with a peristaltic pump through a 2-m-long PTFE tube (L/S Pump Tubing, Masterflex, USA) at depths corresponding to meltwater (surface), the interface between meltwater and seawater (interface), and seawater (bottom). Salinity was measured at each depth by attaching a Cond 315i conductivity sensor to the bottom of the ruler. The tube intake was likewise attached to the bottom of the ruler. Ice melt water and water samples from melt pond and lead were subsampled into a 30-mL glass, screw-cap vials for later delta 18O analysis, a 100-mL polypropylene bottles for salinity, and into 50-mL polyethylene screw-cap vials (Thermo Fisher Scientific Inc., Waltham, MA, USA) for later measurement of nutrient concentrations, after filtration through a 0.22-micro m Durapore polyvinylidene fluoride membrane filter (MILLEX GV Filter unit, Merck Millipore Ltd., Germany). Samples for delta18O were stored at room temperature (+20 degreeC). Salinity was measured with the same conductivity sensor used for the sea ice (Cond 315i, WTW GmbH, Germany). The samples for nutrient measurements were stored in a freezer (-20 degreeC) before analysis. Oxygen isotope analyses were carried out with a mass spectrometer (DELTA-S Finnigan MAT, USA) at the ISOLAB Facility at AWI Potsdam by the equilibration method (details in Meyer et al., 2000; 2022). Nutrient samples were analyzed at the AWI Nutrient Facility between January and March 2021 using a Seal Analytical AA3 continuous flow auto-analyzer, controlled by AACE software version 7.09. Best-practice procedures for the measurement of nutrients were adopted following GO-SHIP recommendations (Becker et al., 2019; Hydes et al., 2010).本数据集针对MOSAiC第5航次（2020年8月至9月）的融冰池冰样、融冰池水及冰间水道（lead）水样开展了多项指标检测，涵盖营养盐浓度（NO₃⁻、NO₂⁻、NH₄⁺、PO₄³⁻及Si(OH)₄）、水体氧同位素组成（δ¹⁸O）与盐度。用于融冰池底部冰及表层冰的冰芯（ice core）采用冰钻（ice corer，Mark II取芯系统，Kovacs Enterprises, Inc.，美国印第安纳波利斯）采集。此外，研究人员通过用标尺戳刺的方式收集脱落并漂浮至融冰池表面的小块池底冰。完成冰样采集后，研究人员即刻在冰面钻孔，并采用针型温度传感器（Testo 110 NTC，Brandt Instruments, Inc.，美国）测定冰温。冰芯以10 cm为间隔进行分段；脱落冰则被切割为0.25 m × 0.25 m的规格。所有冰样均被装入融样袋（Smart bags PA，AAK 5L，GL Sciences Inc.，日本），并于避光环境下在+4 ℃条件下融解。针对融冰池及冰间水道的离散水样采集，研究人员首先将电导传感器（Cond 315i，WTW GmbH，德国）安装于2 m长标尺上，将标尺插入冰间水道水中，直至该传感器测得的盐度在融水-海水界面处出现上升，以此确定融水层的垂直结构与深度，所用钻孔与RINKO剖面仪（ASTD152，JFE Advantech，日本）的钻孔一致。随后，通过蠕动泵（peristaltic pump）经2 m长聚四氟乙烯（PTFE）管（L/S泵管，Masterflex，美国）抽取不同深度的水样：融水层（表层）、融水-海水界面（界面层）及海水（底层）。将电导传感器安装于标尺底端，在各采样深度处测定盐度；泵管进水口同样固定于标尺底端。融冰冰样及融冰池、冰间水道的水样均需先经0.22 μm Durapore聚偏氟乙烯（PVDF）膜滤器（MILLEX GV滤器单元，Merck Millipore Ltd.，德国）过滤，随后分装至不同容器以待后续分析：30 mL玻璃螺口瓶用于δ¹⁸O分析，100 mL聚丙烯瓶用于盐度测定，50 mL聚乙烯螺口瓶（Thermo Fisher Scientific Inc.，美国马萨诸塞州沃尔瑟姆）用于营养盐浓度测定。其中，δ¹⁸O样品储存于室温（+20 ℃）环境；盐度测定采用与海冰检测相同的电导传感器（Cond 315i，WTW GmbH，德国）；营养盐检测样品则于-20 ℃冰柜中储存直至分析。氧同位素分析采用平衡法（详细步骤见Meyer等，2000；2022），于阿尔弗雷德·魏格纳研究所波茨坦分所同位素实验室（ISOLAB Facility, AWI Potsdam）使用质谱仪（DELTA-S Finnigan MAT，美国）完成。营养盐样品于2021年1月至3月间在AWI营养盐实验室完成检测，所用设备为Seal Analytical AA3连续流动自动分析仪，由AACE软件7.09版本控制。本次检测遵循GO-SHIP指南（Becker等，2019；Hydes等，2010）中的最佳实践操作流程。