Sea-ice biomarkers, benthic and planktonic foraminiferal abundance, and total organic carbon in Holocene sediments from outer Petermann Fjord, Greenland@en

Composite sediment core OD1507-03TC-41GC-03PC was collected at an average water depth of 976 m in outer Petermann Fjord during The Petermann 2015 Expedition to Petermann Fjord and adjacent Hall Basin in Nares Strait, northern Greenland. Previous results showed that the splice covers large parts of the Holocene, from the present to 6,900 cal yrs BP (Reilly et al. 2019). The core was sampled approximately every 5 cm for sea-ice related biomarker and total organic carbon (TOC) analyses and approximately every 10 cm for foraminiferal abundance counts. Where enough material was available, the depth of foraminiferal samples match the depth of biomarker samples. Sea-ice related biomarkers (IP25, HBI II, Brassicasterol, Cholesterol, Dinosterol, Campesterol, and β-sitosterol) where extracted using saponification (5% potassium hydroxide (KOH) in methanol (MeOH):H2O (9:1, v/v); 70°C, 1 h) followed by extraction of the non-saponifiable lipids into hexane (3 x 2 mL). After sample purification the different biomarkers were analysed on an Agilent 7890B GC fitted with an HP-5ms Ultra Inert column (30 m x 250 μm x 0.25 μm) coupled to a 5977A series mass selective detector and equipped with a Gerstel multipurpose sampler (MPS) at Aarhus University. TOC measurements and analysis of the carbon isotopic composition of the TOC were performed on 10 mg of the same sample material as for biomarker analyses. The samples were treated with 35% HCl prior to analyses, to remove inorganic carbon. The stable isotope δ13Corg and % wt TOC were measured using a continuous-flow IsoPrime IRMS coupled to an Elementar PyroCube elemental analyser at the Aarhus AMS Centre (AARAMS), Aarhus University, Denmark. Samples for foraminiferal abundance counts were wet sieved at 63 µm and counted wet, submerged in a 'storage' solution of 70 % distilled water and 30 % ethanol with baking soda to preserve fragile calcareous and agglutinated tests. A wet splitter was used when necessary to achieve a count of at least 200-300 benthic foraminifers.在针对格陵兰北部内尔斯海峡彼得曼峡湾及邻近霍尔盆地开展的2015年彼得曼科考航次中，科研人员于彼得曼峡湾外平均水深976米处采集了复合沉积物岩芯OD1507-03TC-41GC-03PC。既往研究结果表明，该拼接岩芯覆盖了全新世的大部分时段，即从现代至6900个校准年前（cal yrs BP），相关成果发表于Reilly等人2019年的研究中。该岩芯以约5厘米的间隔取样，用于海冰相关生物标志物及总有机碳（total organic carbon, TOC）分析；以约10厘米的间隔取样，用于有孔虫丰度计数。当样品材料充足时，有孔虫分析样品的取样深度与生物标志物分析样品的取样深度保持一致。海冰相关生物标志物包含IP25、HBI II、Brassicasterol、Cholesterol、Dinosterol、Campesterol及β-sitosterol，其提取流程为：先采用皂化试剂（5%氢氧化钾（potassium hydroxide, KOH）溶于甲醇（methanol, MeOH）与水的混合液，体积比9:1），于70℃下反应1小时进行皂化，随后将非皂化脂质用正己烷萃取3次，每次2毫升。样品纯化完成后，科研人员在奥胡斯大学使用搭载HP-5ms超低惰性色谱柱（30 m × 250 μm × 0.25 μm）的Agilent 7890B气相色谱仪（GC），联用5977A系列质谱选择检测器，并配备Gerstel多功能自动进样器（multipurpose sampler, MPS），对各类生物标志物进行分析。总有机碳（TOC）含量测定及TOC碳同位素组成分析，采用与生物标志物分析相同的10毫克样品开展。分析前需用35%盐酸处理样品以去除无机碳。总有机碳的稳定同位素δ¹³Corg及重量百分比TOC含量，在丹麦奥胡斯大学奥胡斯AMS中心（AARAMS），通过连续流 IsoPrime同位素比率质谱仪（isotope ratio mass spectrometer, IRMS）联用Elementar PyroCube元素分析仪完成测定。用于有孔虫丰度计数的样品，经63微米湿法筛分后进行湿样计数，样品保存于由70%蒸馏水、30%乙醇及小苏打组成的"保存液"中，以保护易碎的钙质及胶结质壳。必要时使用湿式分样器，以确保计数至少包含200~300个底栖有孔虫。