Physical properties of sea ice cores from L sites measured on leg 1 of the MOSAiC expedition

We present sea ice temperature and salinity data from first-year ice (FYI) and second-year ice (SYI) relevant to the temporal development of sea ice permeability and brine drainage efficiency from the early growth phase in October 2019 to the onset of spring warming in May 2020. Our dataset was collected in the central Arctic Ocean during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) Expedition in 2019 to 2020. MOSAiC was an international transpolar drift expedition in which the German icebreaker RV Polarstern anchored into an ice floe to gain new insights into Arctic climate over a full annual cycle. In October 2019, RV Polarstern moored to an ice floe in the Siberian sector of the Arctic at 85 degrees north and 137 degrees east to begin the drift towards the North Pole and the Fram Strait via the Transpolar Drift Stream. The data presented here were collected during the first three legs of the expedition, so all the coring activities took place on the same floe. The end dates of legs 1, 2, and 3 were 13 December, 24 February, and 4 June, respectively. The dataset contributed to a baseline study entitled, Deciphering the properties of different Arctic ice types during the growth phase of the MOSAiC floes: Implications for future studies. The study highlights downward directed gas pathways in FYI and SYI by inferring sea ice permeability and potential brine release from several time series of temperature and salinity measurements. The physical properties presented in this paper lay the foundation for subsequent analyses on actual gas contents measured in the ice cores, as well as air-ice and ice-ocean gas fluxes. Sea ice cores were collected with a Kovacs Mark II 9 cm diameter corer. To measure ice temperatures, about 4.5 cm deep holes were drilled into the core (intervals varied by site and leg) . The temperatures were measured by a digital thermometer within minutes after the cores were retrieved. The ice cores were placed into pre-labelled plastic sleeves sealed at the bottom end. The ice cores were transported to RV Polarstern and stored in a -20 degrees Celsius freezer. Each of the cores was sub-sampled, melted at room temperature, and processed for salinity within one or two days. The practical salinity was estimated by measuring the electrical conductivity and temperature of the melted samples using a WTW Cond 3151 salinometer equipped with a Tetra-Con 325 four-electrode conductivity cell. The practical salinity represents the the salinity estimated from the electrical conductivity of the solution. The dataset also contains derived variables, including sea ice density, brine volume fraction, and the Rayleigh number.

本数据集公开了2019年10月海冰早期生长阶段至2020年5月春季升温起始阶段内，一年海冰（first-year ice, FYI）与次年海冰（second-year ice, SYI）的温度及盐度数据，该数据关联海冰渗透率与盐水排出效率的时间演化过程。
本数据集采集于2019-2020年北极气候多学科漂流观测站（Multidisciplinary drifting Observatory for the Study of Arctic Climate, MOSAiC）科考任务期间的北冰洋中部海域。
MOSAiC是一项国际跨极漂流科考任务，德国破冰船RV Polarstern锚定在一块浮冰上，以获取完整年度周期内北极气候的全新认知。2019年10月，RV Polarstern锚定在北极西伯利亚海域北纬85度、东经137度的一块浮冰上，随后借助跨极漂流海流（Transpolar Drift Stream）开始向北极点与弗拉姆海峡漂流。
本次公开的数据采集于该科考任务的前三个航段，所有冰芯取芯作业均在同一块浮冰上完成。三个航段的结束日期分别为12月13日、2月24日与6月4日。
本数据集支撑了一项题为《解析MOSAiC浮冰生长阶段不同北极冰型的特性：对后续研究的启示》的基准性研究。该研究通过多组温度与盐度实测时间序列，反演海冰渗透率与潜在盐水释放量，揭示了一年海冰与次年海冰中向下延伸的气体通道。本文公开的物理特性数据，为后续开展冰芯实测气体含量、气-冰与冰-海气体通量的相关分析奠定了基础。
海冰冰芯采用Kovacs Mark II型直径9厘米的取芯器采集。为测量冰温，研究人员在冰芯上钻取约4.5厘米深的孔（钻孔间隔因采样点与航段而异），并在冰芯取回后的数分钟内使用数字温度计完成温度测量。
采集后的冰芯被放入底端密封的预标记塑料套管中，随后运送至RV Polarstern号科考船并储存在-20℃的冷冻柜内。每根冰芯均被分样，在室温下融化，并在1至2天内完成盐度检测流程。实用盐度通过测量融化样品的电导率与温度估算得到，所用设备为搭载Tetra-Con 325四电极电导池的WTW Cond 3151型盐度计。实用盐度指通过溶液电导率反演得到的盐度值。
本数据集还包含衍生变量，涵盖海冰密度、盐水体积分数与瑞利数（Rayleigh number）。