Sea ice records over more than a century at an observatory facing the Okhotsk coast of Hokkaido, Japan

Time series of sea ice dates and amounts at Abashiri. The dataset contains four directories: raw_data, csv_data, codes, and figs. raw_data directory contains manually created data in an ascii format: Si_dates_1892-2025.txt: yearly first and last sea ice dates (FD_sight, FD_shore, LD_sight, and LD_shore) during 1892-2025. Total_ice_1956-2021.txt: daily total ice amounts during 1956-2021. Drift_ice_1930-2021.txt: daily drift ice amounts during 1930-2021. In Total_ice_1956-2021.txt and Drift_ice_1930-2021.txt, six monthly lines with daily values from previous December to May are described for each year; for the daily data, 0-9 denote the area fraction in quantile, * denotes full ice cover (10), + and - denote 0+ and 10-, respectively. csv_data directory contains data files in a csv format: Si_dates_1892-2025.csv, Total_ice_1956-2021.csv, and Drift_ice_1930-2021.csv. Dates are described in an ISO 8601 format ("YYYY-MM-DD"; "0000-00-00" denotes date not defined; "9999-99-99" denotes missing observation). For total/drift ice amounts, *, -, and + are converted to 10.0, 9.75, and 0.25, respectively. codes directory contains shared codes: txt2csv_dates.py converts Si_dates_1892-2025.txt to Si_dates_1982-2025.csv. txt2csv_ice.py converts ice amount files (.txt to .csv). plot_fig6a.py and plot_fig7a.py plot ice amount time series (Figs. 6a and 7a) from the csv files. cumul_dev_si_dates.F90 (or cumul_dev_si_dates.py) calculates cumulative deviation from the mean (CDM) values, which are written as cumul_dev_si_dates.dat (cumul_dev_si_dates.csv). cumul_dev_si_dates_plot.gs (plot_cumul_dev_si_dates.py) draws a plot for the CDM time series. figs directory contains figures.

网走（Abashiri）地区海冰日期与海冰覆盖量时间序列数据集。本数据集包含四个目录：raw_data、csv_data、codes及figs。
raw_data目录存放手动整理的ASCII（American Standard Code for Information Interchange）格式数据，包含三个文件：Si_dates_1892-2025.txt：1892年至2025年的年度首次与末次海冰出现日期（含FD_sight、FD_shore、LD_sight及LD_shore四项指标）；Total_ice_1956-2021.txt：1956年至2021年的每日总海冰覆盖量数据；Drift_ice_1930-2021.txt：1930年至2021年的每日流冰覆盖量数据。
在Total_ice_1956-2021.txt与Drift_ice_1930-2021.txt中，每年对应6条月度数据行，涵盖前一年12月至当年5月的每日海冰量；每日数据以0至9表示分位数对应的覆盖面积占比，*代表全冰覆盖（覆盖占比为10），+与-分别代表0+与10-的覆盖区间。
csv_data目录存放CSV（Comma-Separated Values）格式数据文件，包含Si_dates_1892-2025.csv、Total_ice_1956-2021.csv及Drift_ice_1930-2021.csv三个文件。日期采用ISO 8601格式标注（格式为"YYYY-MM-DD"；"0000-00-00"代表未定义日期，"9999-99-99"代表观测值缺失）。总海冰/流冰覆盖量数据中，*、-与+分别被转换为10.0、9.75与0.25。
codes目录存放共享代码：txt2csv_dates.py用于将Si_dates_1892-2025.txt转换为Si_dates_1982-2025.csv；txt2csv_ice.py用于将海冰量文本文件（.txt格式）转换为CSV格式文件；plot_fig6a.py与plot_fig7a.py用于从CSV数据文件绘制海冰量时间序列图（对应图6a与图7a）；cumul_dev_si_dates.F90（或cumul_dev_si_dates.py）用于计算距平累积值（Cumulative Deviation from the Mean，CDM），计算结果保存为cumul_dev_si_dates.dat（或cumul_dev_si_dates.csv）；cumul_dev_si_dates_plot.gs（或plot_cumul_dev_si_dates.py）用于绘制距平累积值时间序列图。
figs目录存放生成的各类图表。