Modeling polar bear (Ursus maritimus) snowdrift den habitat on Alaska's Beaufort Sea coast using SnowDens-3D and ArcticDEM data

Pregnant polar bears (Ursus maritimus) excavate maternal dens in seasonal snowdrifts during fall along Alaska's Beaufort Sea coast to shelter their altricial young during birth and development. With recent sea ice decreases, bears are denning more frequently on land. Each year, the weather and blowing-snow conditions control the creation of snowdrifts across the landscape, and the available snowdrift den habitat can vary widely from one year to the next, depending on the late fall and early winter air temperature, snowfall, and wind speed and direction. We implemented a physics-based, spatiotemporal, polar bear snowdrift den habitat model (SnowDens-3D) across the eastern Alaska Beaufort Sea coast (an area of approximately 17,000 km^2^). High-resolution (2.0 m) topography data were provided by the ArcticDEM, and daily meteorological forcings were provided by NASA's MERRA-2 reanalysis. A 21-year (2000–2020) SnowDens-3D simulation was performed, and model outputs were compared with 91 historical polar bear den locations. The year-specific simulations produced viable den habitat for 98% of the observed den locations. The interannual variation in den habitat area over the 21-year period increased by approximately a factor of three from the minimum year (2001; 554 km^2^) to the maximum year (2017; 1,566 km^2^). This data archive provides the key den and den-habitat datasets produced, used, and analyzed by this project.

怀孕的北极熊（Ursus maritimus）会在秋季于阿拉斯加波弗特海沿岸的季节性积雪堆中挖掘母兽巢穴，以在幼崽出生和发育阶段为其晚成幼崽提供庇护。近年来随着海冰减少，北极熊在陆地筑巢的频率显著升高。每年，区域内积雪堆的形成受天气与吹雪条件调控，而可利用的积雪堆巢穴栖息地年际差异极大，其变化取决于晚秋与早冬的气温、降雪量、风速及风向。本研究构建了一套基于物理过程的时空分布式北极熊积雪堆巢穴栖息地模型（SnowDens-3D），模拟覆盖范围为阿拉斯加波弗特海东部沿岸区域（面积约17000平方千米）。研究采用了分辨率为2.0米的ArcticDEM高分辨率地形数据，以及美国国家航空航天局（NASA）MERRA-2再分析数据集提供的每日气象强迫数据。本研究开展了2000年至2020年共21年的SnowDens-3D模拟，并将模型输出结果与91处历史北极熊巢穴位置进行比对验证。结果显示，当年的栖息地模拟可覆盖98%的观测巢穴位置。21年间，巢穴栖息地面积的年际变化幅度较最低年份（2001年，554平方千米）提升了约3倍，最高年份为2017年（1566平方千米）。本数据集档案包含了本项目中生成、使用与分析的核心巢穴及巢穴栖息地数据集。