Modeling the Spatio-Temporal Variability in Subsurface Thermal Regimes Across a Low-Relief Polygonal Tundra Landscape: Modeling Archive

Vast carbon stocks stored in permafrost soils of Arctic tundra are under risk of release to atmosphere under warming climate. Ice--wedge polygons in the low-gradient polygonal tundra create a complex mosaic of microtopographic features. The microtopography plays a critical role in regulating the fine scale variability in thermal and hydrological regimes in the polygonal tundra landscape underlain by continuous permafrost. Modeling of thermal regimes of this sensitive ecosystem is essential for understanding the landscape behaviour under current as well as changing climate. We present here an end-to-end effort for high resolution numerical modeling of thermal hydrology at real-world field sites, utilizing the best available data to characterize and parameterize the models. We develop approaches to model the thermal hydrology of polygonal tundra and apply them at four study sites at Barrow, Alaska spanning across low to transitional to high-centered polygon and representative of broad polygonal tundra landscape. A multi--phase subsurface thermal hydrology model (PFLOTRAN) was developed and applied to study the thermal regimes at four sites. Using high resolution LiDAR DEM, microtopographic features of the landscape were characterized and represented in the high resolution model mesh. Best available soil data from field observations and literature was utilized to represent the complex heterogeneous subsurface in the numerical model. This data collection provides the complete set of input files, forcing data sets and computational meshes for simulations using PFLOTRAN for four sites at Barrow Environmental Observatory. It also documents the complete computational workflow for this modeling study to allow verification, reproducibility and follow up studies. This dataset includes two zipped files and one .pdf file. The Next-Generation Ecosystem Experiments: Arctic (NGEE Arctic), was a research effort to reduce uncertainty in Earth System Models by developing a predictive understanding of carbon-rich Arctic ecosystems and feedbacks to climate. NGEE Arctic was supported by the Department of Energy's Office of Biological and Environmental Research. The NGEE Arctic project had two field research sites: 1) located within the Arctic polygonal tundra coastal region on the Barrow Environmental Observatory (BEO) and the North Slope near Utqiagvik (Barrow), Alaska and 2) multiple areas on the discontinuous permafrost region of the Seward Peninsula north of Nome, Alaska. Through observations, experiments, and synthesis with existing datasets, NGEE Arctic provided an enhanced knowledge base for multi-scale modeling and contributed to improved process representation at global pan-Arctic scales within the Department of Energy's Earth system Model (the Energy Exascale Earth System Model, or E3SM), and specifically within the E3SM Land Model component (ELM).

北极苔原永久冻土土壤中储存着海量碳库，在气候变暖的背景下存在向大气释放的风险。低坡度多边形冻土中的冰楔多边形，可形成复杂的微地形镶嵌格局。在连续永久冻土覆盖的多边形冻土景观中，这类微地形对调控热水文状况的精细尺度变异性发挥着关键作用。对这一敏感生态系统的热状况开展建模研究，对于理解当前及气候变化情境下的景观动态至关重要。

本研究开展了一套端到端的高分辨率数值建模工作，针对真实野外场地的热水文过程进行模拟，采用现有最优数据对模型进行特征表征与参数化。我们开发了适用于多边形冻土热水文过程的建模方法，并将其应用于阿拉斯加巴罗地区的四个研究站点：这些站点涵盖了低中心、过渡型到高中心的各类冰楔多边形，能够代表广泛分布的多边形冻土景观。我们研发了多相地下热水文模型（PFLOTRAN），并将其用于这四个站点的热状况研究。通过高分辨率激光雷达（LiDAR）数字高程模型（DEM），我们对景观的微地形特征进行了表征，并将其纳入高分辨率模型网格。同时，我们利用野外观测与文献中的最优土壤数据，在数值模型中刻画了复杂的非均质地下介质。

本数据集提供了在巴罗环境观测站四个站点开展PFLOTRAN模拟所需的全部输入文件、强迫数据集与计算网格，同时完整记录了本次建模研究的计算流程，以保障研究可验证、可重复，并可为后续研究提供支撑。本数据集包含两个压缩文件与一个PDF文件。

下一代生态系统实验：北极（Next-Generation Ecosystem Experiments: Arctic, NGEE Arctic）项目旨在通过深化对富碳北极生态系统的预测性理解及其对气候的反馈机制，降低地球系统模型的不确定性。该项目由美国能源部生物与环境研究办公室资助。NGEE Arctic设有两个野外研究站点：1）位于阿拉斯加乌特恰维克（Utqiagvik，旧称巴罗）附近北坡的巴罗环境观测站（Barrow Environmental Observatory, BEO）北极多边形冻土沿海区域；2）位于阿拉斯加诺姆以北苏华德半岛的不连续永久冻土区多个区域。通过观测、实验以及与现有数据集的综合分析，NGEE Arctic为多尺度建模提供了增强的知识库，并助力美国能源部地球系统模型——能源极端尺度地球系统模型（Energy Exascale Earth System Model, E3SM），尤其是其陆面模型组件（ELM），在泛北极全球尺度上改进了过程表征。