Cosmogenic Nuclide-Based Boundary Conditions for Numerical Ice Sheet Models: A Simulation of the Fennoscandian Ice Sheet through A Glacial Cycle

[1384886]冰盖模式在气候研究中成功应用的主要限制来自于模式校准的有限野外数据。这可能导致对冰盖开始、生长和衰减的模拟不现实，并且在重建冰盖基础边界条件和表面剖面时存在不确定性。例如，在某些地点，边线和风化差异被解释为以前冰盖高度的指标，而斯堪的纳维亚冰川侵蚀模式的制图和基于宇宙形成核素的评估表明，这些特征在某些情况下代表湿（暖）基侵蚀冰和干（冷）基非侵蚀冰之间的内部热边界。这种解释上的巨大差异对重建的冰盖厚度、动态和范围以及基于冰盖重建的古气候解释产生了深远的影响。在斯堪的纳维亚半岛，在多次冰盖覆盖事件的已知范围内发现了未被侵蚀的地区，这一事实表明，这些未被侵蚀的地区在整个冰盖的形成、生长和衰变过程中，一定是作为未被侵蚀（可能是冻土）的斑块幸存下来的。这一观测结果为冰盖模型的基础热条件提供了一个重要的新约束，并表明基于野外的地貌学和冰川地质学可以提供约束类型，以加强冰盖模型的工作。在过去的三年里，斯德哥尔摩大学的首席研究员Arjen Stroeven和澳大利亚国立大学的Derek Fabel在美国国家科学基金会（NSF）和瑞典国家科学基金会（NSF）的支持下，共同研究了芬诺斯坎德冰原（FIS）核心区瑞典北部山区的消冰年代学、侵蚀模式和景观保护。研究结果为下一步工作奠定了基础，他们将在末次冰期旋回的关键时期（海洋同位素阶段[MIS] 5d或5b，初始阶段，MIS 2，末次盛冰期（LGM）阶段，和末次盛冰期，）重建FIS厚度、范围和动态（包括总冰体积引起的海平面变化）。MIS 1，消冰期)。通过冰期循环，FIS的古地形（高度）将使用最先进的热力学数值冰盖模型进行模拟，其关键边界条件受到基于宇宙成因核素的冰下条件重建和均衡模型的约束。这项工作的团队已经扩大到包括爱丁堡大学的艾伦·哈伯德，澳大利亚国立大学的库尔特·兰贝克和斯德哥尔摩大学的Jens-Ove Naslund，他们在冰川学和均衡建模领域。新的重建可能具有广泛的意义，无论是对欧洲冰盖和古气候的重建，还是对海平面低水位（地球上陆地总冰的代表）证据的评估，以及鼓励对全球其他主要冰盖的形成、生长和衰减的动态进行重新评估。

0138486HarborMajor limitations in the successful use of ice sheet models for climate research arise from limited field data for model calibration. This may result in unrealistic simulations of ice sheet inception, growth, and decay, and uncertainties in reconstructing ice sheet basal boundary conditions and surface profiles. For example, trimlines and weathering differences have been interpreted as indicators of former ice sheet height in some locations, while mapping and cosmogenic nuclide-based assessment of glacial erosion patterns in Scandinavia suggest that such features in some cases represent internal thermal boundaries between wet-(warm) based erosive ice and dry-(cold) based non-erosive ice. Such radical differences in interpretation have profound impacts on reconstructed ice sheet thickness, dynamics, and extent, and paleoclimates interpretations derived from ice sheet reconstructions. The fact that uneroded areas have been identified in Scandinavia within the known limits of multiple ice sheet overriding events indicates that these uneroded areas must have survived as non-eroding (presumably frozen-bed) patches throughout ice sheet inception, growth, and decay. This observation represents a significant new constraint on basal thermal conditions for ice sheet models and is indicative of the types of constraints that field-based geomorphology and glacial geology can provide to enhance ice sheet modeling efforts. Over the past three years the Principal Investigator Arjen Stroeven, Stockholm University, and Derek Fabel, Australian National University, have worked collaboratively with support from National Science Foundation (NSF) and Swedish NSF to examine deglaciation chronology and patterns of erosion and landscape preservation in the northern Swedish mountains, the core area of the Fennoscandian Ice Sheet (FIS). The results provide the groundwork for proposing the next phase of this work, in which they will reconstruct FIS thickness, extent, and dynamics (including total ice volume-induced sea level change) over critical periods of the last glacial cycle (Marine Isotope Stage [MIS] 5d or 5b, inception phase; MIS 2, Last Glacial Maximum (LGM) phase, and; MIS 1, deglaciation phase). The paleotopography (height) of the FIS through a glacial cycle will be simulated using a state-of-the-art thermomechanical numerical ice sheet model, with key boundary conditions constrained both by cosmogenic nuclide-based reconstructions of subglacial conditions, and by an isostatic model. The team for this work has been expanded to include Alun Hubbard, University of Edinburgh, Kurt Lambeck, Australian National University, and Jens-Ove Naslund, Stockholm University, in the areas of glaciological and isostatic modeling. New reconstructions will likely have wide significance, both to European ice sheet and paleoclimate reconstructions and evaluations of evidence of sea level low-stands (proxy for total land-based ice on earth) and also in encouraging re-evaluation of the dynamics of inception, growth, and decay of other major ice sheets worldwide.