Glacial-cycle simulations of the Antarctic Ice Sheet with the Parallel Ice Sheet Model (PISM) - Part 2: Parameter ensemble analysis
Glacial-cycle simulations of the Antarctic Ice Sheet with the Parallel Ice Sheet Model (PISM) - Part 2: Parameter ensemble analysis
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DOI：
10.5194/tc-14-633-2020
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发表时间：
2020-02-14
期刊：
影响因子：
5.2
通讯作者：
Levermann, Anders
中科院分区：
文献类型：
--
作者：
Albrecht, Torsten;Winkelmann, Ricarda;Levermann, Anders
将平行冰盖模式（PISM）应用于最近两个冰期（约21万年）的南极冰盖，分辨率为16 km。256个模型运行的合奏进行了分析，其中四个相关的模型参数已被系统地使用全因子参数抽样变化。参数和合理的参数范围已经在配套论文中确定（Albrecht等人，2020年），并与冰动力学，气候强迫，基底滑动和床变形，并代表不同类别的模型的不确定性。该模型的得分对现代和地质数据，包括重建的接地线位置，海拔年龄数据，冰的厚度，表面速度和隆起率。为每个集合成员计算聚合得分，该集合成员测量整体模型-数据失配，包括高斯误差模型方面的测量不确定性（Briggs和Tarasov，2013）。用于分析集合模拟结果的统计方法紧密遵循Pollard et al.（2016）中描述的简单平均方法。该分析揭示了最佳拟合参数组合的集群，因此可能是相关模型和边界参数的范围，而不是单个最佳拟合参数。南极冰盖体积重建历史的集合提供了自末次冰期最高峰（LGM）以来海平面贡献的得分加权可能范围为9.4 +/-4.1米（或6.5 +/- 2.0 x 10（6）km（3）），这是大多数先前研究的上限。最后一次冰消发生在所有集合模拟中，大约12000年前，因此在融水脉冲1A（MWP 1a）之后。我们的系综分析还提供了一个参数的不确定性界限的估计，可用于PISM预测未来的海平面的贡献，从南极冰盖的现今状态。
The Parallel Ice Sheet Model (PISM) is applied to the Antarctic Ice Sheet over the last two glacial cycles (approximate to 210 000 years) with a resolution of 16 km. An ensemble of 256 model runs is analyzed in which four relevant model parameters have been systematically varied using full-factorial parameter sampling. Parameters and plausible parameter ranges have been identified in a companion paper (Albrecht et al., 2020) and are associated with ice dynamics, climatic forcing, basal sliding and bed deformation and represent distinct classes of model uncertainties. The model is scored against both modern and geologic data, including reconstructed grounding-line locations, elevation-age data, ice thickness, surface velocities and uplift rates. An aggregated score is computed for each ensemble member that measures the overall model-data misfit, including measurement uncertainty in terms of a Gaussian error model (Briggs and Tarasov, 2013). The statistical method used to analyze the ensemble simulation results follows closely the simple averaging method described in Pollard et al. (2016).This analysis reveals clusters of best-fit parameter combinations, and hence a likely range of relevant model and boundary parameters, rather than individual best-fit parameters. The ensemble of reconstructed histories of Antarctic Ice Sheet volumes provides a score-weighted likely range of sea-level contributions since the Last Glacial Maximum (LGM) of 9.4 +/- 4.1m (or 6.5 +/- 2.0 x 10(6) km(3)), which is at the upper range of most previous studies. The last deglaciation occurs in all ensemble simulations after around 12 000 years before present and hence after the meltwater pulse 1A (MWP1a). Our ensemble analysis also provides an estimate of parametric uncertainty bounds for the present-day state that can be used for PISM projections of future sea-level contributions from the Antarctic Ice Sheet.