Modeling the role of the last ice age for the present and future sea-level contribution from Antarctica

模拟最后一个冰河时代对南极洲当前和未来海平面贡献的作用

• 批准号: 238027547
• 负责人: Professor Dr. Anders Levermann
• 金额: --
• 依托单位: Potsdam-Institut für Klimafolgenforschung (PIK)
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 财政年份: 2013
• 资助国家: 德国
• 起止时间: 2012-12-31 至 2016-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/238027547?language=en
• 关键词: Modeling; role; last; ice; age

The project “Modeling the role of the last ice age for the present and future sea-level contribution from Antarctica” will encompass the numerical simulation of at least four glacial cycles of the Antarctic sheet-shelf system using the Parallel Ice Sheet Model (PISM). The objective of the research plan is to determine the role of the past development of the Antarctic Ice Sheet for its sea-level contribution of the past and future century. To this end we investigate the influence of past climate evolution, especially the last deglaciation, on its present dynamic state: The ongoing changes in terms of mass balance, disregarding anthropogenic climate change, during the 20th and 21st centuries are influenced by the history of the advance and retreat of the ice during the last glacial cycles. Instead of aiming at a best-guess simulation, we will work on providing an ensemble of model simulations that incorporates uncertainties from climate boundary conditions and internal process-modeling and ice parameter choices. Apart from answering the above mentioned research question concerning the influence of the history of the ice sheet on its present day dynamics, we will also take an important step towards a new generation of projections of future ice discharge from Antarctica: It is important to know how much sea-level contribution, if any, is not caused by anthropogenic climate change.The program encompasses the development and short-term testing of physical improvements to the model that are needed in order to perform four glacial cycles (4GC) simulations and to provide a comprehensive ensemble. The currently implemented climate boundary conditions, both for the upper surface of the ice sheet and the underside of the ice shelves in contact with the ocean, will be examined and expanded to be suitable for 4GC-simulations. Process-based model components, concerning the numerical representation of the transition zone between ice sheet and ice shelf will be evaluated and improved. High-resolution nested simulation approaches will be developed for PISM in order to better resolve these crucial zones in order the further close the gap between finite differences models like PISM using shallow approximations of the stress balance and higher-order models. Sensitivity tests within 4GC-simulations will shed light on how the above mentioned new methods, climate boundary conditions in general and internal model parameters, influence the 4GC-simulation and ultimately the modeled present day state. An ensemble selection process will take place, excluding those parameter and climate-boundary combinations that are not conform to available geologic data for the past and observations of the present day state of the Antarctic ice sheet. This can be thought of as a “blind selection” of the dynamic present-day state of the ice sheet. By that “dynamic state” we mean the responsiveness of the modeled ice sheet to external forcing, which can vary drastically among a set of modeled ice sheets that are quite similar with respect to vertical and horizontal ice extent.We will therefore provide an uncertainty range for Antarctica´s sea-level contribution in the 20th and 21th century caused by the ice-sheets history.

“模拟最后一个冰河期对南极洲目前和今后海平面变化的作用”项目将包括利用平行冰盖模型对南极冰盖-大陆架系统的至少四个冰川周期进行数值模拟。研究计划的目标是确定南极冰盖过去的发展对过去和未来世纪海平面的影响。为此，我们调查过去的气候演变，特别是最后一次冰消期，对目前的动态状态的影响：在物质平衡方面的持续变化，忽略人为气候变化，在20世纪和21世纪的影响，在最后一次冰期循环的冰的前进和后退的历史。而不是针对最佳猜测模拟，我们将致力于提供一个模型模拟的集合，其中包括气候边界条件和内部过程建模和冰参数选择的不确定性。除了回答上述关于冰盖历史对其当今动态的影响的研究问题外，我们还将朝着新一代南极洲未来冰排放预测迈出重要一步：重要的是要知道有多少海平面的贡献，如果有的话，不是由人为气候变化引起的。该计划包括发展和短期-对模型进行物理改进的长期测试，以便进行四个冰川循环（4GC）模拟并提供全面的集合。目前实施的气候边界条件，无论是冰盖的上表面和与海洋接触的冰架的底面，将进行检查和扩展，以适合4GC模拟。将评价和改进以过程为基础的模型组成部分，涉及冰盖和冰架之间过渡区的数字表示。将为PISM开发高分辨率嵌套模拟方法，以便更好地解决这些关键区域，以便进一步缩小PISM等有限差分模型之间的差距，使用应力平衡和高阶模型的浅层近似。4GC模拟中的敏感性测试将揭示上述新方法、一般气候边界条件和内部模型参数如何影响4GC模拟并最终影响模拟的当前状态。将进行总体选择过程，排除那些不符合过去现有地质数据和南极冰盖现状观测的参数和气候边界组合。这可以被认为是对冰盖动态现状的“盲目选择”。所谓“动态”，我们指的是模拟冰盖对外部强迫的响应，这可能会在一组模拟冰盖之间发生巨大变化，这些冰盖在垂直和水平冰范围方面非常相似。因此，我们将为冰盖历史造成的南极洲海平面在20和21世纪世纪的贡献提供一个不确定性范围。