Pliocene Model Intercomparison Project (PlioMIP2) simulations using the Model for Interdisciplinary Research on Climate (MIROC4m)
Pliocene Model Intercomparison Project (PlioMIP2) simulations using the Model for Interdisciplinary Research on Climate (MIROC4m)
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DOI：
10.5194/cp-16-1523-2020
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发表时间：
2020-08-17
影响因子：
4.3
通讯作者：
Abe-Ouchi, Ayako
中科院分区：
文献类型：
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作者：
Chan, Wing-Le;Abe-Ouchi, Ayako
上新世模式相互比较项目（PlioMIP2）的第二阶段吸引了许多气候模拟小组继续努力，以更好地了解大气二氧化碳最近一次最接近当今水平的皮亚琴世中期暖期（mPWP）的气候。与第一阶段PlioMIP1一样，它是一个国际协调的倡议，允许以类似于古气候模拟比对项目（PMIP）的方式对各种模式进行系统比较。模式比对和模式资料比对目前主要集中在海洋同位素阶段KM5c （3.205 Ma）的间冰期，实验设计不仅基于新的边界条件，而且包括各种敏感性实验。在这项研究中，我们展示了使用日本CCSR、NIES和FRCGC研究所开发的MIROC4m（气候跨学科研究模式）大气-海洋耦合环流模式进行长期模式整合的结果。在二氧化碳浓度设定为百万分之400的核心实验中，与工业化前时期相比，气温上升了3.1摄氏度，其中三分之二的变暖归因于二氧化碳的增加。虽然这一升温水平低于等效PlioMIP1实验，但与PRISM3 （PRISM -上新世研究解释和天气制图）地点的替代海表温度（SST）数据的一致性略好，特别是在PlioMIP1模式数据差异较大的北大西洋北部地区。在这两个阶段的核心实验中，降水和海冰的空间变化相似，北极在夏季保持无冰状态。与代海温资料和代地表气温资料的比较表明，模式结果的极性放大较弱。与PlioMIP1不同的是，大西洋经向翻转环流（AMOC）现在比工业化前时期更强，尽管二氧化碳的增加往往会削弱它。这种较强的AMOC是PlioMIP2古地理中白令海峡封闭的结果。此外，当现今的边界条件被上新世的边界条件所取代时，AMOC强度对CO2的依赖性显著减弱。敏感性测试表明，较低的CO2值给出的全球海温总体上与PlioMIP1中提出的PRISM3海温场更为一致，而许多PRISM4站点的海温仍然过高，无法与任何模式结果相一致。另一方面，核心实验的热带太平洋海温与最近的代理数据吻合良好，这表明PRISM3海温被高估了。未来利用代理数据重建的气候将继续有助于评估模式结果。在未来使用MIROC4m进行mPWP的实验中，应考虑包括动态植被和KM5c以外所有可能的极端轨道构型的影响。
The second phase of the Pliocene Model Intercomparison Project (PlioMIP2) has attracted many climate modelling groups in its continuing efforts to better understand the climate of the mid-Piacenzian warm period (mPWP) when atmospheric CO2 was last closest to present-day levels. Like the first phase, PlioMIP1, it is an internationally coordinated initiative that allows for a systematic comparison of various models in a similar manner to the Paleoclimate Modelling Intercomparison Project (PMIP). Model intercomparison and model-data comparison now focus specifically on the interglacial at marine isotope stage KM5c (3.205 Ma), and experimental design is not only based on new boundary conditions but includes various sensitivity experiments. In this study, we present results from long-term model integrations using the MIROC4m (Model for Interdisciplinary Research on Climate) atmosphere-ocean coupled general circulation model, developed at the institutes CCSR, NIES and FRCGC in Japan. The core experiment, with CO2 levels set to 400 ppm, shows a warming of 3.1 degrees C compared to the pre-industrial period, with two-thirds of the warming being attributed to the increase in CO2. Although this level of warming is less than that in the equivalent PlioMIP1 experiment, there is slightly better agreement with proxy sea surface temperature (SST) data at PRISM3 (PRISM - Pliocene Research Interpretation and Synoptic Mapping) locations, especially in the northern North Atlantic where there were large model-data discrepancies in PlioMIP1. Similar spatial changes in precipitation and sea ice are seen and the Arctic remains ice-free in the summer in the core experiments of both phases. Comparisons with both the proxy SST data and proxy surface air temperature data from paleobotanical sites indicate a weaker polar amplification in model results. Unlike PlioMIP1, the Atlantic Meridional Overturning Circulation (AMOC) is now stronger than that of the pre-industrial period, even though increasing CO2 tends to weaken it. This stronger AMOC is a consequence of a closed Bering Strait in the PlioMIP2 paleogeography. Also, when present-day boundary conditions are replaced by those of the Pliocene, the dependency of the AMOC strength on CO2 is significantly weakened. Sensitivity tests show that lower values of CO2 give a global SST which is overall more consistent with the PRISM3 SST field presented in PlioMIP1, while SSTs at many of the PRISM4 sites are still too high to be reconciled with any of the model results. On the other hand, tropical Pacific SST in the core experiment agrees well with more recent proxy data, which suggested that PRISM3 SST there was overestimated. Future availability of climate reconstructions from proxy data will continue to help evaluate model results. The inclusion of dynamical vegetation and the effects of all possible extreme orbital configurations outside KM5c should be considered in future experiments using MIROC4m for the mPWP.