全新世北半球典型冷事件的模拟研究

Characteristics of Holocene cold events in the Northern Hemisphere from the TraCE-21 ka model simulation

全新世冷事件期间的气候格局及其成因是过去气候变化研究的热点问题.利用基于通用气候系统模式开展的TraCE-21ka气候模拟试验资料,在定义和提取典型冷事件的基础上,分析了全强迫试验模拟的全新世北半球多次冷事件的规模及冷事件发生时温度与降水的空间特征,并结合全强迫试验中使用的4个外强迫序列(淡水注入、轨道强迫、大气温室气体、大陆冰盖)及其对应的单因子敏感性试验,初步探讨了部分典型冷事件的成因.结果表明: TraCE-21ka模拟的冷事件年份与重建/集成序列的冷事件年份对应较好,模式较好地模拟出了全新世北半球的冷事件;全新世期间,北半球共发生了 10 次典型冷事件( 9. 7 ka B. P.、 8. 3 ka B. P.、 7. 3 ka B. P.、6. 2 ka B. P.、 5. 2 ka B. P.、 4. 2 ka B. P.、 3. 4 ka B. P.、 2. 1 ka B. P.、 1. 0 ka B. P.和 0. 2 ka B. P.);每次冷事件发生时,北半球大范围降温和变干,温度变化呈现明显的纬度地带性差异,中高纬地区降温最显著,低纬10°N附近降水减少最显著;在 8. 3 ka B. P.、 7. 3 ka B. P.、 6. 2 ka B. P.、 5. 2 ka B. P.、 4. 2 ka B. P.、 3. 4 ka B. P.、 2. 1 ka B. P.和1. 0 ka B. P.共8次冷事件中,北半球温度和降水的空间变化较为相似,北大西洋经圈翻转流( Atlantic Meridional Overturning Circulation,简称 AMOC)变弱导致了冷事件,格陵兰岛南部的北大西洋海域降温和变干尤为显著;9. 7 ka B. P.和3. 4 ka B. P.的冷事件可能与轨道强迫有关,淡水注入造成了8. 3 ka B. P.和7. 3 ka B. P.的冷事件, 0. 2 ka B. P.冷事件可能与大气温室气体波动有关.地球系统内部变率对于冷事件的发生可能也有一定影响.

The climate pattern and cause during the Holocene cold event periods is a hot issue in past climate change research.Transient Climate Evolution of the last 21000 years simulated by the CCSM 3 is used to define and choose the typical cold events in all forcing experiment in the Northern Hemisphere during the Holocene.Magnitudes and the spatial characteristics of temperature and precipitation anomalies in each typical cold event are analyzed.By comparing four external forcings (Orbital Forcing, Atmospheric Greenhouse Gases, Ice Sheets and Paleogeography and Meltwater Forcing) used in all forcing simulation and corresponding 4 single forcing sensitive experiments, causes of cold events are also discussed.The results show that the cold events simulated by TraCE-21ka match well with those found in reconstructions or integrated temperature data sets, TraCE-21ka can reproduce the cold events during Holocene properly.During the Holocene, 10 typical cold events occurred at 9.7 ka B.P., 8.3 ka B.P., 7.3 ka B.P., 6.2 ka B.P., 5.2 ka B.P., 4.2 ka B.P., 3.4 ka B.P., 2.1 ka B.P., 1.0 ka B.P.and 0.2 ka B.P.in the Northern Hemisphere in simulation.Holocene cold event periods are characterized by temperature decrease and precipitation reduction over the Northern Hemisphere, and the temperature decreases significantly in the middle and high latitudes of the Northern Hemisphere while precipitation reduces most around 10°N, the temperature shows distinct latitude-belt distribution characteristics.The spatial characteristics of temperature and precipitation are similar in 8 events from 8.3 ka B.P.to 1.0 ka B.P., with significant decrease in temperature and precipitation from North Atlantic Ocean to the south of Greenland.Cold events at 9.7 ka B.P.and 3.4 ka B.P.may be related to the orbital forcing, Meltwater Forcing caused cold events at 8.3 ka B.P.and 7.3 ka B.P., and cold events at 0.2 ka B.P.may be related to the Atmospheric Greenhouse Gases.The internal variability of the climate system may have some effect on cold events.