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过去2000年台湾东北部及邻近海域年际-百年尺度的气候变率
赵松1,2
学位类型硕士
导师常凤鸣
2017-05-12
学位授予单位中国科学院大学
学位授予地点北京
学位专业海洋地质
关键词台湾东北部 降水 海表温度 年际-百年尺度 过去2000年
摘要现代器测资料的时长限制了对历史时期年际-百年尺度气候变率的认识以及对未来气候变化趋势的准确预测。同时,过去2000年高分辨率气候代用资料的匮乏,导致对历史时期温度和降水的重建结果仍然存在很大的不确定性。台湾东北部及邻近海域是北半球高纬大气环流与热带太平洋大气环流的交汇区,其气候水文变化对高-低纬气候变化非常敏感。本文利用台湾东北部及邻近海域的现代器测SST(Sea Surface Temperature)资料以及MD05-2907岩心的TOC%、TOC/TN、δ13Corg、粒度和碳酸盐含量等代用指标,研究了过去2000年台湾东北部及邻近海域多种时间尺度的气候变化特征,揭示了现代暖期台湾东北部海域SST的季节与年际异常及其影响因素,重建了过去2000年台湾东北部地区降水的年际-百年变化过程及可能的控制机制,得到以下几点结论和认识:
(1)现代暖期台湾东北部海域SST季节与年际异常及其与东亚冬季风、ENSO的联系。利用NOAA的全球海表温度最优插值资料(NOAA_OI_SST_V2)、Hadley中心的全球海表温度数据(HadISST1)以及MEI(Multivariate ENSO Index)逐月指数,分析了现代全球变暖背景下台湾东北部海域SST季节与年际异常及其控制因素。季节尺度上,受东亚冬季风的影响,研究海区的冬季SST变化比夏季更为剧烈,冬季SST控制着该海域年均SST和SST季节性的变化。现代器测和古气候记录表明该现象在年际-百年尺度上可能一直存在。年际尺度上,SST异常与ENSO(El Niño-Southern Oscillation)事件存在密切的联系。在历史气候重建中区分气候变化的多尺度性和替代指标的季节性、认识历史气候对ENSO及东亚冬季风的响应特征和机制,这将有助于进一步理解现代全球气候变暖的原因。
(2)台湾东北部海洋沉积物δ13Corg记录中的休斯效应。台湾东北部MD05-2907岩心的δ13Corg记录显示,该海域海底沉积物的δ13Corg值在19世纪末之后发生了快速负偏现象,其负偏速度在此之前从未发生,该现象与人类活动导致的休斯效应密不可分。进入工业革命以来,化石能源燃烧导致大气CO2浓度急剧升高,大气CO2中碳同位素组成也发生了显著的变化。台湾东北部海洋沉积物中的休斯效应证实了人类活动对海洋沉积物的有机质碳同位素组成有不可忽视的影响。
(3)过去2000年台湾东北部降水的变化特征。对MD05-2907岩心的五种降水代用指标及其第一主成分(PC1)进行了分析,重建了过去2000年台湾东北部的降水记录。结果表明台湾东北部的降水在过去2000年中呈现明显的百年尺度变化,在罗马暖期(AD 0-300)降水较少,黑暗冷期(AD 500-800)降水较多,处于湿润状态,中世纪异常期(AD 1000-1300)降水减少,小冰期(AD 1400-1700)降水较少,处于干旱状态,进入现代暖期(AD 1850-2005)后降水增多。在年际-百年尺度上,台湾东北部的降水明显受到太阳辐射量、ENSO/PDO(Pacific Decadal Oscillation)及NAO(Northern Atlantic Oscillation)的影响,黑暗冷期由于较强的热带太平洋年代际信号(ENSO/PDO)和增强的沃克环流,台湾东北部降水较多;然而小冰期由于显著偏低的太阳辐射量和较强的北大西洋大气环流异常(NAO),台湾东北部降水显著减少。
(4)过去2000年台湾东北部降水与热带太平洋和北半球高纬大气环流的联系。台湾东北部地区处于北半球高纬大气环流与热带太平洋大气环流交汇处,该地区在黑暗冷期处于湿润状态,而且东亚-西太平洋地区的黑暗冷期降水分布格局正好符合现代沃克环流控制下的区域降水分布,表明黑暗冷期台湾东北部降水主要受热带太平洋沃克环流驱动。小冰期台湾东北部处于干旱状态,同时整个东亚-西太平洋地区小冰期的降水分布格局与NAO控制的降水分布一致,暗示着小冰期台湾东北部降水主要受北半球高纬大气环流驱动。
其他摘要
The scarcity of modern observational data hampers the understanding of inter-annual to centennial climate variability in historical period and the accurate prediction of future climate change. Besides, the sufficiently long and high temporal resolution proxies over the past two millennia are very deficient, and results of temperature and precipitation reconstructions over the past two millennia are still controversial. Northeastern Taiwan and its adjacent sea area is intersection of the circulation in northern high latitudes and the circulation in tropical Pacific. Thus, the variability of  hydroclimate in this area is very sensitive to the high- low latitudes’ climate change. In this thesis, modern observation data and TOC%, TOC/TN, δ13Corg, grain-size, carbonate content of the MD05-2907, which was collected from the sea area offshore northeastern Taiwan, were used to analyze the multiple-time-scales climate variability in the northeastern Taiwan and its adjacent sea area, and reveal the seasonal and inter-annual anomalies of sea surface temperature(SST) offshore northeastern Taiwan and its influence factors in recent warm period, and discuss the process of inter-annual to centennial precipitation changes in the northeastern Taiwan over the past two millennia and its potential control mechanisms. Main conclusions of this thesis are outlined as follows:
(1) Seasonal and inter-annual anomalies of SST offshore northeastern Taiwan and its link to East Asian Winter Monsoon(EAWM) and El Niño-Southern Oscillation (ENSO). Based on NOAA's monthly sea surface temperature data, monthly SST data from Hadley Center and monthly Multivariate ENSO Index (MEI), the seasonal and inter-annual anomalies of SST and their influencing factors offshore northeastern Taiwan under the background of modern global warming are analyzed in order to further understand modern global warming and historical climate changes. On seasonal timescales, winter SST always display greater variation range than summer SST, and its influence on the annual mean SST and SST seasonality is more serious, which could be contributed to the effects of EAWM. Modern instrumental data and paleoclimate records show that greater variabilities of winter SST than summer SST possibly also exist on the inter-annual to centennial scale. On inter-annual timescales, the SST anomalies offshore northeastern Taiwan exhibit a significant link to ENSO. It is crucial to distinguish the different multi-scales of climate change and seasonal explanations of temperature proxies when reconstructing the past temperature variation. And, insight to the responses of historical climate to ENSO and EAWM would be helpful to further understand the cause of modern global warming.
(2) The suess effect in the δ13Corg record of marine sediments offshore northeastern Taiwan. The δ13Corg record of MD05-2907 offshore northeastern Taiwan shows that the δ13Corg values of marine sediments had a rapid negative shift since the end of 19 century, and the rate of this negative shift never happened over the past two millennia. This phenomenon had a close relationship with human activities- induced suess effect. The atmospheric CO2 concentration sharply raised and the δ13C in atmospheric CO2 significantly changed since the industrial revolution as a result of combustion of fossil fuels. The suess effect in the δ13Corg record of MD05-2907 offshore northeastern Taiwan substantiates a strong influence of human activities on the organic carbon isotopic composition in marine sediments.
(3) Characteristics of precipitation changes in the northeastern Taiwan over the past two millennia. This study reconstructed precipitation changes in the northeastern Taiwan over the past two millennia using multiple proxies(TOC%, TOC/TN, δ13Corg, grain-size, carbonate content and their PC1) as precipitation indicators. Our results show that this region received more precipitation during the Dark Ages Cold Period(DACP, AD 500-800) and Current Warm Period(CWP, AD 1850-2005), and less precipitation during the Roman Warm Period(RWP, AD 0-300), Medieval Climate Anomaly(MCA, AD1000-1300) and Little Ice Age(LIA, AD 1400-1700). On the inter-annual to centennial scale, the precipitation in this region was significantly influenced by solar irradiance, ENSO/PDO and NAO. In the DACP, this region received more precipitation owing to the stronger decadal tropical Pacific variability(ENSO/PDO) and stronger Walker circulation. In the LIA, this region received significantly lessprecipitation due to the weaker solar irradiance and stronger North Atlantic circulation anomalies(NAO).
(4) The connection between precipitation in northeastern Taiwan and circulations in tropical Pacific and northern high latitudes over the past two millennia. The multiple proxies suggest that the northeastern Taiwan, which is the intersection of circulations in northern high latitudes and tropical Pacific, was wetter in the DACP, and distribution pattern of precipitation in East Asian-Western Pacific during the DACP is exactly consistent with the regional precipitation distribution controlled by modern Walker circulation, suggesting that the precipitation of northeastern Taiwan in the DACP was driven by tropical Pacific Walker circulation. However, the multiple proxies show that the northeastern Taiwan was drier in the LIA, and at the same time the distribution pattern of precipitation in East Asian-Western Pacific during the LIA is accordant with the regional precipitation distribution driven by modern NAO, indicating that the precipitation of northeastern Taiwan in the LIA was controlled by circulation in northern high latitudes.
文献类型学位论文
条目标识符http://ir.qdio.ac.cn/handle/337002/136572
专题海洋地质与环境重点实验室
作者单位1.中国科学院海洋研究所
2.中国科学院大学
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赵松. 过去2000年台湾东北部及邻近海域年际-百年尺度的气候变率[D]. 北京. 中国科学院大学,2017.
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