Expedition 363 summary
Expedition 363 summary
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DOI：
10.14379/iodp.proc.363.101.2018
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发表时间：
2018-06
期刊：
影响因子：
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通讯作者：
Y. Rosenthal;A. Holbourn;D. Kulhanek;I. Aiello;T. Babila;G. Bayon;L. Beaufort;S. C. Bova;J.-H. Chun;H. Dang;A. Drury;T. Jones;P. Eichler;A.G.S. Fernando;K. Gibson;R. G. Hatfield;D. Johnson;Y. Kumagai;Tonglin Li;B. Linsley;N. Meinicke;G. Mountain;B. Opdyke;P.N. Pearson;C. R. Poole;A. Ravelo;T. Sagawa;A. Schmitt;J. B. Wurtzel;Jian Xu;Masanobu Yamamoto;Yi Ge Zhang
中科院分区：
文献类型：
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作者：
Y. Rosenthal;A. Holbourn;D. Kulhanek;I. Aiello;T. Babila;G. Bayon;L. Beaufort;S. C. Bova;J.-H. Chun;H. Dang;A. Drury;T. Jones;P. Eichler;A.G.S. Fernando;K. Gibson;R. G. Hatfield;D. Johnson;Y. Kumagai;Tonglin Li;B. Linsley;N. Meinicke;G. Mountain;B. Opdyke;P.N. Pearson;C. R. Poole;A. Ravelo;T. Sagawa;A. Schmitt;J. B. Wurtzel;Jian Xu;Masanobu Yamamoto;Yi Ge Zhang
国际海洋发现计划第363次探险试图记录印度太平洋暖池（IPWP）气候变化（例如温度、降水和生产力）的区域表达和驱动机制，因为它与新近纪气候在千年、轨道和地质时间尺度上的演变有关。为了实现我们的目标，我们选择了地理分布广泛且海洋学和沉积环境变化的地点。第363次考察共在9个地点取芯，在875-3421m水深中共回收了6956m的沉积物，在39.6天的现场作业期间平均回收率为101.3%。两个中等沉积速率（~3-10 cm/ky）地点位于澳大利亚西北部近海，IPWP 西南最大范围，跨越中新世晚期至今。九个地点中的七个位于西太平洋暖池（WPWP）的中心，包括巴布亚新几内亚北缘的两个地点，在过去~450 ky的时间内具有非常高的沉积速率（>60 cm/ky），马努斯盆地（巴布亚新几内亚北部）的两个地点具有中等的沉积速率（~4-14 cm/ky），恢复了上新统上部到现在的序列，以及三个沉积速率较低的地点（~1-3） cm/ky），横跨中新世早期至今的欧里皮克隆起南部和北部。岩心广泛的空间分布、可变的堆积速率、特殊的生物地层和古地磁年龄限制，以及大多数优秀或非常好的有孔虫保存，将使我们能够以不同的时间分辨率追踪新近纪IPWP的演化，满足第363次探险的主要目标。具体而言，巴布亚新几内亚附近的高沉积率岩心将使我们能够更好地限制影响WPWP千年尺度变化的机制，及其与高纬度的联系。气候变化，以及在变化的平均状态气候条件下对该地区温度和降水的影响。此外，高积累率提供了研究先前温暖时期气候变化的机会，其分辨率类似于现有的全新世研究。由于恢复良好，Expedition 363站点适合于中中新世至更新世的轨道和亚轨道分辨率的详细古海洋学重建，因此将用于细化新近纪时间尺度（例如中新世晚期）内迄今约束较差的间隔的天文调谐、生物地层学、磁力地层学和同位素地层学，并重建亚洲-澳大利亚的历史轨道和构造时间尺度上的季风和印度尼西亚贯穿流。结果 Y. Rosenthal 等人。第 363 次远征在选定地点进行的高分辨率间隙水采样总结将用于重建末次盛冰期期间赤道西太平洋深水的密度剖面。对这一构造活跃地区的间隙水样本进行的额外地球化学分析将用于研究火山矿物和碳酸盐风化及其对新近纪气候演变的可能影响。简介 西太平洋暖池（WPWP）通常由 28°C 等温线定义，是印度太平洋暖池（IPWP）中最温暖的部分，横跨赤道太平洋西部水域和东印度洋（图 F1）。该地区是大气热量和湿气的主要来源，也是大气深层对流和强降雨的所在地。 WPWP海面温度（SST）的小扰动会影响哈德利环流环流和沃克环流上升翼的对流位置和强度，从而影响行星尺度的大气环流、大气加热和热带水文（Neale和Slingo，2003年；Wang和Mehta，2008年）。这些扰动还可能影响 WPWP 温跃层的热量吸收和储存，以及通过印度尼西亚通流 (ITF) 输送到印度洋。这些过程由于影响赤道太平洋的海洋-大气动态耦合，也构成了气候系统的重要反馈，从而对全球气温和大气pCO2产生强烈影响(Oppo和Rosenthal，2010)。详细的古海洋学记录，例如第 363 次远征期间发现的记录，为研究 WPWP 在不同平均状态背景条件下的行为及其对区域和全球气候的影响提供了机会。 WPWP 的季节到年际气候变化主要由与季风季节进军相关的降水量波动、热带辐合带（ITCZ）迁移以及与厄尔尼诺南方涛动（ENSO）变化相关的年际变化所主导（例如，Ropelewski 和 Halpert，1987；Halpert 和 Ropelewski，1992；Rasmusson 和Arkin，1993）（图 F2）。目前，与季风和 ENSO 系统相关的预期天气模式的偏离影响着热带地区和世界许多地区许多人的生活。例如，厄尔尼诺事件与几乎全球性的温度和降水异常指纹有关（Ropelewski 和 Halpert，1987；Rasmusson 和 Arkin，1993；Cane 和 Clement，1999）。然而，热带太平洋气候（主要是降水）对温室气体浓度上升的反应存在相当大的不确定性，因为我们对 WPWP 过去的变化了解有限，而且数据与模型的结果相互矛盾。例如，模拟赤道太平洋对温室气体强迫的响应的模型对于纬向温度梯度是否会增加或减少以及对沃克环流和热带水文循环的影响存在分歧（Forster等，2007）。这些模拟通常使用 ENSO 类比来预测未来气候；与ENSO年际变化类似，赤道太平洋平均气候状态的长期变化通常主要通过东西海温梯度的变化来评估。然而，其他对全球变暖效应的模拟表明，热带太平洋并没有因温室气体增加而变得更像厄尔尼诺或拉尼娜现象（DiNezio 等，2009）。相反，这些模拟表明了一种不同的平衡状态，即浅滩和赤道太平洋温跃层倾斜度的增加与信风的减弱有关，但纬向海温模式没有随之变化，这反对使用 ENSO 作为热带条件长期变化的模拟（DiNezio 等，2010）。反过来，温跃层结构的变化会对海洋热含量产生重大影响，从而对全球气候产生重大影响，也会对 ENSO 变化的特征产生重大影响，这一点已在末次盛冰期 (LGM) 中得到记录（Ford 等，2015）。温跃层温度/结构的变化也被认为是导致 2000 年至 2014 年地表变暖减缓的可能机制（例如，England 等人，2014 年）。这次考察的主要目标是评估图 F1 中 WPWP 内气候变化的区域表现（例如降水、温度、pCO2 和生物生产力）。 IPWP 内的年平均海面温度以及第 363 次探险期间取芯地点的位置（黄色圆圈）。黑色箭头标记了印度尼西亚贯通流的路径。红色箭头 = Leeuwin 当前。蓝色箭头 = 南赤道流。数据来源：ODV 世界海洋地图集 (https://odv.awi.de/en/data/ocean/world-ocean-atlas-2013)。
International Ocean Discovery Program Expedition 363 sought to document the regional expression and driving mechanisms of climate variability (e.g., temperature, precipitation, and productivity) in the Indo-Pacific Warm Pool (IPWP) as it relates to the evolution of Neogene climate on millennial, orbital, and geological timescales. To achieve our objectives, we selected sites with a wide geographical distribution and variable oceanographic and depositional settings. Nine sites were cored during Expedition 363, recovering a total of 6956 m of sediment in 875–3421 m water depth with an average recovery of 101.3% during 39.6 days of on-site operations. Two moderate sedimentation rate (~3–10 cm/ky) sites are located off northwestern Australia at the southwestern maximum extent of the IPWP and span the late Miocene to present. Seven of the nine sites are situated at the heart of the Western Pacific Warm Pool (WPWP), including two sites on the northern margin of Papua New Guinea with very high sedimentation rates (>60 cm/ky) spanning the past ~450 ky, two sites in the Manus Basin (north of Papua New Guinea) with moderate sedimentation rates (~4–14 cm/ky) recovering upper Pliocene to present sequences, and three sites with low sedimentation rates (~1–3 cm/ky) on the southern and northern Eauripik Rise spanning the early Miocene to present. The wide spatial distribution of the cores, variable accumulation rates, exceptional biostratigraphic and paleomagnetic age constraints, and mostly excellent or very good foraminifer preservation will allow us to trace the evolution of the IPWP through the Neogene at different temporal resolutions, meeting the primary objectives of Expedition 363. Specifically, the high–sedimentation rate cores off Papua New Guinea will allow us to better constrain mechanisms influencing millennial-scale variability in the WPWP, their links to high-latitude climate variability, and implications for temperature and precipitation in this region under variable mean-state climate conditions. Furthermore, the high accumulation rates offer the opportunity to study climate variability during previous warm periods at a resolution similar to that of existing studies of the Holocene. With excellent recovery, Expedition 363 sites are suitable for detailed paleoceanographic reconstructions at orbital and suborbital resolution from the middle Miocene to Pleistocene and thus will be used to refine the astronomical tuning, biostratigraphy, magnetostratigraphy, and isotope stratigraphy of hitherto poorly constrained intervals within the Neogene timescale (e.g., the late Miocene) and to reconstruct the history of the Asian-Australian monsoon and the Indonesian Throughflow on orbital and tectonic timescales. Results Y. Rosenthal et al. Expedition 363 summary from high-resolution interstitial water sampling at selected sites will be used to reconstruct density profiles of the western equatorial Pacific deep water during the Last Glacial Maximum. Additional geochemical analyses of interstitial water samples in this tectonically active region will be used to investigate volcanogenic mineral and carbonate weathering and their possible implications for the evolution of Neogene climate. Introduction The Western Pacific Warm Pool (WPWP), often defined by the 28°C isotherm, is the warmest part of the Indo-Pacific Warm Pool (IPWP), which spans the western waters of the equatorial Pacific and eastern Indian Ocean (Figure F1). The region is a major source of heat and moisture to the atmosphere and a location of deep atmospheric convection and heavy rainfall. Small perturbations in the sea-surface temperature (SST) of the WPWP influence the location and strength of convection in the rising limbs of the Hadley and Walker cells, affecting planetary-scale atmospheric circulation, atmospheric heating, and tropical hydrology (Neale and Slingo, 2003; Wang and Mehta, 2008). These perturbations may also influence heat uptake and storage in the WPWP thermocline, as well as transport to the Indian Ocean through the Indonesian Throughflow (ITF). These processes also constitute important feedbacks in the climate system due to their influence on the dynamic ocean-atmosphere coupling in the equatorial Pacific, thereby exerting a strong influence on global temperatures and atmospheric pCO2 (Oppo and Rosenthal, 2010). Detailed paleoceanographic records, such as those recovered during Expedition 363, offer the opportunity to study the behavior of the WPWP under different mean-state background conditions and its effects on both regional and global climate. Seasonal to interannual climate variations in the WPWP are dominated by fluctuations in precipitation associated with the seasonal march of the monsoons, migration of the Intertropical Convergence Zone (ITCZ), and interannual changes associated with variability of the El Niño Southern Oscillation (ENSO) (e.g., Ropelewski and Halpert, 1987; Halpert and Ropelewski, 1992; Rasmusson and Arkin, 1993) (Figure F2). At present, departures from expected weather patterns associated with the monsoon and ENSO systems impact the lives of many people in the tropics and many regions around the world. For example, El Niño events are associated with a nearly global fingerprint of temperature and precipitation anomalies (Ropelewski and Halpert, 1987; Rasmusson and Arkin, 1993; Cane and Clement, 1999). However, considerable uncertainty exists regarding the response of the tropical Pacific climate, primarily precipitation, to rising greenhouse gas concentrations because of our limited understanding of the past variability of the WPWP and conflicting results from data compared to models. For example, models simulating the response of the equatorial Pacific Ocean to greenhouse gas forcing disagree about whether the zonal temperature gradient will increase or decrease and what the implications will be for the Walker circulation and the hydrologic cycle in the tropics (Forster et al., 2007). These simulations typically use an ENSO analogy to predict future climate; in a similar way to interannual ENSO variability, long-term changes in the mean climate state of the equatorial Pacific are often evaluated primarily as changes in the east–west SST gradient. However, other simulations of global warming effects suggest that the tropical Pacific does not become more El Niñoor La Niña-like in response to increased greenhouse gases (DiNezio et al., 2009). Instead, these simulations suggest a different equilibrium state, whereby shoaling and increased tilt of the equatorial Pacific thermocline is associated with weakening of the trade winds without a concomitant change in the zonal SST pattern, which argues against using ENSO as an analog for long-term changes in tropical conditions (DiNezio et al., 2010). In turn, changes in the structure of the thermocline can have a major effect on the ocean heat content, and thus global climate, and also on the character of ENSO variability, which has been documented for the Last Glacial Maximum (LGM) (Ford et al., 2015). Changes in thermocline temperature/structure have also been suggested as a possible mechanism responsible for the slowdown in surface warming from ~2000 to 2014 (e.g., England et al., 2014). A primary goal of this expedition was to assess the regional expression of climate variability (e.g., precipitation, temperature, pCO2, and biological productivity) within the WPWP in the context Figure F1. Mean annual sea-surface temperature within the IPWP with locations of sites cored during Expedition 363 (yellow circles). Black arrows mark the path of the Indonesian Throughflow. Red arrow = Leeuwin Current. Blue arrow = South Equatorial Current. Data source: ODV World Ocean Atlas (https://odv.awi.de/en/data/ocean/world-ocean-atlas-2013).