IODP Expedition 351, Philippine Sea: Neogene NW Pacific Deep Water Circulation

IODP 351 探险队，菲律宾海：新近纪西北太平洋深水环流

• 批准号: NE/M017370/1
• 负责人: Sev Kender
• 金额: $ 3.87万
• 依托单位: University of Nottingham
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2014
• 资助国家: 英国
• 起止时间: 2014 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FM017370%2F1
• 关键词: IODP; Expedition; 351; Philippine; Sea

Deep thermohaline circulation of the world's oceans, specifically in relation to meridional (from polar to polar regions) overturning circulation, is closely linked to long and short term climate changes in the geological past. As circulation pathways, flow speeds, and upwelling of the oceans changes, the amount of CO2 (which is held in ocean water) in contact with the atmosphere changes, and heat (also held in ocean water) transport between high and low latitudes changes. Climate both impacts deep ocean circulation (e.g. growth of sea ice in the Quaternary), and is impacted by oceanic changes (e.g. glacial CO2 storage in the deep Southern Ocean; transport of warm water through the Isthmus of Panama). Despite its importance, however, the history of deep (greater than about 4 km water depth) Pacific Ocean circulation, the most extensive of the world's oceans, has not yet been constrained for the Neogene (the last 26 million years). Modern Pacific circulation is composed largely of lower salinity surface water flowing broadly southwards, driven by Circumpolar Deep Water from the south (greater than about 4 km water depth) flowing northwards. This important Circumpolar Deep Water is composed of a mixture of Antarctic Bottom Water and North Atlantic Deep Water, formed by cold dense sinking high latitude water masses outside of the Pacific. Circumpolar Deep Water fills the deep Pacific, and is a source of the shallower (~1-3 km water depth) return southern flow Pacific Central Water. The Neogene (~23 Ma to Recent) has seen large changes in global climate, from a mid Miocene warm world (before 14 million years ago), to the 'ice-house' of Northern Hemisphere Glaciation (after 3 million years ago). Understanding the strength of the Pacific meridional overturning circulation in a warmer world is yet to be resolved, with some studies suggesting enhanced circulation and others reduced in the Eocene (around 50 million years ago). Several studies have attempted to reconstruct Pacific deep circulation over the Miocene (23 to 5 million yeas ago), but have focussed on intermediate depth Pacific Central Water largely due to available material. Some studies suggest there was a waning influence of Atlantic waters as the Isthmus of Panama closed through the Neogene. Others suggest the mid Miocene Pacific had a slower circulation, but with a similar southern source to today. If true, we would expect bottom waters in the North Pacific to have a greater Circumpolar Deep Water 'signature' after 14 Ma. This hypothesis can be tested with new International Ocean Discovery Program cores from the Philippine Sea (NW Pacific), that were monitoring deep waters (4.5 km water depth) throughout the Neogene, and have an excellent record of fish teeth with which to measure Nd isotopes as a water mass tracer proxy. Southern Ocean water Nd isotopes have a more negative value (-8) than Pacific Central Water (-3.5), and the Southern Ocean's influence on Circumpolar Deep Water is shown in modern Nd isotope profiles from the NW Pacific.

世界各大洋的深层温盐环流，特别是与纬向（从两极到两极）翻转环流有关的环流，与过去地质时期的长期和短期气候变化密切相关。随着环流路径、流速和海洋上涌的变化，与大气接触的二氧化碳（海水中的）量也会发生变化，高纬度和低纬度之间的热量（海水中的）传输也会发生变化。气候既影响深海环流（如第四纪海冰的增长），又受到海洋变化的影响（如南大洋深处的冰川二氧化碳储存;通过巴拿马地峡的温水输送）。然而，尽管其重要性，深（大于约4公里水深）太平洋环流的历史，世界上最广泛的海洋，尚未被限制为新近纪（过去2600万年）。现代太平洋环流主要由低盐度的表面水组成，这些水广泛地向南流动，由从南方（水深大于约4公里）向北流动的绕极深层水驱动。这个重要的环极深水是由南极底层水和北大西洋深水的混合物组成的，由太平洋以外的寒冷密集下沉的高纬度水团形成。环极深水充满太平洋深处，是较浅（约1-3 km水深）的回流南太平洋中央水的来源。新近纪（~23 Ma至最近）见证了全球气候的巨大变化，从中新世中期的温暖世界（1400万年前）到北方半球冰川的“冰库”（300万年前）。了解太平洋纬向翻转环流在一个温暖的世界中的强度还有待解决，一些研究表明，在始新世（大约5000万年前），环流增强，另一些则减少。有几项研究试图重建中新世（2300万年至500万年前）的太平洋深层环流，但主要集中在中间深度的太平洋中央水，这主要是由于可用的材料。一些研究表明，随着巴拿马地峡在新近纪关闭，大西洋沃茨的影响逐渐减弱。另一些人认为，中新世中期的太平洋环流较慢，但与今天的南方来源相似。如果这是真的，我们预计北太平洋的底部沃茨在14 Ma后会有更大的环极深水“特征”。这一假设可以用菲律宾海（西北太平洋）的新的国际海洋发现计划岩心进行检验，这些岩心在整个新近纪监测深水沃茨（水深4.5 km），并有一个很好的鱼牙记录，可以用来测量Nd同位素作为水体示踪剂代理。南大洋水Nd同位素的负值（-8）大于太平洋中部水的负值（-3.5），南大洋对环极深水的影响在西北太平洋现代Nd同位素剖面上得到了反映。

项目成果

Neodymium Evidence for Increased Circumpolar Deep Water Flow to the North Pacific During the Middle Miocene Climate Transition

• DOI: 10.1029/2017pa003309
• 发表时间: 2018-07
• 期刊: Paleoceanography and Paleoclimatology
• 影响因子: 3.5
• 作者: S. Kender;K. Bogus;T. Cobb;D. J. Thomas

Reply to 'Unclear causes for subduction'

• DOI: 10.1038/ngeo2704
• 发表时间: 2016-05
• 期刊: Nature Geoscience
• 影响因子: 18.3
• 作者: R. Arculus;O. Ishizuka;K. Bogus;M. Gurnis;R. Hickey‐Vargas;M. Aljahdali;A. N. Bandini-Maeder;A. Barth;P. Brandl;L. Drab;R. M. Guerra;M. Hamada;F. Jiang;K. Kanayama;S. Kender;Y. Kusano;He Li;L. Loudin;M. Maffione;K. Marsaglia;A. McCarthy;S. Meffre;A. Morris;M. Neuhaus;I. Savov;C. Sena;F. Tepley;C. Land;G. Yogodzinski;Zhaohui Zhang

A record of spontaneous subduction initiation in the Izu-Bonin-Mariana arc

• DOI: 10.1038/ngeo2515
• 发表时间: 2015-09-01
• 期刊: NATURE GEOSCIENCE
• 影响因子: 18.3
• 作者: Arculus, Richard J.;Ishizuka, Osamu;Zhang, Zhaohui
• 通讯作者: Zhang, Zhaohui