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Reconstruction of Ocean Structure and Circulation during the Extreme Warmth of the early-middle Eocene

始新世早中期极端温暖时期海洋结构与环流的重建

基本信息

批准号：
1948164
负责人：
金额：
--
依托单位：
The Open University
依托单位国家：
英国
项目类别：
Studentship
财政年份：
2017
资助国家：
英国
起止时间：
2017 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=studentship-1948164
关键词：
Reconstruction Ocean Structure Circulation during

项目摘要

Project Highlights - Join a world-leading team striving to understand how carbon cycles around Earths surface during extreme climatic warmthLearn cutting-edge geochemical analyses for reconstructing past carbon cycling and climatic changeTest hypotheses that the size and volatility of carbon reservoirs at or near Earth's surface vary with background climate stateDetermine the deep-sea temperature response to large-scale perturbations of the carbon cycle1,2 during Eocene extreme greenhouse warmthOverview - During the early Eocene epoch, Earth witnessed its warmest temperatures of the past 90 million years, with the deep oceans up to 14degreesC warmer than today. These greenhouse climates have traditionally been regarded as uniformly warm and climatically stable, or equable. However, the last decade has seen the discovery of a number of hyperthermals (Fig. 1; rapid global warming events not dissimilar to our current anthropogenic warming) driven by large-scale releases of carbon from some as yet unknown source(s), challenging these traditional views of equability, and instead suggesting that greenhouse climates may be marked by pronounced instability.The most well-studied hyperthermals occur during a ~6 million year-long interval of progressive global warming culminating in the peak warmth of the early Eocene from 52 to 50 Myr ago1 (Fig. 1). The occurrence and relative size of these hyperthermals have been explained by a thermodynamic threshold for carbon release and a decrease in the size of carbon reservoirs during times of extreme warmth1. However, these hypotheses have proven difficult to test owing to the lack of continuous records from within the early Eocene and from the subsequent climatic cooling during the middle Eocene. This project will test hypotheses that the size and volatility of isotopically depleted carbon reservoirs should diminish during extreme global warmth1 and the corollary hypothesis that these carbon reservoirs should grow and become more volatile with subsequent cooling into the middle Eocene (an interval for which almost no high resolution records exist, Fig. 1). It will also evaluate the deep-sea temperature response2,4 to these carbon cycle-driven hyperthermals to provide valuable information on the sensitivity of Earths climate to large-scale carbon releases.This project will take advantage of new sequences from the Atlantic Ocean with the highest sedimentation rates available for the Eocene to allow an evaluation of the sensitivity of climate and the carbon cycle to Earths orbital cycles during extreme greenhouse warmth1,2,4 & subsequent global cooling.Methodology reconstruct orbital-scale variability in deep-sea temperatures and carbon cycling using high resolution isotope analyses of benthic foraminifera2,4 from expanded sequences from the equatorial Atlantic (IODP Exp. 207) and North Atlantic (IODP Exp. 342). O and C isotope (13C, 18O) analyses will be performed on the in-house Thermo-Scientific Delta+ stable isotope mass spectrometer. This project will also use ultra-high resolution XRay Fluorescence (XRF) scanning of the chemical elemental contents of sediment cores housed at Bremen to develop detailed astronomical age models. Because of the excellent preservation of planktic foraminifera, opportunity also exists to reconstruct the response of the surface ocean and thermocline across hyperthermal events and their longer-term response to the termination of the early Eocene greenhouse and onset of climatic cooling.

项目亮点-加入一个世界领先的团队，努力了解在极端气候变暖期间地球表面的碳循环如何学习尖端的地球化学分析，以重建过去的碳循环和气候变化测试假设，即地球表面或附近的碳库的大小和挥发性随背景气候状态而变化确定深海温度对碳循环大规模扰动的响应1，2始新世期间的极端温室效应概述-在始新世早期，地球见证了过去9000万年来最温暖的温度，深海温度比今天高出14摄氏度。这些温室气候传统上被认为是均匀温暖和气候稳定的，或平静的。然而，在过去的十年里，（图一;快速的全球变暖事件与我们目前的人为变暖没有什么不同）由一些未知来源的大规模碳释放驱动，挑战了这些传统的平等观点，相反，这表明温室气候可能具有明显的不稳定性。研究得最充分的高温气流发生在大约600万年-全球变暖的长时间间隔，在5200万~ 5000万年前始新世早期达到最高温度1（图1）。这些高温气流的发生和相对大小已经被解释为碳释放的热力学阈值和极端温暖时期碳库大小的减少。然而，这些假设已被证明难以测试，由于缺乏连续的记录，从早始新世和随后的气候冷却在始新世中期。该项目将测试同位素耗尽的碳储层的大小和挥发性在极端全球变暖期间应该减少的假设，以及这些碳储层应该随着随后的冷却而增长并变得更加挥发的推论假设，直到始新世中期（几乎没有高分辨率记录的时间间隔，图1）。它还将评估深海温度反应2，4这些碳循环驱动的超高温提供了宝贵的信息，地球气候的敏感性，以大-该项目将利用大西洋始新世沉积速率最高的新序列，以评估气候和碳循环对极端气候期间地球轨道周期的敏感性。方法学使用来自赤道大西洋扩展序列的底栖有孔虫的高分辨率同位素分析重建深海温度和碳循环的轨道尺度变化2，4（IODP Exp. 207)北大西洋（IODP Exp.）342）。将在内部Thermo-Scientific Delta+稳定同位素质谱仪上进行O和C同位素（13 C，18 O）分析。该项目还将使用超高分辨率X射线荧光扫描仪对存放在不莱梅的沉积物岩心的化学元素含量进行扫描，以建立详细的天文年龄模型。由于南极有孔虫保存完好，也有机会重建表层海洋和温跃层对超高温事件的反应，以及它们对始新世早期温室效应结束和气候变冷开始的长期反应。