Coupled change in global climate and the carbon cycle across the Eocene-Oligocene transition: New insight from the Pacific Ocean, IODP Exp 320

全球气候与始新世-渐新世过渡时期碳循环的耦合变化：来自太平洋的新见解，IODP Exp 320

• 批准号: NE/I006168/1
• 负责人: Paul Wilson
• 金额: $ 33.84万
• 依托单位: University of Southampton
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2010
• 资助国家: 英国
• 起止时间: 2010 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FI006168%2F1
• 关键词: Coupled; change; global; climate; carbon

Carbon dioxide, CO2, is a powerful greenhouse gas and its concentration in Earth's atmosphere has increased by around 35% since the start of the Industrial Revolution (in a ca. 250 yr time period) to a level that is higher than at any time in the past 800 thousand years as measured in air bubbles from ice cores. If man-made (anthropogenic) CO2 emissions to the atmosphere follow projected rates, then by 2100, concentrations will reach values not seen on Earth since the Palaeogene epoch (ca. 65-23 million years ago, Ma). These startling observations mean that we must improve our understanding of Palaeogene climate. Arguably, the pivotal Palaeogene climate event occurred around 34 Ma when, the first large Antarctic ice sheets were rapidly established across the Eocene/Oligocene transition, EOT. Results of ice-sheet-climate model experiments indicate that this event might represent a 'tipping point' response to slow decline in atmospheric CO2 levels (many orders of magnitude slower than the rate of anthropogenic increase). The results of our own previous research show that the growth of ice sheets on Antarctica across the EOT occurred in lock-step with a deepening (by more than a kilometer) in the calcite compensation depth (CCD) in the tropical Pacific Ocean. The CCD is the depth at which calcium carbonate sediments are dissolved in the ocean and can be thought of as 'an ocean acidity indicator'. Ocean de-acidification across the EOT demonstrates that the switch from a largely non-glaciated 'greenhouse' world to one with large ice sheets on Antarctica was closely associated with a big disruption in the global carbon cycle. What linked ice sheet growth on Antarctica to the acidity of the tropical deep Pacific Ocean? Previously we have suggested that growth of ice sheets on the Antarctic continent causes sea level to fall, killing off the large expanse of calcium carbonate (CaCO3)-secreting reefs that previously flourished on the continental shelves. This would have caused an imbalance between the inputs (from rivers) and outputs (sediment burial) of dissolved CaCO3 to the global ocean requiring a deepening in the CCD until balance was restored through increased CaCO3 sedimentation in the deep ocean. In numerical 'box model' tests, this 'shelf-to-basin CaCO3 switching' mechanism performed better than competing mechanisms proposed to explain EOT events. Yet shelf-basin-switching has been called into question on a number of grounds. For example, it has been suggested that the carbon cycle changes across the EOT were driven by changes in surface ocean productivity. In 2009, Integrated Ocean Drilling Program Expedition 320 drilled a series of holes across the Pacific Ocean on ocean crust of different age. The EOT was captured in four new sites at successively shallower depths. Our plan is to compare the chemistry of this EOT 'age-depth transect' of new sites with our existing records from a latitudinal transect of sites drilled previously in the region (ODP Leg 199). Hypotheses for the EOT that invoke CCD deepening in response to changes in global deep ocean carbonate chemistry (eg. shelf-basin-switching) should produce a pattern of sedimentation that is a simple function of depth whereas we predict the imprint of latitude from changes in surface productivity. One key to our work is the potential for unprecedented age-control in our target sediments. Other key aspects are the availability of two new sites that are richer in CaCO3 and calcareous microfossils across the EOT (specifically the latest Eocene) than the best previously available Pacific site (ODP 1218) and new geochemical techniques for determining changes in carbonate chemistry of the ancient oceans.

二氧化碳二氧化碳是一种强大的温室气体，自工业革命开始以来，其在地球大气中的集中度增加了35％左右（在大约250年的时间内）至比过去80万年前的任何时间，因为在冰芯中以气泡中的气泡中测量了过去的80万年。如果对大气的人为（人为）二氧化碳排放遵循预计的速率，则到2100年，浓度将达到自古代时代以来（大约65-2300万年前，马萨诸塞州）以来未见的值。这些令人震惊的观察结果意味着我们必须提高对古生物气候的理解。可以说，关键的古代气候事件发生在34 Ma左右，当时第一个大型南极冰盖迅速在始新世/渐新世过渡（EOT）中迅速建立。冰原气候模型实验的结果表明，此事件可能代表了对大气中二氧化碳水平缓慢下降的“临界点”响应（许多数量级比人为增加的速度慢得多）。我们自己先前的研究的结果表明，在锁定状态下，南极洲的冰盖生长发生在热带太平洋的方解石补偿深度（CCD）中，加深了（超过一公里）。 CCD是将碳酸钙沉积物溶解在海洋中的深度，可以被认为是“海洋酸度指标”。跨EOT的海洋去酸化表明，从很大程度上非酸化的“温室”世界转变为南极上的大型冰盖的转变与全球碳循环的大破坏密切相关。是什么将南极上的冰盖生长与热带深太平洋的酸度联系起来？以前，我们已经提出，南极大陆上的冰盖生长会导致海平面下降，杀死了碳酸钙钙（CACO3）的大面积 - 销售以前在大陆架子上繁荣的珊瑚礁。这将导致输入（来自河流）与溶解的CACO3的输入（从河流埋葬）到全球海洋之间的失衡，需要加深CCD，直到通过在深海中增加的CACO3沉积物恢复平衡为止。在数值“框模型”测试中，此“货架至巴蛋白CACO3切换”机制的表现要好于提议解释EOT事件的竞争机制。然而，在许多理由上，货架 - 巴斯转换受到了质疑。例如，已经提出，EOT的碳循环变化是由表面海洋生产率变化驱动的。 2009年，综合海洋钻井计划Expedition 320在太平洋上钻了一系列的孔，这些洞是不同年龄的海洋地壳。该EOT在较浅的深度连续四个新地点被捕获。我们的计划是将新站点的EOT“深度横断面”的化学反应与我们从以前在该地区钻探的地点的纬度样品的现有记录进行比较（ODP Leg 199）。响应全球深海碳酸盐化学变化（例如，架子 - 巴斯蛋白转换）的变化而引起CCD加深的EOT的假设应产生一种沉积模式，这是深度的简单功能，而我们可以预测表面生产力的变化而预测纬度的痕迹。我们工作的关键之一是我们目标沉积物中前所未有的年龄控制的潜力。其他关键方面是，与以前最好的先前可用的太平洋站点（ODP 1218）和新的地球化学技术相比，在EOT（特别是最新的始新世）中更丰富的CACO3和钙质微化石和钙质微化石的可用性以及用于确定古老海洋碳酸化学的变化。

项目成果

A record of Neogene seawater d<sup>11</sup>B reconstructed from paired d<sup>11</sup>B analyses on benthic and planktic foraminifera

新近纪海水d记录

• DOI: 10.5194/cp-2015-177
• 发表时间: 2016
• 作者: Greenop R

Calibration of the boron isotope proxy in the planktonic foraminifera Globigerinoides ruber for use in palaeo-CO2 reconstruction

• DOI: 10.1016/j.epsl.2012.12.029
• 发表时间: 2013-02-15
• 期刊: EARTH AND PLANETARY SCIENCE LETTERS
• 影响因子: 5.3
• 作者: Henehan, Michael J.;Rae, James W. B.;Elliott, Tim
• 通讯作者: Elliott, Tim

Estimating the impact of the cryptic degassing of Large Igneous Provinces: A mid-Miocene case-study

• DOI: 10.1016/j.epsl.2014.06.040
• 发表时间: 2014-10-01
• 期刊: EARTH AND PLANETARY SCIENCE LETTERS
• 影响因子: 5.3
• 作者: Armstrong McKay, David I.;Tyrrell, Toby;Foster, Gavin L.
• 通讯作者: Foster, Gavin L.

Global carbon cycle perturbation across the Eocene-Oligocene climate transition

• DOI: 10.1002/2015pa002818
• 发表时间: 2016-02
• 期刊: Paleoceanography
• 作者: D. A. McKay;T. Tyrrell;P. Wilson

Geochemical response of the mid-depth Northeast Atlantic Ocean to freshwater input during Heinrich events 1 to 4

海因里希事件1至4期间东北大西洋中深度对淡水输入的地球化学响应

• DOI: 10.1016/j.quascirev.2016.08.035
• 发表时间: 2016
• 期刊: Quaternary Science Reviews
• 影响因子: 4
• 作者: Crocker A