A biomarker goldmine in Wilkes Land, Antarctica: nuggets from the Eocene Greenhouse (BIGWIG).

公众概要：综合海洋钻探计划（IODP）第318次南极威尔克斯陆缘考察的目的是破译南极洲的长期气候和环境：从冰期前的温室世界，通过南极东部冰盖（EAIS）的多次生长和崩塌的历史以及相关的海平面变化。探险队使用专业钻探船“乔迪斯决议号”来回收深海沉积物。南极大陆的岩石和土壤受到持续的侵蚀，这些沉积物沉积在深海的接受环境中，在那里，沉积层一层接一层的沉积层可以不受干扰地连续沉积。这些沉积物是过去环境和海洋学变化的信息库。在IODP 318考察队回收的沉积物岩心中发现了丰富的有机分子化石（生物标志物）和有机壁微化石。某些化合物（尤其是脂类）具有很强的抗腐性，因此在生产生物体过期后，生物标记物被保存在沉积物中。这些生物标记物可以被提取、测量并用于重建参数的变化，如海洋和陆地温度在数千年至数百万年间的变化；使我们能够定量地重建过去气候和环境的变化。在IODP 318考察中，这些化石最丰富的是可追溯到南极冰盖出现之前的温室时期（始新世早期，距今4800万年至5500万年）的岩心。生物标志物化石和有机壁微化石的存在为研究始新世早期冰期前南极提供了一个独特的机会，这一时期的特征是大气二氧化碳含量高，全球平均气温达到长期最高值。此外，叠加在这种长期变暖之上的是一系列相对较快（不到几万年）的极端变暖事件，即所谓的超热现象。我们将结合最先进的分子有机生物标志物技术和孢粉学（有机壁微化石）分析，以高分辨率重建陆地和海洋温度、大气二氧化碳、碳循环变化、陆地蒸发/降水、海洋生产力和盐度的变化。对这一温室期和高温事件的研究是至关重要的，因为自工业化以来，大气中二氧化碳的浓度比过去200万年中的任何时候都要高。在同一时期，由于人类活动，其他温室气体（温室气体：甲烷、氧化亚氮等）的浓度显著增加。如果排放继续不减，到2035年，大气中的二氧化碳含量将比工业化前时期增加一倍（二氧化碳当量为550 ppm）。换句话说，从大气的角度来说，我们正迅速回到始新世时期，那时地球比现在更温暖，行星冰量比现在少得多，海平面比现在高得多。我们请求资助，这将允许PI James Bendle协调项目团队，并领导多代理，分子生物标志物分析。如果英国科学要利用IODP 318暂停期（2011年6月到期）的竞争优势，那么来自2010年4月NERC UK-IODP呼吁的资金对于促进我们提出的分析和结果至关重要。

Summary for General Public: The aim of Integrated Ocean Drilling Programme (IODP) expedition 318, to the Wilkes Land margin of Antarctica, is to decipher the long-term climate and environmental Antarctica: from the pre-glacial Greenhouse world, through the history of multiple growth and collapse of the East Antarctic Ice Sheet (EAIS) and related sea-level changes. The expedition used the specialist drill ship, the Joides Resolution, to recover deep sea sediments. There has been a continuous process of erosion of rocks and soils from the Antarctic continent and deposition of these sediments in the receptive environment of the deep ocean, where layer upon layer of sediment can be laid down in undisturbed succession. These sediments are a repository of information on past environmental and oceanographic changes. Abundant organic molecular fossils (biomarkers) and organic walled microfossils were found in the sediment cores recovered by the IODP 318 expedition. Certain compounds (especially lipids) are quite resistant to decay, so after the producer organisms expire, the biomarkers are preserved in sediments. These biomarkers can be extracted, measured and used to reconstruct changes in parameters such ocean and land temperature over thousands to millions of years; allowing us to quantitatively reconstruct past changes in climate and environments. In expedition IODP 318 these fossils are most abundant is cores dating from the Greenhouse period before ice-sheets were present on Antarctica (the Early Eocene Period, 48 to 55 million years before the present). The presence of the biomarker fossils and organic walled microfossils offers a unique opportunity to study the pre-glacial Antarctic during the critical Early Eocene period, which was characterised by high atmospheric CO2 and mean global temperatures that reached a long-term maximum. Moreover, superimposed on this long-term warmth were a series of relatively rapid (less than a few tens of thousands of years), extreme warm events known as hyperthermals. We will combine state-of-the-art molecular organic biomarker techniques and palynological (organic-walled microfossils) analyses to reconstruct, at high-resolution, changes in land and sea temperatures, atmospheric CO2, carbon cycle changes, terrestrial evaporation/precipitation, marine productivity and salinity. Study of this Greenhouse period and the hyperthermal events is crucial because, since industrialisation, atmospheric concentrations of CO2 have grown to be higher now than at any time in the last 2 million years (Myr). Over the same period, concentrations of other greenhouse gasses (GHGs: methane, nitrous oxides etc) have increased markedly due to human activity. If emissions continue unabated, by 2035 we will have effectively doubled the amount of carbon dioxide in the atmosphere (550 ppm CO2e), compared to the preindustrial period. In other words, atmospherically speaking, we are rapidly heading back towards the Eocene period during which the planet was warmer, planetary ice volumes were much lower and sea-levels much higher than present. We request funding which will allow the PI, James Bendle to co-ordinate project team and lead in the multi-proxy, molecular biomarker analyses. If UK science is to take competitive advantage of the IODP 318 moratorium period (which expires in June 2011), then funding from the April 2010 NERC UK-IODP call is critical to facilitate our proposed analyses and outcomes.