Palaeotemperatures and carbon cycling in the southern Tethys during the Late Cretaceous

特提斯南部晚白垩世古气温和碳循环

• 批准号: NE/R012369/1
• 负责人: Stuart Robinson
• 金额: $ 6.44万
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2018
• 资助国家: 英国
• 起止时间: 2018 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FR012369%2F1
• 关键词: Palaeotemperatures; carbon; cycling; southern; Tethys

For much of Earth history atmospheric CO2 levels and average global temperatures are thought to have been much higher than at present. These periods of time are known as 'greenhouse' climates. The Cretaceous (145 to 65 million years ago) was an extreme end-member of a greenhouse climate. Then the climate was much warmer than it is today; there was little or no polar ice and sea-levels were high. In polar areas, like Alaska and Antarctica, which are cold today, dinosaurs, crocodiles and tropical plants flourished. However, what the actual temperature of the ocean was during the Cretaceous is still much debated. The Cretaceous ocean was also sensitive to changes in oxygen concentration, and, at times, became completely devoid of oxygen over widespread areas (so-called 'oceanic anoxic events' or OAEs). The relationship between climate change and these events is of great interest as they may well have been a response to brief periods of additional warming and so may have lessons for how the planet responds to future climate change over 1000s of years.Modern techniques allow us to use the chemical remains of single-celled microorganisms organisms (bacteria and archaea) found in ancient sediments to estimate what sea-surface temperatures were like in the past. To date, much of the work using this technique has focused on the Atlantic Ocean, which was relatively narrow during the Cretcaeous. Hence, it is not clear if the temperatures generated from the Atlantic are representative of the entire globe. Particularly puzzling are data from near the Falkland Islands in the South Atlantic that suggest extremely high temperatures at ~60 degrees S, which climate models have struggled to reproduce. Are these results biased or representative of conditions at 60 degrees S in the Cretaceous? Drilling during Expedition 369 will provide new cores from offshore Australia, also at ~60 degrees S, that will permit this question to be addressed. These new cores will also recover evidence for local oceanographic conditions during one of the Cretaceous OAEs and, thus, also the opportunity to reconstruct the relationship between climate and low-oxygen conditions in the southern hemisphere for the first time.

在地球历史的大部分时间里，大气中的二氧化碳水平和平均全球温度被认为比目前高得多。这些时期被称为“温室”气候。白垩纪（145至6500万年前）是温室气候的极端成员。然后气候比今天温暖得多。几乎没有或没有极地冰，海平面很高。如今，如今寒冷的阿拉斯加和南极，如阿拉斯加和南极，恐龙，鳄鱼和热带植物蓬勃发展。但是，在白垩纪期间，海洋的实际温度仍在争论。白垩纪海洋也对氧气浓度的变化也很敏感，有时会在广泛的地区完全没有氧气（所谓的“海洋缺氧事件”或OAE）。气候变化与这些事件之间的关系引起了人们的极大兴趣，因为它们很可能是对短暂的额外变暖时期的回应，因此可能会为地球如何应对1000年以上的未来气候变化而有教训。使用在古代沉积物中发现的单细胞微生物（细菌和古细菌）的化学遗迹来估计过去的海面温度是什么样的。迄今为止，使用这种技术的许多工作都集中在大西洋，该大西洋在杂乱的过程中相对较窄。因此，尚不清楚大西洋产生的温度是否代表了整个世界。特别令人困惑的是来自南大西洋福克兰群岛附近的数据表明，在〜60度S的温度极高，气候模型一直在努力繁殖。这些结果是否有偏见或代表白垩纪的60度S条件？探险369期间的钻探将提供来自澳大利亚离岸的新核心（也约为60度），这将允许解决这个问题。这些新的核心还将在白垩纪OAE中回收有关局部海洋学状况的证据，因此，也是首次重建气候与低氧条件之间关系的机会。