The timing and amplitude of Pleistocene sea-level lowstands and deglacials from U-Th chronology of Great Barrier Reef corals (Expedition 325)

根据大堡礁珊瑚 U-Th 年表得出的更新世海平面低位和冰消期的时间和幅度（第 325 次探险）

• 批准号: NE/H014136/1
• 负责人: Gideon Henderson
• 金额: $ 15.9万
• 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: 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%2FH014136%2F1
• 关键词: timing; amplitude; Pleistocene; sea; level

The study of past sea level is of great interest to researchers seeking to understand the Earth's climate. Sea level is a proxy for the amount of water locked up on the land as ice sheets. The study of sea level therefore can tell us about the past state of the climate - low sea levels reflect colder, glacial, periods in Earth history when ice sheets were larger; high sea levels reflect warmer, interglacial, intervals. Our knowledge of how modern ice sheets will respond to anthropogenic warming is not yet comprehensive. One of the most important questions surrounding ice sheet behaviour is the determination of collapse rates in response to warming, which will influence future rates of sea level rise. One way to approach this question is to examine past rates of sea level rise associated with known periods of ice sheets collapse under the non-anthropogenic conditions Quaternary glacial-interglacial transition. Fossil corals provide an indirect measurement of past sea level and therefore answering questions about how (and when) it has changed in the past. Coral only live below sea level and it is also possible to determine how far below sea level they grew. This water depth estimation is based on the types of coral we find and the other fauna and flora we find associated with them. Along with the elevation that we recovered the coral from, this water depth estimation enables us to reconstruct the height of past sea level. The time that this reconstructed sea level represents can also be measured from the coral. We use the uranium (and the product of its radioactive decay - thorium) naturally incorporated into the coral's skeleton during growth to calculate an age for the coral. This U-Th dating technique can find the age of corals from 1 to 600,000 years old. There is, however, a problem in investigating past sea levels which were much lower than present (during the most recent glacial period sea level was c. 120m below modern levels). The corals that grew when sea level was low are hard to access now sea level has risen to its modern level - they are deep underwater. To solve this problem and recover samples from deeper localities, there will be an IODP drilling expedition to the Great Barrier Reef. This Expedition will drill into fossil coral reefs that have been identified by their morphology by a previous site survey. These fossil reefs are at water depths of 44 to 123m and preserve an archive of corals from lower sea levels. It is our plan to take samples from these fossil reefs, use U-Th dating to determine their ages, and then reconstruct sea level for glacial periods while sea level was low. These estimates of low stand sea level will be used to investigate mechanisms that drive the Earth's natural climate system. The timing and rate of changes from low to high sea level are particularly important in this respect, allowing us to test any lead-lag relationship between a potential forcing (changes in the Earth's orbit around the Sun, or internal climate forcing such as atmospheric CO2 concentration) and climatic response (sea level).

寻求了解地球气候的研究人员对过去海平面的研究非常感兴趣。海平面代表了陆地上作为冰盖锁存的水量。因此，对海平面的研究可以告诉我们过去的气候状况——低海平面反映了地球历史上冰盖较大的较冷、冰川时期；高海平面反映了温暖的间冰期。我们对现代冰盖如何应对人为变暖的了解尚不全面。围绕冰盖行为的最重要问题之一是确定变暖引起的崩塌率，这将影响未来海平面上升的速度。解决这个问题的一种方法是研究在非人为条件下第四纪冰川-间冰期转变下与已知冰盖崩塌时期相关的过去海平面上升率。珊瑚化石可以间接测量过去的海平面，从而回答有关过去海平面如何（以及何时）变化的问题。珊瑚只生活在海平面以下，也可以确定它们生长在海平面以下多远。这种水深估计是基于我们发现的珊瑚类型以及我们发现的与它们相关的其他动植物群。连同我们恢复珊瑚的海拔高度，这种水深估计使我们能够重建过去海平面的高度。重建的海平面所代表的时间也可以通过珊瑚来测量。我们使用在生长过程中自然融入珊瑚骨骼中的铀（及其放射性衰变的产物 - 钍）来计算珊瑚的年龄。这种 U-Th 测年技术可以确定珊瑚的年龄从 1 到 600,000 岁。然而，调查远低于现在的过去海平面存在一个问题（在最近的冰期海平面比现代海平面低约 120m）。海平面低时生长的珊瑚很难到达，现在海平面已上升到现代水平 - 它们位于水下深处。为了解决这个问题并从更深的地方回收样本，将会对大堡礁进行 IODP 钻探考察。这次探险将钻探珊瑚礁化石，这些珊瑚礁已在之前的现场调查中通过其形态进行了识别。这些化石礁位于水深 44 至 123 m 之间，保存了较低海平面的珊瑚档案。我们计划从这些化石礁中采集样本，利用 U-Th 测年来确定它们的年龄，然后在海平面较低时重建冰期的海平面。这些对低海平面的估计将用于研究驱动地球自然气候系统的机制。从低海平面到高海平面变化的时间和速率在这方面尤其重要，使我们能够测试潜在强迫（地球绕太阳轨道的变化，或内部气候强迫，例如大气二氧化碳）之间的任何超前滞后关系。浓度）和气候响应（海平面）。

项目成果

Intensification of the meridional temperature gradient in the Great Barrier Reef following the Last Glacial Maximum.

• DOI: 10.1038/ncomms5102
• 发表时间: 2014-06-17
• 期刊: Nature communications
• 影响因子: 16.6
• 作者: Felis T;McGregor HV;Linsley BK;Tudhope AW;Gagan MK;Suzuki A;Inoue M;Thomas AL;Esat TM;Thompson WG;Tiwari M;Potts DC;Mudelsee M;Yokoyama Y;Webster JM
• 通讯作者: Webster JM

Coral Record of Younger Dryas Chronozone Warmth on the Great Barrier Reef

• DOI: 10.1029/2020pa003962
• 发表时间: 2020-12
• 期刊: Paleoceanography and Paleoclimatology
• 影响因子: 3.5
• 作者: Logan D. Brenner;B. Linsley;J. Webster;D. Potts;T. Felis;M. Gagan;M. Inoue;H. McGregor;A. Suzuki;A. Tudhope;T. Esat;Alex L. Thomas;W. Thompson;S. Fallon;M. Humblet;M. Tiwari;Y. Yokoyama

Assessing subsidence rates and paleo water-depths for Tahiti reefs using U-Th chronology of altered corals

使用蚀变珊瑚的 U-Th 年表评估塔希提岛珊瑚礁的沉降率和古水深

• DOI: 10.1016/j.margeo.2011.12.006
• 发表时间: 2012
• 期刊: Marine Geology
• 影响因子: 2.9
• 作者: Thomas A