Collaborative Research: Sea level induced hydrothermal activity as a trigger for glacial terminations

合作研究：海平面引起的热液活动作为冰川终止的触发因素

• 批准号: 1558641
• 负责人: David Lund
• 金额: $ 28万
• 依托单位: University of Connecticut
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-07-01 至 2018-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1558641&HistoricalAwards=false
• 关键词: Collaborative; Research; Sea; level; induced

The last million years of earth's history are characterized the growth and decay of continental ice sheets that covered large portions of North America and Europe. Growth of the ice sheets transferred water from the ocean to the continents and caused sea level to drop by nearly 400 feet. While it has long been known that the pacing of the ice ages is related to changes in the Earth's orbit around the sun, the triggering mechanism for the end ice ages, known as terminations, has yet to be fully explained. Lowering of sea level releases pressure on the global mid-ocean ridge system, a nearly continuous chain of submerged volcanoes that span 30,000 miles of the sea floor. The pressure release should drive enhanced submarine volcanism, which may in turn influence climate by introducing heat and carbon dioxide into the deep ocean. The aim of the proposed work is to assess magmatism along mid-ocean ridges in the eastern South Pacific using geologic archives of volcanic activity. Sediment cores retrieved from the East Pacific Rise (EPR) and Pacific Antarctic Ridge (PAR) will be used to assess hydrothermal plume activity near the ridge crest. Hydrothermal plumes are created through superheating of cold deep ocean water by hot oceanic crust, which is itself heated by magma. Thus, sedimentary archives can be used to assess glacial-interglacial changes in magmatism and test whether enhanced submarine volcanism occurs during glacial terminations. The proposed work will focus on a series of cores from 10°S to 40°S along the EPR and PAR. Preliminary oxygen isotope data indicates that sediments in this region accumulate at a rate sufficient to constrain glacial-interglacial timescales. Hydrothermal activity will be inferred by estimating the flux of Fe, Mn, V, and As to ridge crest sediments. All fluxes will be constrained using the 3He normalization technique. A finding of coherent variations in metal flux at multiple sites would indicate there were regional changes in magmatic activity. Additionally, the timing of anomalous metal fluxes will be compared with climate proxies to assess the feasibility that mid-ocean ridge magmatism acts as a negative feedback on ice sheet size. Finally, a petrologic model will be used to simulate the impact of sea level variations on CO2-bearing melt production in the upper mantle. Simulations of carbon flux from the global mid-ocean ridge system will be used to assess whether variations in carbon flux could have feasibly driven atmospheric CO2 on glacial-interglacial timescales. The proposed work could transform our understanding of the climate system by constraining the interactions between the fluid and solid earth on glacial-interglacial timescales. The broader educational impacts of the proposed work includes the participation of a postdoctoral scholar and two undergraduates at the University of Connecticut, plus an additional undergraduate at Caltech.

地球历史的最后一百万年的特点是覆盖北美和欧洲大部分地区的大陆冰盖的生长和腐烂。 冰盖的增长将海水从海洋转移到大陆，导致海平面下降近 400 英尺。 虽然人们早就知道冰河时代的节奏与地球绕太阳轨道的变化有关，但冰河时代结束（称为终止）的触发机制尚未得到充分解释。 海平面下降释放了全球洋中脊系统的压力，该系统是一条几乎连续的水下火山链，横跨海底 30,000 英里。 压力释放会加剧海底火山活动，从而可能通过将热量和二氧化碳引入深海来影响气候。 拟议工作的目的是利用火山活动的地质档案评估南太平洋东部洋中脊沿线的岩浆活动。 从东太平洋海隆 (EPR) 和太平洋南极海脊 (PAR) 取回的沉积岩芯将用于评估海脊顶部附近的热液羽流活动。 热液羽流是通过热洋地壳使寒冷的深海水过热而产生的，而洋地壳本身又被岩浆加热。 因此，沉积档案可用于评估冰期-间冰期岩浆作用的变化，并测试冰期终止期间是否发生增强的海底火山活动。拟议的工作将重点关注 EPR 和 PAR 沿线 10°S 至 40°S 的一系列核心。 初步的氧同位素数据表明，该地区沉积物的积累速度足以限制冰期-间冰期的时间尺度。 通过估计山脊沉积物中铁、锰、钒和砷的通量来推断热液活动。 所有通量都将使用 3He 归一化技术进行约束。 在多个地点发现金属通量的一致变化将表明岩浆活动存在区域性变化。 此外，异常金属通量的时间将与气候指标进行比较，以评估洋中脊岩浆作用对冰盖尺寸负反馈的可行性。 最后，岩石学模型将用于模拟海平面变化对上地幔含二氧化碳熔体生产的影响。 对全球大洋中脊系统碳通量的模拟将用于评估碳通量的变化是否可以在冰期-间冰期时间尺度上驱动大气中的二氧化碳。 拟议的工作可以通过限制冰川-间冰期时间尺度上的流体和固体地球之间的相互作用来改变我们对气候系统的理解。 拟议工作的更广泛的教育影响包括康涅狄格大学的一名博士后学者和两名本科生以及加州理工学院的一名本科生的参与。