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

地球上最后一百万年的历史以覆盖北美和欧洲大部分地区的大陆冰盖的消长为特征。冰盖的增长将水从海洋转移到大陆，导致海平面下降了近400英尺。虽然人们早就知道冰河时代的起伏与地球围绕太阳的轨道变化有关，但冰河时代结束的触发机制，即所谓的终结，还没有完全解释清楚。海平面的降低释放了全球大洋中脊系统的压力，大洋中脊系统是一个几乎连续的淹没火山链，横跨30,000英里的海底。压力释放应该会推动海底火山活动的加强，这可能反过来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沿南太平洋东部大洋中脊的岩浆活动。从东太平洋海隆(EPR)和太平洋南极海脊(PAR)提取的沉积物岩芯将用于评估海脊附近的热液羽流活动。热液羽流是由高温的洋壳将冰冷的深海水过热而形成的，而洋壳本身又受到岩浆的加热。因此，沉积档案可以用来评估岩浆作用中的冰期-间冰期变化，并测试在冰川终止期间是否发生了增强的海底火山作用。拟开展的工作将集中在沿EPR和PAR从10°S到40°S的一系列岩芯上。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。热液活动将通过估算Fe、Mn、V和As到山脊沉积物的通量来推断。所有的通量都将使用3He归一化技术进行约束。在多个地点发现金属通量的相干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，以评估大洋中脊岩浆作用作为冰盖大小负反馈的可行性。最后，一个岩石学模型将被用来模拟海平面变化对上地幔含二氧化碳熔体产生的影响。来自全球大洋中脊系统的碳通量模拟将被用来评估碳通量的变化是否可能在冰期-间冰期的时间尺度上驱动大气二氧化碳。这项拟议的工作可以通过限制冰川-间冰期时间尺度上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。这项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，以及加州理工大学的一名额外本科生。

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.