Improving seawater chemistry reconstructions using the biogenic silica archive

Exp的主要目标之一。395是研究北大西洋海洋环流变化与岩浆脉动引起的水深变化之间的联系。使用实验期间收集的额外沉积物。395C，我将针对支持这一总体巡航目标的两个问题。第一个问题是，我们能否定量地了解沉积后生物硅氧同位素组成的变化？生物硅是沉积记录的重要组成部分。全球超过50%的初级生产是由于硅藻，而高纬度环境保存生物硅远远优于其他流行的古档案（碳酸盐）。然而，在硅藻中观察到难以量化的偏移，使得难以理解海洋的原始化学信号在这种化石中保留了多少。因此，我们需要提高我们的理解，然后才能放心地使用这个档案。这一目标的目的是准确地确定在沉积序列中特定深度影响生物硅的成岩作用的数量，使硅藻和海绵骨针化石更有信心地应用于气候重建。我将使用一种新的先进的分析组合（碳酸盐块同位素分析和三重氧同位素分析）对碳酸盐和生物硅化石从同一样品的核心材料来解决这个问题。第二个问题是，什么过程是有关的模式，在实验室观察到的初始沉积。395C站点？这些过程与流通的变化有什么关系呢？Exp. 395（计划于2023年）和Exp. 395C都有一个首要的主要巡航目标，即了解冰岛羽流的岩浆脉动是否引起了深海环流的变化。该区域的环流与北大西洋的深水形成直接相关，对全球气候有重大影响。最初沉积在该地区新的海洋板块上的沉积物，无论年龄如何，似乎都非常相似（从实验室的原始岩心照片中观察到）。395 C）。这些最初的沉积物也与覆盖的沉积物有着惊人的不同，而覆盖的沉积物与北大西洋通常发现的沉积物更相似。解读导致观察到的不同模式的原因和机制将使我们能够了解在沉积开始期间该地区发生了什么，并确定这些初始沉积物是否适合限制循环的变化。

One of the primary goals of Exp. 395 is to examine the connection between changes in oceanic circulation in the North Atlantic and changes in bathymetry due to magmatic pulsing. Using the additional sediment collected during Exp. 395C, I will target two questions which support this overarching cruise goal. The first question is, can we quantitatively understand post-depositional changes in the oxygen isotope composition of biogenic silica? Biogenic silica is an important component of the sedimentary record. Over 50% of global primary production is due to diatoms, while high latitude environments preserve biogenic silica far better than the other popular palaeo-archive (carbonate). However, difficult to quantify offsets have been observed in diatoms, making it difficult understanding how much of the original chemical signal of the ocean is preserved in this fossil. Consequently, we need to improve our understanding before we can use this archive with confidence. The aim of this objective is to accurately identify the amount of diagenesis affecting biogenic silica at specific depths in the sedimentary sequence, enabling more confident application of diatom and sponge spicule fossils for climate reconstructions. I will use a novel combination of advanced analyses (carbonate clumped isotope analysis and triple oxygen isotope analysis) on both carbonate and biogenic silica fossils from the same samples of core material to tackle this problem.The second question is, what processes are related to the patterns of initial sedimentation observed at the Exp. 395C sites? And how, if at all, are these processes related to changes in circulation? Exp. 395 (scheduled for 2023) and Exp. 395C both have the overarching major cruise objective of understanding whether magmatic pulsing of the Iceland plume has caused changes in deep oceanic circulation. Circulation in this region is directly related to deep water formation in the North Atlantic, which has a major influence on global climate. The sediments initially deposited on new oceanic plate in the region, regardless of age, seem to be incredibly similar (as observed from initial core photos from Exp. 395C). These initial sediments are also strikingly different from overlying sediments which are more similar to those normally found across the North Atlantic. Deciphering the causes and mechanisms leading to the different patterns observed will allow us to understand what was happening in the region during the onset of sedimentation and determine if these initial sediments are suitable for constraining changes in circulation.