Paleoceanographic reconstruction of the Antarctic Intermediate Water in the South East Pacific throughout the last 1 Ma

近几十年来，中间水域对全球海洋环流和气候的重要性日益受到科学界的重视。特别是，南极中间水(AAIW)作为世界上分布最广泛的中间水团，是二氧化碳从大气向海洋水库转移的关键组成部分，也是经向翻转环流快速重组的关键因素，此外，它还提供了一种将发生在高南纬地区的过程与海洋其他地区联系起来的手段。尽管AAIW在一些海洋和气候过程中发挥了作用，但需要对AAIW进行古海洋学重建，以评估它在一系列强迫条件下在这些过程中的作用，这方面的资料很少。这在一定程度上是由于在中等深度缺乏长的、连续的沉积序列。该项目旨在通过开发智利边缘的两个沉积岩芯来填补这一空白，即接近目前AAIW的主要形成区域。短重力岩芯GeoB3359-3(~3.8m)是从AAIW的今天岩芯中采集的，靠近其形成地点，这一环境似乎也解释了最后一次冰期。长长的Mebo岩芯GeoB15020(~78m)今天已经从AAIW的上边界和最北端被取回。在过去的12个冰川时期，它可能受到了这种水团的更强烈的影响。我们建议在海底有孔虫中进行稳定的同位素和微量元素分析，(I)重建AAIW类型特征的变化，从现在(GeoB3359-3)到现在(GeoB3359-3)，(Ii)确定AAIW在最后1 Ma(GeoB15020)期间的几何形状和向北扩展，(Iii)将该水团的扩展变化与其生产率的变化联系起来，以及(Iv)评估AAIW在最后~1 Ma期间的长期演化，可能覆盖中更新世过渡(GeoB15020)。由于没有可供比较的档案，这套记录将成为对AAIW演变过程最完整和最广泛的再现。

The importance of intermediate waters for the global ocean circulation and climate is being increasingly highlighted in the scientific community in recent decades. Particularly, Antarctic Intermediate Water (AAIW) as the most widespread intermediate water mass worldwide arises as a key component in transferring CO2 from atmospheric to marine reservoirs and vice versa, as a key player in rapid reorganizations of the meridional overturning circulation, and furthermore it provides a means of connection between processes occurring at high austral latitudes and the rest of the oceans. Despite its role in a number of oceanic and climatic processes, paleoceanographic reconstructions of the AAIW needed to assess its role within these processes under a range of forcing conditions are scarce. This is partly due to the lack of long, continuous sedimentary sequences at intermediate depths. This project aims to fill in this gap by exploiting two sediment cores from the Chilean margin, i.e. close to the main area of formation of the AAIW nowadays. The short gravity core GeoB3359-3 (~3.8 m) is collected from todays core of the AAIW close to its formation site, a setting plausibly accounting also for the last glacial period. The long MeBo core GeoB15020 (~78 m) has been retrieved from the upper boundary and northernmost reaches of the AAIW today. Probably it was under an even stronger influence of this water mass during the past 12 glacial periods. We propose to perform stable isotope and trace element analyses in benthic foraminifera (i) to reconstruct changes in the type characteristics of the AAIW from 24 to 7 ka before present (GeoB3359-3), (ii) to define the geometry and northward spreading of the AAIW during the last ~1 Ma (GeoB15020), (iii) to relate changes in the spreading of this water mass to shifts in its production rate, and (iv) to assess the long-term evolution of the AAIW during the last ~1 Ma, potentially covering the Mid Pleistocene Transition (GeoB15020). As there are no comparable archives available, this set of records will become the most complete and extensive reconstruction of the evolution of the AAIW.