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

近几十年来，科学界日益强调中间沃茨对全球海洋环流和气候的重要性。特别是，南极中层水（AAIW）作为世界范围内最广泛的中间水团，是将CO2从大气库转移到海洋库的关键组成部分，反之亦然，是纬向翻转环流快速重组的关键角色，此外，它还提供了一种连接南半球高纬度地区和海洋其他地区的过程的手段。尽管它在一些海洋和气候过程中的作用，古海洋重建的AAIW需要评估其在这些过程中的作用，在一系列的强迫条件下是稀缺的。部分原因是在中间深度缺乏长而连续的沉积序列。该项目旨在填补这一空白，方法是开采智利边缘的两个沉积物岩心，即接近目前AAIW的主要形成区。短重力岩心GeoB 3359 -3（~3.8 m）是从AAIW的现今岩心中采集的，靠近其形成地点，这一背景也可以解释末次冰期。MeBo长岩心GeoB 15020（~78 m）已从AAIW的上边界和最北端取回。在过去的12个冰期里，它可能受到了更强烈的影响。我们建议通过对底栖有孔虫的稳定同位素和微量元素分析，重建24 ~ 7 ka前AAIW类型特征的变化（GeoB 3359 -3），（ii）确定近1 Ma以来AAIW的几何形状和向北扩展（GeoB 15020），（iii）将该水团的扩展变化与其生产率的变化联系起来，（iv）评估过去~1 Ma期间AAIW的长期演化，可能覆盖中更新世过渡（GeoB 15020）。由于没有可比的档案，这套记录将成为AAIW演变过程中最完整和最广泛的重建。

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.