Biogenic opal isotopes - new tool for evaluation of past nutrient cycling and hydrographic structure in the Pacific Southern Ocean in relation to climate and Antarctic cryosphere evolution

生物蛋白石同位素 - 评估南太平洋过去养分循环和水文结构与气候和南极冰冻圈演化相关的新工具

• 批准号: 257126812
• 负责人: Dr. Edith Maier
• 金额: --
• 依托单位: Alfred-Wegener-Institut (AWI) Helmholtz-Zentrum für Polar- und Meeresforschung
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/257126812?language=en
• 关键词: Biogenic; opal; isotopes; new; tool

Atmospheric CO2 concentrations present a repetitive pattern of gradual decline and rapid increase during the past climate cycles, closely related to temperature and global ice volume history. It has been recognized that the Southern Ocean (SO) represents a key area governing past and present CO2 change. However, the sensitivity of this carbon modulator to climate-change induced reorganizations in wind patterns, ocean circulation, stratification, sea ice extent and biological production remains under debate. Data on past SO hydrography and productivity are mainly from the Atlantic sector. To obtain a more comprehensive picture of SO processes it remains to be tested to what extent Atlantic processes can be translated to the yet little studied Pacific sector. This sector is not only the largest part of the Southern Ocean, but it also represents the main drainage area of the marine-based West Antarctic Ice Sheet (WAIS). The proposed study aims to generate paleo-data sets from two sediment core transects across the Pacific SO using a newly-established method, which comprises combined oxygen and silicon isotope measurements of purified diatoms and radiolarians. The selected sediment intervals and sites will allow to describe for the first time the evolution in physical and nutrient properties at surface and subsurface water depth during different climate conditions, from colder than present (e.g. Last Glacial Maximum) to warmer than present (e.g. Marine Isotope Stage 5.5), and from different environmental settings in the eastern and western polar Pacific SO. The study will allow to test hypotheses concerning the SO´s role in the climate system by evaluation of (1) the sensitivity of the Pacific SO ecosystems to dust-borne micronutrient deposition (iron fertilization) and related Si-uptake rates, (2) the formation and extent of surface water stratification and (3) the 'silicic-acid leakage' hypothesis, postulating high-low latitude nutrient exchange critical for understanding productivity and carbon sequestration in the ocean. The new proxies will also provide information on the timing of surface ocean salinity anomalies resulting from meltwater shedding to gain information on WAIS stability and to test the assumption of a total WAIS draw down during MIS 5.5. Obtained paleo-records will be compared with simulations with an atmosphere-ocean general circulation model combined with a biogeochemical model including Si isotopes from an ongoing SPP1158-DFG project (CAU Kiel, PI B. Schneider). This should allow for better separation and statistically supported analysis of the individual impacts of ocean circulation and biological production on the air-sea CO2 exchange. Basic information on dust and biogenic deposition rates, physical ocean parameters (e.g. sea ice, sea surface temperature) and the generation of appropriate age models will be available in close cooperation with ongoing research in the frame of other national and international projects.

大气中的二氧化碳浓度表现出与温度和全球冰量历史密切相关的过去气候周期中级别下降和快速增加的重复模式。人们已经认识到，南大洋（So）代表了统治过去和现在的二氧化碳变化的关键区域。然而，该碳调节剂对气候变化的敏感性在风模式，海洋循环，分层，海冰范围和生物产量中引起的重组仍在争论中。关于过去的水文和生产力的数据主要来自大西洋部门。为了获得SO过程的更全面的图片，它仍有待测试的大西洋过程可以转化为尚未研究的太平洋部门。该部门不仅是南大洋最大的部分，而且还代表了海洋基西南冰盖（WAIS）的主要排水区。拟议的研究旨在从整个太平洋的两个沉积物核心样品中产生古数据集，因此使用新建立的方法，包括纯化硅藻和放射性硅藻的氧气和硅同位素测量。所选的沉积物间隔和位点将首次描述在不同气候条件下表面和地下水深的物理和营养特性的演变，从比现在更冷（例如，最后一次冰川最大值）到比现在的（例如，海洋同位素阶段5.5），以及来自东部和西极地方区的不同环境环境。该研究将允许通过评估（1）太平洋对生态系统对粉尘 - 粉尘微量营养素沉积（铁受精）和相关的SI摄取率的生态系统的敏感性来测试有关气候系统中SO作用的假设海洋中的生产力和碳固相。新的代理还将提供有关融化脱水的表面海洋盐度异常的信息，以获取有关WAIS稳定性的信息，并测试MIS 5.5期间总WAIS的假设。将获得的古录制将与具有大气 - 海洋循环模型的模拟进行比较，并结合了一个生物地球化学模型，其中包括正在进行的SPP1158-DFG项目（Cau Kiel，Pi B. Schneider）中的SI同位素。这应该可以更好地分离和统计支持对海洋循环和生物生产对空气海洋二氧化碳交换的影响的分析。有关尘埃和生物沉积速率，物理海洋参数（例如海冰，海面温度）和适当年龄模型的产生的基本信息，将与其他国家和国际项目的框架进行密切合作。