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.

在过去的气候周期中，大气二氧化碳浓度呈现出逐渐下降和快速增加的重复模式，与温度和全球冰量历史密切相关。人们已经认识到，南大洋（SO）是控制过去和现在二氧化碳变化的关键区域。然而，这种碳调节剂对气候变化引起的风型、海洋环流、分层、海冰范围和生物生产的敏感性仍然存在争议。过去的SO水文学和生产力数据主要来自大西洋部门。 SO 过程的更全面的描述大西洋过程在多大程度上可以转化为尚未被研究的太平洋区域还有待测试。该区域不仅是南大洋的最大部分，而且还代表了以海洋为基础的西方的主要流域。南极冰盖 (WAIS) 拟议的研究旨在使用新建立的方法从太平洋上的两个沉积物核心横断面生成古数据集，其中包括对纯化的硅藻和放射虫的组合氧和硅同位素测量。间隔和地点将首次描述不同气候条件下地表水和地下水深度的物理和营养特性的演变，从比现在凉爽（例如末次盛冰期）到比现在温暖（例如海洋同位素阶段 5.5），以及从该研究将通过评估（1）太平洋SO生态系统对尘埃微量营养素沉积的敏感性来检验有关SO在气候系统中的作用的假设。 （铁施肥）和相关的硅吸收率，（2）地表水分层的形成和程度，以及（3）“硅酸泄漏”假说，假设高低纬度养分交换对于理解生产力和碳封存至关重要新的代理还将提供有关融水脱落导致的表面海洋盐度异常的时间信息，以获得有关 WAIS 稳定性的信息，并测试 MIS 期间 WAIS 总量下降的假设。 5.5. 获得的古记录将与大气-海洋大气环流模型和生物地球化学模型（包括来自正在进行的 SPP1158-DFG 项目的硅同位素）的模拟进行比较（CAU Kiel，PI B. Schneider）。海洋环流和生物生产对海气二氧化碳交换的单独影响的统计支持分析 有关灰尘和生物沉积速率、物理海洋参数（例如，海洋参数）的基本信息。海冰、海面温度）和适当年龄模型的生成将与其他国家和国际项目框架内正在进行的研究密切合作。