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CO2浓度呈现出逐渐下降和快速上升的重复模式，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CO2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重组的敏感性仍在争论之中。关于过去SO水文地理和生产力的数据主要来自大西洋部门。为了更全面地了解SO过程，大西洋过程在多大程度上可以转化为尚未研究的太平洋部分仍有待检验。这一部分不仅是南大洋最大的部分，而且也是以海洋为基础的西南极冰盖（WAIS）的主要流域。 拟议的研究旨在使用一种新建立的方法，其中包括纯化硅藻和放射虫的氧和硅同位素测量相结合，从两个横跨太平洋SO的沉积物芯样带生成古数据集。选定的沉积物间隔和网站将允许描述的物理和营养特性的演变，在不同的气候条件下，在地表和地下水深度，从比现在更冷（如末次冰期最大）比现在更暖（如海洋同位素阶段5.5），并从不同的环境设置在东部和西部极地太平洋SO。该研究将通过评估（1）太平洋SO生态系统对尘埃携带的微量营养素沉积的敏感性，检验有关SO在气候系统中作用的假设（铁施肥）和相关的硅吸收率，（2）地表水分层的形成和程度和（3）“硅酸渗漏”假说，假设高-低纬度营养交换对于了解海洋生产力和碳固存至关重要。新的代理还将提供有关融水脱落导致的表层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 5.5期间WAIS总下降的假设。获得的古记录将与大气-海洋环流模型结合地球化学模型的模拟进行比较，该模型包括来自正在进行的SPP 1158-DFG项目（CAU基尔，PI B. Schneider）。这将有助于更好地分离和统计分析海洋环流和生物生产对海气二氧化碳交换的个别影响。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，提供关于尘埃和生物沉积率、海洋物理参数（例如海冰、海面温度）和生成适当年龄模型的基本信息。