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Investigation of mechanism driving glacial/interglacial variability in stratification/mixing and biological productivity of the Pacific Southern Ocean and potential implications on air-sea CO2-exchange: synthesis of climate and ocean biogeochemical modeli

研究驱动南太平洋分层/混合和生物生产力的冰川/间冰期变异的机制以及对海气二氧化碳交换的潜在影响：气候和海洋生物地球化学模型的综合

基本信息

批准号：
219462646
负责人：
Dr. Andrea Abelmann
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：
2012
资助国家：
德国
起止时间：
2011-12-31 至 2020-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/219462646?language=en
关键词：
Investigation mechanism driving glacial interglacial

项目摘要

Atmospheric CO2 concentrations present a repetitive pattern of gradual decline and rapid increase during the last climate cycles, closely related to temperature and sea level change. During the Last Glacial Maximum (LGM; 23-19 kyr BP), when sea level was ca. 120 m below present, the ocean must have stored additionally about 750 Gt carbon. There is consensus that the Southern Ocean represents a key area governing past and present CO2 change. The latter is not only of high scientific but also of socio-economic and political concern since the Southern Ocean provides the potential for an efficient sink of anthropogenic carbon. However, the sensitivity of this carbon sink to climate-change induced reorganizations in wind patterns, ocean circulation, stratification, sea ice extent and biological production remains under debate. Models were not yet able to reproduce the necessary mechanisms involved, potentially due to a lack of the dynamic representation/resolution of atmospheric and oceanic circulation as well as missing carbon cycling. Data on past Southern Ocean hydrography and productivity are mainly from the Atlantic sector, thus do not adequately document conditions in the 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). In the proposed study we aim to generate paleo-data sets with a newly established proxy method from sediment core transects across the Pacific Southern Ocean. This will enhance the baselines for the understanding and modeling of the Southern Ocean´s role in carbon cyling, i.e. ocean/atmosphere CO2 exchange and carbon sequestration. It will also allow insight into the response of the WAIS to past warmer than present conditions. Paired isotope measurements (oxygen, silicon) will be made on purified diatoms and radiolarians to describe glacial/interglacial contrasts in physical and nutrient properties at surface and subsurface water depth. This will be used to test (i) the impact of yet unconsidered dust-borne micronutrient deposition on the glacial South Pacific on shifts of primary productivity, Si-uptake rates and carbon export, (ii) the “silicic-acid leakage” hypothesis (SALH) and (iii) the formation and extent of surface water stratification. Diatom and radiolarian oxygen isotopes will provide information on the timing of surface ocean salinity anomalies resulting from WAIS melt water. Climate model simulations using a complex coupled atmosphere ocean general circulation model (AOGCM) in combination with a sophisticated ocean biogeochemical model including Si-isotopes will be used for comparison with the paleo records. The analysis will cover spatial as well as temporal variability patterns of Southern Ocean hydrography, nutrient cycling and air-sea CO2-exchange. With the help of the climate model we aim to better separate and statistically analyse the individual impacts of ocean circulation and biological production on the air-sea CO2-exchange.

在最近的气候周期中，大气CO2浓度呈现出逐渐下降和快速增加的重复模式，与温度和海平面变化密切相关。在末次盛冰期（LGM; 23-19 kyr BP），当海平面低于现在约120 m时，海洋必须额外储存约750 Gt碳。人们一致认为，南大洋是控制过去和现在二氧化碳变化的关键区域。后者不仅具有高度的科学意义，而且也具有社会经济和政治意义，因为南大洋具有有效吸收人为碳的潜力。然而，这种碳汇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重组的敏感性仍然存在争议。模式还不能重现所涉及的必要机制，这可能是由于缺乏大气和海洋环流的动态表示/分辨率以及缺少碳循环。关于过去南大洋水文和生产力的数据主要来自大西洋部分，因此没有充分记录太平洋部分的情况。这一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南极西部冰盖（WAIS）的主要流域。在提出的研究中，我们的目标是用一种新建立的代理方法从太平洋南大洋的沉积物岩心样带生成古数据集。这将提高对南大洋在碳循环（即海洋/大气二氧化碳交换和碳固存）中的作用的理解和建模的基线。它还将使我们深入了解WAIS对过去比现在更温暖的条件的反应。将对纯化硅藻和放射虫进行配对同位素测量（氧、硅），以描述地表和地下水深的冰期/间冰期物理和营养特性的对比。这将用于测试(i)尚未考虑到的南太平洋冰川上粉尘携带的微量营养素沉积对初级生产力、硅吸取率和碳输出的变化的影响，（ii）“硅酸泄漏”假说（SALH）和（iii）地表水分层的形成和程度。硅藻和放射虫氧同位素将提供有关WAIS融水引起的表面海洋盐度异常时间的信息。利用复杂耦合大气-海洋环流模式（AOGCM）和包括硅同位素在内的复杂海洋生物地球化学模式进行气候模式模拟，并与古记录进行比较。该分析将涵盖南大洋水文、养分循环和海气二氧化碳交换的时空变化模式。在气候模型的帮助下，我们的目标是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。