Did the Southern Ocean drive deglacial atmospheric CO2 rise?

地球科学近代史上一些最惊人的数据都是从极地冰帽的钻探中获得的。其中最重要的是揭示了末次冰期最大期大气中的二氧化碳含量比过去1万年的温暖时期低约三分之一（约80 ppmV）。因此，人们普遍认为，大气中二氧化碳的变化强烈放大了冰川-间冰期气候变化。虽然一个明确的解释尚未出现所观察到的CO2在冰川期间下降，并在间冰期上升，质量平衡的论点清楚地指出，海洋交换的主要调制器的CO2变化在这些时间尺度上。最近的研究指出，由于南半球高纬度地区的二氧化碳水平和气候之间的紧密联系，南大洋是一个重要的研究领域。一个涉及SO的流行模型设想，在末次冰期循环（冰消期）气候重组结束时，海冰覆盖的减少和风场的加强可能会将富含碳和营养物质的深海沃茨搅动到表面，释放出在冰期储存在深海中的CO2。然而，这种模式存在一个悖论。在现代SO中，CO2的物理释放大致由藻类在海面光合作用期间利用在重新浮出水面的深水沃茨中伴随CO2的营养物吸收碳来补偿。因此，对于CO 2释放模型的工作条件SO应该是不利的生物吸收，使全球显着的CO2 effluxtower.In的建议，我们假设，一个潜在的因素，可能会限制生物CO 2吸收SO是铁的缺乏在藻类生长。在冰消期的尘埃输入（铁的重要来源）的大幅下降记录在Anatrctic冰芯借给支持这一想法。因此，我们建议通过调查海洋生产力的性质和幅度，相对常量营养素利用率（硝酸盐和柠檬酸），微量营养素（铁和锌）的生物利用率，并在一组精心挑选的海洋沉积物岩心覆盖这一时期，调查生产力对二氧化碳从SO流出的作用。我们建议应用国家的最先进的地球化学和同位素工具，最近开发的包括硅和氮同位素作为代理的常量营养素利用和铁结合的痕量金属作为示踪剂的Fe和Zn的生物利用度结合更传统的代理生产力和灰尘的投入。通过这样做，我们建议解决一个基本的和挥之不去的问题，在地球系统科学-这是“什么是控制冰川间冰期二氧化碳的变化？"

Some of the most spectacular data in the recent history of earth science have been derived from the drilling of the polar ice caps. Foremost amongst these is the revelation that the atmospheric CO2 content was about one-third lower (roughly 80ppmV) during the Last Glacial Maximum than during the warmer period of the past 10 thousand years. Thus, it is widely believed that changes in atmospheric CO2 strongly amplified glacial-interglacial climate change. Although a clear explanation has yet to emerge for the observed CO2 decline during glacials and rise during interglacials, mass balance arguments clearly point to the ocean exchange as the primary modulator of the CO2 changes on these time scales. Recent studies have pointed to the Southern Ocean due to the tight coupling between carbon dioxide levels and climate in the southern hemisphere high latitudes. One prevailing model involving the SO envisions that at the end of the last glacial cycle (deglacial) climate reorganisation, the reduction in sea ice cover and strengthening wind fields may have stirred up deep ocean waters rich in carbon and nutrients to the surface releasing CO2 that has been stored in the deep ocean during the glacial period. However, this model presents a paradox. In the modern SO, the physical release of CO2 is roughly compensated by the uptake of carbon by algae during photosynthesis at the sea surface utilising the nutrients that accompany CO2 in the resurfacing deep waters. Therefore for the CO2 release model to work conditions in SO should have been unfavourable for the biological uptake allowing globally significant CO2 efflux to occur.In the proposal we hypothesize that one potential factor that could have constrained biological CO2 uptake in the SO is the dearth of Fe during algal growth. The substantial decline in dust inputs (important source of Fe) during the deglacial recorded in Anatrctic ice cores lends support to this idea. Therefore, we propose to investigate the role of productivity on CO2 efflux from the SO during the last deglaciation by investigating the nature and magnitude of marine productivity, relative macronutrient utilisation (nitrate and silicic acid), micronutrient (Fe & Zn) bio-availability and in a carefully selected set of marine sediment cores covering this period. We propose to apply state-of-art geochemical and isotopic tools recently developed including silicon and nitrogen isotopes as proxies for macronutrient utilisation and diatom-bound trace metals as tracers of Fe and Zn biological availability in combination with more conventional proxies of productivity and dust inputs. By doing so, we propose to address a fundamental and lingering question in Earth System Science- that is "What are the controls on glacial-interglacial CO2 change?"