The Biological Pump During the Last Glacial Maximum and Early Deglaciation

气候科学中一个重要的悬而未决的问题是，在最后一次冰川消退期间，是什么导致了大气中二氧化碳浓度的增加。在2万年前最后一个冰河时代的高峰时期，气候寒冷，二氧化碳浓度很低，约为百万分之180。随后，二氧化碳浓度上升到280 ppm左右，导致气候变暖，冰盖融化，海平面上升。最后一次冰川消退是地球历史上最后一次全球气候大幅变暖，与未来几个世纪预计的变暖相当。目前，气候与碳循环之间的相互作用还没有得到很好的理解，这可能会影响未来气候预测的准确性。这个项目将有助于更好地了解地球的耦合气候-碳循环系统。先前的研究表明，冰河时期大气中缺失的碳可能储存在海洋的某个地方，但目前尚不清楚它们在哪里，如何到达那里，或者在冰川消融期间是什么机制控制了它们从海洋向大气的释放。该项目将综合海洋沉积物的碳同位素数据，并将其与详细的模型模拟相结合，以便更好地了解距今2万至1.3万年的末次冰消期早期的海洋环流和碳循环。数据综合将通过一个国际合作项目（OC3：海洋环流和碳循环）来完成。包括三维海洋物理、生物地球化学循环、碳氮同位素和沉积物在内的新开发的全球气候模型将受到OC3碳同位素合成和其他现有古海洋学数据集（如最近合成的氮同位素数据和正在进行的放射性碳汇编）的限制。目标是定量重建海洋碳储量如何受到不同过程的影响，如生物泵、海冰覆盖、海洋环流、分层、铁施肥、海平面和沉积物相互作用。该项目有可能提高我们对冰川融化的海洋环流及其碳循环的理解，并可能为大气中二氧化碳的增加提供解释。资助博士后研究人员，并为本科生提供研究机会。

An important unanswered question in climate science is what caused the increase of atmospheric carbon dioxide (CO2) concentrations during the last deglaciation. During the height of the last ice age, 20,000 years ago, climate was cold and CO2 concentrations were low, around 180 parts per million (ppm). Subsequently CO2 concentrations rose to about 280 ppm causing the climate to warm, ice sheets to melt and sea levels to rise. The last deglaciation was the last time in Earth's history when global climate warmed substantially, comparable to the warming projected for the coming centuries. Currently interactions between climate and the carbon cycle are not well understood, with possible implications for the accuracy of future climate projections. This project it will contribute to a better understanding of Earth's coupled climate-carbon cycle system. Previous research suggests that the carbon that was missing in the atmosphere during the ice age may have been stored somewhere in the ocean, but at present it is not clear where it was, how it got there, or what mechanisms may have controlled its outgassing from the ocean to the atmosphere during the deglaciation. This project will synthesize carbon isotope data from ocean sediments and combine them with detailed model simulations in order to better understand the ocean's circulation and carbon cycle during the early part of the last deglaciation from 20,000 to 13,000 years before the present. The data synthesis will be accomplished through an international collaborative project (OC3: Ocean Circulation and Carbon Cycling). A newly developed global climate model that includes three-dimensional ocean physics, biogeochemical cycles, isotopes of carbon and nitrogen, and sediments will be constrained by the OC3 carbon isotope synthesis and other existing paleoceanographic datasets such as a recent synthesis of nitrogen isotope data and an ongoing radiocarbon compilation. The goal is to reconstruct quantitatively how ocean carbon storage was affected by different processes, such as the biological pump, sea ice cover, ocean circulation, stratification, iron fertilization, sea level and sediment interactions. The project has the potential to improve our understanding of the deglacial ocean circulation, its carbon cycling, and it may provide explanations for the rise in atmospheric CO2. Funding supports a postdoctoral researcher, and provides research opportunities for undergraduate students.