The Biological Pump During the Last Glacial Maximum and Early Deglaciation

气候科学中一个尚未回答的重要问题是，在上一次冰川消退期间，是什么导致了大气中二氧化碳（CO2）浓度的增加。在20，000年前的最后一个冰河时代的高峰期，气候寒冷，二氧化碳浓度较低，约为百万分之180（ppm）。随后，二氧化碳浓度上升到约280 ppm，导致气候变暖，冰盖融化，海平面上升。最后一次冰消期是地球历史上最后一次全球气候大幅变暖，与未来几个世纪的变暖预测相当。目前，气候与碳循环之间的相互作用尚未得到很好的理解，这可能影响未来气候预测的准确性。该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中的某个地方，但目前还不清楚它在哪里，它是如何到达那里的，或者是什么机制控制了它在冰川消退期间从海洋到大气的释气。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20 000至13 000年前最后一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（OC 3：海洋环流和碳循环）完成。一个新开发的全球气候模型，包括三维海洋物理，地球化学循环，碳和氮的同位素，沉积物将受到OC 3碳同位素合成和其他现有的古海洋学数据集，如最近的合成氮同位素数据和正在进行的放射性碳汇编。目标是定量重建海洋碳储存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消期海洋环流及其碳循环的理解，并可能为大气中二氧化碳的上升提供解释。资金支持博士后研究人员，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.