Antarctic Bottom Water Circulation during the Last Deglaciation: Quantitative Constraints from Stable Isotope Tracer Budgets

末次冰消期的南极底层水循环：稳定同位素示踪剂预算的定量限制

• 批准号: 1003500
• 负责人: David Lund
• 金额: $ 31.49万
• 依托单位: Regents of the University of Michigan - Ann Arbor
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-08-15 至 2014-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1003500&HistoricalAwards=false
• 关键词: Antarctic; Bottom; Water; Circulation; during

At the Last Glacial Maximum (LGM; ~20,000 years ago), atmospheric carbon dioxide (CO2) levels were ~30% lower than pre-industrial values. Because most of the carbon in the climate system resides in the deep ocean, it likely plays the primary role in regulating atmospheric CO2 on time-scales of several millennia. Tracers of the ocean circulation suggest the deep ocean was more stratified during the LGM, potentially creating a 'trap' for CO2 in the abyss. Reduced mixing between deep waters may have aided storage of CO2, but data supporting this idea have remained elusive. This research uses a new tracer budget for Antarctic Bottom Water based on the oxygen isotopic composition of microscopic shells in marine sediments.The aims of the work are two-fold: 1) to evaluate the circulation of Antarctic Bottom Water during the LGM when atmospheric CO2 was low, and 2) to do the same for the last deglaciation as ice sheets melted back and atmospheric CO2 increased. Preliminary analysis suggests that vertical mixing in the deep Atlantic was lower during the LGM. This research tests this result using an expanded set of well-dated sediment cores from the South and North Atlantic. The investigators also evaluate whether tracer gradients, and hence the deep circulation, changed in step with atmospheric CO2 during the last deglaciation. If this were the case, it would support the idea that circulation of the deep ocean plays a primary role in regulating CO2 on glacial timescales.Funding supports a new faculty member with no prior NSF funding, as well as graduate and undergraduate involvement in research. Results of this study will shed light on the ocean's role in CO2 storage, and will help refine ocean-climate models.

在最后一次冰川盛期(LGM；大约2万年前)，大气二氧化碳(CO2)水平比工业化前的水平低约30%。由于气候系统中的大部分碳存在于深海，它很可能在几千年的时间尺度上对大气二氧化碳的调节起着主要作用。对海洋环流的追踪表明，在末次盛冰期期间，深海的分层程度更高，这可能会在深渊中形成一个二氧化碳“陷阱”。减少深水之间的混合可能有助于二氧化碳的储存，但支持这一想法的数据仍然难以捉摸。这项研究基于海洋沉积物中微观贝壳的氧同位素组成，对南极底层水使用了新的示踪剂预算。这项工作的目的有两个：1)评估大气二氧化碳含量较低的末次盛冰期南极底层水的环流；2)对冰盖融化和大气二氧化碳增加的最后一次冰川消融进行同样的评估。初步分析表明，在末次盛冰期，大西洋深层的垂直混合程度较低。这项研究使用了一组来自南大西洋和北大西洋的测年准确的沉积物岩芯，对这一结果进行了检验。研究人员还评估了在最后一次冰川消融期间，示踪剂梯度以及深层环流是否与大气二氧化碳同步变化。如果是这样的话，它将支持深海环流在调节冰川时间尺度上的二氧化碳方面发挥主要作用的观点。Funding支持一名没有先前NSF资金的新教员，以及研究生和本科生参与研究。这项研究的结果将有助于阐明海洋在二氧化碳储存中的作用，并将有助于完善海洋气候模型。