Carbon Cycle Variations during the Last Glacial Period Based on Atmospheric Delta 14C

摘要我们最近利用AMS 14C和TIMS U/Th和U/Pa对巴哈马一个洞穴中发现的石笋进行了耦合测年，得到了11-45 ka BP之间的大气长记录（Beck et al.,2001;Richards et al., in Press）。这一记录揭示了末次冰期，特别是在45 ~ 33 ka BP之间，14c的高度升高。在14c的宽峰上叠加着许多快速漂移，其中最大的一次发生在44.3 - 43.3 ka之间。虽然该记录中揭示的一些结构与地球磁场的变化明显相关，但其他结构似乎与GISP2 18O记录中揭示的Dansgaard/Oeschger变化相关，或与海因里希事件H1-H5有关。碳循环箱模型表明，这一记录的主要特征不可能仅由太阳或地球磁场调制产生，还需要全球碳循环的显著波动。在本研究中，我们计划通过生成额外的洞穴D14C记录来验证现有的大气14c记录，并利用碳循环箱模型，利用沉积Cd/Ca、Ba/Ca、、C、15N和冰芯18o的适当输入，进一步探索观测到的波动原因，以约束海洋通气率和生物泵变异。现有的36Cl和10Be冰芯记录将与SINT-200和NAPIS-75古地磁记录以及新的石笋10Be和129i记录结合使用，以约束由太阳和磁场强迫引起的14c波动。这些工作的一个特别重点将是评估可能伴随海因里希事件H1、H2、H3、H4和H5以及Dansgaard/Oeschger周期1-12的碳循环中气候引起的变化。这项拟议的工作的更广泛影响之一是更好地了解气候与碳循环之间的潜在联系，以增强向极地海洋的淡水通量。这项工作将与英国布里斯托尔大学和英国伦敦大学皇家霍洛威大学的研究人员合作进行。这项合作工作将利用已经在布里斯托尔收集的石笋，并在适当的年龄范围内确定为这项工作的良好候选者。这项研究的英国部分已经通过NERC和Leverhulme信托基金会的拨款获得了单独的资金，用于生成TIMS U/Th年表、稳定同位素记录和部分建模工作（见支持信）。作为英国工作的一部分，石笋18O记录也将生成，用于将14c波动与GISP2气候记录相关联（Wang et al.,2001; Dorale et al.,1998）。本提案要求资金仅用于支持这项工作的AMS 14c测量部分，以及支持亚利桑那大学耦合碳循环建模工作的部分。

AbstractWe have recently generated a long record of atmospheric between 11-45 ka BP using coupled AMS 14C and TIMS U/Th and U/Pa dating of a stalagmite recovered from a cave in the Bahamas (Beck et al.,2001;Richards et al., in Press).This record reveals highly elevated 14 C during the last glacial period, especially between 45 and 33 ka BP.Superimposed on this broad peak of 14 C are numerous rapid excursions, the largest of which occurs between 44.3 and 43.3 ka. While some of the structure revealed in this record is clearly linked to variations in the terrestrial magnetic field, other structures appear to be correlated with Dansgaard/Oeschger variations revealed in the GISP2 18O record, or linked to Heinrich events H1-H5.Carbon cycle box models suggest that the major features of this record cannot be produced with solar or terrestrial magnetic field modulation alone, but also require significant fluctuations in the global carbon cycle as well. In this proposal, we plan to validate this existing atmospheric 14 C record by generating additional speleothem D14C records, and to further explore the causes of the observed fluctuations using carbon cycle box models using appropriate inputs from sedimentary Cd/Ca,Ba/Ca,, C, 15N and ice core 18 O to constrain ocean ventilation rates and biological pump variability. Existing ice core records of 36Cl and 10Be will be used in conjunction with the SINT-200 and NAPIS-75 paleomagnetic records, and with new stalagmite 10 Be and 129 I records to constrain 14 C fluctuations stemming from solar and magnetic forcing. A particular focus of these efforts will be evaluation of climate induced changes in the carbon cycle that may have accompanied Heinrich events H1,H2,H3, H4 and H5 and Dansgaard/Oeschger cycles 1-12. Among the broader impacts of this proposed work is a better understanding of the potential linkages between climate and the carbon cycle for conditions of enhanced freshwater flux to the polar oceans.This work will be conducted in collaboration with researchers at the University of Bristol, England, and Royal Holloway, University of London, England. This collaborative effort will utilize stalagmites already in the Bristol collection and identified as good candidates in the appropriate age range for this exercise. Separate funding for the UK portion of this research for generation of TIMS U/Th chronology, stable isotope records, and part of the modeling effort has already been procured through grants from NERC and the Leverhulme Trust foundation (see letter of support). Stalagmite 18O records will also be generated as part of the UK effort, to be used for correlating 14 C fluctuations with GISP2 climate records (Wang et al.,2001; Dorale et al.,1998). Funds are requested in this proposal to only support the AMS 14 C measurement component of this effort, and to support the University of Arizona component of the coupled carbon cycle modeling effort.