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

最近，我们利用AMS 14 C和TIMS U/Th和U/Pa测年技术，对巴哈马一个洞穴中的石笋进行了11-45 ka BP之间的大气长记录（Beck等人，2001;理查兹等人，这一记录揭示了在末次冰期，特别是在45 - 33 ka BP之间，14 C的高度升高。叠加在这个14 C的宽峰上的是许多快速的漂移，其中最大的发生在44.3 - 43.3 ka之间。虽然这个记录中揭示的一些结构显然与地磁场的变化有关，但其他结构似乎与GISP 2 18 O记录中揭示的Dansgaard/Oeschger变化有关，或与Heinrich事件H1-H5有关。碳循环盒模型表明，这个记录的主要特征不能单独由太阳或地磁场调制产生，但也需要全球碳循环的显著波动。在这项提案中，我们计划通过生成额外的洞穴沉积物D14 C记录来验证现有的大气14 C记录，并进一步探索使用碳循环箱模型观察到的波动的原因，该模型使用来自沉积物Cd/Ca，Ba/Ca，，C，15 N和冰芯18 O的适当输入来限制海洋通风率和生物泵的变化。现有的冰芯记录的36 Cl和10 Be将与SINT-200和NAPIS-75古地磁记录，并与新的石笋10 Be和129 I记录，以限制14 C波动来自太阳和磁场强迫。这些努力的一个特别重点是评估可能伴随海因里希事件H1、H2、H3、H4和H5以及Dansgaard/Oeschger循环1-12的气候引起的碳循环变化。 这项拟议工作的更广泛影响之一是更好地了解气候和碳循环之间的潜在联系，以增加流向极地海洋的淡水流量，这项工作将与英国布里斯托大学和英国伦敦大学皇家霍洛威的研究人员合作进行。这项合作努力将利用布里斯托收集的石笋，并确定为适当年龄范围内的良好候选人。这项研究的英国部分用于生成TIMS U/Th年代学，稳定同位素记录和部分建模工作的单独资金已经通过NERC和Leverhulme信托基金会的赠款获得（见支持信）。石笋18 O记录也将作为英国努力的一部分生成，用于将14 C波动与GISP 2气候记录相关联（Wang等人，2001; Dorale等人，1998年）。本提案中要求提供的资金仅用于支持这项工作的AMS 14 C测量部分，并支持亚利桑那大学的耦合碳循环建模工作。

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.