Testing the Tropical Greenhouse Forcing Hypothesis Using a Halmahera Proxy SST Record

摘要：根据该奖项，支持者将测试一个新的假设：过去几十万年来热带海洋温度的变化主要是由温室效应的变化驱动的。这一假设将通过开发一个新的代理海表温度（SST）记录在西赤道太平洋暖池位于印尼Halmahera以东的网站进行测试。由中国上海同济大学合作者从该站点采集的高沉积速率岩心（~15 cm/ky）将用于开发~30-140 y分辨率的代用SST记录。SST将重建使用镁含量的表面居住的浮游有孔虫Globigerinoides橡胶。代用指标、分辨率和时间尺度的选择将允许对热带温室强迫假设进行三次检验。在每种情况下，将比较哈马黑拉SST记录与既定的温室气体记录，以确定SST方差中有多少部分可以由温室强迫解释，而不是其他潜在的气候强迫机制。第一个测试使用了最近一次冰消期大气CO2中的近单调上升和中期上升高原，这是冰芯和海洋记录中最好的部分。第二个测试使用了在海洋同位素阶段（MIS）3发生在6.5万至2万年前的大气CO2中的四种不同振荡。第三个测试使用大气中CO2的轨道尺度（23- 100 ky）振荡，这在几个南极冰芯中得到了很好的记录。其他气候影响将作为备选假设加以评价，哈马黑拉代用SST记录的编制将增加现有的热带太平洋气候变化百年至千年和轨道时间尺度记录。冰消期和MIS 3期间的暖池SST的高分辨率（~30-70年）记录与这些时间间隔内快速气候变化的测试模型直接相关。此外，如果温室强迫是热带气候变率的主要控制因素，那么强迫和温度变化之间的过去关系提供了气候敏感性的直接度量。 这项研究的结果将促进独立确定气候敏感性的古气候数据。 更广泛的影响包括与中国科学家的合作以及教学和培养研究生的记录。

Abstract: Under this award the proponents will test a new hypothesis: tropical ocean temperature variability over the last several hundred thousand years is dominantly driven by changes in greenhouse forcing. This hypothesis will be tested by developing a new proxy sea surface temperature (SST) record from a site in the western equatorial Pacific warm pool lying just east of Halmahera, Indonesia. A high sedimentation rate core (~15 cm/ky) from this site taken by collaborators from Tongji University in Shanghai, China will be targeted for development of a ~30-140 y resolution proxy SST record. SSTs will be reconstructed using the Mg content of the surface-dwelling planktonic foraminifera Globigerinoides rubber. The choice of proxy, resolutions and timescales will allow for three tests of the tropical greenhouse forcing hypothesis. In each case, the Halmahera SST record will be compared to the established greenhouse gas record to determine what fraction of the SST variance can be explained by greenhouse forcing, as opposed to other potential climate forcing mechanisms. The first test uses the near-monotonic rise and mid-rise plateau in atmospheric CO2 over the last deglaciation, the most well dated portion of both the ice core and marine records. The second test uses the four distinct oscillations in atmospheric CO2 that occurred between 65 and 20 thousand years before present during marine isotope stage (MIS) 3. The third test uses orbital scale (23- 100 ky) oscillations in atmospheric CO2 that are well documented in several Antarctic ice cores. Other climate influences will be evaluated as alternative hypotheses.The development of the Halmahera proxy SST record will add to available records of tropical Pacific climate variability on both centennial-to-millennial and orbital timescales. A high resolution (~30-70 y) record of warm pool SSTs during the deglaciation and MIS 3 has direct relevance to testing models of rapid climate change during these time intervals. In addition, if greenhouse forcing is the main control on tropical climate variability, the past relationship between forcing and temperature change provides a direct measure of climate sensitivity. Results from this study will advance independent determinations of climate sensitivity from paleoclimatic data. Broader impacts include collaboration with scientists in China and record of teaching and developing graduate students.