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

摘要：根据这一奖项，支持者将检验一个新的假设：过去数十万年来热带海洋温度的变化主要是由温室气体强迫的变化驱动的。这一假说将通过在印度尼西亚哈尔马赫拉以东的西赤道太平洋暖池的一个地点开发一个新的替代海洋表面温度(SST)记录来验证。上海同济大学的合作者从这个地点采集了一个高沉积速率的岩芯(~15 cm/Ky)，中国将被用于开发~30-140y分辨率的代理海温记录。SSTs将利用地表浮游有孔虫Globigerinoides橡胶中的镁含量重建。代理、分辨率和时间尺度的选择将允许对热带温室压力假说进行三次测试。在每种情况下，Halmahera的SST记录将与已建立的温室气体记录进行比较，以确定与其他潜在的气候强迫机制相反，SST变化的多大部分可以由温室强迫来解释。第一个测试使用了上一次冰川消融期间大气二氧化碳的近乎单调上升和中等上升平台期，这是冰芯和海洋记录中最准确的年代部分。第二个测试使用了在海洋同位素阶段(MIS3)之前65至20000年间发生的四种不同的大气二氧化碳振荡。第三个测试使用了轨道尺度(23-100 Ky)的大气二氧化碳振荡，这些振荡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替代假设进行评估。Halmahera替代SST记录的发展将增加百年至千年和轨道时间尺度上热带太平洋气候变化的现有记录。冰川消融和MIS3期间暖池海温的高分辨率(~30-70年)记录与检验这些时段的快速气候变化模式有直接关系。此外，如果温室强迫是热带气候变异性的主要控制因素，那么过去强迫与温度变化之间的关系提供了气候敏感性的直接衡量标准。这项研究的结果将推进从古气候数据独立确定气候敏感性。更广泛的影响包括与中国的科学家合作，以及教授和发展研究生的记录。

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.