Glacial-Interglacial Changes in Central Tropical Pacific Sea Surface Temperature

古气候数据集可以用来帮助验证和改进用于预测未来变化的气候模型。特别有用的是来自最后一次冰川盛期的数据，那是一个大气二氧化碳含量较低的时期，合理地理解了强迫，并可能覆盖广泛的数据。如果要使用地质记录中的数据来限制平衡气候敏感性--定义为全球平均温度对大气二氧化碳倍增的反应--，对海洋表面温度的准确估计也是至关重要的。研究表明，气候敏感性和上一次冰川最高温度之间的联系在热带地区最强，那里的温室气体强迫主导了温度信号。虽然热带太平洋西部和东部的最后一次冰川最高温度受到多个海面温度指标的限制，但热带中部的现有数据很少。过去的估计是高度不确定的，表明该地区的温度变化很小，这一结果与根据最后一次冰川最大边界条件强制进行的气候模型的重建不相容。最近在热带太平洋中部的莱恩群岛海脊采集了一系列沉积物岩心，范围从赤道到北纬7度。PI在这里建议测量表层浮游有孔虫的镁/钙比率，以重建上一次冰川周期的温度变化。根据在一定纬度和水深范围内收集的岩心进行的温度重建将有助于评估新的海洋表面温度估计中的不确定性。同一套沉积岩心表层浮游有孔虫的氧同位素比值表明，在冰川时代，南北梯度增加。PIS将使用镁/钙温度指标来确定这是否对应于海表面温度南北梯度的增加。这些数据将被用来更好地了解热带太平洋大气和海洋环流对冰川边界条件的响应，将有助于了解热带气候变化的机制。研究小组将向气候模型界提供这些数据，作为该项目的一部分，年龄模型信息和关于物理循环的推断将作为使用这组沉积物岩芯进行其他调查的有用基础。资金还支持对科学界代表性不足的群体成员的教育和指导。

Paleoclimate data sets can be used to help validate and improve the climate models that are used to predict future change. Of particular use have been data from the Last Glacial Maximum, a time with lowered atmospheric carbon dioxide, reasonably well understood forcing, and potentially broad data coverage. Accurate estimates of sea surface temperature are also essential if data from the geologic record is to be used to constrain equilibrium climate sensitivity -- defined as the global mean temperature response to a doubling of atmospheric carbon dioxide. Studies have shown that the connection between climate sensitivity and Last Glacial Maximum temperature is strongest in the tropics, where greenhouse gas forcing dominates the temperature signal. While Last Glacial Maximum temperature in the Western and Eastern Tropical Pacific is constrained by multiple sea surface temperature proxies, there is little existing data in the Central Tropical Pacific. Past estimates are highly uncertain and suggest little temperature change in this region, a result that is incompatible with reconstructions from climate models forced with Last Glacial Maximum boundary conditions. A series of sediment cores has recently been collected from the Line Islands Ridge in the Central Tropical Pacific, spanning a range of latitude from the equator to 7 degrees North. The PIs propose here to measure Mg/Ca ratios in surface dwelling planktonic foraminifera in order to reconstruct temperature changes over the last glacial cycle. Temperature reconstructions from cores collected over a range of latitude and water depth will help to assess the uncertainty in the new sea surface temperature estimates. Oxygen isotope ratios in surface dwelling planktonic foraminifera from the same set of sediment cores show an increased North-South gradient during glacial times. The PIs will use the Mg/Ca temperature proxy to determine if this corresponds to an increase in the North-South gradient in sea surface temperature. This data will be used to better understand how Tropical Pacific atmospheric and ocean circulation responded to glacial boundary conditions will aid in the understanding of the mechanisms for climate change in the tropics.The research team will make the data available to the climate modeling community, and the age model information and the inferences about the physical circulation generated as part of this project will serve as a useful base for other investigations using this set of sediment cores. Funding also supports education and mentoring of members of groups that are under-represented in science.