Origin of the 100-kyr Climate Cycle: Isolating Temperature and Ice Volume, 0-2Ma.

根据这一奖励，pi将测试关于100 kyr气候周期起源的假设——100 kyr气候周期是过去1万年地球气候系统的主要特征。这些知识是理解全球地球系统内部运作的基础。pi将使用详细的氧同位素和Mg/Ca古温度估计来反褶积d18O上过去200万年的冰体积和温度成分的历史，这一过渡时期通常被称为“中更新世过渡”（MPT）。在此之前，底栖有孔虫氧同位素数据揭示了一个主导的41-kyr气候，随后是一个持续到现在的100-kyr循环的相对突然的开始。在这一转变过程中，以及在MPT前后相对稳定的状态中，温度和冰体积的相对影响仍然未知。关于100 kyr气候周期起源的假设检验，无论是冰动力、风化层侵蚀、逐渐的二氧化碳变化，还是热带触发的结果，都主要依赖于海洋同位素作为冰体积记录的解释。这种解释现在受到质疑，因此，对这些假设的真正检验等待更可靠的全球冰量记录的发展。作为温度代理，pi将使用一种新的创新方法来分析Mg/Ca，称为流动时间分辨分析，或FT-TRA，该方法几乎消除了污染物相的影响，并提供了对d18O分析的同一物种有孔虫钙化温度估计的精度和准确性。他们将把我们的分析重点放在两个新的钻探点上，这些地点由ODP第202号法案回收。这些地点（1238和1242）位于热带太平洋东部的“冷舌”和“暖池”，位于监测太平洋中部水域的水深。

Under this award the PIs will test the hypotheses regarding the origin of the 100-kyr climate cycle - the dominant feature of Earth's climate system over the past ~1 Ma. This knowledge is fundamental to understanding the inner workings of the global Earth system. The PIs will employ detailed oxygen isotope and Mg/Ca paleotemperature estimates to deconvolve the history of the ice-volume and temperature components on d18O over the past two million years, a time of transition commonly referred to as the "Mid-Pleistocene Transition" (MPT). Prior to that time, benthic foraminiferal oxygen isotope data reveal a dominant 41-kyr climate, followed by a relative abrupt onset of a 100-kyr cycle that persists to the present. The relative influence of temperature and ice volume across this transition, and in the relatively stationary regimes before and after the MPT, remains unknown. Tests of hypotheses on the origin of the 100 kyr climate cycle, whether a result of ice dynamics, regolith erosion, gradual CO2 change, or tropical triggering, have relied on interpretation of the marine isotopes as primarily an ice volume record. This interpretation is now in questions and thus, true tests of these hypotheses await the development of more reliable records of global ice volume. As a temperature proxy the PIs will analyze Mg/Ca using a new and innovative method called flow through time resolved analysis, or FT-TRA which virtually eliminates effects of contaminant phases and provided precision and accuracy of estimates of calcification temperature in the same species of foraminifera analyzed for d18O. They will focus our analyses on two new drill sites, recovered by ODP Leg 202. These sites (1238 and 1242) are placed in the eastern tropical Pacific "cool tongue" and "warm pool", and are at water depths situated to monitor Pacific Central Water.