Variations in tropical west Pacific climate and its role in glacial-interglacial cycles

热带海洋是高纬度地区热量和水分的主要来源，因此在全球气候系统中扮演着关键角色。在现代气候条件下，观测到与El Niño-Southern涛动有关的热带气候的强烈年际变率，这影响了周围陆地块和世界范围内的气候。虽然这一现象在当今已经得到了很好的研究，但热带气候在更长的时间尺度上的行为及其在全球气候大变化中的作用还没有得到很好的理解。在本研究中，我们将使用婆罗洲的石笋作为档案来评估热带西太平洋过去的降水和温度变化，涵盖了几个冰期-间冰期旋回。水文循环的变化将由方解石氧同位素组成的变化来重建。由于石笋可以在非常高的分辨率下进行连续重建，因此拟议的工作应该产生一个古气候记录，不仅可以评估平均状态的变化，还可以评估气候的变异性。此外，通过u系列测年法进行精确的年龄控制，将能够检验热带气候与高纬度地区相比变化的相对时间。除了已建立的氧同位素方法外，我们建议将两种新方法应用于石笋，即用于超高分辨率元素（和潜在同位素）比率测量的NanoSIMS和最近提出的基于碳酸盐同位素的古温计。因此，拟议的研究将有助于提供有价值的古气候记录，并扩大古气候学家的工具箱。

The tropical oceans are a major source of heat and moisture for the high latitudes, making them a key player in the global climate system. Under modern climate conditions, strong inter-annual variability in tropical climate related to El Niño-Southern Oscillation has been observed, which affects climate in the surrounding land masses and also worldwide. While this phenomenon has been well studied for the present-day, the behavior of tropical climate on longer timescales and its role during large global climate shifts is not yet well understood. In the proposed study, we will use stalagmites from Borneo as archives to assess past changes in precipitation and temperature in the tropical west Pacific, covering several glacial-interglacial cycles. Variations in the hydrological cycle will be reconstructed from changes in the oxygen isotopic composition of calcite. As stalagmites allow continuous reconstructions at very high resolution, the proposed work should yield a paleoclimate record that permits assessing not only changes in the mean state but also in the variability of climate. Furthermore, precise age control through U-series dating will allow examining the relative timing of changes in tropical climate in comparison to higher latitudes. In addition to the well-established oxygen isotope approach, we propose to apply two new methods to the stalagmites, namely NanoSIMS for ultra-high resolution measurements of elemental (and potentially isotopic) ratios and a recently proposed paleothermometer based on carbonate isotopologues. The proposed study will therefore both contribute a valuable paleoclimate record and expand the toolbox of paleoclimatologists.