NOAA/WDS Paleoclimatology - Terciopelo Cave, Costa Rica Speleothem Oxygen Isotope Data

We present a high-resolution terrestrial archive of Central American rainfall over the period 100-24 and 8.1-6.5 ka, based on d18O time series from U-series dated stalagmites collected from a cave on the Pacific Coast of Costa Rica. Our results indicate substantial d18O variability on millennial to orbital time scales that is interpreted to reflect rainfall variations over the cave site. Correlations with other paleoclimate proxy records suggest that the rainfall variations are forced by sea surface temperatures (SST) in the Atlantic and Pacific Oceans in a fashion analogous to the modern climate cycle. Higher rainfall is associated with periods of a warm tropical North Atlantic Ocean and large SST gradients between the Atlantic and Pacific Oceans. Rainfall variability is likely linked to the intensity and/or latitudinal position of the intertropical convergence zone (ITCZ). Periods of higher rainfall in Costa Rica are also associated with an enhanced sea surface salinity gradient on either side of the isthmus, suggesting greater freshwater export from the Atlantic Basin when the ITCZ is stronger and/or in a more northerly position. Further, wet periods in Central America coincide with high deuterium excess values in Greenland ice, suggesting a direct link between low latitude SSTs, tropical rainfall, and moisture delivery to Greenland. Our results indicate that a stronger tropical hydrological cycle during warm periods and large inter-ocean SST gradients enhanced the delivery of low latitude moisture to Greenland.

本研究基于采自哥斯达黎加太平洋沿岸某洞穴的铀系测年石笋的氧同位素18（d¹⁸O）时间序列，构建了覆盖距今100~24 ka及8.1~6.5 ka时段的中美洲降雨高分辨率陆地记录。研究结果显示，在千年至轨道时间尺度上存在显著的氧同位素18波动，该波动被认为反映了研究点区域的降雨变化。与其他古气候代用指标记录的对比表明，降雨变化受大西洋与太平洋海表温度（sea surface temperatures，SST）驱动，其驱动模式与现代气候周期相似。降雨偏多时段对应热带北大西洋海温偏暖、大西洋与太平洋间海表温度梯度较大的时期。降雨波动可能与热带辐合带（intertropical convergence zone，ITCZ）的强度及/或纬度位置相关。哥斯达黎加的降雨偏多时段同样与地峡两侧海表盐度梯度（sea surface salinity gradient）增强相关，这表明当热带辐合带强度更高且/或位置更偏北时，大西洋盆地的淡水输出量更大。此外，中美洲的湿润时段与格陵兰冰芯中的高氘盈余（deuterium excess）值同步出现，这表明低纬度海表温度、热带降雨与向格陵兰的水汽输送之间存在直接关联。本研究结果显示，暖期更强的热带水文循环以及大洋间显著的海表温度梯度，增强了低纬度水汽向格陵兰的输送。