NOAA/WDS Paleoclimatology - Holmgren et al. 2003 Cold Air Cave Stalagmite 25KYr Stable Isotope Data

Data from stalagmites in the Makapansgat Valley, South Africa, document regional climatic change in southern Africa in the Late Pleistocene and Holocene. A new TIMS U-series dated stalagmite indicates speleothem growth from 24.4 to 12.7 ka and from 10.2 to 0 ka, interrupted by a 2.5 ka hiatus. High-resolution oxygen and carbon stable isotope data suggest that postglacial warming was first initiated ~17 ka, was interrupted by cooling, probably associated with the Antarctic Cold Reversal, and was followed by strong warming after 13.5 ka. The Early Holocene experienced warm, evaporative conditions with fewer C4 grasses. Cooling is evident from ~6 to 2.5 ka, followed by warming between 1.5 and 2.5 ka and briefly at ~AD 1200. Maximum Holocene cooling occurred at AD 1700. The new stalagmite largely confirms results from shorter Holocene stalagmites reported earlier. The strongest variability superimposed on more general trends has a quasi-periodicity between 2.5 and 4.0 ka. Also present are weaker ~1.0 ka and ~100-year oscillations, the latter probably solar induced. Given similarities to the Antarctic records, the proximate driving force producing millennial- and centennial-scale changes in the Makapansgat record is postulated to be atmospheric circulation changes associated with change in the Southern Hemisphere circumpolar westerly wind vortex.

南非马卡潘斯盖特谷（Makapansgat Valley）的石笋数据，记录了更新世晚期及全新世时期非洲南部的区域气候变化。本次研究中一件经热电离质谱（TIMS）铀系测年的新型石笋显示，其沉积时段为24.4~12.7 ka以及10.2~0 ka，其间存在一段2.5 ka的沉积间断。高分辨率氧、碳稳定同位素数据表明，冰期后升温始于约17 ka，期间曾因降温过程中断——该降温事件或与南极冷反转（Antarctic Cold Reversal）相关——随后在13.5 ka之后出现显著升温。全新世早期气候温暖且蒸发强烈，C4草本植物占比较低。约6~2.5 ka期间存在显著降温，随后在1.5~2.5 ka以及公元1200年左右出现短暂升温。全新世最强降温事件发生于公元1700年。本次研究的新型石笋结果，在很大程度上验证了此前报道的、基于较短全新世石笋的研究结论。叠加于整体气候趋势之上的最强信号，其准周期为2.5~4.0 ka。此外还存在周期约1.0 ka和100年的较弱气候振荡，其中百年尺度振荡或由太阳活动驱动。鉴于该记录与南极气候记录存在相似性，我们推测驱动马卡潘斯盖特记录中千年、百年尺度气候变化的近程驱动力，是与南半球环极西风涡旋（Southern Hemisphere circumpolar westerly wind vortex）变化相关的大气环流调整。