NOAA/WDS Paleoclimatology - Aurora Cave, Calcite Cave (Mt Luxmore, Fiordland), Te Reinga Cave, Waiau Cave, Doubtful Xanadu, Disbelief Cave Geochemical Data from 11200 to 170 Cal Yr BP

A primary step in the interpretation of speleothem stable isotope records (18O/16O and 13C/12C) is to conduct a comparison with other local palaeoclimate proxies. Here, two new master speleothem δ18O and δ13C records (one from eastern North Island, and the other from western/southern South Island, New Zealand) are evaluated against independent precipitation and temperature proxy information to assess their palaeoclimate reconstruction potential. This comparison also resulted in a serendipitous opportunity to reconstruct past circulation using climate regime classification [Lorrey, A.M., Fowler, A.M., Salinger, J., 2007a. Regional climate regime classification as a qualitative tool for interpreting multi-proxy palaeoclimate data spatial patterns: a New Zealand case study. Palaeo-3, in press], specifically because these two regional climate districts are hyper-sensitive to westerly circulation changes, and in many cases, exhibit contrasting climate character in response to circulation anomalies.
For both the western South Island and the eastern North Island master speleothem δ13C records, variations tracked changes in relative regional precipitation. The δ18O master speleothem record for both regions varied with temperature change. Both records contain strong regional climate signals that suggest they have good value for palaeoclimate reconstruction. The ensuing attempt at a multi-proxy reconstruction of regional climate regimes from the compiled proxies indicates past circulation in the New Zealand sector has varied considerably during the past four millennia. Centennial-scale circulation changes for the past 4000 years are evident, and are analogous to modern Blocking, Zonal and Trough regime types [Kidson J. W., 2000. An analysis of New Zealand synoptic types and their use in defining weather regimes. International Journal of Climatology 20, 299–316] that characterise changes in present-day (prevailing) westerly circulation. This palaeoclimate reconstruction indicates modern regional climate regime classification can be extended at least as far back as the temporal coverage of the records presented here, and it can likely be improved on with better dating control and the addition of new records with higher resolution. It is also anticipated that future work will expand to include more proxy data from across New Zealand to improve the clarity of past climate regime occurrence for the Late Holocene.

对洞穴碳酸盐沉积（speleothem）稳定同位素记录（δ¹⁸O/δ¹⁶O与δ¹³C/δ¹²C比值）进行解译的首要步骤，是将其与其他本地古气候代用指标（palaeoclimate proxies）开展对比。本文针对两份全新建立的主洞穴碳酸盐沉积记录（master speleothem records）——即δ¹⁸O与δ¹³C记录，一份采自新西兰北岛东部，另一份采自新西兰南岛西部/南部区域——结合独立的降水与温度代用指标信息开展评估，以验证其古气候重建（palaeoclimate reconstruction）潜力。本次对比还意外获得了一个契机：借助气候态分类（climate regime classification）方法重建过去的环流特征[Lorrey, A.M., Fowler, A.M., Salinger, J., 2007a. 区域气候态分类作为解读多代用指标（multi-proxy）古气候数据空间格局的定性工具：新西兰案例研究. 古气候学报（Palaeo-3）, 待刊]——这是因为上述两个区域气候区对西风环流（westerly circulation）变化极为敏感，且在多数情况下会对环流异常呈现出截然不同的气候响应特征。
针对新西兰南岛西部与北岛东部的主洞穴碳酸盐沉积δ¹³C记录，其同位素变化均追踪了区域相对降水的波动；而两个区域的主洞穴碳酸盐沉积δ¹⁸O记录则随温度变化发生偏移。两份记录均蕴含显著的区域气候信号，表明其具备优异的古气候重建应用价值。
基于整合后的代用指标开展区域气候态多代用重建的后续尝试显示，新西兰周边海域过去4000年以来的古环流曾发生显著变化。过去4000年中出现的百年尺度环流变化，与现今（盛行）西风环流变化对应的阻塞型（Blocking）、纬向型（Zonal）与槽型（Trough）天气型特征[Kidson J. W., 2000. 新西兰天气型分析及其在界定气候态中的应用. 国际气候学杂志, 20, 299–316]高度相似。
本次古气候重建结果表明，现代区域气候态分类方法至少可以延伸至本文所呈现记录的时间跨度范围内，且通过优化定年精度、新增更高分辨率的记录，该方法的可靠性可进一步提升。此外，未来研究有望将新西兰全域更多的代用指标数据纳入分析，以更清晰地阐明晚全新世（Holocene）以来区域气候态的发生规律。