Determining the natural length of the current interglacial
Determining the natural length of the current interglacial
复制标题
DOI：
10.1038/ngeo1358
复制
发表时间：
2012-02-01
影响因子：
18.3
通讯作者：
Skinner, L. C.
中科院分区：
文献类型：
--
作者：
Tzedakis, P. C.;Channell, J. E. T.;Skinner, L. C.
在目前大气CO2浓度为390 ppmv的情况下，预计不会发生冰川初期（参考文献1）。事实上，模型实验表明，在目前的轨道配置，其特点是在夏季日照弱最低，冰川的开始将需要低于工业化前水平的280 ppmv的CO2浓度（参考文献2-4）。然而，精确的二氧化碳阈值（4-6）以及假设的下一次冰川期的时间（7）仍然不清楚。过去的间冰期可以用来与现在进行类比，只要知道它们的持续时间。在这里，我们建议，最小年龄的冰川开始受到双极跷跷板气候变率，这需要足够大的冰盖产生冰山排放，破坏海洋环流的发病。我们确定的两极跷跷板在冰芯和北大西洋海洋记录的外观，一个明显的分阶段的半球间的气候和水文变化和冰筏碎片。海洋同位素子阶段19 c期间的冰川开始，与现在的间冰期非常相似，发生在夏季日照最低值附近，表明间冰期并没有因减弱的辐射强迫而延长（7）。假设冰的生长主要是对太阳辐射和CO2强迫的响应，这个类比表明，如果大气中CO2浓度不超过240 +/- 5 ppmv，当前间冰期的结束将在未来1500年内发生。
No glacial inception is projected to occur at the current atmospheric CO2 concentrations of 390 ppmv (ref. 1). Indeed, model experiments suggest that in the current orbital configuration-which is characterized by a weak minimum in summer insolation-glacial inception would require CO2 concentrations below preindustrial levels of 280 ppmv (refs 2-4). However, the precise CO2 threshold(4-6) as well as the timing of the hypothetical next glaciation(7) remain unclear. Past interglacials can be used to draw analogies with the present, provided their duration is known. Here we propose that the minimum age of a glacial inception is constrained by the onset of bipolar-seesaw climate variability, which requires ice-sheets large enough to produce iceberg discharges that disrupt the ocean circulation. We identify the bipolar seesaw in ice-core and North Atlantic marine records by the appearance of a distinct phasing of interhemispheric climate and hydrographic changes and ice-rafted debris. The glacial inception during Marine Isotope sub-Stage 19c, a close analogue for the present interglacial, occurred near the summer insolation minimum, suggesting that the interglacial was not prolonged by subdued radiative forcing(7). Assuming that ice growth mainly responds to insolation and CO2 forcing, this analogy suggests that the end of the current interglacial would occur within the next 1500 years, if atmospheric CO2 concentrations did not exceed 240 +/- 5 ppmv.