School of Geography, Earth and Atmospheric Sciences, University of Melbourne, Melbourne, Victoria, Australia.
Department of Geological Sciences and the Human Evolution Research Institute, University of Cape Town, Rondebosch, Western Cape, South Africa.
Nature. 2024 Feb;626(7998):319-326. doi: 10.1038/s41586-023-06989-3. Epub 2024 Feb 7.
Late Pleistocene ice-age climates are routinely characterized as having imposed moisture stress on low- to mid-latitude ecosystems. This idea is largely based on fossil pollen evidence for widespread, low-biomass glacial vegetation, interpreted as indicating climatic dryness. However, woody plant growth is inhibited under low atmospheric CO (refs. ), so understanding glacial environments requires the development of new palaeoclimate indicators that are independent of vegetation. Here we show that, contrary to expectations, during the past 350 kyr, peaks in southern Australian climatic moisture availability were largely confined to glacial periods, including the Last Glacial Maximum, whereas warm interglacials were relatively dry. By measuring the timing of speleothem growth in the Southern Hemisphere subtropics, which today has a predominantly negative annual moisture balance, we developed a record of climatic moisture availability that is independent of vegetation and extends through multiple glacial-interglacial cycles. Our results demonstrate that a cool-moist response is consistent across the austral subtropics and, in part, may result from reduced evaporation under cool glacial temperatures. Insofar as cold glacial environments in the Southern Hemisphere subtropics have been portrayed as uniformly arid, our findings suggest that their characterization as evolutionary or physiological obstacles to movement and expansion of animal, plant and, potentially, human populations should be reconsidered.
更新世晚期的冰期气候通常被认为给低纬和中纬生态系统带来了水分胁迫。这种观点主要基于广泛存在的低生物量冰川植被的化石花粉证据，这些证据被解释为表明气候干燥。然而，树木的生长受到大气 CO2（参考文献）含量的抑制，因此，理解冰川环境需要开发新的与植被无关的古气候指标。在这里，我们表明，与预期相反，在过去的 350 千年来，澳大利亚南部气候水分可用性的峰值主要局限于冰川期，包括末次冰盛期，而温暖的间冰期则相对干燥。通过测量南亚热带洞穴石笋的生长时间，我们开发了一种与植被无关的气候水分可用性记录，该记录可以延伸到多个冰期-间冰期循环。我们的结果表明，凉爽湿润的反应在澳大利亚南部亚热带地区是一致的，部分原因可能是在寒冷的冰川温度下蒸发减少。由于南半球亚热带的寒冷冰川环境一直被描绘为普遍干旱，我们的发现表明，应该重新考虑将其描述为动物、植物，以及可能人类种群迁移和扩张的进化或生理障碍。
