Quantitative estimates of tropical temperature change in lowland Central America during the last 42 ka
Quantitative estimates of tropical temperature change in lowland Central America during the last 42 ka
复制标题
DOI：
10.1016/j.epsl.2016.01.001
复制
发表时间：
2016-03
影响因子：
5.3
通讯作者：
Anna-Lena Grauel;D. Hodell;S. Bernasconi
中科院分区：
文献类型：
--
作者：
Anna-Lena Grauel;D. Hodell;S. Bernasconi
确定末次冰期热带气温变化幅度是古气候研究中的一个基本问题。从海洋和陆地档案推断的热带冷却估计存在很大的差异。在这里，我们提出了一个重建的温度为过去42 ka从佩滕伊察湖，危地马拉，位于17°N在低地中美洲的湖泊沉积物核心。我们比较了三种独立的冰川温度重建方法：基于花粉的温度估计，串联测量生物碳酸盐和石膏水化水中的δ 18 O，以及聚集同位素测温法。花粉提供了一个几乎连续的记录的温度变化的大部分冰期，但发生的无模拟花粉组合在寒冷，干燥的stadials呈现温度估计不可靠的这些间隔。相比之下，石膏水化和凝块同位素方法主要限于石膏和生物碳酸盐共生的阶段。孢粉学和地球化学方法的结合导致连续记录的热带温度变化在低地中美洲在过去的42 ka。此外，石膏水化水方法和凝块同位素测温法不仅提供了温度的独立估计，而且还提供了湖水的δ 18 O，这取决于湖面及其集水区蒸发和降水之间的水文平衡。结果表明，中美洲低地的平均冰川温度比全新世低5-10 °C。最冷和最干燥的时期发生在北大西洋的海象事件期间，特别是海因里希海象事件（HS），当时的温度比今天下降了6至10 °C。这种冷却的幅度是远远大于估计来自加勒比海的海洋记录和模式simulation.The极端干燥和寒冷的条件下，在HSs在中美洲的低地与淡水强迫在北大西洋，这导致减少大西洋经向翻转环流，冷却北大西洋，南推进海冰，和南移的热带辐合带。虽然一些模型正确地预测了温度和降水变化的迹象，但它们始终低估了中美洲低地陆地上观测到的降温和降水减少的程度。
Determining the magnitude of tropical temperature change during the last glacial period is a fundamental problem in paleoclimate research. Large discrepancies exist in estimates of tropical cooling inferred from marine and terrestrial archives. Here we present a reconstruction of temperature for the last 42 ka from a lake sediment core from Lake Petén Itzá, Guatemala, located at 17°N in lowland Central America. We compared three independent methods of glacial temperature reconstruction: pollen-based temperature estimates, tandem measurements ofδ18O in biogenic carbonate and gypsum hydration water, and clumped isotope thermometry. Pollen provides a near-continuous record of temperature change for most of the glacial period but the occurrence of a no-analog pollen assemblage during cold, dry stadials renders temperature estimates unreliable for these intervals. In contrast, the gypsum hydration and clumped isotope methods are limited mainly to the stadial periods when gypsum and biogenic carbonate co-occur. The combination of palynological and geochemical methods leads to a continuous record of tropical temperature change in lowland Central America over the last 42 ka. Furthermore, the gypsum hydration water method and clumped isotope thermometry provide independent estimates of not only temperature, but also theδ18O of lake water that is dependent on the hydrologic balance between evaporation and precipitation over the lake surface and its catchment. The results show that average glacial temperature was cooler in lowland Central America by 5–10 °C relative to the Holocene. The coldest and driest times occurred during North Atlantic stadial events, particularly Heinrich stadials (HSs), when temperature decreased by up to 6 to 10 °C relative to today. This magnitude of cooling is much greater than estimates derived from Caribbean marine records and model simulations.The extreme dry and cold conditions during HSs in the lowland Central America were associated with fresh water forcing in the North Atlantic, which led to reduced Atlantic Meridional Overturning Circulation, cooling of the North Atlantic, southern advance of sea-ice, and southward shift of the Intertropical Convergence Zone. Although some models correctly predict the sign of temperature and precipitation changes, they consistently underestimate the degree of observed cooling and decreased precipitation over land in lowland Central America.