Surface changes in the eastern Labrador Sea around the onset of the Little Ice Age

Surface changes in the eastern Labrador Sea around the onset of the Little Ice Age

Despite the relative climate stability of the present interglacial, it has been punctuated by several centennial-scale climatic oscillations; the latest of which are often colloquially referred to as the Medieval Climatic Anomaly (MCA) and the Little Ice Age (LIA). The most favored explanation for the cause of these anomalies is that they were triggered by variability in solar irradiance and/or volcanic activity and amplified by ocean-atmosphere-sea ice feedbacks. As such, changes in the strength of the Atlantic Meridional Overturning Circulation (AMOC) are widely believed to have been involved in the amplification of such climatic oscillations. The Labrador Sea is a key area of deep water formation. The waters produced here contribute approximately one third of the volume transport of the deep limb of the AMOC and drive changes in the North Atlantic surface hydrography and subpolar gyre circulation. In this study, we present multiproxy reconstructions from a high-resolution marine sediment core located south of Greenland that suggest an increase in the influence of polar waters reaching the Labrador Sea close to MCA-LIA transition. Changes in freshwater forcing may have reduced the formation of Labrador Sea Water and contributed toward the onset of the LIA cooling.Key PointsThe Labrador Sea is a key deep water formation site Evidence for surface cooling at the onset of the Little Ice Age (similar to 1400 years A.D.) Increase influence of polar waters may have reduced deep water formation

尽管当前间冰期气候相对稳定，但也被几次百年尺度的气候振荡所打断；其中最近的几次通常通俗地被称为中世纪气候异常（MCA）和小冰期（LIA）。对于这些异常现象的成因，最受青睐的解释是它们由太阳辐照度和/或火山活动的变化所引发，并由海洋 - 大气 - 海冰反馈所放大。因此，人们普遍认为大西洋经向翻转环流（AMOC）强度的变化参与了此类气候振荡的放大过程。拉布拉多海是深水形成的关键区域。这里产生的海水约占AMOC深层分支体积输送量的三分之一，并驱动北大西洋表层水文和亚极地环流的变化。在这项研究中，我们展示了来自格陵兰岛南部一个高分辨率海洋沉积岩芯的多指标重建结果，该结果表明在接近MCA - LIA过渡时期，到达拉布拉多海的极地海水的影响有所增加。淡水强迫的变化可能减少了拉布拉多海水的形成，并促成了小冰期变冷的开始。 要点 拉布拉多海是一个关键的深水形成地点 小冰期开始时（约公元1400年）表面变冷的证据 极地海水影响的增加可能减少了深水形成