Institute for Interdisciplinary Mountain Research, Austrian Academy of Sciences, Innsbruck, Austria.
Department of Environmental Sciences, Informatics and Statistics, Ca'Foscari University of Venice, Venice, Italy.
Sci Rep. 2020 Dec 17;10(1):20513. doi: 10.1038/s41598-020-77518-9.
Detailed knowledge of Holocene climate and glaciers dynamics is essential for sustainable development in warming mountain regions. Yet information about Holocene glacier coverage in the Alps before the Little Ice Age stems mostly from studying advances of glacier tongues at lower elevations. Here we present a new approach to reconstructing past glacier low stands and ice-free conditions by assessing and dating the oldest ice preserved at high elevations. A previously unexplored ice dome at Weißseespitze summit (3500 m), near where the "Tyrolean Iceman" was found, offers almost ideal conditions for preserving the original ice formed at the site. The glaciological settings and state-of-the-art micro-radiocarbon age constraints indicate that the summit has been glaciated for about 5900 years. In combination with known maximum ages of other high Alpine glaciers, we present evidence for an elevation gradient of neoglaciation onset. It reveals that in the Alps only the highest elevation sites remained ice-covered throughout the Holocene. Just before the life of the Iceman, high Alpine summits were emerging from nearly ice-free conditions, during the start of a Mid-Holocene neoglaciation. We demonstrate that, under specific circumstances, the old ice at the base of high Alpine glaciers is a sensitive archive of glacier change. However, under current melt rates the archive at Weißseespitze and at similar locations will be lost within the next two decades.
详细了解全新世气候和冰川动态对于变暖山区的可持续发展至关重要。然而，小冰期之前阿尔卑斯山全新世冰川覆盖的信息主要来自研究较低海拔处冰川舌的前进。在这里，我们通过评估和确定保存在高海拔地区的最古老的冰来提出一种重建过去冰川低位和无冰条件的新方法。在 Weißseespitze 山顶（3500 米），一个以前未被探索的冰穹顶提供了保存原始冰的几乎理想条件，该冰穹顶位于发现“蒂罗尔冰人”的地方附近。冰川学背景和最先进的微碳测年限制表明，该山顶已经被冰川覆盖了大约 5900 年。结合其他高山冰川的已知最大年龄，我们提供了新冰期开始的海拔梯度的证据。它表明，在阿尔卑斯山，只有最高的海拔地点在整个全新世都保持着冰雪覆盖。就在冰人生活之前，高阿尔卑斯山的山顶刚刚从几乎无冰的条件下显露出来，这是中全新世新冰期的开始。我们证明，在特定情况下，高山冰川底部的旧冰是冰川变化的敏感档案。然而，根据目前的融化速度，在 Weißseespitze 和类似地点的档案将在未来二十年左右内消失。
