Geological Survey of Finland, P.O. Box 77, FI-96101 Rovaniemi, Finland.
Department of Environmental Sciences, University of Helsinki, P.O. Box 65, FI-00014, Finland.
Sci Rep. 2016 Jul 1;6:29054. doi: 10.1038/srep29054.
Old sedimentological and geochronological records can be preserved underneath the central parts of the continental ice sheets under non-erosive, cold-based subglacial conditions. Organic deposits that predate the last deglaciation are of particular value for the information held on glacial-time climate and environmental conditions. In this study, we present multiproxy data derived from a well-preserved MIS 3 interstadial (55-25 ka ago) organic layer from inside the Arctic Circle in the Finnish Lapland. Biological proxy evidence, namely coming from aquatic plant species, indicates July temperatures as high as 14.4 °C, i.e. higher than those of today for the study site. Macrofossil evidence demonstrates for the first time the presence of pines accompanied by tree birch during the MIS 3 interstadial in northern Fennoscandia. These results concur with contemporary insolation model outcomes but contradict with the previous proxy-based view of open tundra conditions during the MIS 3. The data suggest that there are highly dynamic interstadial continental ice-sheet dynamics following changes in orbital forcing. Warm climate enabled the establishment of forests on exposed landscape. Moreover, we suggest that in the light of these new data, previous MIS 3 pollen data could be re-interpreted.
旧的沉积学和地球年代学记录可以在大陆冰盖中心部分的非侵蚀性、冷基底冰下条件下保存下来。在末次冰消期之前的有机沉积物对于记录冰川时期的气候和环境条件具有特别重要的意义。在这项研究中，我们提供了来自芬兰拉普兰北极圈内保存完好的 MIS 3 间冰期（55-25 千年前）有机层的多指标数据。生物指标证据，即来自水生植物物种的证据表明，7 月的温度高达 14.4°C，即比研究地点的今天还要高。大型植物证据首次证明，在北芬诺斯堪的亚的 MIS 3 间冰期期间，松树与桦树一起存在。这些结果与当代太阳辐射模型的结果一致，但与之前基于代理的 MIS 3 期间开阔冻原条件的观点相矛盾。这些数据表明，在轨道强迫变化的情况下，大陆冰盖存在高度动态的间冰期动态。温暖的气候使森林能够在裸露的地貌上建立起来。此外，我们建议，根据这些新数据，以前的 MIS 3 花粉数据可以重新解释。
