Warm summers and rich biotic communities during N-Hemisphere deglaciation

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Helmens , K , Katrantsiotis , C , Salonen , J S , Shala , S , Bos , J , Engels , S , Kuosmanen , N , Luoto , T P , Väliranta , M M , Luoto , M , Ojala , A , Risberg , J & Weckström , J B 2018 , ' Warm summers and rich biotic communities during N-Hemisphere deglaciation ' , Global and Planetary Change , vol. 167 , pp. 61-73 . https://doi.org/10.1016/j.gloplacha.2018.05.004

Title: Warm summers and rich biotic communities during N-Hemisphere deglaciation
Author: Helmens, Karin; Katrantsiotis, Christos; Salonen, Jaakko Sakari; Shala, Shyhrete; Bos, Johanna; Engels, Stefan; Kuosmanen, Niina; Luoto, Tomi P.; Väliranta, Minna Maria; Luoto, Miska; Ojala, Antti; Risberg, Jan; Weckström, Jan Björn
Contributor: University of Helsinki, Department of Geosciences and Geography
University of Helsinki, Ecosystems and Environment Research Programme
University of Helsinki, Ecosystems and Environment Research Programme
University of Helsinki, Department of Geosciences and Geography
University of Helsinki, Helsinki Institute of Sustainability Science (HELSUS)
Date: 2018-08
Language: eng
Number of pages: 13
Belongs to series: Global and Planetary Change
ISSN: 0921-8181
URI: http://hdl.handle.net/10138/315576
Abstract: Detailed studies on fossil remains of plants or animals in glacial lake sediments are rare. As a result, environmental conditions right at the moment of deglaciation of the large N-Hemisphere ice-sheets remain largely unknown. Here we study three deglacial phases of the Fennoscandian Ice Sheet as a unique, repeated element in a long sediment record preserved at Sokli in northern Finland. We summarize extensive multi-proxy data (diatoms, phytoliths, chironomids, pollen, spores, non-pollen palynomorphs, macrofossils, lithology, loss-on-ignition, C/N) obtained on glacial lake sediments dated to the early Holocene (ca. 10 kyr BP), early MIS 3 (ca. 50 kyr BP) and early MIS 5a (ca. 80 kyr BP). In contrast to the common view of an unproductive ice-marginal environment, our study reconstructs rich ecosystems both in the glacial lake and along the shores with forest on recently deglaciated land. Higher than present-day summer temperatures are reconstructed based on a large variety of aquatic taxa. Rich biota developed due to the insolation-induced postglacial warming and high nutrient levels, the latter resulting from erosion of fresh bedrock and sediment, leaching of surface soils, decay of plant material under shallow water conditions, and sudden decreases in lake volume. Aquatic communities responded quickly to deglaciation and warm summers and reflect boreal conditions, in contrast to the terrestrial ecosystem which responded with some delay probably due to time required for slow soil formation processes. Birch forest is reconstructed upon deglaciation of the large LGM ice-sheet and shrub tundra following the probably faster melting smaller MIS 4 and MIS 5b ice-sheets. Our study shows that glacial lake sediments can provide valuable palaeo-environmental data, that aquatic biota and terrestrial vegetation rapidly accommodated to new environmental conditions during deglaciation, and that glacial lake ecosystems, and the carbon stored in their sediments, should be included in earth system modeling.
Subject: 1171 Geosciences
1172 Environmental sciences
Glacial lake sediment
Ice-marginal environment
Climate
Ecosystem response
Carbon storage
Fennoscandian Ice Sheet
GLACIAL LAKE AGASSIZ
WATER BRYOZOANS BRYOZOA
EASTERN EUROPEAN RUSSIA
MARINE ISOTOPE STAGE-3
SUB-ARCTIC FINLAND
EARLY-HOLOCENE
FINNISH LAPLAND
NORTHEASTERN FENNOSCANDIA
NORTHERN FENNOSCANDIA
ENVIRONMENTAL-CHANGE
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