Holocene development of the Vaisjeäggi palsa mire, Finnish Lapland |
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| Authors: | PIRITA O OKSANEN |
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| Institution: | Arctic Centre, University of Lapland, P.O. Box 122, FIN-96101 Rovaniemi, Finland |
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| Abstract: | A palsa mire in Finnish Lapland is studied by means of plant macrofossil analysis, physico-chemical analysis and AMS radiocarbon dating of peat deposits in order to reconstruct its development. Emphasis was on permafrost dynamics during the Holocene. Mire initiation recorded at four studied sites took place between 8240 and 5210?yr?BP, first through terrestrialization of a pond and, beginning from 6780?yr?BP, through paludification of birch-dominated uplands. Slow lateral expansion of the mire suggests relatively dry conditions in the region. Rich wet fens prevailed until the late Holocene, when changes connected with permafrost development occurred. First permafrost aggradation is recorded in a high palsa site at c. 2460?yr?BP. The pathway of permafrost formation possibly points to a climate cooler than today. Permafrost aggradation in a ridge palsa site is dated to c. 645?yr?BP, indicating an early Little Ice Age date. The long-time average carbon accumulation rate in the four peat profiles is 16?gC/m2yr. In the older, high palsa, carbon accumulation during the palsa stage has been low (9?gC/m2yr), while in the younger, ridge palsa site it has been very high (73?gC/m2yr). |
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