| 1. |
- Kjellman, Sofia E., et al.
(författare)
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Holocene development of subarctic permafrost peatlands in Finnmark, northern Norway
- 2018
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Ingår i: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 28:12, s. 1855-1869
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Tidskriftsartikel (refereegranskat)abstract
- Subarctic permafrost peatlands are important soil organic carbon pools, and improved knowledge about peat properties and peatland sensitivity to past climate change is essential when predicting future response to a warmer climate and associated feedback mechanisms. In this study, Holocene peatland development and permafrost dynamics of four subarctic peat plateaus in Finnmark, northern Norway have been investigated through detailed analyses of plant macrofossils and geochemical properties. Peatland inception occurred around 9800 cal. yr BP and 9200 cal. yr BP at the two continental sites Suossjavri and Iskoras. Younger basal peat ages were found at the two coastal locations Lakselv and Karlebotn, at least partly caused by the time lag between deglaciation and emergence of land by isostatic uplift. Here, peatland development started around 6150 cal. yr BP and 5150 cal. yr BP, respectively. All four peatlands developed as wet fens throughout most of the Holocene. Permafrost aggradation, causing frost heave and a shift in the vegetation assemblage from wet fen to dry bog species, probably did not occur until during the last millennium, ca. 950 cal. yr BP in Karlebotn and ca. 800 cal. yr BP in Iskoras, and before ca. 150 cal. yr BP in Lakselv and ca. 100 cal. yr BP in Suossjavri. In Karlebotn, there are indications of a possible earlier permafrost phase around 2200 cal. yr BP due to climatic cooling at the late Subboreal to early Subatlantic transition. The mean long-term Holocene carbon accumulation rate at all four sites was 12.3 +/- 4.1 gC m(-2) yr(-1) (+/- SD) and the mean soil organic carbon storage was 97 +/- 46 kgC m(-2).
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| 2. |
- Orme, L. C., et al.
(författare)
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Climatic impacts on an Arctic lake since 1300 AD : a multi-proxy lake sediment reconstruction from Prins Karls Forland, Svalbard
- 2023
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Ingår i: Journal of Paleolimnology. - : Springer Science and Business Media LLC. - 0921-2728 .- 1573-0417. ; 69:3, s. 249-266
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Tidskriftsartikel (refereegranskat)abstract
- On the remote Arctic archipelago of Svalbard, there is increasing evidence of environmental impacts from climate change. The analysis of lake sedimentary records can be used to assess how strongly these recent changes have altered lake ecosystems. Sediments deposited during the last millennium from Lake Blokkvatnet, Prins Karls Forland, were analysed using a multiproxy approach, including stable isotope and X-ray fluorescence analysis. The results were interpreted as reflecting variability of (1) soil organic matter inwash, and potentially catchment and lake primary production, and (2) catchment weathering and erosion. Organic content began increasing after 1920 AD to the present, likely in response to warming. Earlier peaks of a similar magnitude occurred on three occasions since 1300 AD, with evidence indicating that these may have coincided with multidecadal-scale periods with higher temperatures, reduced sea ice and negative phases of the North Atlantic Oscillation. Catchment weathering and fluvial erosion began to increase around 1800 AD and peaked during the early twentieth century, potentially due to rising temperatures in autumn and winter causing increased liquid water availability. The records suggest that similar levels of erosion and weathering occurred between approximately 1300 and 1600 AD, spanning the transition from the Medieval Climate Anomaly to the Little Ice Age.
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| 3. |
- Alsos, Inger Greve, et al.
(författare)
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Ancient sedimentary DNA shows rapid post-glacial colonisation of Iceland followed by relatively stable vegetation until the Norse settlement (Landnam) AD 870
- 2021
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Ingår i: Quaternary Science Reviews. - : Elsevier. - 0277-3791 .- 1873-457X. ; 259
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Tidskriftsartikel (refereegranskat)abstract
- Understanding patterns of colonisation is important for explaining both the distribution of single species and anticipating how ecosystems may respond to global warming. Insular flora may be especially vulnerable because oceans represent severe dispersal barriers. Here we analyse two lake sediment cores from Iceland for ancient sedimentary DNA to infer patterns of colonisation and Holocene vegetation development. Our cores from lakes Torfdalsvatn and Nykurvatn span the last c. 12,000 cal yr BP and c. 8600 cal yr BP, respectively. With near-centennial resolution, we identified a total of 191 plant taxa, with 152 taxa identified in the sedimentary record of Torfdalsvatn and 172 plant taxa in the sedimentary record of Nykurvatn. The terrestrial vegetation at Torfdalsvatn was initially dominated by bryophytes, arctic herbs such as Saxifraga spp. and grasses. Around 10,100 cal yr BP, a massive immigration of new taxa was observed, and shrubs and dwarf shrubs became common whereas aquatic macrophytes became dominant. At Nykurvatn, the dominant taxa were all present in the earliest samples; shrubs and dwarf shrubs were more abundant at this site than at Torfdalsvatn. There was an overall steep increase both in the local accumulated richness and regional species pool until 8000 cal yr BP, by which time 3/4 of all taxa identified had arrived. The period 4500-1000 cal yr BP witnessed the appearance of a a small number of bryophytes, graminoids and forbs that were not recorded in earlier samples. The last millennium, after human settlement of the island (Landnam), is characterised by a sudden disappearance of Juniperus communis, but also reappearance of some high arctic forbs and dwarf shrubs. Notable immigration during the Holocene coincides with periods of increased incidence of sea ice, and we hypothesise that this may have acted as a dispersal vector. Thus, although ongoing climate change might provide a suitable habitat in Iceland for a large range of species only found in the neighbouring regions today, the reduction of sea ice may in fact limit the natural colonisation of new plant species.
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| 4. |
- Schomacker, Anders, et al.
(författare)
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Postglacial relative sea level change and glacier activity in the early and late Holocene: Wahlenbergfjorden, Nordaustlandet, Svalbard
- 2019
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- Sediment cores from Kløverbladvatna, a threshold lake in Wahlenbergfjorden, Nordaustlandet, Svalbard were used to reconstruct Holocene glacier fluctuations. Meltwater from Etonbreen spills over a threshold to the lake, only when the glacier is significantly larger than at present. Lithological logging, loss-on-ignition, ITRAX scanning and radiocarbon dating of the cores show that Kløverbladvatna became isolated from Wahlenbergfjorden c. 5.4 cal. kyr BP due to glacioisostatic rebound. During the Late Holocene, laminated clayey gyttja from lacustrine organic production and surface runoff from the catchment accumulated in the lake. The lacustrine sedimentary record suggests that meltwater only spilled over the threshold at the peak of the surge of Etonbreen in AD 1938. Hence, we suggest that this was the largest extent of Etonbreen in the (mid-late) Holocene. In Palanderbukta, a tributary fjord to Wahlenbergfjorden, raised beaches were surveyed and organic material collected to determine the age of the beaches and reconstruct postglacial relative sea level change. The age of the postglacial raised beaches ranges from 10.7 cal. kyr BP at 50 m a.s.l. to 3.13 cal. kyr BP at 2 m a.s.l. The reconstructed postglacial relative sea level curve adds valuable spatial and chronological data to the relative sea level record of Nordaustlandet.
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| 5. |
- Voldstad, Linn H., et al.
(författare)
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A complete Holocene lake sediment ancient DNA record reveals long-standing high Arctic plant diversity hotspot in northern Svalbard
- 2020
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Ingår i: Quaternary Science Reviews. - : Elsevier. - 0277-3791 .- 1873-457X. ; 234
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Tidskriftsartikel (refereegranskat)abstract
- Arctic hotspots, local areas of high biodiversity, are potential key sites for conservation of Arctic biodiversity. However, there is a need for improved understanding of their long-term resilience. The Arctic hotspot of Ringhorndalen has the highest registered diversity of vascular plants in the Svalbard archipelago, including several remarkable and isolated plant populations located far north of their normal distribution range. Here we analyze a lake sediment core from Ringhorndalen for sedimentary ancient DNA (sedaDNA) and geochemical proxies to detect changes in local vegetation and climate. Half of the plant taxa appeared already before 10,600 cal. yr BP, indicating rapid colonization as the ice retreated. Thermophilous species had a reoccurring presence throughout the Holocene record, but stronger signal in the early than Late Holocene period. Thus, thermophilous Arctic plant species had broader distribution ranges during the Early Holocene thermal maximum c. 10,000 cal. yr BP than today. Most of these thermophilous species are currently not recorded in the catchment area of the studied lake, but occur locally in favourable areas further into the valley. For example, Empetrum nigrum was found in >40% of the sedaDNA samples, whereas its current distribution in Ringhorndalen is highly restricted and outside the catchment area of the lake. Our findings support the hypothesis of isolated relict populations in Ringhorndalen. The findings are also consistent with main Holocene climatic shifts in Svalbard identified by previous studies and indicate an early warm and species-rich postglacial period until c. 6500 cal. yr BP, followed by fluctuating cool and warm periods throughout the later Holocene.
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