| 1. |
- Yang, Bingjie, et al.
(författare)
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Quantitative landscape reconstruction and erosion history during the past 1,100 years in the Skogaryd Research Catchment, southern Sweden
- 2020
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Ingår i: Vegetation History and Archaeobotany. - : Springer Science and Business Media LLC. - 0939-6314 .- 1617-6278. ; 29:6, s. 657-70
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Tidskriftsartikel (refereegranskat)abstract
- A sediment sequence from a small forest lake in southwestern Sweden was investigated to explore the effects of forestry and land-use on catchment erosion and delivery of organic and minerogenic matter to the lake. Catchment-scale vegetation changes during the last 1,100 years were reconstructed quantitatively at 50-year resolution using pollen analysis and the Landscape reconstruction algorithm (LRA). Variations in terrestrial organic matter input to lake sediments were assessed by total organic carbon (TOC) content and carbon to nitrogen (C/N) ratios. Changes in minerogenic matter were analysed using X-ray fluorescence (XRF) scanning. The results show that Skogaryd was not intensively used for agriculture throughout the past 1,100 years, but its land-use changes were very sensitive to societal changes. Between ca. ad 950 and 1350, local land-use was characterized by small-scale agricultural activities associated with the Medieval expansion, and enhanced soil erosion was recorded by increased K, Ti and Rb deposition. Around ad 1350 much of the farmland was abandoned, most likely in response to outbreaks of plague. The abandonment of farmland caused increased coniferous woodland cover and lower soil erosion. From the 16th century land-use expanded and gradually intensified, concurrent with a population increase documented in the study area between ca. ad 1600 and 1850. Intensive exploitation of the forest led to soil erosion and increased terrestrial organic and minerogenic matter export to the lake. These processes peaked with the artificial drainage of a nearby wetland for agricultural purposes. During the 20th century, modern forestry management started with the plantation of conifers, and soil erosion declined.
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| 2. |
- Eccleshall, Sarah V., et al.
(författare)
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Constraining the chronology of Pleistocene glaciations on Svalbard: Kapp Ekholm re-visited
- 2016
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Ingår i: Boreas. - : Wiley. - 0300-9483 .- 1502-3885. ; 45:4, s. 790-803
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Tidskriftsartikel (refereegranskat)abstract
- © 2016 Collegium Boreas. Published by John Wiley & Sons LtdThe Kapp Ekholm site, in central Spitsbergen, shows alternating units of glaciomarine sandy silt and diamicton representing three glacial cycles and is key in reconstructing the Late Pleistocene glacial history of Svalbard. Part of the site is reinvestigated here by focusing on re-dating two units (B and F) interpreted as interglacial/interstadial glaciomarine deposits, in order to constrain the controversial chronology. A combination of Optical Stimulated Luminescence (OSL) on quartz, infrared stimulated luminescence with a 50°C readout temperature (IRSL50) and post infrared-infrared stimulated luminescence (pIR), both on feldspar, was applied. While Formation B was beyond the dateable range of OSL, IRSL50 and pIR ages lead to the conclusion that this unit represents the Last Interglacial, Marine Isotope Stage (MIS) 5e, and the underlying diamicton the MIS 6 glacial. Formation F yielded ages implying that the formation represents the MIS 5a interstadial and the underlying diamicton is interpreted to represent the MIS 5b stadial. This agrees with conclusions drawn concerning the Pleistocene glaciations elsewhere on Svalbard.
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| 3. |
- Emile-Geay, J., et al.
(författare)
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Data Descriptor: A global multiproxy database for temperature reconstructions of the Common Era
- 2017
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Ingår i: Scientific Data. - : Springer Science and Business Media LLC. - 2052-4463. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- Reproducible climate reconstructions of the Common Era (1 CE to present) are key to placing industrial-era warming into the context of natural climatic variability. Here we present a community-sourced database of temperature-sensitive proxy records from the PAGES2k initiative. The database gathers 692 records from 648 locations, including all continental regions and major ocean basins. The records are from trees, ice, sediment, corals, speleothems, documentary evidence, and other archives. They range in length from 50 to 2000 years, with a median of 547 years, while temporal resolution ranges from biweekly to centennial. Nearly half of the proxy time series are significantly correlated with HadCRUT4.2 surface temperature over the period 1850-2014. Global temperature composites show a remarkable degree of coherence between high-and low-resolution archives, with broadly similar patterns across archive types, terrestrial versus marine locations, and screening criteria. The database is suited to investigations of global and regional temperature variability over the Common Era, and is shared in the Linked Paleo Data (LiPD) format, including serializations in Matlab, R and Python. Since the pioneering work of D'Arrigo and Jacoby1-3, as well as Mann et al. 4,5, temperature reconstructions of the Common Era have become a key component of climate assessments6-9. Such reconstructions depend strongly on the composition of the underlying network of climate proxies10, and it is therefore critical for the climate community to have access to a community-vetted, quality-controlled database of temperature-sensitive records stored in a self-describing format. The Past Global Changes (PAGES) 2k consortium, a self-organized, international group of experts, recently assembled such a database, and used it to reconstruct surface temperature over continental-scale regions11 (hereafter, ` PAGES2k-2013'). This data descriptor presents version 2.0.0 of the PAGES2k proxy temperature database (Data Citation 1). It augments the PAGES2k-2013 collection of terrestrial records with marine records assembled by the Ocean2k working group at centennial12 and annual13 time scales. In addition to these previously published data compilations, this version includes substantially more records, extensive new metadata, and validation. Furthermore, the selection criteria for records included in this version are applied more uniformly and transparently across regions, resulting in a more cohesive data product. This data descriptor describes the contents of the database, the criteria for inclusion, and quantifies the relation of each record with instrumental temperature. In addition, the paleotemperature time series are summarized as composites to highlight the most salient decadal-to centennial-scale behaviour of the dataset and check mutual consistency between paleoclimate archives. We provide extensive Matlab code to probe the database-processing, filtering and aggregating it in various ways to investigate temperature variability over the Common Era. The unique approach to data stewardship and code-sharing employed here is designed to enable an unprecedented scale of investigation of the temperature history of the Common Era, by the scientific community and citizen-scientists alike.
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| 4. |
- Gjerde, M., et al.
(författare)
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Holocene glacier variability and Neoglacial hydroclimate at Alfotbreen, western Norway
- 2016
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791. ; 133, s. 28-47
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Tidskriftsartikel (refereegranskat)abstract
- Glaciers and small ice caps respond rapidly to climate perturbations (mainly winter precipitation, and summer temperature), and the mass-balance of glaciers located in western Norway is governed mainly by winter precipitation (Pw). Records of past Pw can offer important insight into long-term changes in atmospheric circulation, but few proxies are able to accurately capture winter climate variations in Scandinavia. Reconstructions of equilibrium-line-altitude (ELA) variations from glaciers that are sensitive to changes in Pw therefore provide a unique opportunity to quantify past winter climate in this region. Here we present a new, Holocene glacier activity reconstruction for the maritime ice cap Alfotbreen in western Norway, based on investigations of distal glacier-fed lake sediments and modern mass balance measurements (1963-2010). Several lake sediment cores have been subject to a suite of laboratory analyses, including measurements of physical parameters such as dry bulk density (DBD) and loss-on-ignition (LOI), geochemistry (XRF), surface magnetic susceptibility (MS), and grain size distribution, to identify glacial sedimentation in the lake. Both radiocarbon (AMS C-14) and Pb-210 dating were applied to establish age-depth relationships in the sediment cores. A novel approach was used to calibrate the sedimentary record against a simple ELA model, which allowed reconstruction of continuous ELA changes for Alfotbreen during the Neoglacial (when Alfotbreen was present, i.e. the last similar to 1400 years). Furthermore, the resulting ELA variations were combined with an independent summer temperature record to calculate Neoglacial Pw using the 'Liestol equation'. The resulting Pw record is of higher resolution than previous reconstructions from glaciers in Norway and shows the potential of glacier records to provide high-resolution data reflecting past variations in hydroclimate. Complete deglaciation of the Alfotbreen occurred similar to 9700 cal yr BP, and the ice cap was subsequently absent or very small until a short-lived glacier event is seen in the lake sediments similar to 8200 cal yr BP. The ice cap was most likely completely melted until a new glacier event occurred around similar to 5300 cal yr BP, coeval with the onset of the Neoglacial at several other glaciers in southwestern Norway. Alfotbreen was thereafter absent (or very small) until the onset of the Neoglacial period similar to 1400 cal yr BP. The 'Little Ice Age' (LIA) similar to 650-50 cal yr BP was the largest glacier advance of Alfotbreen since deglaciation, with a maximum extent at similar to 400-200 cal yr BP, when the ELA was lowered approximately 200 m relative to today. The late onset of the Neoglacial at Alfotbreen is suggested to be a result of its low altitude relative to the regional ELA. A synthesis of Neoglacial ELA fluctuations along the coast of Norway indicates a time transgressive trend in the maximum extent of the LIA, which apparently seems to have occurred progressively later as we move northwards. We suggest that this trend is likely due to regional winter precipitation differences along the coast of Norway. (C) 2015 The Authors. Published by Elsevier Ltd.
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| 5. |
- Gjerde, M., et al.
(författare)
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Holocene multi-proxy environmental reconstruction from lake Hakluytvatnet, Amsterdamoya Island, Svalbard (79.5 degrees N)
- 2018
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791. ; 183, s. 164-176
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Tidskriftsartikel (refereegranskat)abstract
- High resolution proxy records of past climate are sparse in the Arctic due to low organic production that restricts the use of radiocarbon dating and challenging logistics that make data collection difficult. Here, we present a new lake record from lake Hakluytvatnet at Amsterdamoya island (79.5 degrees N), the north-westernmost island on Svalbard. Multi-proxy analyses of lake sediments in combination with geomorphological mapping reveal large environmental shifts that have taken place at Amsterdamoya during the Holocene. A robust chronology has been established for the lake sediment core through 28 AMS radiocarbon ages, and this gives an exceptionally well-constrained age control for a lake at this latitude. The Holocene was a period with large changes in the Hakluytvatnet catchment, and the onset of the Neoglacial (ca. 5 ka) marks the start of modern-day conditions in the catchment. The Neoglacial is characterized by fluctuations in the minerogenic input to the lake as well as internal productivity, and we suggest that these fluctuations are driven by atmospherically forced precipitation changes as well as sea ice extent modulating the amount of moisture that can reach Hakluytvatnet. (C) 2017 Elsevier Ltd. All rights reserved.
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| 6. |
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| 7. |
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| 8. |
- Nicolle, M, et al.
(författare)
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Climate variability in subarctic area for the last two millennia
- 2018
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Ingår i: Climate of the Past. - : Copernicus GmbH. - 1814-9324 .- 1814-9332. ; 14:1, s. 101-116
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Tidskriftsartikel (refereegranskat)abstract
- To put recent climate change in perspective, it is necessary to extend the instrumental climate records with proxy data from paleoclimate archives. Arctic climate variability for the last 2 millennia has been investigated using statistical and signal analyses from three regionally averaged records from the North Atlantic, Siberia and Alaska based on many types of proxy data archived in the Arctic 2k database v1.1.1. In the North Atlantic and Alaska, the major climatic trend is characterized by long-term cooling interrupted by recent warming that started at the beginning of the 19th century. This cooling is visible in the Siberian region at two sites, warming at the others. The cooling of the Little Ice Age (LIA) was identified from the individual series, but it is characterized by wide-range spatial and temporal expression of climate variability, in contrary to the Medieval Climate Anomaly. The LIA started at the earliest by around AD1200 and ended at the latest in the middle of the 20th century. The widespread temporal coverage of the LIA did not show regional consistency or particular spatial distribution and did not show a relationship with archive or proxy type either. A focus on the last 2 centuries shows a recent warming characterized by a well-marked warming trend parallel with increasing greenhouse gas emissions. It also shows a multidecadal variability likely due to natural processes acting on the internal climate system on a regional scale. A ∼16–30-year cycle is found in Alaska and seems to be linked to the Pacific Decadal Oscillation, whereas ∼20–30- and ∼50–90-year periodicities characterize the North Atlantic climate variability, likely in relation with the Atlantic Multidecadal Oscillation. These regional features are probably linked to the sea ice cover fluctuations through ice–temperature positive feedback.
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| 9. |
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| 10. |
- Philipps, W., et al.
(författare)
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Late Holocene glacier activity at inner Hornsund and Scottbreen, southern Svalbard
- 2017
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Ingår i: Journal of Quaternary Science. - : Wiley. - 0267-8179. ; 32:4, s. 501-515
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Tidskriftsartikel (refereegranskat)abstract
- New Be-10 dating on two late Holocene maximum moraines on the Treskelen Peninsula and at Scottbreen, Svalbard, improve constraints on the timing and character of Holocene glacial activity in this region. Average moraine ages of 1.9 +/- 0.3 ka (n=4) on the Treskelen Peninsula and 1.7 +/- 0.1 ka (n=5) on Scottbreen indicate the timing of a glacial culmination. The age of moraine abandonment at Treskelen and Scottbreen correlates with snowline lowering and glacier expansion between approximate to 2.0 and 1.5 ka observed elsewhere on Svalbard. Both Scottbreen and the glaciers near Treskelen have surged in the instrumental record, like many glaciers across Svalbard. Yet, the age relation between our possible surge-related moraines and other glacier records leads us to hypothesize that on centennial and longer timescales, climate forcing outweighs surge dynamics, which exerts a stronger control on glacier length on centennial timescales at our study sites.
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