| 1. |
- Dalton, A. S., et al.
(författare)
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An updated radiocarbon-based ice margin chronology for the last deglaciation of the North American Ice Sheet Complex
- 2020
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791. ; 234
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Tidskriftsartikel (refereegranskat)abstract
- The North American Ice Sheet Complex (NAISC; consisting of the Laurentide, Cordilleran and Innuitian ice sheets) was the largest ice mass to repeatedly grow and decay in the Northern Hemisphere during the Quaternary. Understanding its pattern of retreat following the Last Glacial Maximum is critical for studying many facets of the Late Quaternary, including ice sheet behaviour, the evolution of Holocene landscapes, sea level, atmospheric circulation, and the peopling of the Americas. Currently, the most up-to-date and authoritative margin chronology for the entire ice sheet complex is featured in two publications (Geological Survey of Canada Open File 1574 [Dyke et al., 2003]; 'Quaternary Glaciations - Extent and Chronology, Part II' [Dyke, 2004]). These often-cited datasets track ice margin recession in 36 time slices spanning 18 ka to 1 ka (all ages in uncalibrated radiocarbon years) using a combination of geomorphology, stratigraphy and radiocarbon dating. However, by virtue of being over 15 years old, the ice margin chronology requires updating to reflect new work and important revisions. This paper updates the aforementioned 36 ice margin maps to reflect new data from regional studies. We also update the original radiocarbon dataset from the 2003/2004 papers with 1541 new ages to reflect work up to and including 2018. A major revision is made to the 18 ka ice margin, where Banks and Eglinton islands (once considered to be glacial refugia) are now shown to be fully glaciated. Our updated 18 ka ice sheet increased in areal extent from 17.81 to 18.37 million km(2), which is an increase of 3.1% in spatial coverage of the NAISC at that time. Elsewhere, we also summarize, region-by-region, significant changes to the deglaciation sequence. This paper integrates new information provided by regional experts and radiocarbon data into the deglaciation sequence while maintaining consistency with the original ice margin positions of Dyke et al. (2003) and Dyke (2004) where new information is lacking; this is a pragmatic solution to satisfy the needs of a Quaternary research community that requires up-to-date knowledge of the pattern of ice margin recession of what was once the world's largest ice mass. The 36 updated isochrones are available in PDF and shapefile format, together with a spreadsheet of the expanded radiocarbon dataset (n = 5195 ages) and estimates of uncertainty for each interval. (C) 2020 Elsevier Ltd. All rights reserved.
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| 2. |
- Sundqvist, Hanna S., et al.
(författare)
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Arctic Holocene proxy climate database - new approaches to assessing geochronological accuracy and encoding climate variables
- 2014
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Ingår i: Climate of the Past. - : Copernicus GmbH. - 1814-9324 .- 1814-9332. ; 10:4, s. 1605-1631
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Tidskriftsartikel (refereegranskat)abstract
- We present a systematic compilation of previously published Holocene proxy climate records from the Arctic. We identified 170 sites from north of 58 degrees N latitude where proxy time series extend back at least to 6 cal ka (all ages in this article are in calendar years before present - BP), are resolved at submillennial scale (at least one value every 400 +/- 200 years) and have age models constrained by at least one age every 3000 years. In addition to conventional meta-data for each proxy record (location, proxy type, reference), we include two novel parameters that add functionality to the database. First, climate interpretation is a series of fields that logically describe the specific climate variable(s) represented by the proxy record. It encodes the proxy-climate relation reported by authors of the original studies into a structured format to facilitate comparison with climate model outputs. Second, geochronology accuracy score (chron score) is a numerical rating that reflects the overall accuracy of C-14-based age models from lake and marine sediments. Chron scores were calculated using the original author-reported C-14 ages, which are included in this database. The database contains 320 records (some sites include multiple records) from six regions covering the circumpolar Arctic: Fennoscandia is the most densely sampled region (31% of the records), whereas only five records from the Russian Arctic met the criteria for inclusion. The database contains proxy records from lake sediment (60 %), marine sediment (32 %), glacier ice (5 %), and other sources. Most (61 %) reflect temperature (mainly summer warmth) and are primarily based on pollen, chironomid, or diatom assemblages. Many (15 %) reflect some aspect of hydroclimate as inferred from changes in stable isotopes, pollen and diatom assemblages, humification index in peat, and changes in equilibrium-line altitude of glaciers. This comprehensive database can be used in future studies to investigate the spatio-temporal pattern of Arctic Holocene climate changes and their causes. The Arctic Holocene data set is available from NOAA Paleoclimatology.
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| 3. |
- Young, N. E., et al.
(författare)
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Deglaciation of coastal south-western Spitsbergen dated with in situ cosmogenic Be-10 and C-14 measurements
- 2018
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Ingår i: Journal of Quaternary Science. - : Wiley. - 0267-8179. ; 33:7, s. 763-776
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Tidskriftsartikel (refereegranskat)abstract
- The Svalbard-Barents ice sheet was predominantly a marine-based ice sheet and reconstructing the timing and rate of its decay during the last deglaciation informs predictions of future decay of marine-based ice sheets (e.g. West Antarctica). Records of ice-sheet change are routinely built with cosmogenic surface exposure ages, but in some regions, this method is complicated by the presence of isotopic inheritance yielding artificially old and erroneous exposure ages for the most recent deglaciation. We present 46 Be-10 ages from south-western Spitsbergen that, when paired with in situ(14)C measurements (n=5), constrain the timing of coastal deglaciation following the last glacial maximum. Be-10 and in situ(14)C measurements from bedrock along a approximate to 400-m elevation transect reveal inheritance-skewed Be-10 ages, whereas in situ(14)C measurements constrain 400m of ice-sheet thinning and coastal deglaciation at 17.4 +/- 1.5 ka. Our in situ(14)C-dated transect, combined with three additional Be-10-dated coastal sites, show that the south-western margin of the Svalbard-Barents ice sheet retreated out of the Norwegian Sea between approximate to 18 and 16 ka. In situ(14)C measurements provide key chronological information on ice-sheet response to the last termination in cases where measurements of long-lived nuclides are compromised by isotopic inheritance.
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| 4. |
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| 5. |
- 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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