| 1. |
- Beaudoin, Anne, et al.
(författare)
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Palaeoenvironmental history of the last six centuries in the Nettilling Lake area (Baffin Island, Canada) : A multi-proxy analysis
- 2016
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Ingår i: The Holocene. - : Sage Publications. - 0959-6836 .- 1477-0911. ; 26:11, s. 1835-1846
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Tidskriftsartikel (refereegranskat)abstract
- The Baffin Island region in the eastern Canadian Arctic has recently experienced a rapid warming, possibly unprecedented in millennia. To investigate theresponse of freshwater environments to this warming and place it in a secular perspective, we analyzed a 90-cm-long sediment core from Nettilling Lake,the largest lake of the Canadian Arctic Archipelago. The core was taken from a part of the lake basin that receives meltwater and sediment inputs from thenearby Penny Ice Cap. The core time scale, established using 137Cs and palaeomagnetic techniques, spans an estimated 600 years. A multi-proxy approachwas used to document changes in the physical, chemical, and biological properties of the sediments. We found evidence for a relatively warm period (mid/late 15th century to mid/late 16th century) during the early part of the ‘Little Ice Age’ (LIA), characterized by high sedimentation rates and laminations.This was followed by colder, drier, and windier conditions corresponding to the coldest phase of LIA and coinciding with the latest and most extensiveperiod of regional ice cap expansion (early 16th to late 19th centuries). A rapid warming occurred at the beginning of the 20th century. Variations intitanium (Ti) content in the core, a proxy for detrital sediment inputs, showed good agreement with reconstructed secular variations in summer meltrates on Penny Ice Cap between the mid-14th century and the present-day, providing supporting evidence for a climatic–hydrological connection betweenthe ice cap and Nettilling Lake.
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| 2. |
- Beaudoin, Anne, et al.
(författare)
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Paleoenvironmental reconstructions of Nettilling Lake area (Baffin Island, Nunavut) : A multi-proxy analysis
- 2014
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Konferensbidrag (refereegranskat)abstract
- The paleoclimate and paleolimnological history of several Arctic regions remains poorly known. This is the casefor the area around Nettilling Lake (Baffin Island, Nunavut), the largest lake of the Canadian Arctic Archipelago.To reconstruct the past environmental history of this area, a highly innovative multi-proxy approach combiningphysical, magnetic, chemical and biological properties preserved in lake sediments was used. One particular goalof this study was to investigate the possible coupling between sedimentation processes observed in the lake andmelt rates of nearby Penny Ice Cap.A 1-m long sediment core was retrieved from a small bay in the northeastern part of Nettilling Lake duringthe summer of 2010. This sampling area was chosen based on the hypothesis that incoming glacial meltwatersfrom Penny Ice Cap would leave a strong climate-modulated signal that would be reflected in the sedimentarysequence. The core was analyzed by both non-destructive (X-radiography (X-ray), microfluorescence-X (-XRF),magnetic susceptibility) and destructive (Loss On Ignition, grain size, water content, thin sections, diatoms)techniques. Radiometric AMS 14C and 210Pb/137Cs age determinations, as well as paleomagnetic measurements,were used to develop the core chronology, yielding an estimated bottom age of approximately 1365 AD.The sedimentation rate (0.15 cm.yr-1) in Nettilling Lake was found to be high compared to other Arctic lakes,due to inputs of highly turbid meltwaters from Penny Ice Cap with high suspended sediment loads. Significantcorrelations were found between geochemical profiles of elements linked to detrital inputs (Si, Ti, K, Ca) and meltrates from Penny Ice Cap since the 19th century. This suggests that variations in detrital elements in NettillingLake sediments might be used as an indirect indicator of regional climate fluctuations (e.g., summer temperatures) that determine glacier melt rates.
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| 3. |
- Jennings, Anne E., et al.
(författare)
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Baffin Bay paleoenvironments in the LGM and HS1 : Resolving the ice-shelf question
- 2018
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Ingår i: Marine Geology. - : Elsevier BV. - 0025-3227 .- 1872-6151. ; 402, s. 5-16
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Tidskriftsartikel (refereegranskat)abstract
- Core HU2008029-12PC from the Disko trough mouth fan on the central West Greenland continental slope is used to test whether an ice shelf covered Baffin Bay during the Last Glacial Maximum (LGM) and at the onset of the deglaciation. We use benthic and planktic foraminiferal assemblages, stable isotope analysis of planktic forams, algal biomarkers, ice-rafted detritus (IRD), lithofacies characteristics defined from CT scans, and quantitative mineralogy to reconstruct paleoceanographic conditions, sediment processes and sediment provenance. The chronology is based on radiocarbon dates on planktic foraminifers using a Delta R of 140 +/- 30 C-14 years, supplemented by the varying reservoir estimates of Stern and Lisiecki (2013) that provide an envelope of potential ages. HU2008029-12PC is bioturbated throughout. Sediments between the core base at 11.3 m and 4.6 m (LGM through HS1) comprise thin turbidites, plumites and hemipelagic sediments with Greenlandic provenance consistent with processes active at the Greenland Ice Sheet margin grounded at or near the shelf edge. Abundance spikes of planktic forams coincide with elevated abundance of benthic forams in assemblages indicative of chilled Atlantic Water, meltwater and intermittent marine productivity. IRD and IP25 are rare in this interval, but brassicasterol, an indicator of marine productivity reaches and sustains low levels during the LGM. These biological characteristics are consistent with a sea-ice covered ocean experiencing periods of more open water such as leads or polynyas in the sea ice cover, with chilled Atlantic Water at depth, rather than full iceshelf cover. They do not support the existence of a full Baffin Bay ice shelf cover extending from grounded ice on the Davis Strait. Initial ice retreat from the West Greenland margin is manifested by a pronounced lithofacies shift to bioturbated, diatomaceous mud with rare IRD of Greenlandic origin at 467 cm (16.2 cal ka BP; Delta R = 140 yrs) within HS1. A spike in foraminiferal abundance and ocean warmth indicator benthic forams precedes the initial ice retreat from the shelf edge. At the end of HS1, IP 25 , brassicasterol and benthic forams indicative of sea-ice edge productivity increase, indicating warming interstadial conditions. Within the Bolling/Allerod interstadial a strong rise in IP 25 content and IRD spikes rich in detrital carbonate from northern Baffin Bay indicate that northern Baffin Bay ice streams were retreating and provides evidence for increased open water, advection of Atlantic Water in the West Greenland Current, and formation of an IRD belt along the W. Greenland margin.
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| 4. |
- Kliem, Pierre, et al.
(författare)
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Lithology, radiocarbon chronology and sedimentological interpretation of the lacustrine record from Laguna Potrok Aike, southern Patagonia
- 2013
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 71, s. 54-69
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Tidskriftsartikel (refereegranskat)abstract
- The 106 m long composite profile from site 2 of ICDP expedition 5022 (PASADO) at Laguna Potrok Aike documents a distinct change in sedimentation patterns from pelagic sediments at the top to dominating mass movement deposits at its base. The main lithological units correspond to the Holocene, to the Lateglacial and to the last glacial period and can be interpreted as the result of distinct environmental variations. Overflow conditions might have been achieved during the last glacial period, while signs of desiccation are absent in the studied sediment record. Altogether, 58 radiocarbon dates were used to establish a consistent age-depth model by applying the mixed-effect regression procedure which results in a basal age of 51.2 cal. ka BP. Radiocarbon dates show a considerable increase in scatter with depth which is related to the high amount of reworking. Validation of the obtained chronology was achieved with geomagnetic relative paleointensity data and tephra correlation.
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| 5. |
- West, Gabriel, 1978-
(författare)
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A multimethod approach to dating Quaternary sediments from the Arctic Ocean
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The marine sedimentary environment in the polar regions is different from the rest of the world’s oceans, as it is greatly influenced by the cryosphere. In the Arctic, sea ice and icebergs can transport vast amounts of sediments, delivered by extensive fluvial systems from the surrounding continents, which have been shaped by the waxing and waning of large terrestrial ice sheets during the Quaternary period. Reconstructing palaeoenvironmental changes in the Arctic Ocean during this time requires the accurate dating of marine sediment cores, something that has been more difficult than in most other marine environments.This thesis investigates and integrates less developed methods to date marine sediments in the Arctic Ocean. It focuses on applying amino acid racemization geochronology and optically stimulated luminescence dating to sediments from across the Arctic Ocean, accompanied by palaeo- and rock magnetic measurements, and sedimentological analyses.The presented results show that racemization of aspartic and glutamic acids in foraminifera follow a predictable rate at the Yermak Plateau and the Greenland and Iceland Seas, and existing calibrated age equations can be used to confidently date late Quaternary sediments in these regions. Purportedly high rates of racemization are observed in the benthic foraminifera, Cibicidoides wuellerstorfi from central Arctic sediments, confirming that the high rates cannot be attributed to taxonomic effects. Their possible causes, which include variable environmental and diagenetic conditions are considered. Optically stimulated luminescence dating of quartz grains from the Lomonosov Ridge provide much needed absolute age control for sediments from this area, further constraining the timing of glacial activity near the Siberian margin and illustrating the potentials of luminescence dating as a geochronological tool in the Arctic. Palaeomagnetic and rock magnetic analyses provide additional evidence that putative polarity reversals and excursions are not always due to geomagnetic field behaviour but are possibly linked to glacial/interglacial modulation of the magnetic mineralogy.
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