Isotopic analyses (18O, 13C, 14C) of two meromictic lakes in the Canadian Arctic Archipelago (original) (raw)
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Geochemistry of ice-covered, meromictic Lake A in the Canadian High Arctic
2002
The geochemical processes occurring within meromictic Lake A (max depth 120 m) on northern Ellesmere Island, Canada, were investigated to determine the history of the lake and to provide a baseline for future studies. The lake contained seawater diluted by freshwater input that had been mixed prior to the lake's isolation from tidal action. Input of freshwater after isolation of the lake created vertical stratification resulting in the creation of distinct oxic, suboxic and anoxic zones. Dissolved oxygen was present to 13 m, and sulphide beneath 32 m. Manganese and iron cycling dominated the redox chemistry between these depths. Total manganese concentrations reached 176 µM, higher than in most other natural stratified lake or marine environments.
Radiocarbon Geochemistry of Modern and Ancient Arctic Lake Systems, Baffin Island, Canada
Quaternary Research, 1996
prior to being transported into the lake system. The combina-The accuracy of Arctic lake chronologies has been assessed by tion of these factors commonly leads to radiocarbon ages measuring the 14 C activities of modern carbon sources and that are apparently too old. Discrete macrofossils are rarely applying these isotopic mass balances to dating fossil lake materifound in sufficient quantities for AMS 14 C dates. Even when als. Small (õ1 km 2 ) shallow (õ25 m) Arctic lakes with watersheds plant macrofossils are present, their geologic ages are sus-õ12 km 2 have soil and peat stratigraphic sections with 14 C activipect because macrofossils and sedimentary carbon can be ties ranging from 98 to 51% Modern. The 14 C activity of particulate reworked from preexisting sediments and soils, and the meorganic carbon, dissolved organic carbon, and dissolved inorganic tabolism of ancient carbon can generate a significant resercarbon from lake and stream waters ranges from 121 to 95% voir effect for living aquatic plants .
Recent climate and stable isotopes in modern surface waters of northernmost Ungava Peninsula, Canada
Canadian Journal of Earth Sciences, 2007
The isotope composition (δ 18 O and δD) of surface waters were measured over a 26-month period near three localities situated along the northern coast of Ungava Peninsula (Québec, Canada). In order to caracterize the present-day local hydrological settings, the oxygen and hydrogen isotope ratios were measured from precipitation and these were compared to local and regional climate data. We show that the modern surface waters contain information on climate and that this relationship is likely to be transferred to biotic components within the lakes. These components, once sedimented, are therefore likely to form an archive of climate change. The new data presented here show the possibility of isotope paleoclimatic investigation based on lake sediments in the northern coastal region of Ungava Peninsula.
Recent changes in a remote Arctic lake are unique within the past 200,000 years
Proceedings of the National Academy of Sciences, 2009
The Arctic is currently undergoing dramatic environmental transformations, but it remains largely unknown how these changes compare with long-term natural variability. Here we present a lake sediment sequence from the Canadian Arctic that records warm periods of the past 200,000 years, including the 20th century. This record provides a perspective on recent changes in the Arctic and predates by approximately 80,000 years the oldest stratigraphically intact ice core recovered from the Greenland Ice Sheet. The early Holocene and the warmest part of the Last Interglacial (Marine Isotope Stage or MIS 5e) were the only periods of the past 200,000 years with summer temperatures comparable to or exceeding today's at this site. Paleoecological and geochemical data indicate that the past three interglacial periods were characterized by similar trajectories in temperature, lake biology, and lakewater pH, all of which tracked orbitally-driven solar insolation. In recent decades, however, t...
Quaternary Science Reviews
Nettilling Lake is located on Baffin Island, Nunavut, Canada between the areas of past warming (Canadian High Arctic to the North) and climatic stability (Northern Quebec and Labrador region to the South). Despite being the largest lake in the Nunavut region with a postglacial marine to lacustrine transition history only a few paleo-environmental investigations were completed in this area. The oxygen isotope composition of diatoms (d 18 O diatom) can provide valuable insights into paleo-environmental conditions. Here, the recent (isotope) hydrology and hydrochemical data from the lake are presented to facilitate the interpretation of a d 18 O diatom record from an 82 cm sediment core (Ni-2B). The well-mixed lake (d 18 O water ¼ À17.4‰) is influenced by a heavier (less negative) isotope composition (À18.80‰) from Amadjuak River draining Amadjuak Lake to the South and water of lighter (more negative) isotopic composition (À16.4‰) from the Isurtuq River originating from Penny Ice Cap in the NorthEast. From the d 18 O water and d 18 O diatom of the topmost sample of core Ni-2B a D 18 O silica-water of 1000 ln a (silica-water) ¼ 40.2‰ for sub-recent diatoms of Nettilling Lake was calculated matching the known water-silica fractionation for fossil sediments well and thereby showing the general applicability of this proxy for paleo-reconstructions in this region. Extremely large d 18 O diatom variations in the core of more than 13‰ are mainly induced by changes in the isotopic composition of the lake water due to a shift from glaciomarine (d 18 O diatom ¼ þ34.6‰) through brackish (þ23.4 to þ27.2‰) towards lacustrine (þ21.5‰) conditions (transition zones glaciomarine to brackish at 69 cm/7300 yr cal. BP and brackish to lacustrine at 35 cm/6000 yr cal. BP) associated with a shift in the degree of salinity. Our study provides the first evidence that paleo-salinity can be reconstructed by d 18 O diatom. Additionally, for the lacustrine section it could be demonstrated that d 18 O diatom may serve as a proxy for past air temperature within the same core recording a late Holocene cooling of about 4 C being consistent with other published values for the greater Baffin region.
Isotopic signals ( 18 O, 2 H, 3 H) of six major rivers draining the pan-Arctic watershed
Global Biogeochemical Cycles, 2012
1] We present the results of a 4-year collaborative sampling effort that measured d 18 O, d 2 H values and 3 H activities in the six largest Arctic rivers (the Ob, Yenisey, Lena, Kolyma, Yukon and Mackenzie). Using consistent sampling and data processing protocols, these isotopic measurements provide the best available d 2 H and 3 H estimates for freshwater fluxes from the pan-Arctic watershed to the Arctic Ocean and adjacent seas, which complements previous efforts with d 18 O and other tracers. Flow-weighted annual d 2 H values vary from À113.3‰ to À171.4‰ among rivers. Annual 3 H fluxes vary from 0.68 g to 4.12 g among basins. The integration of conventional hydrological and landscape observations with stable water isotope signals, and estimation of areal yield of 3 H provide useful insights for understanding water sources, mixing and evaporation losses in these river basins. For example, an inverse correlation between the slope of the d 18 O-d 2 H relation and wetland extent indicates that wetlands play comparatively important roles affecting evaporation losses in the Yukon and Mackenzie basins. Tritium areal yields (ranging from 0.760 to 1.695 10 À6 g/km 2 per year) are found to be positively correlated with permafrost coverage within the studied drainage basins. Isotope-discharge relationships demonstrate both linear and nonlinear response patterns, which highlights the complexity of hydrological processes in large Arctic river basins. These isotope observations and their relationship to discharge and landscape features indicate that basin-specific characteristics significantly influence hydrological processes in the pan-Arctic watershed.
Quaternary Science Reviews, 2016
Nettilling Lake (Baffin Island, Nunavut) is currently the largest lake in the Canadian Arctic Archipelago. Despite its enormous size, this freshwater system remains little studied until the present-day. Existing records from southern Baffin Island indicate that in the early postglacial period, the region was submerged by the postglacial Tyrell Sea due to isostatic depression previously exerted by the Laurentide Ice Sheet. However, these records are temporally and spatially discontinuous, relying on qualitative extrapolation. This paper presents the first quantitative reconstruction of the postglacial environmental succession of the Nettilling Lake basin based on a 8300 yr-long high resolution sedimentary record. Our multi-proxy investigation of the glacio-isostatic uplift and subsequent changes in paleosalinity and sediment sources is based on analyses of sediment fabric, elemental geochemistry (m-XRF), diatom assemblage composition, as well as on the first diatom-based oxygen isotope record from the eastern Canadian Arctic. Results indicate that the Nettilling Lake basin experienced a relatively rapid and uniform marine invasion in the early Holocene, followed by progressive freshening until about 6000 yr BP when limnological conditions similar to those of today were established. Our findings present evidence for deglacial processes in the Foxe Basin that were initiated at least 400yrs earlier than previously thought.
Arctic, Antarctic, and Alpine Research
In west Greenland, an approximate chronosequence of landscape evolution and weathering exists between the coast, which has been ice free for long periods, and more recently deglaciated areas along the present day ice margin. Traditional geochemical and isotopic analyses (δ 18 O, δ 2 H, 3 H, δ 34 S/δ 18 O (SO4), and 87 Sr/ 86 Sr) along with novel isotopic tools, such as δ 37 Cl and δ 81 Br, were used to provide new insights into lake geochemical processes along a transect of lakes from the coast to the ice margin in the Kangerlussuaq region. Evaporation was found to be a key process impacting lake chemistry and isotopic signatures in the ice marginal area, with decreasing importance toward the coast. Evaporative processes were apparent in the δ 37 Cl and δ 81 Br isotopic signatures of lake-water chemistry. Consistent with previous work elsewhere (e.g., Blum and Erel, 1995) on increased biotite weathering in glaciated environments, 87 Sr/ 86 Sr isotopic ratios were found to be more radiogenic (>0.73) in lakes found in more recently glaciated terrain. Sulfide oxidation was the main source of sulfur (as sulfate) in lakes in the ice marginal area, while the influence of marine aerosols and bacterial sulfate reduction increased further away from the ice sheet around the fjord Kangerlussuaq. Groundwater discharge significant enough to impact lake chemistry was not observed in any of the lakes studied, suggesting that little groundwatersurface water interaction occurs in the study area or that recharge conditions are present in the majority of the lakes studied.
Heightened sensitivity of a poorly buffered high arctic lake to late-Holocene climatic change
Quaternary Research, 2006
A diatom-based paleolimnological investigation was conducted on late Holocene sediments from a poorly buffered lake, informally named “Rock Basin Lake”, on Ellesmere Island, Arctic Canada. The fossil diatom record is unlike any other obtained thus far from high arctic regions, exhibiting dynamic assemblage shifts over the entire ∼3300 yr sedimentary record. Multiple proxies (i.e., diatoms, pH reconstructions, biogenic silica, C/N ratios, total organic carbon) appear to sensitively track rapid limnological changes, which are associated with distinct climate intervals as inferred from other regional proxy records. The highly responsive nature of the diatom assemblages in Rock Basin Lake, relative to those recorded from nearby alkaline sites, appears to be related to this lake's limited ability to buffer changes in pH. The dynamic species responses suggest that the diatoms in Rock Basin Lake are faithfully tracking climatic changes, and that low-alkalinity lakes may provide the mos...