scholarly journals Contrasting the ecological effects of decreasing ice cover versus accelerated glacial melt on the High Arctic's largest lake

2020 ◽  
Vol 287 (1929) ◽  
pp. 20201185
Author(s):  
Neal Michelutti ◽  
Marianne S. V. Douglas ◽  
Dermot Antoniades ◽  
Igor Lehnherr ◽  
Vincent L. St. Louis ◽  
...  
Keyword(s):  
Sediment Cores ◽  
Fold Increase ◽  
Mass Gain ◽  
Ecological Change ◽  
Diatom Assemblages ◽  
Lake Ice ◽  
Glacial Meltwater ◽  
Glacial Runoff ◽  
Common Era ◽  
Ecological Functioning

Lake Hazen, the High Arctic's largest lake, has received an approximately 10-fold increase in glacial meltwater since its catchment glaciers shifted from net mass gain to net mass loss in 2007 common era (CE), concurrent with recent warming. Increased glacial meltwater can alter the ecological functioning of recipient aquatic ecosystems via changes to nutrient budgets, turbidity and thermal regimes. Here, we examine a rare set of five high-resolution sediment cores collected in Lake Hazen between 1990 and 2017 CE to investigate the influence of increased glacial meltwater versus alterations to lake ice phenology on ecological change. Subfossil diatom assemblages in all cores show two major shifts over the past approximately 200 years including: (i) a proliferation of pioneering, benthic taxa at approximately 1900 CE from previously depauperate populations; and (ii) a rise in planktonic taxa beginning at approximately 1980 CE to present-day dominance. The topmost intervals from each sequentially collected core provide exact dates and demonstrate that diatom regime shifts occurred decades prior to accelerated glacial inputs. These data show that diatom assemblages in Lake Hazen are responding primarily to intrinsic lake factors linked to decreasing duration of lake ice and snow cover rather than to limnological impacts associated with increased glacial runoff.

An Assessment of Environmental Changes in Three Lakes from King's County (Nova Scotia, Canada) Using Diatom-Based Paleolimnological Techniques

2008 ◽  
Vol 43 (2-3) ◽  
pp. 85-98 ◽  
Author(s):  
Joshua R. Thienpont ◽  
Brian K. Ginn ◽  
Brian F. Cumming ◽  
John P. Smol
Keyword(s):  
Nova Scotia ◽  
Environmental Changes ◽  
Sediment Cores ◽  
Lake Management ◽  
River System ◽  
210Pb Dating ◽  
Hydroelectric Power ◽  
Diatom Assemblages ◽  
Shoreline Development ◽  
Before And After

Abstract Paleolimnological approaches using sedimentary diatom assemblages were used to assess water quality changes over the last approximately 200 years in three lakes from King's County, Nova Scotia. In particular, the role of recent shoreline development in accelerating eutrophication in these systems was assessed. Sediment cores collected from each lake were analyzed for their diatom assemblages at approximately 5-year intervals, as determined by 210Pb dating. Analyses showed that each system has changed, but tracked different ecosystem changes. Tupper and George lakes recorded shifts, which are likely primarily related to climatic warming, with diatom assemblages changing from a preindustrial dominance by Aulacoseira spp. to present-day dominance by Cyclotella stelligera. In addition to the recent climatic-related changes, further diatom changes in the Tupper Lake core between approximately 1820 and 1970 were coincident with watershed disturbances (farming, forestry, and construction of hydroelectric power infrastructure). Black River Lake has recorded an increase in diatom-inferred total phosphorus since about 1950, likely due to impoundment of the Black River system for hydroelectric generation and subsequent changes in land runoff. Before-and-after (i.e., top-bottom) sediment analyses of six other lakes from King's County provided further evidence that the region is being influenced by climatic change (decreases in Aulacoseira spp., increases in planktonic diatom taxa), as well as showing other environmental stressors (e.g., acidification). However, we recorded no marked increase in diatom-inferred nutrient levels coincident with shoreline cottage development in any of the nine study lakes. Paleolimnological studies such as these allow lake managers to place the current limnological conditions into a long-term context, and thereby provide important background data for effective lake management.

scholarly journals Quantitative and qualitative constraints on hind-casting the formation of multiyear lake-ice covers at Lake El'gygytgyn

2013 ◽  
Vol 9 (3) ◽  
pp. 1253-1269 ◽  
Author(s):  
M. Nolan
Keyword(s):  
Water Exchange ◽  
Sediment Cores ◽  
Ice Cover ◽  
Lake Ice ◽  
Ice Growth ◽  
Temperature Reduction ◽  
Air Temperatures ◽  
Lake El’Gygytgyn ◽  
Oxygen Conditions ◽  
Multiyear Ice

Abstract. Analysis of the 3.6 Ma, 318 m long sediment core from Lake El'gygytgyn suggests that the lake was covered by ice for millennia at a time for much of its history and therefore this paper uses a suite of existing, simple, empirical degree-day models of lake-ice growth and decay to place quantitative constraints on air temperatures needed to maintain a permanent ice cover on the lake. We also provide an overview of the modern climatological and physical processes that relate to lake-ice growth and decay as a basis for evaluating past climate and environmental conditions. Our modeling results indicate that modern annual mean air temperature would only have to be reduced by 3.3 °C ± 0.9 °C to initiate a multiyear ice cover and a temperature reduction of at least 5.5 °C ± 1.0 °C is likely needed to completely eliminate direct air–water exchange of oxygen, conditions that have been inferred at Lake El'gygytgyn from the analysis of sediment cores. Once formed, a temperature reduction of only 1–3 °C relative to modern may be all that is required to maintain multiyear ice. We also found that formation of multiyear ice covers requires that positive degree days are reduced by about half the modern mean, from about +608 to +322. A multiyear ice cover can persist even with summer temperatures sufficient for a two-month long thawing period, including a month above +4 °C. Thus, it is likely that many summer biological processes and some lake-water warming and mixing may still occur beneath multiyear ice-covers even if air–water exchange of oxygen is severely restricted.

Late Holocene precipitation variability recorded in the sediments of Reloncaví Fjord (41°S, 72°W), Chile

2015 ◽  
Vol 84 (1) ◽  
pp. 21-36 ◽  
Author(s):  
Lorena Rebolledo ◽  
Carina B. Lange ◽  
Sébastien Bertrand ◽  
Práxedes Muñoz ◽  
Marco Salamanca ◽  
...  
Keyword(s):  
Late Holocene ◽  
Sediment Cores ◽  
Southern Annular Mode ◽  
Organic Carbon Content ◽  
Diatom Assemblages ◽  
Chilean Patagonia ◽  
Precipitation Seasonality ◽  
Rhizosolenia Setigera ◽  
First Occurrence ◽  
Instrumental Records

We present reconstructions of late Holocene changes in the source of organic matter and siliceous export production in the Relocanví Fjord (41°S, 72°W), Northern Chilean Patagonia, based on organic carbon content, δ13Corg, N/C ratio, diatom assemblages and biogenic silica contents from three sediment cores. The age models are based on a combination of 210Pb profiles, AMS 14C dating, and on the first occurrence of the diatom Rhizosolenia setigera f. pungens, as a stratigraphic marker in the fjords. The cores span the last 300 to 700 yr. Diatoms dominate the siliceous assemblages in the three cores (98% on average). Our results suggest that precipitation seasonality in the region of Reloncaví was high in CE 1300–1400 and CE 1700–1850, with a clear decreasing trend since CE 1850. The latter trend is in agreement with instrumental records and tree-ring reconstructions. These fluctuations seem to be associated with the Southern Annular Mode (SAM).

scholarly journals The Elbrus (Caucasus, Russia) ice core glaciochemistry to reconstruct anthropogenic emissions in central Europe: The case of sulfate

2019 ◽  
Author(s):  
Susanne Preunkert ◽  
Michel Legrand ◽  
Stanislav Kutuzov ◽  
Patrick Ginot ◽  
Vladimir Mikhalenko ◽  
...  
Keyword(s):  
Central Europe ◽  
Ice Core ◽  
Ice Cores ◽  
Fold Increase ◽  
First Century ◽  
Ice Age ◽  
The Caucasus ◽  
Basal Ice ◽  
Common Era

Abstract. This study reports on the glaciochemistry of a deep ice core (182 m long) drilled in 2009 at Mount Elbrus (43°21′ N, 42°26′ E; 5115 m above sea level) in the Caucasus, Russia. Radiocarbon dating of the particulate organic carbon fraction in the ice suggests a basal ice age of ~ 1670 ± 400 cal yr BP. Based on chemical stratigraphy, the upper 168.6 m of the core were dated by counting annual layers. The seasonally resolved chemical records cover the years 1774–2009 (Common Era), thus, being useful to reconstruct many aspects of atmospheric pollution in central Europe from pre-industrial times to present-day. After having examined the extent to which the arrival of large dust plumes originating from Sahara and Middle East modifies the chemical composition of the Elbrus (ELB) snow and ice layers, we focus on the sulfur pollution. The ELB sulfate levels indicate a four- and six-fold increase from 1774–1900 to 1980–1995 in winter and summer, respectively. Remaining close to 116 ± 28 ppb during the nineteen century, the summer sulfate levels started to rise at a mean rate of ~ 6 ppb per year from 1920 to 1950. The summer sulfate increase accelerated between 1950 and 1975 (11 ppb per year), levels reaching a maximum between 1980 and 1990 (730 ± 152 ppb) and subsequently decreasing to 630 ± 130 ppb at the beginning of the twenty first century. Long-term sulfate trends observed in the ELB ice cores are compared with those previously obtained in Alpine ice, the most important difference consists in a more pronounced decrease of the sulfur pollution over the three last decades in western than central Europe.

Organic carbon isotope ratios and paleoenvironmental implications for Holocene sediments in Lake Melville, southeastern Labrador

1987 ◽  
Vol 24 (10) ◽  
pp. 1994-2003 ◽  
Author(s):  
F. C. Tan ◽  
G. Vilks
Keyword(s):  
Organic Carbon ◽  
Carbon Isotope ◽  
Sediment Cores ◽  
Isotope Ratios ◽  
Carbon Isotope Ratios ◽  
Organic Carbon Isotope ◽  
Glacial Runoff ◽  
Bottom Waters ◽  
History Of ◽  
Marine Influence

Stable isotope 13C/12C ratios of organic carbon in sediments and in particulate organic carbon (POC) change from typically marine values in Groswater Bay to those of terrestrial soils in Goose Bay along an offshore–onshore transect in Hamilton Inlet, southeastern Labrator. The δ13C values in POC collected from close to the water surface change relatively little in Lake Melville, indicating that the integrity of the runoff plume is maintained as it spreads in Lake Melville. The organic carbon isotope ratios in POC collected from the near-bottom waters are similar to those of surficial sediments.Downcore δ13C values reflect paleo-oceanographic changes in Hamilton Inlet during and since deglaciation. In two sediment cores that reached sufficiently old sediments (10 000 years BP), the δ13C values change toward the bottom of the cores to values similar to those of the terrestrial organic carbon in soils, signifying greater terrestrial influence during deglaciation and during the early Holocene.According to the history of postglacial isostatic readjustment of the area, Lake Melville basin was more open to the marine waters during the early postglacial marine incursion because of deeper channels leading into Lake Melville. As a consequence, evidence for greater marine influence during that time should be found in sediment cores. The lack of evidence for the deposition of marine organic carbon brought in by the marine counterflow waters suggests a proximal glaciomarine environment in the Lake Melville basin. Glacial runoff diluted the basin waters, and it is possible that the whole inner Labrador Shelf was relatively fresh during that time.

scholarly journals Effects of loss of perennial lake ice on mixing and phytoplankton dynamics: insights from High Arctic Canada

2010 ◽  
Vol 51 (56) ◽  
pp. 56-70 ◽  
Author(s):  
Julie Veillette ◽  
Marie-Josée Martineau ◽  
Dermot Antoniades ◽  
Denis Sarrazin ◽  
Warwick F. Vincent
Keyword(s):  
Water Column ◽  
Open Water ◽  
Fold Increase ◽  
Ice Cover ◽  
High Arctic ◽  
Meromictic Lakes ◽  
Lake Ice ◽  
Wind Speeds ◽  
Arctic Climate Change ◽  
Perennial Ice

AbstractPerennially ice-covered lakes are well known from Antarctica and also occur in the extreme High Arctic. Climate change has many implications for these lakes, including the thinning and disappearance of their perennial ice cover. The goal of this study was to consider the effects of transition to seasonal ice cover by way of limnological observations on a series of meromictic lakes along the northern coastline of Ellesmere Island, Nunavut, Canada. Conductivity-temperature profiles during a rare period of ice-free conditions (August 2008) in these lakes suggested effects of wind-induced mixing of their surface freshwater layers and the onset of entrainment of water at the halocline. Sampling of the mixed layer of one of these meromictic lakes in May and August 2008 revealed a pronounced vertical structure in phytoplankton pigments and species composition, with dominance by cyanobacteria, green algae, chrysophytes, cryptophytes and dinoflagellates, and a conspicuous absence of diatoms. The loss of ice cover resulted in an 80-fold increase in water column irradiance and apparent mixing of the upper water column during a period of higher wind speeds. Zeaxanthin, a pigment found in cyanobacteria, was entirely restricted to the <3μm cell fraction at all depths and increased by a factor of 2–17, with the greatest increases in the upper halocline region subject to mixing. Consistent with the pigment data, picocyanobacterial populations increased by a factor of 3, with the highest concentration (1.65 × 108 cells L−1) in the upper halocline. Chlorophyll a concentrations and the relative importance of phytoplankton groups differed among the four lakes during the open-water period, implying lake-specific differences in phytoplankton community structure under ice-free conditions.

scholarly journals Late Quaternary lake-level changes of Lake El'gygytgyn, NE Siberia

2011 ◽  
Vol 76 (3) ◽  
pp. 441-451 ◽  
Author(s):  
Olaf Juschus ◽  
Maksim Pavlov ◽  
Georg Schwamborn ◽  
Frank Preusser ◽  
Grigory Fedorov ◽  
...  
Keyword(s):  
Water Level ◽  
Lake Level ◽  
Late Quaternary ◽  
Sediment Cores ◽  
Lake Ice ◽  
Oxygen Isotope Stage ◽  
Northeastern Siberia ◽  
Lake El’Gygytgyn ◽  
High Lake Level ◽  
High Lake Levels

AbstractLake El'gygytgyn is situated in a 3.6 Ma old impact crater in northeastern Siberia. Presented here is a reconstruction of the Quaternary lake-level history as derived from sediment cores from the southern lake shelf. There, a cliff-like bench 10 m below the modern water level has been investigated. Deep-water sediments on the shelf indicate high lake levels during a warm Mid-Pleistocene period. One period with low lake level prior to Marine Oxygen Isotope Stage (MIS) 3 has been identified, followed by a period of high lake level (10 m above present). In the course of MIS 2 the lake level dropped to − 10 m. At the end of MIS 2 the bench was formed and coarse beach sedimentation occurred. Subsequently, the lake level rose rapidly to the Holocene level. Changes in water level are likely linked to climate variability. During relatively temperate periods the lake becomes free of ice in summer. Strong wave actions transport sediment parallel to the coast and towards the outlet, where the material tends to accumulate, resulting in lake level rise. During cold periods the perennial lake ice cover hampers any wave activity and pebble-transport, keeping the outlet open and causing the lake level to drop.

Long-term water quality changes in a multiple-stressor system: a diatom-based paleolimnological study of Lake Simcoe (Ontario, Canada)

2012 ◽  
Vol 69 (1) ◽  
pp. 24-40 ◽  
Author(s):  
Jessica Hawryshyn ◽  
Kathleen M. Rühland ◽  
Roberto Quinlan ◽  
John P. Smol
Keyword(s):  
Water Quality ◽  
Regional Climate ◽  
Sediment Cores ◽  
Phosphorus Loading ◽  
Diatom Assemblages ◽  
Late 20Th Century ◽  
System A ◽  
Multiple Stressor ◽  
Lake Simcoe

Diatom-based paleolimnological techniques were used to assess long-term changes in the water quality of Lake Simcoe (Ontario, Canada) using 210Pb-dated sediment cores from four sites across the lake. Modest lake-wide shifts in diatom community composition occurred in the late 19th and early 20th centuries, suggesting that early cultural disturbances (e.g., land clearance and canal construction) had relatively minor effects on Lake Simcoe water quality. However, starting in the 1930s, phosphorus loading to the lake increased, which was closely tracked by increases in diatom taxa indicative of eutrophic conditions. The most pronounced lake-wide shift in diatom assemblages occurred in the mid- to late 20th century, the nature and timing of which strongly suggested a response to regional climate warming. An additional and marked lake-wide shift in diatom assemblages occurred in the mid-1990s, coinciding with the invasion of dreissenid mussels in Lake Simcoe. Our results indicate that Lake Simcoe water quality has been affected by the interaction of numerous environmental stressors over the past two centuries, the complexity of which has been amplified by recent warming.

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