Paleoenvironmental inference models from sediment diatom assemblages in Baffin Island lakes (Nunavut, Canada) and reconstruction of summer water temperature

2001 ◽  
Vol 58 (6) ◽  
pp. 1222-1243 ◽  
Author(s):  
Ernest H Joynt III ◽  
Alexander P Wolfe
Keyword(s):  
Water Temperature ◽  
Lake Water ◽  
Ice Age ◽  
Weighted Averaging ◽  
Baffin Island ◽  
Forward Selection ◽  
Diatom Assemblages ◽  
Inference Models ◽  
The Past ◽  
Environmental Controls

Diatoms from the surface sediments of 61 lakes on Baffin Island, Nunavut, were identified, enumerated, and interpreted quantitatively. The samples span a latitudinal transect from 62 to 74°N, reflecting climatic and vegetational gradients that range from low Arctic to transitional mid-Arctic to high Arctic. While the sampled lakes encompass both predominantly maritime and continental climatic regimes, sites have been deliberately restricted to basins in Precambrian crystalline terrain to mitigate the edaphic consequences of alkaline sedimentary bedrock. Canonical correspondence analysis, using forward selection and Monte Carlo permutation tests, identified pH, conductivity, summer lake water temperature, and mean annual air temperature as significant environmental controls over diatom assemblages. Using weighted-averaging regression and calibration, predictive models for these parameters have been developed. When applied to down-core assemblages, the summer lake water temperature model provides realistic reconstructions when compared with other paleoenvironmental records. Over the past 5000 years, the amplitude of reconstructed summer lake water temperature is on the order of 4.0°C, expressed primarily as progressive Neoglacial cooling culminating in the Little Ice Age. Diatom-inferred summer water temperatures have increased by 2.0°C in the past 150 years, again in agreement with independent paleoclimatic reconstructions.

scholarly journals Episodic Neoglacial expansion and rapid 20th century retreat of a small ice cap on Baffin Island, Arctic Canada, and modeled temperature change

2017 ◽  
Vol 13 (11) ◽  
pp. 1527-1537 ◽  
Author(s):  
Simon L. Pendleton ◽  
Gifford H. Miller ◽  
Robert A. Anderson ◽  
Sarah E. Crump ◽  
Yafang Zhong ◽  
...  
Keyword(s):  
Temperature Change ◽  
Climate Model ◽  
Ice Age ◽  
The Arctic ◽  
Baffin Island ◽  
Radiocarbon Dates ◽  
The Past ◽  
Ice Cap ◽  
Climate Model Simulations ◽  
Glacier Advance

Abstract. Records of Neoglacial glacier activity in the Arctic constructed from moraines are often incomplete due to a preservation bias toward the most extensive advance, often the Little Ice Age. Recent warming in the Arctic has caused extensive retreat of glaciers over the past several decades, exposing preserved landscapes complete with in situ tundra plants previously entombed by ice. The radiocarbon ages of these plants define the timing of snowline depression and glacier advance across the site, in response to local summer cooling. Erosion rapidly removes most dead plants that have been recently exposed by ice retreat, but where erosive processes are unusually weak, dead plants may remain preserved on the landscape for decades. In such settings, a transect of plant radiocarbon ages can be used to construct a near-continuous chronology of past ice margin advance. Here we present radiocarbon dates from the first such transect on Baffin Island, which directly dates the advance of a small ice cap over the past two millennia. The nature of ice expansion between 20 BCE and ∼ 1000 CE is still uncertain, but episodic advances at ∼ 1000 CE, ∼ 1200, and  ∼ 1500 led to the maximum Neoglacial dimensions ~ 1900 CE. We employ a two-dimensional numerical glacier model calibrated using the plant radiocarbon ages ice margin chronology to assess the sensitivity of the ice cap to temperature change. Model experiments show that at least ∼ 0.44 °C of cooling over the past 2 kyr is required for the ice cap to reach its 1900 CE margin, and that the period from ∼ 1000 to 1900 CE must have been at least 0.25° C cooler than the previous millennium, results that agree with regional temperature reconstructions and climate model simulations. However, significant warming since 1900 CE is required to explain retreat to its present position, and, at the same rate of warming, the ice cap will disappear before 2100 CE.

A High-Resolution 11,400-Yr Diatom Record from Lake Victoria, East Africa

1997 ◽  
Vol 47 (1) ◽  
pp. 81-89 ◽  
Author(s):  
J.Curt Stager ◽  
Brian Cumming ◽  
Loren Meeker
Keyword(s):  
Little Ice Age ◽  
Lake Victoria ◽  
Ice Age ◽  
Pollen Record ◽  
Diatom Assemblages ◽  
Climatic Fluctuations ◽  
The Past ◽  
Phytoplankton Communities ◽  
Abrupt Changes ◽  
Globally Distributed

AbstractFine-interval (∼30–45 yr) sampling of a core from Lake Victoria's Damba Channel shows that numerous abrupt changes in the lake's diatom assemblages have occurred in response to climatic fluctuations over the past 11,40014C yr. Four distinct climatic phases bounded by sudden transitions are inferred: (1) variably dry ∼11,400–10,000 yr B.P., (2) humid ∼10,000–7200 yr B.P., (3) more seasonal ∼7200–2200 yr B.P., and (4) more arid ∼2200–0 yr B.P., with a dry “Little Ice Age” event ∼600–200 yr B.P. The diatom-inferred paleoclimatic history for northern Lake Victoria closely resembles that inferred from a well-dated pollen record from Pilkington Bay. Spectral analysis of the diatom record reveals strong periodicities including globally distributed ∼2360–2550, ∼1400, ∼1030–1130, and ∼500 cal-yr cycles. Repeated, rapid shifts betweenAulacoseira- andNitzschia-dominated diatom assemblages suggest that post-1960 changes in the lake's phytoplankton communities have had earlier, climate-driven analogs.

Reconstructing phosphorus levels using models based on the modern diatom assemblages of 55 lakes in southern Quebec

2014 ◽  
Vol 71 (6) ◽  
pp. 887-914 ◽  
Author(s):  
Roxane Tremblay ◽  
Reinhard Pienitz ◽  
Pierre Legendre
Keyword(s):  
Surface Sediments ◽  
Specific Conductivity ◽  
Regression Analyses ◽  
Diatom Assemblages ◽  
Inference Models ◽  
The Past ◽  
Weighted Means ◽  
The World ◽  
Comparison Of The Results ◽  
Phosphorus Levels

This study shows how modern diatom assemblages, obtained from the surface sediments of 55 deep and shallow lakes in southern Quebec and representing a gradient in trophic state and specific conductivity, can be used to reconstruct the historical water column concentrations of total phosphorus (TP) over time. Inference models were developed with the aid of regression analyses based on weighted means. The TP models demonstrate statistical performances equal to or superior to TP models developed in the past for other regions in Canada and elsewhere in the world. A reconstruction of TP values, based on fossil diatom assemblages of Lac Nairne (Charlevoix, QC), was conducted. Comparing the TP inferred values with the measured values and those estimated using export coefficients, the reliability of the model was proven. In addition, the comparison of the results obtained from reconstructions performed with two inference models (Quebec and Ontario lakes) also revealed that models predicted TP and not a collinear variable.

Applications of Commonly Used Numerical Techniques in Diatom-Based Paleoecology

2007 ◽  
Vol 13 ◽  
pp. 13-31 ◽  
Author(s):  
Brian F. Cumming ◽  
Katrina A. Moser
Keyword(s):  
Linear Models ◽  
Weighted Averaging ◽  
Strongly Correlated ◽  
Numerical Techniques ◽  
Diatom Assemblages ◽  
Inference Models ◽  
Significant Relationships ◽  
Ordination Techniques ◽  
Type Ii Errors ◽  
The Impact

Applications of commonly used numerical techniques in diatom-based paleoecology are reviewed including: approaches used to model diatom taxa to important limnological variables; ordination and other commonly used multivariate approaches; and the myriad of approaches that are now being explored to infer environmental variables based on diatom assemblages.Modelling the response of individual diatom taxa to limnologically important variables is consistent with ecological theory and has been largely accomplished using approaches based on generalized linear models. These techniques have established that strong and significant relationships exist between the numerically dominant diatom taxa and important limnological variables (e.g., pH, nutrients, salinity). Null modelling approaches have also been used. However, inclusion of rare taxa in null models results in high rates of type-II errors, and consequently spurious claims that only a minority of diatoms have significant relationships to important limnological variables such as lakewater pH and nutrients.A variety of ordination techniques are widely used in diatom-based paleolimnological studies to aid in summarizing the main directions of variation in diatom assemblages, and to identify limnological variables that are strongly correlated to the diatom assemblages, both in time and space. More advanced ordination techniques, such as partial ordinations, are increasingly being used to assess the shared and unique variance attributable to groups of important limnological variables. Further, diatom-based approaches based on experimental designs with control lakes and appropriate multivariate statistics are now becoming increasingly common to assess, for example, the impact of forestry on water quality.A number of different diatom-based inference models based on the present-day relationships between diatom assemblages and limnological variables are now available for inferring important limnological variables. These approaches vary from simple approaches such as weighted-averaging to more complex approaches involving curve fitting and maximum likelihood, neural networks, and Bayesian statistics. All of these approaches have been shown to result in strong inference models, each using aspects of ecological information available from the diatom assemblages.

Diatom-inferred dissolved organic carbon reconstructions provide assessments of past UV-B penetration in Canadian Shield lakes

2001 ◽  
Vol 58 (3) ◽  
pp. 543-550 ◽  
Author(s):  
Sushil S Dixit ◽  
W (Bill) Keller ◽  
Aruna S Dixit ◽  
John P Smol
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Lake Water ◽  
Significant Proportion ◽  
Strong Relationship ◽  
Canadian Shield ◽  
Weighted Averaging ◽  
Calibration Data ◽  
Inference Models ◽  
Shield Lakes

Paleolimnological approaches have provided strong inference models for lake-water acidity and metal concentrations in Sudbury-area lakes, but calibration data have not yet been explored for inferring lake-water dissolved organic carbon (DOC). A review of available limnological data provided DOC values for 80 of our 105 calibration lakes, allowing us to examine the relative importance of DOC in determining the distribution of diatom assemblages in Canadian Shield lakes, such as those in the Sudbury region. Canonical correspondence analysis (CCA) indicated that lake-water DOC explained a significant proportion of variation in the diatom data. Our weighted-averaging DOC model showed a strong relationship (r2 = 0.63) between measured and inferred DOC. Using this model, we reconstructed historical DOC concentrations in three Sudbury-area lakes, and then estimated temporal changes in UV-B penetration. These reconstructions showed that lake water DOC concentrations and underwater UV-B penetration have changed markedly in two of the three lakes modeled. The close correspondence between inferred and measured DOC for the 1980s in all three lakes provides further evidence that we have accurately inferred DOC concentrations. Quantitative DOC reconstructions in Sudbury-area lakes offer an excellent technique for assessing past changes in DOC concentrations and UV-B penetration in Canadian Shield lakes.

A 2000-yr-long multi-proxy lacustrine record from eastern Baffin Island, Arctic Canada reveals first millennium AD cold period

2011 ◽  
Vol 75 (3) ◽  
pp. 491-500 ◽  
Author(s):  
Elizabeth K. Thomas ◽  
Jason P. Briner ◽  
Yarrow Axford ◽  
Donna R. Francis ◽  
Gifford H. Miller ◽  
...  
Keyword(s):  
Organic Matter ◽  
Cold Climate ◽  
Trophic Levels ◽  
Ice Age ◽  
The Arctic ◽  
Time Interval ◽  
Baffin Island ◽  
Arctic Canada ◽  
The Past ◽  
First Millennium

AbstractWe generate a multi-proxy sub-centennial-scale reconstruction of environmental change during the past two millennia from Itilliq Lake, Baffin Island, Arctic Canada. Our reconstruction arises from a finely subsectioned 210Pb- and 14C-dated surface sediment core and includes measures of organic matter (e.g., chlorophyll a; carbon–nitrogen ratio) and insect (Diptera: Chironomidae) assemblages. Within the past millennium, the least productive, and by inference coldest, conditions occurred ca. AD 1700–1850, late in the Little Ice Age. The 2000-yr sediment record also reveals an episode of reduced organic matter deposition during the 6th–7th century AD; combined with the few other records comparable in resolution that span this time interval from Baffin Island, we suggest that this cold episode was experienced regionally. A comparable cold climatic episode occurred in Alaska and western Canada at this time, suggesting that the first millennium AD cold climate anomaly may have occurred throughout the Arctic. Dramatic increases in aquatic biological productivity at multiple trophic levels are indicated by increased chlorophyll a concentrations since AD 1800 and chironomid concentrations since AD 1900, both of which have risen to levels unprecedented over the past 2000 yr.

Vegetation and environment changes inferred from pollen records since 3000 cal. yr BP in Kanas wetland, Xinjiang

2019 ◽  
Vol 12 (5) ◽  
pp. 907-916
Author(s):  
Yumei Li ◽  
Yun Zhang ◽  
Zhaochen Kong ◽  
Long Zhao ◽  
Li Wang ◽  
...  
Keyword(s):  
Climate Change ◽  
Quantitative Relationship ◽  
Temperature Reconstruction ◽  
Ice Age ◽  
Weighted Averaging ◽  
Mean Annual Temperature ◽  
Least Squares Regression ◽  
The Past ◽  
North Xinjiang ◽  
Pollen Records

Abstract Aims Climate change can significantly affect the vegetation worldwide. Thus, paleovegetation and paleoclimate reconstruction should consider the quantitative relationship between modern vegetation and climate. The specific objectives of this study were (i) to assess the influence of environmental variables on pollen assemblages in the Kanas region, (ii) to reconstruct the evolution of vegetation over the past 3000 years using pollen records and (iii) to quantify historical climate change (including mean annual temperature and total annual precipitation) using a weighted averaging partial least squares regression method (WAPLS) applied to fossil pollen data from the Kanas wetland in Xinjiang, China. Methods A total of 65 surface and 50 fossil samples were collected from the Kanas wetland and analysed for 14C, pollen and grain size. By combining these data with those obtained from 214 samples of surface pollen assemblages in north Xinjiang, the late Holocene climate was reconstructed using a WAPLS model. Important Findings The vegetation in Kanas was dominated by forest for the past 3000 years, undergoing an arbour-vegetation transition from predominantly pine to spruce over that period. The WAPLS model showed that the paleoclimate progressed from cold-wet to warm-dry and subsequently back to cold-wet. Prior to 1350 calibrated years before the present (cal. yr BP), the climate of Kanas was cold and wet, and conditions became increasingly warm and dry until 870 cal. yr BP. The temperature reconstruction model indicated that a ‘Little Ice Age’ occurred ~380 cal. yr BP. These data will help us improve the understanding of abrupt climate change and provide important information regarding the prediction of climate.

scholarly journals Quantifying late-Holocene climate in the Ecuadorian Andes using a chironomid-based temperature inference model

2016 ◽  
Author(s):  
Frazer Matthews-Bird ◽  
Stephen J. Brooks ◽  
Philip B. Holden ◽  
Encarni Montoya ◽  
William D . Gosling
Keyword(s):  
Late Holocene ◽  
Bayesian Method ◽  
Ice Age ◽  
Weighted Averaging ◽  
Mean Annual Temperature ◽  
Calibration Data ◽  
Tropical Andes ◽  
Data Set ◽  
Cold Temperatures ◽  
Inference Models

Abstract. Presented here is the first chironomid calibration dataset for tropical South America. Surface sediments were collected from 59 lakes across Bolivia (15 lakes), Peru (32 lakes) and Ecuador (12 lakes) between 2004 and 2013 over an altitudinal gradient from 150 m above sea level (a.s.l) to 4655 m a.s.l, between 0-­17°S and 64-­78°W. The study sites cover a mean annual temperature (MAT) gradient of 25°C. In total, 55 chironomid taxa were identified in the 59 calibration data-­set lakes. When used as a single explanatory variable, MAT explains 12.9% of the variance (λ1/λ2= 1.431). Two inference models were developed using weighted averaging and Bayesian methods. The best performing model using conventional statistical methods was a WA (inverse) model (R2jack= 0.890, RMSEPjack= 2.404, Mean biasjack= -­0.017, Max biasjack= 4.665). The Bayesian method produced a model with R2jack= 0.909, RMSEPjack= 2.373, Mean biasjack= 0.598, Max biasjack= 3.158. Both models were used to infer past temperatures from a c. 3000 yr record from the tropical Andes of Ecuador, Laguna Pindo. Inferred temperatures fluctuated around modern day conditions but showed significant departures at certain intervals (c. 1600 cal yr BP; c. 3000-­2500 cal yr BP). Both methods (WA/Bayesian) showed similar patterns of temperature variability; however, the magnitude of fluctuations differed. In general the WA method was more variable often inferring unrealistically cold temperatures (c. -­7±2.5°C relative to the modern). The Bayesian method provided temperature anomaly estimates for cool periods that lay within the expected range of the Holocene (c. -­3±3.4°C). The chironomid-­based MAT recon struction from the Laguna Pindo fossil record suggests that periods of low solar output not only affect the tropics through changes in precipitation, but also directly affect tropical temperatures. Inferred temperatures were 2-­3°C colder relative to the modern during the widely recognised 3500-­2500 cal yr BP cooling event. Long-­term cooling during the late-­Holocene culminating in the Little Ice Age (LIA) is not apparent in the Laguna Pindo record. A cooling by 1-­2°C relative to the modern during the LIA is recorded in a single fossil sa

scholarly journals Episodic Neoglacial expansion and rapid 20th Century retreat of a small ice cap on Baffin Island, Arctic Canada and modeled temperature change

2017 ◽  
Author(s):  
Simon L. Pendleton ◽  
Gifford H. Miller ◽  
Robert A. Anderson ◽  
Sarah E. Crump ◽  
Yafang Zhong ◽  
...  
Keyword(s):  
Temperature Change ◽  
Climate Model ◽  
Regional Climate ◽  
Ice Age ◽  
The Arctic ◽  
Baffin Island ◽  
Radiocarbon Dates ◽  
The Past ◽  
Ice Cap ◽  
Climate Model Simulations

Abstract. Records of Neoglacial glacier activity in the Arctic constructed from moraines are often incomplete due to a preservation bias toward the most extensive advance, usually the Little Ice Age. Recent warming in the Arctic has caused extensive retreat of glaciers over the past several decades, exposing preserved landscapes complete with in situ tundra plants previously entombed by ice. The radiocarbon ages of these plants define the timing of snowline depression and glacier advance across the site, in response to local summer cooling. Although most dead plants recently exposed by ice retreat are rapidly removed from the landscape by erosion, where erosive processes are unusually weak, dead plants may remain preserved on the landscape for decades. In such settings, a transect of plant radiocarbon ages can be used to construct a near-continuous chronology of past ice margin advance. Here we present radiocarbon dates from the first such transect on Baffin Island, which directly dates the advance of a small ice cap over the past two millennia. The nature of ice expansion between 20 BCE and ~1000 CE is still uncertain, but episodic advances at ~ 1000, ~ 1200, and ~ 1500 CE led to the maximum Neoglacial dimensions ~ 1900 CE. We employ a two-dimensional numerical glacier model to reconstruct the pattern of ice expansion inferred from the radiocarbon ages and to explore the sensitivity of the ice cap to temperature change. Model experiments show that at least ~ 0.44 °C of cooling over the past 2 ka is required for the ice cap to reach its 1900 margin, and that the period from ~ 1000 to 1900 CE must have been at least 0.25 °C cooler than the previous millennium; results that agree with regional climate model simulations. However, ~ 3 °C of warming since 1900 CE is required to explain retreat to its present position, and, at the same rate of warming, the ice cap will disappear before 2100 CE.

Subfossil insect remains (Chironomidae) and lake-water temperature inference in the Sisimiut–Kangerlussuaq region, southern West Greenland

2000 ◽  
pp. 78-82 ◽  
Author(s):  
Klaus Peter Brodersen ◽  
N. John Anderson
Keyword(s):  
Climate Variability ◽  
Water Temperature ◽  
Lake Water ◽  
Anthropogenic Impact ◽  
Biological Diversity ◽  
Biological Indicators ◽  
Lake Ecosystems ◽  
West Greenland ◽  
Physical Chemical ◽  
Temperature Inference

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Brodersen, K. P., & Anderson, N. J. (2000). Subfossil insect remains (Chironomidae) and lake-water temperature inference in the Sisimiut–Kangerlussuaq region, southern West Greenland. Geology of Greenland Survey Bulletin, 186, 78-82. https://doi.org/10.34194/ggub.v186.5219 _______________ Climate and water temperature have an important influence on the functioning of lake ecosystems. From limnological and palaeolimnological studies of lakes, information on biological diversity and climate variability in time and space can be gleaned from physical, chemical and biological indicators preserved in the lake sediments. The lakes in southern West Greenland are particularly useful for this purpose – they are numerous, diverse and have minimal anthropogenic impact (Anderson & Bennike 1997). Palaeolimnological data are fundamental for understanding the functioning and development of modern lakes and for understanding the causes of climatic change as well as the effect on lake biota.

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