Cosmogenic10Be dating of raised shorelines constrains the timing of lake levels in the eastern Lake Agassiz-Ojibway basin

AbstractSurface exposure dating was applied to erosional shorelines associated with the Angliers lake level that marks an important stage of Lake Ojibway. The distribution of 1510Be ages from five sites shows a main group (10 samples) of coherent10Be ages yielding a mean age of 9.9±0.7 ka that assigns the development of this lake level to the early part of the Lake Ojibway history. A smaller group (3 samples) is part of a more scattered distribution of older10Be ages (with 2 outliers) that points to an inheritance of cosmogenic isotopes from a previous exposure, revealing an apparent mean age of 15.8±0.9 ka that is incompatible with the Ojibway inundation and the regional deglaciation. Our results provide the first direct10Be chronology on the sequence of lake levels in the Ojibway basin, which includes the lake stage presumably associated with the confluence and subsequent drainage of Lakes Agassiz and Ojibway. This study demonstrates the potential of this approach to date glacial lake shorelines and underlies the importance of obtaining additional chronological constraints on the Agassiz-Ojibway shoreline sequence to confidently assign a particular lake stage and/or lake-level drawdown to a specific time interval of the deglaciation.

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Variations in Lake Levels during the Holocene in North America: An Indicator of Changes in Atmospheric Circulation Patterns

Géographie physique et Quaternaire ◽

10.7202/032598ar ◽

2007 ◽

Vol 39 (2) ◽

pp. 141-150 ◽

Cited By ~ 38

Author(s):

S. P. Harrison ◽

S. E. Metcalfe

Keyword(s):

North America ◽

General Circulation ◽

Lake Level ◽

Data Bank ◽

Relative Depth ◽

Lake Levels ◽

Regional Patterns ◽

Air Mass ◽

The Holocene ◽

Lake Status

ABSTRACT Fluctuations in the extent of closed lakes provide a detailed record of regional and continental variations in mean annual water budget. The temporal sequence of hydrological fluctuations during the Holocene in North America has been reconstructed using information from the Oxford Lake-Level Data Bank. This data base includes 67 basins from the Americas north of the equator. Maps of lake status, an index of relative depth, are presented for the period 10,000 to 0 yr BP. The early Holocene was characterised by increasingly arid conditions, which led to widespread low lake levels in the mid-latitudes by 9,000 yr BP. By 6,000 yr BP this zone of low lakes extended from 32o to 51oN. Many of the features of the present day lake-level pattern, particularly high lake levels north of 46oN and along the eastern seaboard, were established by 3.000 yr BP. Four distinctive regional patterns of lake behaviour through time are apparent. Histograms of lake status from 20,000 to 0 yr BP are presented for each of these regions. They illustrate the temporal patterns of lake-level fluctuations on a time scale of 103 — 104 yr. Changes in lake status over North America are interpreted as indicating displacements in major features of the general circulation, specifically the zonal Westerlies and the Equatorial Trough, as reflected by changes in air mass trajectories and hence the position of air mass boundaries over the continent.

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Quantifying recent lake level changes in Patagonia (Argentina and Chile): Back to the future?

10.5194/egusphere-egu21-8467 ◽

2021 ◽

Author(s):

Daniel Ariztegui ◽

Clément Pollier ◽

Andrés Bilmes

Keyword(s):

Water Level ◽

Lake Level ◽

Satellite Images ◽

Meteorological Data ◽

Tierra Del Fuego ◽

Water Level Fluctuations ◽

Lake Levels ◽

The Past ◽

Rainfall Variations ◽

The Impact

Lake levels in hydrologically closed-basins are very sensitive to climatically and/or anthropogenically triggered environmental changes. Their record through time can provide valuable information to forecast changes that can have substantial economical and societal impact.Increasing precipitation in eastern Patagonia (Argentina) have been documented following years with strong El Ni&#241;o (cold) events using historical and meteorological data. Quantifying changes in modern lake levels allow determining the impact of rainfall variations while contributing to anticipate the evolution of lacustrine systems over the next decades with expected fluctuations in ENSO frequencies. Laguna Carrilaufquen Grande is located in the intermontane Maquinchao Basin, Argentina. Its dimension fluctuates greatly, from 20 to 55 km2 water surface area and an average water depth of 3 m. Several well-preserved gravelly beach ridges witness rainfall variations that can be compared to meteorological data and satellite images covering the last ~50 years. Our results show that in 2016 lake level was the lowest of the past 44 years whereas the maximum lake level was recorded in 1985 (+11.8 m above the current lake level) in a position 1.6 km to the east of the present shoreline. A five-years moving average rainfall record of the area was calculated smoothing the extreme annual events and correlated to the determined lake level fluctuations. The annual variation of lake levels was up to 1.2 m (e.g. 2014) whereas decadal variations related to humid-arid periods for the interval 2002 to 2016 were up to 9.4 m. These data are consistent with those from other monitored lakes and, thus, our approach opens up new perspectives to understand the historical water level fluctuations of lakes with non-available monitoring data.&#160;Laguna de los Cisnes in the Chilean section of the island of Tierra del Fuego, is a closed-lake presently divided into two sections of 2.2 and 11.9 km2, respectively. These two water bodies were united in the past forming a single larger lake. The lake level was&#160; ca. 4 m higher than today as shown by clear shorelines and the outcropping of large Ca-rich microbialites. Historical data, aerial photographs and satellite images indicate that the most recent changes in lake level are the result of a massive decrease of water input during the last half of the 20th century triggered by an indiscriminate use of the incoming water for agricultural purposes. The spectacular outcropping of living and fossil microbialites is not only interesting from a scientific point of view but has also initiated the development of the site as a local touristic attraction. However, if the use of the incoming water for agriculture in the catchment remains unregulated the lake water level might drop dangerously and eventually the lake might fully desiccate.These two examples illustrate how recent changes in lake level can be used to anticipate the near future of lakes. They show that ongoing climate changes along with the growing demand of natural resources have already started to impact lacustrine systems and this is likely to increase in the decades to come.

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Glacial-Lake Outburst Erosion of the Grand Valley, Michigan, and Impacts on Glacial Lakes in the Lake Michigan Basin

Quaternary Research ◽

10.1006/qres.1993.1004 ◽

1993 ◽

Vol 39 (1) ◽

pp. 36-44 ◽

Cited By ~ 26

Author(s):

Alan E. Kehew

Keyword(s):

Lake Level ◽

Lake Michigan ◽

Laurentide Ice Sheet ◽

Glacial Lake ◽

Michigan Basin ◽

Lake Agassiz ◽

Lake Algonquin ◽

Lake Michigan Lobe ◽

Possible Cause ◽

Glacial Lake Algonquin

AbstractGeomorphic and sedimentologic evidence in the Grand Valley, which drained the retreating Saginaw Lobe of the Laurentide Ice Sheet and later acted as a spillway between lakes in the Huron and Erie basins and in the Michigan basin, suggests that at least one drainage event from glacial Lake Saginaw to glacial Lake Chicago was a catastrophic outburst that deeply incised the valley. Analysis of shoreline and outlet geomorphology at the Chicago outlet supports J H Bretz's hypothesis of episodic incision and lake-level change. Shoreline features of each lake level converge to separate outlet sills that decrease in elevation from the oldest to youngest lake phases. This evidence, coupled with the presence of boulder lags and other features consistent with outburst origin, suggests that the outlets were deepened by catastrophic outbursts at least twice. The first incision event is correlated with a linked series of floods that progressed from Huron and Erie basin lakes to glacial Lake Saginaw to glacial Lake Chicago and then to the Mississippi. The second downcutting event occurred after the Two Rivers Advance of the Lake Michigan Lobe. Outbursts from the eastern outlets of glacial Lake Agassiz to glacial Lake Algonquin are a possible cause for this period of downcutting at the Chicago outlets.

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Perioperative Hemodynamic Changes During Video-Assisted Thoracoscopic Decortication for empyema

The Open Anesthesiology Journal ◽

10.2174/1874321801711010088 ◽

2017 ◽

Vol 11 (1) ◽

pp. 88-96

Author(s):

Fang-Ting Chen ◽

An-Hsun Chou ◽

Chun-Yu Chen ◽

Pei-Chi Ting ◽

Ming-Wen Yang ◽

...

Keyword(s):

Lung Ventilation ◽

Lateral Decubitus Position ◽

Time Interval ◽

Hemodynamic Parameters ◽

Hemodynamic Changes ◽

Video Assisted ◽

Lateral Decubitus ◽

Group 3 ◽

Group 2 ◽

Group 1

Background and Objective: Hemodynamic consequences during video-assisted thoracoscopic surgery (VATS) with decortication during empyema drainage are unclear. The aim of the study was to assess the perioperative hemodynamic changes decortication during empyema drainage. Methods: A prospective study enrolled 23 patients with empyema who underwent decortication. Hemodynamic parameters were continuously obtained at 15 time points: supine two lung ventilation after induction, lateral decubitus position and two lung ventilation, lateral decubitus position and one-lung ventilation, every 5 min after decortication upto 60 minutes and at the end of surgery. We divided patients into three groups according to microorganisms, group 1: patients with no growth of organism; group 2: patients with staphylococcus aureus and pseudomonas; group 3: patients with streptococcus, yeast and fungus, gram-positive bacilli, and mycobacterium tuberculosis. The hemodynamic variables were recorded by the third-generation Vigileo/FloTracTM system and variables for each time interval were compared with the baseline by Wilcoxon Signed Ranks Test. Results: In group 1, hemodynamic parameters showed no significant changes over time. However, in group 2 and 3, both CO and CI increased 10 to 15 minutes after decortication and remained elevated during the remainder of surgery. However, SVR and SVRI decreased 10 to 15 minutes after decortication in both groups, especially, with a more significant decrease noted in group 2 than group 3. Conclusion: Close perioperative hemodynamic monitoring during decortication in empyema patients is required because of potential hemodynamic disturbances especially patients with toxic microorganisms.

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Lake Levels and Sedimentary Environments During Deposition of the Trego Hot Springs and Wono Tephras in the Lake Lahontan Basin, Nevada, USA

Quaternary Research ◽

10.1016/j.yqres.2009.08.001 ◽

2010 ◽

Vol 73 (1) ◽

pp. 118-129 ◽

Cited By ~ 8

Author(s):

Kenneth D. Adams

Keyword(s):

Lake Level ◽

Hot Springs ◽

Silty Clay ◽

Lake Levels ◽

Sediment Sources ◽

Sedimentary Environments ◽

Depositional Settings ◽

Significant Difference ◽

Predictable Pattern ◽

Lake Size

The Wono and Trego Hot Springs (THS) tephras are widespread in the Lahontan basin and have been identified in a variety of sedimentary environments at different elevations. Davis (1983) reported lake level to be at about 1256 m when the THS tephra was deposited, an interpretation questioned by Benson et al. (1997) who interpreted lake level to be ≤1177 m at that time. This is a significant difference in lake size with important implications for interpreting the climate that prevailed at that time. Based on new interpretations of depositional settings of the THS bed at multiple sites, the larger lake size is correct. Additional sites containing the Wono tephra indicate that it was deposited when lake level was at about 1217 m in the western subbasins and at about 1205 m in the Carson Sink. Sedimentary features associated with progressively deeper paleowater depths follow a predictable pattern that is modulated by proximity to sediment sources and local slope. Fine to coarse sands with wave-formed features are commonly associated with relatively shallow water. Silty clay or clay dominates in paleowater depths >25 m, with thin laminae of sand and ostracods at sites located adjacent to or downslope from steep mountain fronts.

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Multivariate framework for the assessment of key forcing to Lake Malawi level variations in non-stationary frequency analysis

Environmental Monitoring and Assessment ◽

10.1007/s10661-020-08519-4 ◽

2020 ◽

Vol 192 (9) ◽

Author(s):

Cosmo Ngongondo ◽

Yanlai Zhou ◽

Chong-Yu Xu

Keyword(s):

Lake Level ◽

Southern Oscillation ◽

Low Frequency ◽

Lake Malawi ◽

Extreme Value ◽

Information Criteria ◽

Eastern Africa ◽

Water Evaporation ◽

Lake Levels ◽

Indian Ocean Dipole Mode

Abstract Lake Malawi in south eastern Africa is a very important freshwater system for the socio-economic development of the riparian countries and communities. The lake has however experienced considerable recession in the levels in recent years. Consequently, frequency analyses of the lake levels premised on time-invariance (or stationarity) in the parameters of the underlying probability distribution functions (pdfs) can no longer be assumed. In this study, the role of hydroclimate forcing factors (rainfall, lake evaporation, and inflowing discharge) and low frequency climate variability indicators (e.g., El Nino Southern Oscillation-ENSO and the Indian Ocean Dipole Mode-IODM) on lake level variations is investigated using a monthly mean lake level dataset from 1899 to 2017. Non-stationarity in the lake levels was tested and confirmed using the Mann-Kendall trend test (α = 0.05 level) for the first moment and the F test for the second moment (α = 0.05 level). Change points in the series were identified using the Mann-Whitney-Pettit test. The study also compared stationary and non-stationary lake level frequency during 1961 to 2004, the common period where data were available for all the forcing factors considered. Annual maximum series (AMS) and peak over threshold (POT) analysis were conducted by fitting various candidate extreme value distributions (EVD) and parameter fitting methods. The Akaike information criteria (AIC), Bayesian information criteria (BIC), deviance information criteria (DIC), and likelihood ratios (RL) served as model evaluation criteria. Under stationary conditions, the AMS when fitted to the generalized extreme value (GEV) distribution with maximum likelihood estimation (MLE) was found to be superior to POT analysis. For the non-stationary models, open water evaporation as a covariate of the lake levels with the GEV and MLE was found to have the most influence on the lake level variations as compared with rainfall, discharge, and the low frequency climatic forcing. The results are very critical in flood zoning especially with various planned infrastructural developments around the lakeshore.

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Safe Out-of-Hospital Treatment of Chest Pain Without Direct Medical Control

Prehospital and Disaster Medicine ◽

10.1017/s1049023x00042291 ◽

1996 ◽

Vol 11 (1) ◽

pp. 16-19 ◽

Cited By ~ 3

Author(s):

Mara McErlean ◽

Nancy Raccio-Robak ◽

Joel M. Bartfield ◽

Daniel Hermes

Keyword(s):

Chest Pain ◽

Adult Patients ◽

Categorical Variables ◽

Hospital Treatment ◽

Time Interval ◽

Medical Control ◽

Physician Contact ◽

Group 3 ◽

Group 2 ◽

Group 1

AbstractIntroduction:The use of direct medical control (DMC) in the out-of-hospital setting often is beneficial, but has the disadvantage of consuming emergency medical services (EMS) resources.Hypothesis:Uncomplicated, nontrauma, adult patients with chest pain can be treated safely and transported by paramedics without DMC.Methods:Retrospective chart review of all nontrauma, adult patients with chest pain treated in a combined rural and suburban EMS system during a 2-year period (December 1990 through November 1992) was conducted. Before November 1991, DMC was mandatory for all patients with chest pain. Beginning 01 November 1991, if a patient had resolution of pain either spontaneously, with administration of oxygen, or after a single dose of nitroglycerin, DMC was at the discretion of the paramedic. Using the above criteria for inclusion, three study groups were defined: Group 1, before protocol change; Group 2, after protocol change without DMC; and Group 3, after protocol change when physician contact was obtained, but not required. These groups were compared for the following parameters: 1) scene time; 2) time to administration of first dose of nitroglycerin; 3) time interval between measurement of vital signs; 4) oxygen use; 5) intravenous access; and 6) electrocardiographic monitoring. Continuous and categorical variables were analyzed by multivariate and univariate analysis of variance and chi-square tests, respectively.Results:Of 308 nontrauma, adult patients with chest pain, 71 met inclusion criteria in Group 1, 40 in Group 2, and 34 in Group 3. No statistically significant differences were identified in any of the study parameters.Conclusion:Adult patients with chest pain who have no other symptoms or complicating conditions can be treated appropriately by paramedics without DMC.

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The movements of Alpine glaciers throughout the last 10,000 years as sensitive proxies of temperature and climate changes

EPJ Web of Conferences ◽

10.1051/epjconf/202023202002 ◽

2020 ◽

Vol 232 ◽

pp. 02002

Author(s):

Walter Kutschera ◽

Gernot Patzelt ◽

Joerg M. Schaefer ◽

Christian Schlüchter ◽

Peter Steier ◽

...

Keyword(s):

New Zealand ◽

Southern Hemisphere ◽

Northern Hemisphere ◽

Climate Changes ◽

European Alps ◽

Cosmogenic Isotopes ◽

The Holocene ◽

Surface Exposure Dating ◽

Exposure Dating ◽

Alpine Glaciers

A brief review of the movements of Alpine glaciers throughout the Holocene in the Northern Hemisphere (European Alps) and in the Southern Hemisphere (New Zealand Southern Alps) is presented. It is mainly based on glacier studies where 14C dating, dendrochronology and surface exposure dating with cosmogenic isotopes is used to establish the chronology of advances and retreats of glaciers. An attempt is made to draw some general conclusions on the temperature and climate differences between the Northern and Southern Hemisphere.

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Global Maps of Lake-Level Fluctuations since 30,000 yr B.P.

Quaternary Research ◽

10.1016/0033-5894(79)90092-9 ◽

1979 ◽

Vol 12 (1) ◽

pp. 83-118 ◽

Cited By ~ 415

Author(s):

F. Alayne Street ◽

A. T. Grove

Keyword(s):

Lake Level ◽

Ice Sheets ◽

Literature Survey ◽

Sea Surface ◽

Lake Levels ◽

Lake Level Fluctuations ◽

Average Abundance ◽

The Tropics ◽

High Lake Levels ◽

Precipitation And Temperature

This paper presents selected world maps of lake-level fluctuations since 30,000 yr B.P. These are based on a literature survey of 141 lake basins with radiocarbon-dated chronologies. The resulting patterns are subcontinental in scale and show orderly variations in space and time. They reflect substantial changes in continental precipitation, evaporation, and runoff, which are due to glacial/interglacial fluctuations in the atmospheric and oceanic circulations. In the tropics, high lake levels are essentially an interglacial or interstadial phenomenon, although there are important exceptions. Since extensive lakes during the Holocene corresponded with relatively high sea-surface temperatures, and therefore presumably with high evaporation rates on land, they are interpreted as the result of higher precipitation. Tropical aridity culminated in most areas at, or just after, the glacial maximum, although the present day is also characterized by a below-average abundance of surface water. In extratropical regions the mapped patterns are more complex. They vary markedly with latitude and proximity to major ice sheets. In these areas, evidence is at present insufficient to evaluate the relative contributions of precipitation and temperature to the observed lake-level record.

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