scholarly journals The Current Oxygen and Hydrogen Isotopic Status of Lake Baikal

Water ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 3476
Author(s):  
Andrey Fedotov ◽  
Ruslan Gnatovsky ◽  
Vadim Blinov ◽  
Maria Sakirko ◽  
Valentina Domysheva ◽  
...  
Keyword(s):  
Steady State ◽  
Isotopic Composition ◽  
Lake Baikal ◽  
Little Ice Age ◽  
Regional Climate ◽  
Ice Age ◽  
Mean Values ◽  
Baikal Basin ◽  
The Past ◽  
The Mean

This study revises the δ18O and δ2H status of Lake Baikal. The mean values of δ18O and δ2H varied from −15.9 to −15.5‰ and from −123.2 to 122.2‰, respectively, for the past 30 yr. The isotopic composition of the lake remained more ‘‘light” compared to the regional precipitation and rivers inflows. The isotopic composition of the lake has begun to change since ca.1920 after the Little Ice Age; however, Lake Baikal still has not reached the isotopically steady state in the present. The calculated composition of the steady-state should be −12.3‰ for δ18O and −103.6‰ for δ2H. If regional climate parameters do not change dramatically, Lake Baikal will reach these values in ca. 226 yr. Based on isotopic fingerprints of the upper (0 to 150 m) and near-bottom layers (ca. 150 m from the bottom floor), the renewal in the southern and central basins of Lake Baikal has occurred recently compared to the northern Baikal basin, and the size of the mixing-cell of downwelling is close to 30 km.

Seasonal trends in the stable isotopic composition of snow and meltwater runoff in a subarctic catchment at Okstindan, Norway

2004 ◽  
Vol 35 (2) ◽  
pp. 119-137 ◽  
Author(s):  
S.D. Gurney ◽  
D.S.L. Lawrence
Keyword(s):  
Isotopic Composition ◽  
Mean Value ◽  
Mean Values ◽  
Stable Isotopic Composition ◽  
Meltwater Runoff ◽  
Stable Isotopic ◽  
The Mean ◽  
The Difference ◽  
Δ18o And Δd

Seasonal variations in the stable isotopic composition of snow and meltwater were investigated in a sub-arctic, mountainous, but non-glacial, catchment at Okstindan in northern Norway based on analyses of δ18O and δD. Samples were collected during four field periods (August 1998; April 1999; June 1999 and August 1999) at three sites lying on an altitudinal transect (740–970 m a.s.l.). Snowpack data display an increase in the mean values of δ18O (increasing from a mean value of −13.51 to −11.49‰ between April and August), as well as a decrease in variability through the melt period. Comparison with a regional meteoric water line indicates that the slope of the δ18O–δD line for the snowpacks decreases over the same period, dropping from 7.49 to approximately 6.2.This change points to the role of evaporation in snowpack ablation and is confirmed by the vertical profile of deuterium excess. Snowpack seepage data, although limited, also suggest reduced values of δD, as might be associated with local evaporation during meltwater generation. In general, meltwaters were depleted in δ18O relative to the source snowpack at the peak of the melt (June), but later in the year (August) the difference between the two was not statistically significant. The diurnal pattern of isotopic composition indicates that the most depleted meltwaters coincide with the peak in temperature and, hence, meltwater production.

Physiological and biophysical limits to work in the heat for clothed men and women

1978 ◽  
Vol 44 (6) ◽  
pp. 918-925 ◽  
Author(s):  
E. Kamon ◽  
B. Avellini ◽  
J. Krajewski
Keyword(s):  
Steady State ◽  
Vapor Pressure ◽  
Physiological Responses ◽  
Men And Women ◽  
Mean Values ◽  
Air Temperatures ◽  
Significant Difference ◽  
The Mean ◽  
Evaporative Heat Transfer ◽  
The One

Heat-acclimated, lightly clothed men and women (four of each) walked on a treadmill at 25% and 43% VO2 max, respectively, (M =194 W.m-2), under seven air temperatures (Ta) ranging from 36 to 52 degrees C. Each experiment involved 1 h of fixed and a 2nd h of progressively increasing ambient vapor pressure (Pa). The relative steady state of rectal temperature (Tre), mean skin temperature (Tsk), and heart rate (HR) reached in the 1st h were forced upward during the 2nd h by the rising Pa. The critical air vapor pressure (Pcrit) was identified by the Tre point of inflection for each Ta. One man did not fully reach steady state, but inflection could be determined for his physiological responses. The mean values of all points of inflection were calculated for Tre, Tsk, and HR. Significant sex difference in HR was found only by excluding the results of the one man. Tre and Tsk showed no significant difference between men and women. The coefficient for evaporative heat transfer (he), which could be derived using the Pcrit for the low Ta range, was 14.5 +/- 2.2 W.m-1 Torr-1.

scholarly journals Glacier equilibrium line altitude variations during the “Little Ice Age” in the Mediterranean Andes (30◦–37◦ S)

2019 ◽  
Author(s):  
Álvaro González-Reyes ◽  
Claudio Bravo ◽  
Mathias Vuille ◽  
Martin Jacques-Coper ◽  
Maisa Rojas ◽  
...  
Keyword(s):  
Little Ice Age ◽  
Pearson Correlation ◽  
Temporal Changes ◽  
Global Climate Models ◽  
Ice Age ◽  
Equilibrium Line ◽  
Equilibrium Line Altitude ◽  
Mountainous Regions ◽  
The Mean ◽  
The Mediterranean

Abstract. The "Little Ice Age" (LIA; 1500–1850 Common Era (CE)), has long been recognized as the last period when mountain glaciers in many regions of the Northern Hemisphere (NH) recorded extensive growth intervals in terms of their ice mass and frontal position. The knowledge about this relevant paleoclimatic interval is vast in mountainous regions such as the Alps and Rocky Mountains in North America. However, in extra-tropical Andean sub-regions such as the Mediterranean Andes of Chile and Argentina (MA; 30º–37º S), the LIA has been poorly documented. Paradoxically, the few climate reconstructions performed in the MA based on lake sediments and tree rings do not show clear evidence of a LIA climate anomaly as observed in the NH. In addition, recent studies have demonstrated temporal differences between mean air temperature variations across the last millennium between both hemispheres. This motivates our hypothesis that the LIA period was not associated with a significant climate perturbation in the MA region. Considering this background, we performed an experiment using daily climatic variables from three Global Climate Models (GCMs) to force a novel glaciological model. In this way, we simulated temporal variations of the glacier equilibrium-line altitude (ELA) to evaluate the glacier response during the period 1500–1848 CE. Overall, each GCM shows temporal changes in annual ELA, with anomalously low elevations during 1640–1670 and 1800–1848 CE. An interval with high ELA values was identified during 1550–1575 CE. The spectral properties of the mean annual ELA in each GCM present significant periodicities between 2–7 years, and also significant decadal to multi-decadal signals. In addition, significant and coherent cycles at interannual to multi-decadal scales were detected between modeled mean annual ELAs and the first EOF1 extracted from Sea Surface Temperature (SST) within the El Niño 3.4 of each GCM. Finally, significant Pearson correlation coefficients were obtained between the mean annual ELA and Pacific SST on interannual to multi-decadal timescales. According to our findings, we propose that Pacific SST variability was the main modulator of temporal changes of the ELA in the MA region of South America during 1500–1848 CE.

scholarly journals The ENSO teleconnections to the Indian summer monsoon climate through the Last Millennium as simulated by the PMIP3

2018 ◽  
Author(s):  
Charan Teja Tejavath ◽  
Karumuri Ashok ◽  
Supriyo Chakraborty ◽  
Rengaswamy Ramesh
Keyword(s):  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Little Ice Age ◽  
Walker Circulation ◽  
Summer Monsoon Rainfall ◽  
Ice Age ◽  
Boreal Summer ◽  
Last Millennium ◽  
Enso Teleconnections ◽  
The Mean

Abstract. Using seven model simulations from the PMIP3, we study the mean summer (June–September) climate and its variability in India during the Last Millennium (LM; CE 850–1849) with emphasis on the Medieval Warm Period (MWP) and Little Ice Age (LIA), after validation of the simulated current day climate and trends. We find that the above (below) LM-mean summer global temperatures during the MWP (LIA) are associated with relatively higher (lower) number of concurrent El Niños as compared to La Niñas. The models simulate higher (lower) Indian summer monsoon rainfall (ISMR) during the MWP (LIA). This is notwithstanding a strong simulated negative correlation between the timeseries of NINO3.4 index and that of the area-averaged ISMR, Interestingly, the percentage of strong El Niños (La Niñas) causing negative (positive) ISMR anomalies is higher in the LIA (MWP), a non-linearity that apparently is important for causing higher ISMR in the MWP. Distribution of simulated boreal summer velocity potential at 850 hPa during MWP in models, in general, shows a zone of anomalous convergence in the central tropical Pacific flanked by two zones of divergence, suggesting a westward shift in the Walker circulation as compared to the simulations for LM as well as and a majority of historical simulations, and current day observed signal. The anomalous divergence centre in the west also extends into the equatorial eastern Indian Ocean, resulting in an anomalous convergence zone over India and therefore excess rainfall during the MWP as compared to the LM; the results are qualitative, given the inter-model spread.

The Claps of Luc-en-Diois (Drôme, SE France) : evaluation of a lake fill volume based on a morphological model

2004 ◽  
Vol 175 (3) ◽  
pp. 303-312 ◽  
Author(s):  
Gilles Brocard
Keyword(s):  
Little Ice Age ◽  
River Sediment ◽  
Sediment Load ◽  
Ice Age ◽  
Drainage Network ◽  
Erosion Rates ◽  
Lake Volume ◽  
Fill Volume ◽  
Morphological Model ◽  
The Mean

Abstract The Claps Lake near Luc-en-Diois is a naturally dammed palaeo-lake fed by the Drôme River sediment load during the Little Ice Age (LIA). The present assessment is based on a valley reconstruction using a geomorphic model. It illustrates the potentiality and limits of the geomorphic analysis to accurately predict the buried topography. This method indeed may help to reduce the prospecting work required in classical evaluations of fill volumes of such natural dams. The lake was rapidly filled with sediments, indicating enhanced erosion of the watershed during the LIA. Several studies have attempted to quantify the volume of the lake fill and use it to assess erosion rates during the LIA. Very little is known, however, about the geometry of the buried valley. Estimated lake volumes and erosion rates vary depending on how the buried valley is reconstructed and what correcting factors are used for calculating erosion rates. The present assessment is based on a valley reconstruction using a geomorphic model calibrated by the surrounding drainage network, as well as the introduction of correcting factors that improve the corrections applied in the previous works. The resulting lake volume is 71–81.106 m3, and the mean erosion rate at 0.7-1.2 mm.yr-1, a high value compared to previous estimates. This rate is compared to the results obtained by various methods and over different timescales in the surrounding region.

Glacier fluctuations during the past millennium in Garibaldi Provincial Park, southern Coast Mountains, British Columbia

2007 ◽  
Vol 44 (9) ◽  
pp. 1215-1233 ◽  
Author(s):  
Johannes Koch ◽  
John J Clague ◽  
Gerald D Osborn
Keyword(s):  
British Columbia ◽  
Little Ice Age ◽  
Ice Age ◽  
Southern Coast ◽  
Coast Mountains ◽  
The Past ◽  
Glacier Fluctuations ◽  
Garibaldi Provincial Park ◽  
Provincial Park ◽  
Past Millennium

The Little Ice Age glacier history in Garibaldi Provincial Park (southern Coast Mountains, British Columbia) was reconstructed using geomorphic mapping, radiocarbon ages on fossil wood in glacier forefields, dendrochronology, and lichenometry. The Little Ice Age began in the 11th century. Glaciers reached their first maximum of the past millennium in the 12th century. They were only slightly more extensive than today in the 13th century, but advanced at least twice in the 14th and 15th centuries to near their maximum Little Ice Age positions. Glaciers probably fluctuated around these advanced positions from the 15th century to the beginning of the 18th century. They achieved their greatest extent between A.D. 1690 and 1720. Moraines were deposited at positions beyond present-day ice limits throughout the 19th and early 20th centuries. Glacier fluctuations appear to be synchronous throughout Garibaldi Park. This chronology agrees well with similar records from other mountain ranges and with reconstructed Northern Hemisphere temperature series, indicating global forcing of glacier fluctuations in the past millennium. It also corresponds with sunspot minima, indicating that solar irradiance plays an important role in late Holocene climate change.

scholarly journals Accelerating retreat and high-elevation thinning of glaciers in central Spitsbergen

2016 ◽  
Vol 10 (3) ◽  
pp. 1317-1329 ◽  
Author(s):  
Jakub Małecki
Keyword(s):  
Little Ice Age ◽  
High Elevation ◽  
Comprehensive Analysis ◽  
Ice Age ◽  
The Arctic ◽  
Digital Elevation ◽  
Glacier Changes ◽  
The Mean ◽  
Geodetic Mass Balance ◽  
The 1960S

Abstract. Svalbard is a heavily glacier-covered archipelago in the Arctic. Dickson Land (DL), in the central part of the largest island, Spitsbergen, is relatively arid and, as a result, glaciers there are relatively small and restricted mostly to valleys and cirques. This study presents a comprehensive analysis of glacier changes in DL based on inventories compiled from topographic maps and digital elevation models for the Little Ice Age (LIA) maximum, the 1960s, 1990, and 2009/2011. Total glacier area has decreased by  ∼ 38 % since the LIA maximum, and front retreat increased over the study period. Recently, most of the local glaciers have been consistently thinning in all elevation bands, in contrast to larger Svalbard ice masses which remain closer to balance. The mean 1990–2009/2011 geodetic mass balance of glaciers in DL is among the most negative from the Svalbard regional means known from the literature.

Humidity variations spanning the ‘Little Ice Age’ from an upland lake in southwestern China

The Holocene ◽  
2019 ◽  
Vol 30 (2) ◽  
pp. 289-299
Author(s):  
Tingwei Zhang ◽  
Xiaoqiang Yang ◽  
Qiong Chen ◽  
Jaime L Toney ◽  
Qixian Zhou ◽  
...  
Keyword(s):  
Little Ice Age ◽  
Asian Monsoon ◽  
Activity Index ◽  
Ice Age ◽  
Western China ◽  
Southwestern China ◽  
Sunspot Activity ◽  
Precipitation Pattern ◽  
The Past ◽  
Westerly Jet

A number of archives that span the past ~2000 years suggest that recent variability in hydroclimatic conditions that are influenced by the Asian monsoon in China are unusual in the longer term context. However, the lack of high-resolution precipitation records over this period hampered our ability to characterize and constrain the forcing mechanism(s) of the recent humidity variations. Here, we present the ratio of hematite to goethite (Hm/Gt) derived from the semiquantitative evaluation of the diffuse reflectance spectroscopic analysis as a reliable and effective precipitation proxy to reconstruct the humidity variations during the past 1400 years deduced from Tengchongqinghai Lake sediments, southwestern China. Hm/Gt varied synchronously with variations of Chinese temperature reconstructed from the historical documents and sunspot activity index over the past 1400 years. Critical periodicities of ~450 and ~250 years show that solar activity is the dominant control on precipitation change on centennial scales. However, the relationship determined from Hm/Gt in this study contradicts the stalagmite δ18O interpretations from different regions of China, which exhibit a more complex precipitation pattern that is influenced by the strength of westerly jet in addition to the Asian monsoon. The increased westerly jet during the ‘Little Ice Age’ (LIA) caused a humid climate in southern China and dry conditions in northern and western China.

scholarly journals Some Physiological Factors Affecting the Binding of Cortisol by Human Plasma Proteins

1977 ◽  
Vol 14 (1-6) ◽  
pp. 35-38 ◽  
Author(s):  
J. D. Few ◽  
J. R. Haspineall
Keyword(s):  
Steady State ◽  
Human Plasma ◽  
Plasma Proteins ◽  
Gel Filtration ◽  
Physiological Factors ◽  
Mean Values ◽  
Factors Affecting ◽  
Free Cortisol ◽  
The Mean

Steady-state gel filtration has been used to study the binding of cortisol to human plasma proteins in vitro. Raising the temperature from 37°C to 41°C results in the mean proportion of free (non-protein-bound) cortisol rising approximately from 7% to 11%. Addition of cortisol to plasma ≡ 275 nmol/l) also increased the proportion of free cortisol by approximately 50%. Cortisone is less strongly bound to plasma proteins than cortisol. The mean values (±S.D.) for five samples were free cortisol 8.4 ± 1.1% and free cortisone 26.0±3.8%.

Little Ice Age fluctuations of Glaciar Río Manso in the North Patagonian Andes of Argentina

2010 ◽  
Vol 73 (1) ◽  
pp. 96-106 ◽  
Author(s):  
M.H. Masiokas ◽  
B.H. Luckman ◽  
R. Villalba ◽  
A. Ripalta ◽  
J. Rabassa
Keyword(s):  
Little Ice Age ◽  
Ice Age ◽  
Lateral Moraine ◽  
Early Nineteenth Century ◽  
The Past ◽  
The North ◽  
Specific Factors ◽  
Subfossil Wood ◽  
Moraine Ridge ◽  
Patagonian Andes

Little Ice Age (LIA) fluctuations of Glaciar R"o Manso, north Patagonian Andes, Argentina are studied using information from previous work and dendrogeomorphological analyses of living and subfossil wood. The most extensive LIA expansion occurred between the late 1700s and the 1830"1840s. Except for a massive older frontal moraine system apparently predating ca. 2240 14C yr BP and a small section of a south lateral moraine ridge that is at least 300 yr old, the early nineteenth century advance overrode surficial evidence of any earlier LIA glacier events. Over the past 150 yr the gently sloping, heavily debris-covered lower glacier tongue has thinned significantly, but several short periods of readvance or stasis have been identified and tree-ring dated to the mid-1870s, 1890s, 1900s, 1920s, 1950s, and the mid-1970s. Ice mass loss has increased in recent years due to calving into a rapidly growing proglacial lake. The neighboring debris-free and land-based Glaciar Fr"as has also retreated markedly in recent years but shows substantial differences in the timing of the peak LIA advance (early 1600s). This indicates that site-specific factors can have a significant impact on the resulting glacier records and should thus be considered carefully in the development and assessment of regional glacier chronologies.

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