scholarly journals Microbial Membrane Tetraether lipid-inferred paleohydrology and paleotemperature of Lake Chenghai during the Pleistocene-Holocene transition

2019 ◽  
Author(s):  
Weiwei Sun ◽  
Enlou Zhang ◽  
Jie Chang ◽  
James Shulmeister ◽  
Michael I. Bird ◽  
...  
Keyword(s):  
Relative Abundance ◽  
Lake Level ◽  
Southwest China ◽  
Transition Period ◽  
Younger Dryas ◽  
Lake Surface ◽  
Cold Event ◽  
The Past ◽  
Lake Chenghai ◽  
Temperature Records

Abstract. Over the past few decades, paleoenvironmental studies in the Indian Summer Monsoon (ISM) region have mainly focused on precipitation change, with few published terrestrial temperature records from the region. We analyzed the distribution of isoprenoid glycerol dialkyl glycerol tetraethers (isoGDGTs) in the sediments of Lake Chenghai in southwest China across the Pleistocene–Holocene transition, to extract both regional hydrological and temperature signals for this important transition period. Lake-level was reconstructed from the relative abundance of crenarchaeol in isoGDGTs (%cren) and the crenarchaeol'/crenarchaeol ratio. The %cren-inferred lake-level identified a single lowstand (15.4–14.4 cal ka BP), while the crenarchaeol'/crenarchaeol ratio suggests relatively lower lake-level between 15.4–14.4 cal ka BP and 12.5–11.7 cal ka BP, corresponding to periods of weakened ISM during the Heinrich 1 (H1) and Younger Dryas (YD) cold event. A filtered TetraEther indeX consisting of 86 carbon atoms (TEX86 index) revealed that lake surface temperature reached present-day values during the YD cold event, and suggests a substantial warming of ~ 4 °C from the early Holocene to the mid-Holocene. Our paleotemperature record is generally consistent with other records in southwest China, suggesting that the distribution of isoGDGTs in Lake Chenghai sediments has potential for quantitative paleotemperature reconstruction.

scholarly journals Archaeal lipid-inferred paleohydrology and paleotemperature of Lake Chenghai during the Pleistocene–Holocene transition

2020 ◽  
Vol 16 (3) ◽  
pp. 833-845
Author(s):  
Weiwei Sun ◽  
Enlou Zhang ◽  
Jie Chang ◽  
James Shulmeister ◽  
Michael I. Bird ◽  
...  
Keyword(s):  
Lake Level ◽  
Southwest China ◽  
Transition Period ◽  
Monsoon Region ◽  
Lake Surface ◽  
Cold Event ◽  
The Past ◽  
Lake Chenghai ◽  
Temperature Records ◽  
Summer Monsoon Region

Abstract. Over the past decades, paleoenvironmental studies in the Indian summer monsoon region have mainly focused on precipitation change, with few published terrestrial temperature records from the region. We analysed the distribution of isoprenoid glycerol dialkyl glycerol tetraethers (isoGDGTs) in the sediments of Lake Chenghai in southwest China across the Pleistocene–Holocene transition, to extract both regional hydrological and temperature signals for this important transition period. The lake level was reconstructed from the relative abundance of crenarchaeol in isoGDGTs (%cren) and the crenarchaeol′/crenarchaeol ratio. The %cren-inferred lake level identified a single lowstand (15.4–14.4 ka cal BP), while the crenarchaeol′/crenarchaeol ratio suggests a relatively lower lake level between 15.4–14.4 and 12.5–11.7 ka cal BP, corresponding to periods of weakened ISM during the Heinrich 1 and Younger Dryas cold event. A filtered TetraEther indeX consisting of 86 carbon atoms (TEX86 index) revealed that lake surface temperature was similar to present-day values during the last deglacial period and suggests a substantial warming of ∼4 ∘C from the early Holocene to the mid-Holocene. Our paleotemperature record is generally consistent with other records in southwest China, suggesting that the distribution of isoGDGTs in Lake Chenghai sediments has potential for quantitative paleotemperature reconstruction.

Sudden climate transitions during the Quaternary

1999 ◽  
Vol 23 (1) ◽  
pp. 1-36 ◽  
Author(s):  
Jonathan Adams ◽  
Mark Maslin ◽  
Ellen Thomas
Keyword(s):  
Climate Change ◽  
Ocean Circulation ◽  
Younger Dryas ◽  
Ice Cover ◽  
Ice Age ◽  
Cold Event ◽  
Heinrich Events ◽  
The Past ◽  
Eemian Interglacial ◽  
Climate Transitions

The time span of the past few million years has been punctuated by many rapid climate transitions, most of them on timescales of centuries to decades. The most detailed information is available for the Younger Dryas-to-Holocene stepwise change around 11 500 years ago, which seems to have occurred over a few decades. The speed of this change is probably representative of similar but less well studied climate transitions during the last few hundred thousand years. These include sudden cold events (Heinrich events/stadials), warm events (interstadials) and the beginning and ending of long warm phases, such as the Eemian interglacial. Detailed analysis of terrestrial and marine records of climate change will, however, be necessary before we can say confidently on what timescale these events occurred; they almost certainly did not take longer than a few centuries. Various mechanisms, involving changes in ocean circulation and biotic productivity, changes in atmospheric concentrations of greenhouse gases and haze particles, and changes in snow and ice cover, have been invoked to explain sudden regional and global transitions. We do not know whether such changes could occur in the near future as a result of human effects on climate. Phenomena such as the Younger Dryas and Heinrich events might only occur in a ‘glacial’ world with much larger ice sheets and more extensive sea-ice cover. A major sudden cold event, however, did probably occur under global climate conditions similar to those of the present, during the Eemian interglacial around 122 000 years ago. Less intensive, but significant rapid climate changes also occurred during the present (Holocene) interglacial, with cold and dry phases occurring on a 1500-year cycle, and with climate transitions on a decade-to-century timescale. In the past few centuries, smaller transitions (such as the ending of the Little Ice Age at about AD 1650) probably occurred over only a few decades at most. All evidence indicates that long-term climate change occurs in sudden jumps rather than incremental changes.

Quantitative Reconstruction of Younger Dryas to Mid-Holocene Paleoclimates at Le Locle, Swiss Jura, Using Pollen and Lake-Level Data

2001 ◽  
Vol 56 (2) ◽  
pp. 170-180 ◽  
Author(s):  
Michel Magny ◽  
Joël Guiot ◽  
Patrick Schoellammer
Keyword(s):  
Lake Level ◽  
General Pattern ◽  
Younger Dryas ◽  
Growing Season ◽  
Summer Temperature ◽  
Annual Precipitation ◽  
Climatic Parameters ◽  
Cold Event ◽  
Level Data ◽  
Swiss Jura

AbstractPollen and lake-level data from Le Locle in the Swiss Jura were used to quantitatively reconstruct climatic parameters for the Younger Dryas event and the first half of the Holocene period. The Younger Dryas cold event at Le Locle was characterized by (i) a general trend toward a slight increase in summer temperature and a decrease in annual precipitation and (ii) a marked drying phase at ca. 11,900 cal yr B.P. that occurred between two wetter ones. Further phases of major deficit in moisture occured at ca. 11,500 cal yr B.P. (Younger Dryas-Holocene transition), 10,800 cal yr B.P., 8700 cal yr B.P., and 6500 cal yr B.P. Climatic parameters reconstructed here suggest that phases of higher lake level developing at ca. 12,500–12,000, 11,750–11,600, 11,200–10,900 (synchronous with the Preboreal oscillation), 10,400–8900, 8400–8300 (possibly related to the 8200 yr event), and 7800–7000 cal yr B.P. coincided with an increase in annual precipitation, a decrease in summer temperature, and a shorter growing season. Conversely, periods of low lake level corresponded to a decrease in annual precipitation, an increase in summer temperature, and a longer growing season. This general pattern could have resulted from alternate southward-northward displacements of the Atlantic Westerly Jet.

Unstable ice stream in Greenland during the Younger Dryas cold event

Geology ◽  
2014 ◽  
Vol 42 (9) ◽  
pp. 759-762 ◽  
Author(s):  
Vincent Rinterknecht ◽  
Vincent Jomelli ◽  
Daniel Brunstein ◽  
Vincent Favier ◽  
Valérie Masson-Delmotte ◽  
...  
Keyword(s):  
Younger Dryas ◽  
Cold Event ◽  
Ice Stream

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

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

<p>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.</p><p>Increasing precipitation in eastern Patagonia (Argentina) have been documented following years with strong El Niño (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 km<sup>2</sup> 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.</p><p> </p><p>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 km<sup>2</sup>, respectively. These two water bodies were united in the past forming a single larger lake. The lake level was  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 20<sup>th</sup> 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.</p><p>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.</p>

scholarly journals Simplified Lake Surface Area Method for the Minimum Ecological Water Level of Lakes and Wetlands

Water ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 1056 ◽  
Author(s):  
Songpu Shang ◽  
Songhao Shang
Keyword(s):  
Water Level ◽  
Surface Area ◽  
Lake Level ◽  
Lake Ecosystem ◽  
Lake Surface ◽  
Area Method ◽  
Ecosystem Protection ◽  
Lake Morphology ◽  
Lake Surface Area ◽  
Ecological Water Level

The determination of the rational minimum ecological water level is the base for the protection of ecosystems in shrinking lakes and wetlands. Based on the lake surface area method, a simplified lake surface area method was proposed to define the minimum ecological lake level from the lake level-logarithm of the surface area curve. The curve slope at the minimum ecological lake level is the ratio of the maximum lake storage to the maximum surface area. For most practical cases when the curve cannot be expressed as a simple analytical function, the minimum ecological lake level can be determined numerically using the weighted sum method for an equivalent multi-objective optimization model that balances ecosystem protection and water use. This method requires fewer data of lake morphology and is simple to compute. Therefore, it is more convenient to use this method in the assessment of the ecological lake level. The proposed method was used to determine the minimum ecological water level for one freshwater lake, one saltwater lake, and one wetland in China. The results can be used in the lake ecosystem protection planning and the rational use of water resources in the lake or wetland basins.

scholarly journals Lake-level variability in Salar de Coipasa, Bolivia during the past ∼40,000 yr

2018 ◽  
Vol 91 (2) ◽  
pp. 881-891 ◽  
Author(s):  
J. Andrew Nunnery ◽  
Sherilyn C. Fritz ◽  
Paul A. Baker ◽  
Wout Salenbien
Keyword(s):  
Lake Level ◽  
Sediment Accumulation ◽  
Geochemical Data ◽  
South American ◽  
Climate History ◽  
Oxygen Isotope Stage ◽  
The Past ◽  
History Of ◽  
Diatom Stratigraphy ◽  
The Last Glacial

AbstractVarious paleoclimatic records have been used to reconstruct the hydrologic history of the Altiplano, relating this history to past variability of the South American summer monsoon. Prior studies of the southern Altiplano, the location of the world’s largest salt flat, the Salar de Uyuni, and its neighbor, the Salar de Coipasa, generally agree in their reconstructions of the climate history of the past ∼24 ka. Some studies, however, have highly divergent climatic records and interpretations of earlier periods. In this study, lake-level variation was reconstructed from a ∼14-m-long sediment core from the Salar de Coipasa. These sediments span the last ∼40 ka. Lacustrine sediment accumulation was apparently continuous in the basin from ∼40 to 6 ka, with dry or very shallow conditions afterward. The fossil diatom stratigraphy and geochemical data (δ13C, δ15N, %Ca, C/N) indicate fluctuations in lake level from shallow to moderately deep, with the deepest conditions correlative with the Heinrich-1 and Younger Dryas events. The stratigraphy shows a continuous lake of variable depth and salinity during the last glacial maximum and latter stages of Marine Oxygen Isotope Stage 3 and is consistent with environmental inferences and the original chronology of a drill core from Salar de Uyuni.

scholarly journals Cytospora (Diaporthales) in China

2020 ◽  
Vol 45 (1) ◽  
pp. 1-45 ◽  
Author(s):  
X.L. Fan ◽  
J.D.P. Bezerra ◽  
C.M. Tian ◽  
P.W. Crous
Keyword(s):  
New Species ◽  
Host Plants ◽  
Southwest China ◽  
New Combination ◽  
Large Collection ◽  
Dna Phylogeny ◽  
The Past ◽  
Worldwide Distribution ◽  
Wide Range ◽  
Woody Host

Members of the genus Cytospora are often reported as endophytes, saprobes or phytopathogens, primarily causing canker diseases of woody host plants. They occur on a wide range of hosts and have a worldwide distribution. Although several species have in the past been reported from China, the vast majority are not known from culture or DNA phylogeny. The primary aim of the present study was thus to clarify the taxonomy and phylogeny of a large collection of Cytospora species associated with diverse hosts in China. Cytospora spp. were collected in northeast, northwest, north and southwest China, indicating that the cold and dry environments favour these fungi. In this paper, we provide an assessment of 52 Cytospora spp. in China, focussing on 40 species represented by 88 isolates from 28 host genera. Based on a combination of morphology and a six-locus phylogeny (ITS, LSU, act1, rpb2, tef1-α and tub2), 13 new species and one new combination are introduced. The majority of the species investigated here appear to be host-specific, although further collections and pathogenicity studies will be required to confirm this conclusion.

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