scholarly journals Late Miocene megalake regressions in Eurasia

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Dan Valentin Palcu ◽  
Irina Stanislavovna Patina ◽  
Ionuț Șandric ◽  
Sergei Lazarev ◽  
Iuliana Vasiliev ◽  
...  
Keyword(s):  
Food Web ◽  
Extreme Events ◽  
Late Miocene ◽  
Salt Lake ◽  
Global Ocean ◽  
Water Volume ◽  
Forest Steppe ◽  
Vegetation Changes ◽  
Landscape Changes ◽  
Partial Desiccation

AbstractThe largest megalake in the geological record formed in Eurasia during the late Miocene, when the epicontinental Paratethys Sea became tectonically-trapped and disconnected from the global ocean. The megalake was characterized by several episodes of hydrological instability and partial desiccation, but the chronology, magnitude and impacts of these paleoenvironmental crises are poorly known. Our integrated stratigraphic study shows that the main desiccation episodes occurred between 9.75 and 7.65 million years ago. We identify four major regressions that correlate with aridification events, vegetation changes and faunal turnovers in large parts of Europe. Our paleogeographic reconstructions reveal that the Paratethys was profoundly transformed during regression episodes, losing ~ 1/3 of the water volume and ~ 70% of its surface during the most extreme events. The remaining water was stored in a central salt-lake and peripheral desalinated basins while vast regions (up to 1.75 million km2) became emergent land, suitable for development of forest-steppe landscapes. The partial megalake desiccations match with climate, food-web and landscape changes throughout Eurasia, although the exact triggers and mechanisms remain to be resolved.

Magnetostratigraphic dating of late Miocene megalake regressions in Central Eurasia 

2021 ◽  
Author(s):  
Wout Krijgsman ◽  
Dan Palcu ◽  
Irina Patina ◽  
Ionuț Șandric ◽  
Sergei Lazarev ◽  
...  
Keyword(s):  
Late Miocene ◽  
Salt Lake ◽  
Global Ocean ◽  
Water Volume ◽  
Forest Steppe ◽  
Short Term ◽  
Central Eurasia ◽  
Normal Polarity ◽  
Partial Desiccation ◽  
Reversed Polarity

<p>The largest megalake in the record formed in Eurasia during the late Miocene, when the epicontinental Paratethys Sea became tectonically-trapped and disconnected from the global ocean. The Paratethys megalake was characterized by several episodes of hydrological instability and partial desiccation, but the chronology, magnitude and impacts of these paleoenvironmental crises are poorly known. The Panagia section on the Taman Peninsula of Russia is the only place known to host a continuous sedimentary record of the late Miocene hydrological crises of Paratethys. Paleomagnetic measurements allow the development of a polarity pattern that can be used to date the regression events. The Panagia polarity pattern consists of 17 polarity intervals, 9 of normal polarity and 8 of reversed polarity, plus 4 additional short-term polarity fluctuations, that are inferred to correspond to the 11-7.5 Ma interval. We identified four major regressions that correlate with aridification events, vegetation changes and faunal turnovers in large parts of Europe. Our paleogeographic reconstructions reveal that Paratethys was profoundly transformed during the regression episodes, losing ~1/3 of the water volume and ~70% of its surface during the most extreme events. The remaining water was stored in a central salt-lake and peripheral desalinated basins while vast regions (up to 1.75 million km2) became emerged land, suitable for the development of forest-steppe landscapes. The dry episodes of the megalake match with climate, food-web and landscape changes throughout Eurasia but the exact triggers and mechanisms remain to be resolved.</p>

scholarly journals Isotopic fractionation of carbon during uptake by phytoplankton across the South Atlantic subtropical convergence

2019 ◽  
Vol 16 (18) ◽  
pp. 3621-3635 ◽  
Author(s):  
Robyn E. Tuerena ◽  
Raja S. Ganeshram ◽  
Matthew P. Humphreys ◽  
Thomas J. Browning ◽  
Heather Bouman ◽  
...  
Keyword(s):  
Food Web ◽  
Cell Size ◽  
Surface Waters ◽  
Isotopic Fractionation ◽  
Water Masses ◽  
Global Ocean ◽  
Carbon Uptake ◽  
The South ◽  
Marine Food Web ◽  
Marine Food

Abstract. The stable isotopic composition of particulate organic carbon (δ13CPOC) in the surface waters of the global ocean can vary with the aqueous CO2 concentration ([CO2(aq)]) and affects the trophic transfer of carbon isotopes in the marine food web. Other factors such as cell size, growth rate and carbon concentrating mechanisms decouple this observed correlation. Here, the variability in δ13CPOC is investigated in surface waters across the south subtropical convergence (SSTC) in the Atlantic Ocean, to determine carbon isotope fractionation (εp) by phytoplankton and the contrasting mechanisms of carbon uptake in the subantarctic and subtropical water masses. Our results indicate that cell size is the primary determinant of δ13CPOC across the Atlantic SSTC in summer. Combining cell size estimates with CO2 concentrations, we can accurately estimate εp within the varying surface water masses in this region. We further utilize these results to investigate future changes in εp with increased anthropogenic carbon availability. Our results suggest that smaller cells, which are prevalent in the subtropical ocean, will respond less to increased [CO2(aq)] than the larger cells found south of the SSTC and in the wider Southern Ocean. In the subantarctic water masses, isotopic fractionation during carbon uptake will likely increase, both with increasing CO2 availability to the cell, but also if increased stratification leads to decreases in average community cell size. Coupled with decreasing δ13C of [CO2(aq)] due to anthropogenic CO2 emissions, this change in isotopic fractionation and lowering of δ13CPOC may propagate through the marine food web, with implications for the use of δ13CPOC as a tracer of dietary sources in the marine environment.

Zonal Transport from the Western Boundary and Its Role in Warm Water Volume Changes during ENSO

2017 ◽  
Vol 47 (1) ◽  
pp. 211-225 ◽  
Author(s):  
Qing Lu ◽  
Zhenxin Ruan ◽  
Dong-Ping Wang ◽  
Dake Chen ◽  
Qiaoyan Wu
Keyword(s):  
Water Transport ◽  
General Circulation ◽  
Circulation Model ◽  
Extended Period ◽  
Ocean General Circulation Model ◽  
Warm Water ◽  
Global Ocean ◽  
Water Volume ◽  
Western Boundary ◽  
Warm Water Volume

AbstractObservations from TRITON buoys in the warm/fresh pool and a global ocean general circulation model are used to study the interannual variability of the equatorial western Pacific and the relationship between the zonal warm water transport, meridional convergence, and the warm water volume (WWV). The simulated temperature, salinity, and zonal warm water transport are validated with the mooring observations for the period 2000–14. The model results are then used to examine the WWV balance in ENSO cycles in an extended period from 1980 to 2014. It is shown that the zonal transport is highly correlated with meridional convergence and leads by about 4–5 months, and their phase offset determines the WWV changes. This result differs from the recharge paradigm in which the meridional convergence is supposed to be mainly responsible for the WWV changes. There is also no apparent change in relationship between zonal and meridional transports since 2000, unlike that between WWV and SST. The study suggests that the zonal warm water transport from the western boundary could have major implications for ENSO dynamics.

scholarly journals Isotopic fractionation of carbon during uptake by phytoplankton across the South Atlantic subtropical convergence

2019 ◽  
Author(s):  
Robyn E. Tuerena ◽  
Raja S. Ganeshram ◽  
Matthew P. Humphreys ◽  
Thomas J. Browning ◽  
Heather Bouman ◽  
...  
Keyword(s):  
Food Web ◽  
Cell Size ◽  
Surface Waters ◽  
Isotopic Fractionation ◽  
Water Masses ◽  
Global Ocean ◽  
Carbon Uptake ◽  
The South ◽  
Marine Food Web ◽  
Marine Food

Abstract. The stable isotopic composition of particulate organic carbon (δ13CPOC) in the surface waters of the global ocean can vary with the aqueous CO2 concentration ([CO2(aq)]) and affects the trophic transfer of carbon isotopes in the marine food web. Other factors such as cell size, growth rate and carbon concentrating mechanisms decouple this observed correlation. Here, the variability in δ13CPOC is investigated in surface waters across the south subtropical convergence (SSTC) in the Atlantic Ocean, to determine carbon isotope fractionation (εp) by phytoplankton and the contrasting mechanisms of carbon uptake in the subantarctic and subtropical water masses. Our results indicate that cell size is the primary determinant of δ13CPOC across the Atlantic SSTC in summer. Combining cell size estimates with CO2 concentrations, we can accurately estimate εp within the varying surface water masses in this region. We further utilize these results to investigate future changes in εp with increased anthropogenic carbon availability. Our results suggest that smaller cells, which are prevalent in the subtropical ocean, will respond less to increased [CO2(aq)] than the larger cells found south of the SSTC and in the wider Southern Ocean. In the subantarctic water masses, isotopic fractionation during carbon uptake will likely increase, both with increasing CO2 availability to the cell, but also if increased stratification leads to decreases in average community cell size. Coupled with decreasing δ13C of [CO2(aq)] due to anthropogenic CO2 emissions, this change in isotopic fractionation and lowering of δ13CPOC may propagate through the marine food web, with implications for the use of δ13CPOC as a tracer of dietary sources in the marine environment.

scholarly journals DISTRIBUTION OF RESTORATION SUCCESSIONS IN TAIGA AND FOREST-STEPPE LANDSCAPES OF THE PERMSKY PRIKAMYE (ON THE EXAMPLE OF AGRICULTURAL LANDS)

2021 ◽  
Vol 31 (4) ◽  
pp. 416-424
Author(s):  
A.P. Belousova ◽  
N.N. Nazarov
Keyword(s):  
Remote Sensing ◽  
Soil Fertility ◽  
Forest Cover ◽  
Agricultural Land ◽  
Remote Sensing Data ◽  
Forest Steppe ◽  
Landscape Changes ◽  
Agricultural Lands ◽  
Natural Factors ◽  
Agricultural Use

The research of forest cover development on agricultural lands in the Perm Prikamye was carried the example of taiga and forest-steppe types of landscapes. The Babkinsko-Yugovskoy and Irensko-Kungursky landscapes were select for research. Received information about the geosystem condition in different years using remote sensing data. All landscape changes were record during the formed stable snow cover. As a result, was divide into two classes - forested and treeless areas. Established, the main natural factors of land differentiation by an areas and a pace of withdrawal from agricultural use are the small contours of agricultural land and differences in soil fertility. The growth pace of forest geosystems within the forest-steppe landscape was 2.5 times higher than of the taiga. The research of the dynamics of forest cover showed that in the Perm Prikamye in the forest-steppe landscape substitution of anthropogenic geosystems with natural-anthropogenic ("wild") accompanied by the development of forest biogeocenosis, not steppe.

scholarly journals An operational overview of the EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) Northeast Pacific field deployment

Elem Sci Anth ◽  
2021 ◽  
Vol 9 (1) ◽  
Author(s):  
David A. Siegel ◽  
Ivona Cetinić ◽  
Jason R. Graff ◽  
Craig M. Lee ◽  
Norman Nelson ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Optical Properties ◽  
Food Web ◽  
Mixed Layer ◽  
Global Ocean ◽  
Nutrient Concentrations ◽  
Data Set ◽  
Northeast Pacific ◽  
Field Deployment ◽  
Ocean Station Papa

The goal of the EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) field campaign is to develop a predictive understanding of the export, fate, and carbon cycle impacts of global ocean net primary production. To accomplish this goal, observations of export flux pathways, plankton community composition, food web processes, and optical, physical, and biogeochemical (BGC) properties are needed over a range of ecosystem states. Here we introduce the first EXPORTS field deployment to Ocean Station Papa in the Northeast Pacific Ocean during summer of 2018, providing context for other papers in this special collection. The experiment was conducted with two ships: a Process Ship, focused on ecological rates, BGC fluxes, temporal changes in food web, and BGC and optical properties, that followed an instrumented Lagrangian float; and a Survey Ship that sampled BGC and optical properties in spatial patterns around the Process Ship. An array of autonomous underwater assets provided measurements over a range of spatial and temporal scales, and partnering programs and remote sensing observations provided additional observational context. The oceanographic setting was typical of late-summer conditions at Ocean Station Papa: a shallow mixed layer, strong vertical and weak horizontal gradients in hydrographic properties, sluggish sub-inertial currents, elevated macronutrient concentrations and low phytoplankton abundances. Although nutrient concentrations were consistent with previous observations, mixed layer chlorophyll was lower than typically observed, resulting in a deeper euphotic zone. Analyses of surface layer temperature and salinity found three distinct surface water types, allowing for diagnosis of whether observed changes were spatial or temporal. The 2018 EXPORTS field deployment is among the most comprehensive biological pump studies ever conducted. A second deployment to the North Atlantic Ocean occurred in spring 2021, which will be followed by focused work on data synthesis and modeling using the entire EXPORTS data set.

Study on the Process of Potassium Sulfate Production from Lop Nur Salt Lake Brine Resource

2012 ◽  
Vol 518-523 ◽  
pp. 1831-1836 ◽  
Author(s):  
Hao Li ◽  
Zhen Chen ◽  
Guang Yuan Lei
Keyword(s):  
Potassium Chloride ◽  
Salt Lake ◽  
Water Shortage ◽  
Potassium Sulfate ◽  
Raw Material ◽  
Water Volume ◽  
Sulfate Production ◽  
Low Magnesium ◽  
Lop Nur ◽  
Mixed Salts

Lop Nur salt Lake is the largest potassium brine deposits discovered in China. Its brine is a kind of magnesium sulfate sub-type brine and can be used to produce potassium sulfate fertilizer. In this paper, response to the feature of various potassium salts in brine evaporation and crystallization product and the great variety with evaporation temperature, the potassium sulfate production process was studied in detail. The mixed salts were pre-conversed and post-floated to form schoenite with the desirable potassium grade. In view of the natural conditions of severe water shortage in Lop Nur, carnallite from post-stage of brine evaporation was decomposed creatively by low-magnesium saturated brine to produce coarse potassium chloride. Eventually, conversion experiment was carried out to produce potassium sulfate by adding water into schoenite and coarse potassium chloride. Raw material ratio, water volume, conversion time, conversion temperature, stirring intensity and other conditions was tested and determined. Optimized product of superior quality for agricultural use, with 57.54% conversion rate and 43.27% potassium sulfate, was achieved.

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