Deducing the role of eolian dust sedimentation during soil forming periods on mineral magnetic records and its implications for paleoclimate reconstructions

2020 ◽  
Author(s):  
Diana Jordanova ◽  
Neli Jordanova
Keyword(s):  
Grain Size ◽  
Conceptual Model ◽  
Climate Models ◽  
Soil Depth ◽  
Soil Formation ◽  
Magnetic Characteristics ◽  
Magnetic Fraction ◽  
Maximum Enhancement ◽  
The Past ◽  
Terrestrial Environments

<p>Obtaining reliable global and regional records of the past climatic changes during the glacial Pleistocene is of prime importance for building up consistent climate models of the near and far future. Magnetic signature along sequences of alternating loess and (paleo)soil units from the terrestrial environments is considered as semi-continuous record of climate change in the geological past. However, soil formation in aeolian landscapes may occur under different and changing conditions of dust sedimentation. Viewing from this standpoint the depth variations of several rock magnetic characteristics along profiles of Holocene soils from low Danube area allowed us to establish a set of criteria for identification of the past regimes of aeolian sedimentation persisted during the soil forming periods. A conceptual model for the time evolution of the grain size of the pedogenic magnetic fraction  with soil depth is proposed,  which is build upon  the mechanism of soil formation – accretional or  stable land surfaces,  or a combination of the two. According to the proposed conceptual model, discrimination between accretional soils and soils developed without dust additions during soil forming period can be done. Accretional soils are characterized by parallel changes in grain size sensitive magnetic proxies. Soils, developed at stable landscape conditions show gradation of the depths at which maximum enhancement of various proxies occurs with deepest occurrence of the maximum in frequency dependent magnetic susceptibility, followed by depth of maximum anhysteretic susceptibility and the normalized anhysteretic to isothermal remanence acquired at 100mT field. It is shown that the mean coercivity of the pedogenic component of accretional soils is higher than that of soils developed without eolian input at equal temperature conditions because of the soils’ thermal gradient and different depths, at which pedogenic minerals form in the two settings.</p>

scholarly journals The distribution of soil phosphorus for global biogeochemical modeling

2013 ◽  
Vol 10 (4) ◽  
pp. 2525-2537 ◽  
Author(s):  
X. Yang ◽  
W. M. Post ◽  
P. E. Thornton ◽  
A. Jain
Keyword(s):  
Spatial Databases ◽  
Climate Models ◽  
Soil Depth ◽  
Soil Formation ◽  
Terrestrial Ecosystems ◽  
Parent Material ◽  
Large Uncertainty ◽  
Soil P ◽  
Mineral Particles ◽  
Microbial Utilization

Abstract. Phosphorus (P) is a major element required for biological activity in terrestrial ecosystems. Although the total P content in most soils can be large, only a small fraction is available or in an organic form for biological utilization because it is bound either in incompletely weathered mineral particles, adsorbed on mineral surfaces, or, over the time of soil formation, made unavailable by secondary mineral formation (occluded). In order to adequately represent phosphorus availability in global biogeochemistry–climate models, a representation of the amount and form of P in soils globally is required. We develop an approach that builds on existing knowledge of soil P processes and databases of parent material and soil P measurements to provide spatially explicit estimates of different forms of naturally occurring soil P on the global scale. We assembled data on the various forms of phosphorus in soils globally, chronosequence information, and several global spatial databases to develop a map of total soil P and the distribution among mineral bound, labile, organic, occluded, and secondary P forms in soils globally. The amount of P, to 50cm soil depth, in soil labile, organic, occluded, and secondary pools is 3.6 ± 3, 8.6 ± 6, 12.2 ± 8, and 3.2 ± 2 Pg P (Petagrams of P, 1 Pg = 1 × 1015g) respectively. The amount in soil mineral particles to the same depth is estimated at 13.0 ± 8 Pg P for a global soil total of 40.6 ± 18 Pg P. The large uncertainty in our estimates reflects our limited understanding of the processes controlling soil P transformations during pedogenesis and a deficiency in the number of soil P measurements. In spite of the large uncertainty, the estimated global spatial variation and distribution of different soil P forms presented in this study will be useful for global biogeochemistry models that include P as a limiting element in biological production by providing initial estimates of the available soil P for plant uptake and microbial utilization.

Precipitation and aridity constraints from paleolakes on early Mars

Geology ◽  
2020 ◽  
Vol 48 (12) ◽  
pp. 1189-1193
Author(s):  
Gaia Stucky de Quay ◽  
Timothy A. Goudge ◽  
Caleb I. Fassett
Keyword(s):  
Climate Models ◽  
Remote Sensing Data ◽  
Coupled Systems ◽  
Closed Basin ◽  
The Past ◽  
Precipitation Estimates ◽  
Terrestrial Environments ◽  
Early Mars ◽  
Model Scenarios

Abstract The ancient climate of Mars remains an enigma despite the abundance of in situ and remote-sensing data revealing hydrological activity in the past. The crux of this debate—informed by geomorphic studies, chemical alteration observations, and numerical climate models—is the amount, distribution, and nature of surface water and precipitation (i.e., rain vs. snow). Here, we combined measurements of 96 open- and closed-basin lakes with simple hydrological balances to constrain catchment-averaged precipitation, PT, integrated over a given runoff episode of indeterminate length during early Mars history. We included 13 systems containing both open- and closed-basin lakes, providing fully bounded precipitation estimates (coupled systems). We show that, on average, PT was ≳4 m and ≲159 m; however, local precipitation was spatially variable and consistent with a complex, planetwide climate. Aridity indexes of open-basin lakes indicate some regions may have been at least as humid as semiarid terrestrial environments. Our results offer widely distributed, quantitative hydro-climate constraints that can be used to test paleoclimate model scenarios, working toward bridging the gap between geological observations and climate theory for early Mars.

scholarly journals The distribution of soil phosphorus for global biogeochemical modeling

2012 ◽  
Vol 9 (11) ◽  
pp. 16347-16380 ◽  
Author(s):  
X. Yang ◽  
W. M. Post ◽  
P. E. Thornton ◽  
A. Jain
Keyword(s):  
Spatial Databases ◽  
Climate Models ◽  
Soil Depth ◽  
Soil Formation ◽  
Terrestrial Ecosystems ◽  
Parent Material ◽  
Large Uncertainty ◽  
Soil P ◽  
Mineral Particles ◽  
Microbial Utilization

Abstract. Phosphorus (P) is a major element required for biological activity in terrestrial ecosystems. Although the total P content in most soils can be large, only a small fraction is available or in an organic form for biological utilization because it is bound either in incompletely weathered mineral particles, adsorbed on mineral surfaces, or, over the time of soil formation, made unavailable by secondary mineral formation (occluded). In order to adequately represent phosphorus availability in global biogeochemistry-climate models, a representation of the amount and form of P in soils globally is required. We develop an approach that builds on existing knowledge of soil P processes and databases of parent material and soil P measurements to provide spatially explicit estimates of different forms of soil P on the global scale. We assembled data on the various forms of phosphorus in soils globally, chronosequence information, and several global spatial databases to develop a map of total soil P and the distribution among mineral bound, labile, organic, occluded, and secondary P forms in soils globally. The amount of P, to 50 cm soil depth, in soil labile, organic, occluded, and secondary pools is 3.5 ± 3, 8.7 ± 6, 13.2 ± 9, and 3.3 ± 2 Pg P respectively. The amount in soil mineral particles to the same depth is estimated at 12.5 ± 9 Pg P for a global soil total of 41.2 ± 20 Pg P. The large uncertainty in our estimates reflects our limited understanding of the processes controlling soil P transformations during pedogenesis and lack of measurements of soil P. In spite of the large uncertainty, the estimated global spatial variation and distribution of different soil P forms presented in this study will be useful for global biogeochemistry models that include P as a limiting element in biological production by providing initial estimates of the available soil P for plant uptake and microbial utilization.

scholarly journals Global climatology and trends in convective environments from ERA5 and rawinsonde data

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Mateusz Taszarek ◽  
John T. Allen ◽  
Mattia Marchio ◽  
Harold E. Brooks
Keyword(s):  
Large Scale ◽  
Climate Models ◽  
Global Climate ◽  
Convective Available Potential Energy ◽  
Global Climate Models ◽  
Convective Precipitation ◽  
The Past ◽  
The Tropics ◽  
Rawinsonde Data

AbstractGlobally, thunderstorms are responsible for a significant fraction of rainfall, and in the mid-latitudes often produce extreme weather, including large hail, tornadoes and damaging winds. Despite this importance, how the global frequency of thunderstorms and their accompanying hazards has changed over the past 4 decades remains unclear. Large-scale diagnostics applied to global climate models have suggested that the frequency of thunderstorms and their intensity is likely to increase in the future. Here, we show that according to ERA5 convective available potential energy (CAPE) and convective precipitation (CP) have decreased over the tropics and subtropics with simultaneous increases in 0–6 km wind shear (BS06). Conversely, rawinsonde observations paint a different picture across the mid-latitudes with increasing CAPE and significant decreases to BS06. Differing trends and disagreement between ERA5 and rawinsondes observed over some regions suggest that results should be interpreted with caution, especially for CAPE and CP across tropics where uncertainty is the highest and reliable long-term rawinsonde observations are missing.

East Asian winter monsoon variation during the last 3000 years as recorded in a subtropical mountain lake, northeastern Taiwan

The Holocene ◽  
2021 ◽  
pp. 095968362110190
Author(s):  
Tsai-Wen Lin ◽  
Stefanie Kaboth-Bahr ◽  
Kweku Afrifa Yamoah ◽  
André Bahr ◽  
George Burr ◽  
...  
Keyword(s):  
Grain Size ◽  
East Asian Winter Monsoon ◽  
East Asian ◽  
Winter Monsoon ◽  
Mountain Lake ◽  
Sediment Grain Size ◽  
Global Monsoon ◽  
Asian Winter Monsoon ◽  
The Past ◽  
Monsoon System

The East Asian Winter Monsoon (EAWM) is a fundamental part of the global monsoon system that affects nearly one-quarter of the world’s population. Robust paleoclimate reconstructions in East Asia are complicated by multiple sources of precipitation. These sources, such as the EAWM and typhoons, need to be disentangled in order to understand the dominant source of precipitation influencing the past and current climate. Taiwan, situated within the subtropical East Asian monsoon system, provides a unique opportunity to study monsoon and typhoon variability through time. Here we combine sediment trap data with down-core records from Cueifong Lake in northeastern Taiwan to reconstruct monsoonal rainfall fluctuations over the past 3000 years. The monthly collected grain-size data indicate that a decrease in sediment grain size reflects the strength of the EAWM. End member modelling analysis (EMMA) on sediment core and trap data reveals two dominant grain-size end-members (EMs), with the coarse EM 2 representing a robust indicator of EAWM strength. The downcore variations of EM 2 show a gradual decrease over the past 3000 years indicating a gradual strengthening of the EAWM, in agreement with other published EAWM records. This enhanced late-Holocene EAWM can be linked to the expansion of sea-ice cover in the western Arctic Ocean caused by decreased summer insolation.

scholarly journals Exploring the historical distribution of Dracaena cinnabari using ethnobotanical knowledge on Socotra Island, Yemen

2021 ◽  
Vol 17 (1) ◽  
Author(s):  
Abdulraqeb Al-Okaishi
Keyword(s):  
Climate Models ◽  
World Heritage Site ◽  
Place Names ◽  
Dragon’S Blood ◽  
The Past ◽  
Unesco World Heritage Site ◽  
Socotra Island ◽  
Large Populations ◽  
Socotra Archipelago ◽  
Dracaena Cinnabari

Abstract Background In this study, we present and analyze toponyms referring to Socotra Island’s endemic dragon’s blood tree (Dracaena cinnabari) in four areas on the Socotra Archipelago UNESCO World Heritage site (Republic of Yemen). The motivation is the understanding of the past distribution of D. cinnabari trees which is an important part of conservation efforts by using ethnobotanical data. We assumed that dragon’s blood trees had a wider distribution on Socotra Island in the past. Methods This research was based on field surveys and interviews with the indigenous people. The place names (toponyms) were recorded in both Arabic and the indigenous Socotri language. We grouped all toponyms into five different categories according to the main descriptor: terrain, human, plant, water, and NA (unknown). Also, this study identified current and historical Arabic names of dragon’s blood trees of the genus Dracaena through literature review. Results A total of 301 toponyms were recorded from the four study areas in Socotra Island. Among names related to plants, we could attribute toponyms to nine different plants species, of which six toponyms referred to the D. cinnabari tree, representing 14.63% of the total phytotoponyms in the category. Three historical naming periods prior to 2000 could be identified. The most commonly used name for dragon’s blood trees (D. cinnabari, D. serrulata, D. ombet) appears to be “ahrieb” “إعريهب” and its resin “dum al-akhawin” “دم الأخوين,” while derived (mixed-cooked) products are called “eda’a” “إيدع,” while regionally different names can be found. Conclusion The place names that refer to D. cinnabari are herein suggested to represent remnant areas of once large populations. Therefore, the toponyms may support known hypotheses based on climate models that D. cinnabari had a wider distribution on Socotra Island in the past. This study also confirmed the historical importance of dragon’s blood.

scholarly journals Ensemble models on palaeoclimate to predict India's groundwater challenge

2013 ◽  
Vol 2 (3) ◽  
Author(s):  
Partha Sarathi Datta
Keyword(s):  
Climate Change ◽  
Climate Models ◽  
Global Climate ◽  
Global Climate Models ◽  
Humid Climate ◽  
Ensemble Models ◽  
North West ◽  
The Past ◽  
The North ◽  
14C Age

In many parts of the world, freshwater crisis is largely due to increasing water consumption and pollution by rapidly growing population and aspirations for economic development, but, ascribed usually to the climate. However, limited understanding and knowledge gaps in the factors controlling climate and uncertainties in the climate models are unable to assess the probable impacts on water availability in tropical regions. In this context, review of ensemble models on δ18O and δD in rainfall and groundwater, 3H- and 14C- ages of groundwater and 14C- age of lakes sediments helped to reconstruct palaeoclimate and long-term recharge in the North-west India; and predict future groundwater challenge. The annual mean temperature trend indicates both warming/cooling in different parts of India in the past and during 1901–2010. Neither the GCMs (Global Climate Models) nor the observational record indicates any significant change/increase in temperature and rainfall over the last century, and climate change during the last 1200 yrs BP. In much of the North-West region, deep groundwater renewal occurred from past humid climate, and shallow groundwater renewal from limited modern recharge over the past decades. To make water management to be more responsive to climate change, the gaps in the science of climate change need to be bridged.

First Report of the Welding Research Committee. A Preliminary Research into the Effect of Heat Treatment of Welds

1933 ◽  
Vol 124 (1) ◽  
pp. 569-599
Author(s):  
L. W. Schuster
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
High Temperature ◽  
Future Research ◽  
Considerable Variability ◽  
Research Committee ◽  
High Class ◽  
The Past ◽  
Cutting Out ◽  
Preliminary Research

With such considerations as the releasing of internal stress, the effect on corrodibility, and the practicability of carrying out high-temperature treatments, the present research does not deal. The experiments concern solely the changes in toughness brought about by heat treatment, and they represent a trial set of tests in which a particular high-class electrode was used, the results being intended as a guide for future research. In the past there has been considerable variability in the results obtained from a normalizing treatment by different experimenters, and as this was considered to be partly due to a difference in manner of cutting out the samples and a difference in the method of carrying out the treatment, the present treatments were all kept under careful control. The upper and lower “runs” were tested separately so that the effect of heat treatment on the coarse metal of the upper run and the fine metal of the lower runs might be subdivided. Throughout, microscopic examinations were made so that the change in structure might be correlated as far as possible with the change in the shock value. The particular weld metal tested gave very consistent results and the change in Izod value was found largely to follow the change in grain size.

scholarly journals Green Synthesis of Magnetic Iron Oxide Nanoparticle for Antibacterial Activity: A Review

2021 ◽  
Vol 64 (2) ◽  
pp. 202-210
Author(s):  
Muhammad Isa Khan ◽  
Aliza Zahoor ◽  
Tahir Iqbal ◽  
Abdul Majid ◽  
Mohsin Ijaz
Keyword(s):  
Iron Oxide ◽  
Green Synthesis ◽  
Biomedical Applications ◽  
Synthesis Method ◽  
Antibacterial Activities ◽  
Magnetic Characteristics ◽  
Iron Oxide Nanoparticle ◽  
The Past ◽  
Wide Range ◽  
Oxide Nanoparticle

  Recently, different researchers find nanoparticles as an auspicious alternative to antibacterial agents due to their antibacterial behaviour. This antibacterial behaviour contributes in many biomedical applications including; tissue engineering, drug and gene delivery and, imaging. Furthermore, iron oxide nanoparticle gains much importance due to their magnetic characteristics and wide range of application. Iron oxide nanoparticle (IONPs) have exhibits great potential against bacteria. During the past decade, various routes were developed to synthesize iron oxide nanoparticle with suitable size and composition. This article reviews the recent iron oxide nanoparticle obtained by green synthesis with a focus on their response to antibacterial activities. The iron nanoparticles synthesized by green synthesis method has accumulated a vital attention over the last couple of years due to their unique characteristic as it makes sure environmental friendly, nontoxic and safe reagents.

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