Evaporite dynamics and their effects on global climate and oxygen

2021 ◽  
Author(s):  
Graham Shields ◽  
Benjamin Mills
Keyword(s):  
Time Scales ◽  
Calcium Ions ◽  
Calcium Sulfate ◽  
Global Climate ◽  
Sulfur Cycle ◽  
Silicate Weathering ◽  
Carbonate Precipitation ◽  
Sulfate Deposition ◽  
Biogeochemical Models

<p>Evaporite weathering and deposition are seldom in balance even on million-year time-scales with grand depositional events superimposed against a background of more slowly varying weathering. Despite such imbalance, biogeochemical models generally assume that evaporite weathering and deposition rates are equal on all time scales. Changes in evaporite dynamics through time will likely impact oxidant budgets through the sulfur cycle and we have shown this to have been especially significant during Proterozoic times. Recently, we proposed that imbalances between evaporite weathering and deposition can also affect climate through the process of carbonate sedimentation. Calcium sulfate weathering supplies calcium ions to the ocean unaccompanied by carbonate alkalinity, so that increased carbonate precipitation strengthens greenhouse forcing through transfer of carbon dioxide to the atmosphere. Conversely, calcium sulfate deposition weakens greenhouse forcing, while the high depositional rates of evaporite giants may overwhelm the silicate weathering feedback, causing several degrees of planetary cooling. Non-steady-state evaporite dynamics and related feedbacks have hitherto been overlooked as drivers of long-term carbon cycle change. In this talk, we illustrate the importance of evaporite deposition, in particular, by showing how a series of massive depositional events contributed to global cooling during the mid–late Miocene. Further studies are required to quantify gypsum deposition over time and its possible effects on deoxygenation of the surface environment, especially at times of mass extinction, as well as on climate.</p>

scholarly journals Evaporite weathering and deposition as a long-term climate forcing mechanism

Geology ◽  
2020 ◽  
Author(s):  
Graham A. Shields ◽  
Benjamin J.W. Mills
Keyword(s):  
Calcium Sulfate ◽  
Climate Forcing ◽  
Silicate Weathering ◽  
Carbonate Precipitation ◽  
Sulfate Deposition ◽  
Mutual Dependence ◽  
Carbonate Sedimentation ◽  
Global Cooling ◽  
First Time

Although it is widely accepted that Earth’s long-term surface temperature is regulated by the mutual dependence of silicate weathering and climate on CO2, the root causes of some climatic events remain unresolved. We show here for the first time that imbalances between evaporite weathering and deposition can affect climate through the process of carbonate sedimentation. Calcium sulfate weathering supplies Ca2+ ions to the ocean unaccompanied by carbonate alkalinity, so that increased carbonate precipitation strengthens greenhouse forcing through transfer of CO2 to the atmosphere. Conversely, calcium sulfate deposition weakens greenhouse forcing, while the high depositional rates of evaporite giants may overwhelm the silicate weathering feedback, causing several degrees of planetary cooling. Non-steady-state evaporite dynamics and related feedbacks have hitherto been overlooked as drivers of long-term carbon cycle change. Here, we illustrate the importance of evaporite deposition, in particular, by showing how a series of massive depositional events contributed to global cooling during the mid–late Miocene.

Atmospheric O2 over Phanerozoic Time

2004 ◽  
Author(s):  
Robert A. Berner
Keyword(s):  
Forest Fires ◽  
Calcium Sulfate ◽  
Atmospheric Oxygen ◽  
Experimental Studies ◽  
Indirect Evidence ◽  
Sulfur Cycle ◽  
Minor Role ◽  
Appreciable Effect ◽  
A Minor

The chemical reactions that affect atmospheric O2 on a multimillion-year time scale involve the most abundant elements in the earth’s crust that undergo oxidation and reduction. This includes carbon, sulfur, and iron. (Other redox elements, such as manganese, are not abundant enough to have an appreciable effect on O2.) Iron is the most abundant of the three, but it plays only a minor role in O2 control (Holland, 1978). This is because during oxidation the change between Fe+2 and Fe+3 involves the uptake of only one-quarter of an O2 molecule, whereas the oxidation of sulfide to sulfate involves two O2 molecules, and the oxidation of reduced carbon, including organic matter and methane, involves between one and two O2 molecules. The same stoichiometry applies to reduction of the three elements. Because iron is not sufficiently abundant enough to counterbalance its low relative O2 consumption/release, the iron cycle is omitted in most discussions of controls on atmospheric oxygen. In contrast, the sulfur cycle, although subsidiary to the carbon cycle as to its effect on atmospheric O2, is nevertheless non-negligible and must be included in any discussion of the evolution of atmospheric O2. In this chapter the methods and results of modeling the long-term carbon and sulfur cycles are presented in terms of calculations of past levels of atmospheric oxygen. The modeling results are then compared with independent, indirect evidence of changes in O2 based on paleobiological observations and experimental studies that simulate the response of forest fires to changes in the levels of O2. Because the sulfur cycle is not discussed anywhere else in this book, it is briefly presented first. The long-term sulfur cycle is depicted as a panorama in figure 6.1. Sulfate is added to the oceans, via rivers, originating from the oxidative weathering of pyrite (FeS2) and the dissolution of calcium sulfate minerals (gypsum and anhydrite) on the continents. Volcanic, metamorphic/hydrothermal, and diagenetic reactions add reduced sulfur to the oceans and atmosphere where it is oxidized to sulfate. Sulfur is removed from the oceans mainly via formation of sedimentary pyrite and calcium sulfate.

On Climate Change Risks of Long-Term Socio-Economic Development in Russia

2019 ◽  
pp. 79-95
Author(s):  
N.E. Terentiev
Keyword(s):  
Climate Change ◽  
Economic Development ◽  
Technological Innovation ◽  
Global Climate Change ◽  
Global Climate ◽  
Climate Risk ◽  
Climate Change Risks ◽  
Socio Economic Development ◽  
Management Policies

Based on the latest data, paper investigates the dynamics of global climate change and its impact on economic growth in the long-term. The notion of climate risk is considered. The main directions of climate risk management policies are analyzed aimed, first, at reducing anthropogenic greenhouse gas emissions through technological innovation and structural economic shifts; secondly, at adaptation of population, territories and economic complexes to the irreparable effects of climate change. The problem of taking into account the phenomenon of climate change in the state economic policy is put in the context of the most urgent tasks of intensification of long-term socio-economic development and parrying strategic challenges to the development of Russia.

The Spread of Pollutants from Harbour Sludge Depots

1984 ◽  
Vol 16 (3-4) ◽  
pp. 623-633
Author(s):  
M Loxham ◽  
F Weststrate
Keyword(s):  
Time Scales ◽  
Molecular Diffusion ◽  
Near Field ◽  
Parameter Analysis ◽  
Migration Patterns ◽  
Long Time ◽  
Dilution Effects ◽  
Short Time ◽  
Harbour Sludge

It is generally agreed that both the landfill option, or the civil techniques option for the final disposal of contaminated harbour sludge involves the isolation of the sludge from the environment. For short time scales, engineered barriers such as a bentonite screen, plastic sheets, pumping strategies etc. can be used. However for long time scales the effectiveness of such measures cannot be counted upon. It is thus necessary to be able to predict the long term environmenttal spread of contaminants from a mature landfill. A model is presented that considers diffusion and adsorption in the landfill site and convection and adsorption in the underlaying aquifer. From a parameter analysis starting form practical values it is shown that the adsorption behaviour and the molecular diffusion coefficient of the sludge, are the key parameters involved in the near field. The dilution effects of the far field migration patterns are also illustrated.

scholarly journals 1005 Antibiotic-Impregnated Calcium Sulfate Beads Are Not Effective in the Primary Prevention of Infection in Open Femur and Tibia Fractures

2021 ◽  
Vol 108 (Supplement_2) ◽  
Author(s):  
A Fung ◽  
A Ward ◽  
K Patel ◽  
M Krkovic
Keyword(s):  
Primary Prevention ◽  
Infection Rate ◽  
Calcium Sulfate ◽  
Acute Infection ◽  
Open Fractures ◽  
Prevention Of Infection ◽  
Significant Difference ◽  
Tibia Fractures ◽  
Systemic Antibiotics

Abstract Introduction Infection is a major complication of open fractures. Antibiotic-impregnated calcium sulfate (AICS) beads are widely used as an adjuvant to systemic antibiotics. Whilst their efficacy in the secondary prevention of infection is established, we present the first retrospective study evaluating AICS beads in the primary prevention of infection in open fractures. Method 214 open femur and tibia fractures in 207 patients were reviewed over a seven-year period. 148 fractures received only systemic antibiotic prophylaxis. 66 fractures also received AICS beads. The occurrence of acute infection (wound infection and acute osteomyelitis) was recorded, as well as that of long-term complications (chronic osteomyelitis, non-union and death). Results Fractures that received AICS with systemic antibiotics had an overall acute infection rate of 42% (28/66), compared to 43% (63/148) in fractures that received only systemic antibiotics (p > 0.05). There was no significant difference in infection rate even when fractures were stratified by Gustilo-Anderson grade. There was also no significant difference in the rate of long-term complications. Conclusions Our results indicate that the adjuvant use of AICS beads is not effective for the primary prevention of acute infection or long-term complications in open leg fractures. Further research is needed to elucidate the factors influencing the outcomes of AICS use.

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.

scholarly journals Co-variation of silicate, carbonate and sulfide weathering drives CO2 release with erosion

2021 ◽  
Vol 14 (4) ◽  
pp. 211-216
Author(s):  
Aaron Bufe ◽  
Niels Hovius ◽  
Robert Emberson ◽  
Jeremy K. C. Rugenstein ◽  
Albert Galy ◽  
...  
Keyword(s):  
Erosion Rate ◽  
Global Climate ◽  
Stream Water ◽  
Sulfide Oxidation ◽  
Silicate Weathering ◽  
Emission Rates ◽  
Mountain Ranges ◽  
Weathering Rates ◽  
Southern Taiwan ◽  
Co2 Release

AbstractGlobal climate is thought to be modulated by the supply of minerals to Earth’s surface. Whereas silicate weathering removes carbon dioxide (CO2) from the atmosphere, weathering of accessory carbonate and sulfide minerals is a geologically relevant source of CO2. Although these weathering pathways commonly operate side by side, we lack quantitative constraints on their co-variation across erosion rate gradients. Here we use stream-water chemistry across an erosion rate gradient of three orders of magnitude in shales and sandstones of southern Taiwan, and find that sulfide and carbonate weathering rates rise with increasing erosion, while silicate weathering rates remain steady. As a result, on timescales shorter than marine sulfide compensation (approximately 106–107 years), weathering in rapidly eroding terrain leads to net CO2 emission rates that are at least twice as fast as CO2 sequestration rates in slow-eroding terrain. We propose that these weathering reactions are linked and that sulfuric acid generated from sulfide oxidation boosts carbonate solubility, whereas silicate weathering kinetics remain unaffected, possibly due to efficient buffering of the pH. We expect that these patterns are broadly applicable to many Cenozoic mountain ranges that expose marine metasediments.

scholarly journals Meridional changes in the South Atlantic Subtropical Gyre during Heinrich Stadials

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Tainã M. L. Pinho ◽  
Cristiano M. Chiessi ◽  
Rodrigo C. Portilho-Ramos ◽  
Marília C. Campos ◽  
Stefano Crivellari ◽  
...  
Keyword(s):  
Global Climate ◽  
South Atlantic ◽  
Subtropical Gyre ◽  
Climate System ◽  
The South ◽  
Foraminiferal Species ◽  
Ocean Gyres ◽  
Long Term Monitoring ◽  
Term Monitoring

AbstractSubtropical ocean gyres play a key role in modulating the global climate system redistributing energy between low and high latitudes. A poleward displacement of the subtropical gyres has been observed over the last decades, but the lack of long-term monitoring data hinders an in-depth understanding of their dynamics. Paleoceanographic records offer the opportunity to identify meridional changes in the subtropical gyres and investigate their consequences to the climate system. Here we use the abundance of planktonic foraminiferal species Globorotalia truncatulinodes from a sediment core collected at the northernmost boundary of the South Atlantic Subtropical Gyre (SASG) together with a previously published record of the same species from the southernmost boundary of the SASG to reconstruct meridional fluctuations of the SASG over last ca. 70 kyr. Our findings indicate southward displacements of the SASG during Heinrich Stadials (HS) 6-4 and HS1, and a contraction of the SASG during HS3 and HS2. During HS6-4 and HS1, the SASG southward displacements likely boosted the transfer of heat to the Southern Ocean, ultimately strengthening deep-water upwelling and CO2 release to the atmosphere. We hypothesize that the ongoing SASG poleward displacement may further increase oceanic CO2 release.

scholarly journals Transient rhyolite melt extraction to produce a shallow granitic pluton

2021 ◽  
Vol 7 (21) ◽  
pp. eabf0604
Author(s):  
Allen J. Schaen ◽  
Blair Schoene ◽  
Josef Dufek ◽  
Brad S. Singer ◽  
Michael P. Eddy ◽  
...  
Keyword(s):  
Time Scales ◽  
Explosive Eruptions ◽  
Upper Crust ◽  
Saturation Model ◽  
Granitic Pluton ◽  
Melt Extraction ◽  
High Silica ◽  
Melt Segregation ◽  
Zircon Saturation

Rhyolitic melt that fuels explosive eruptions often originates in the upper crust via extraction from crystal-rich sources, implying an evolutionary link between volcanism and residual plutonism. However, the time scales over which these systems evolve are mainly understood through erupted deposits, limiting confirmation of this connection. Exhumed plutons that preserve a record of high-silica melt segregation provide a critical subvolcanic perspective on rhyolite generation, permitting comparison between time scales of long-term assembly and transient melt extraction events. Here, U-Pb zircon petrochronology and 40Ar/39Ar thermochronology constrain silicic melt segregation and residual cumulate formation in a ~7 to 6 Ma, shallow (3 to 7 km depth) Andean pluton. Thermo-petrological simulations linked to a zircon saturation model map spatiotemporal melt flux distributions. Our findings suggest that ~50 km3 of rhyolitic melt was extracted in ~130 ka, transient pluton assembly that indicates the thermal viability of advanced magma differentiation in the upper crust.

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