scholarly journals Orbital pacing of carbon fluxes by a ∼9-My eccentricity cycle during the Mesozoic

2015 ◽  
Vol 112 (41) ◽  
pp. 12604-12609 ◽  
Author(s):  
Mathieu Martinez ◽  
Guillaume Dera
Keyword(s):  
Carbon Cycle ◽  
Orbital Forcing ◽  
Time Intervals ◽  
Sea Level Fluctuations ◽  
The Past ◽  
Paleoenvironmental Changes ◽  
Chaotic Diffusion ◽  
Orbital Cycles ◽  
Short Time

Eccentricity, obliquity, and precession are cyclic parameters of the Earth’s orbit whose climatic implications have been widely demonstrated on recent and short time intervals. Amplitude modulations of these parameters on million-year time scales induce ‟grand orbital cycles,” but the behavior and the paleoenvironmental consequences of these cycles remain debated for the Mesozoic owing to the chaotic diffusion of the solar system in the past. Here, we test for these cycles from the Jurassic to the Early Cretaceous by analyzing new stable isotope datasets reflecting fluctuations in the carbon cycle and seawater temperatures. Our results document a prominent cyclicity of ∼9 My in the carbon cycle paced by changes in the seasonal dynamics of hydrological processes and long-term sea level fluctuations. These paleoenvironmental changes are linked to a great eccentricity cycle consistent with astronomical solutions. The orbital forcing signal was mainly amplified by cumulative sequestration of organic matter in the boreal wetlands under greenhouse conditions. Finally, we show that the ∼9-My cycle faded during the Pliensbachian, which could either reflect major paleoenvironmental disturbances or a chaotic transition affecting this cycle.

scholarly journals Mid-Pleistocene transition in glacial cycles explained by declining CO2and regolith removal

2019 ◽  
Vol 5 (4) ◽  
pp. eaav7337 ◽  
Author(s):  
M. Willeit ◽  
A. Ganopolski ◽  
R. Calov ◽  
V. Brovkin
Keyword(s):  
Climate Variability ◽  
Carbon Cycle ◽  
Northern Hemisphere ◽  
Seasonal Variations ◽  
Ice Sheets ◽  
Glacial Cycles ◽  
Solar Insolation ◽  
The Past ◽  
Transient Simulations

Variations in Earth’s orbit pace the glacial-interglacial cycles of the Quaternary, but the mechanisms that transform regional and seasonal variations in solar insolation into glacial-interglacial cycles are still elusive. Here, we present transient simulations of coevolution of climate, ice sheets, and carbon cycle over the past 3 million years. We show that a gradual lowering of atmospheric CO2and regolith removal are essential to reproduce the evolution of climate variability over the Quaternary. The long-term CO2decrease leads to the initiation of Northern Hemisphere glaciation and an increase in the amplitude of glacial-interglacial variations, while the combined effect of CO2decline and regolith removal controls the timing of the transition from a 41,000- to 100,000-year world. Our results suggest that the current CO2concentration is unprecedented over the past 3 million years and that global temperature never exceeded the preindustrial value by more than 2°C during the Quaternary.

scholarly journals Airborne surface profiling of glaciers: a case-study in Alaska

1996 ◽  
Vol 42 (142) ◽  
pp. 538-547 ◽  
Author(s):  
Κ. A. Echelmeyer ◽  
W. D. Harrison ◽  
C. F. Larsen ◽  
J. Sapiano ◽  
Mitchell J. E. ◽  
...  
Keyword(s):  
Time Intervals ◽  
Glacier Surface ◽  
Alaska Range ◽  
Thickness Change ◽  
Surface Profiling ◽  
Bear Lake ◽  
South Central ◽  
Short Time

AbstractA relatively lightweight and simple airborne system for surface elevation profiling of glaciers in narrow mountain valleys has been developed and tested. The aircraft position is determined by kinematic global positioning system (GPS) methods. The distance to the glacier surface is determined with a laser ranger. The accuracy is about 0.3 m, sufficient to permit future changes to be observed over short time intervals. Long-term changes can be estimated by comparison of profiles with existing maps. Elevation profiles obtained in 1993–94 from three glaciers in central and south-central Alaska are compared with maps made about 1950. The resulting area-averaged, seasonally corrected thickness changes during the interval are: Gulkana Glacier (central Alaska Range)–11 m, Worthington Glacier (central Chugach Mountains) +7 m, and Bear Lake Glacier (Kenai Mountains) −12 m. All three glaciers retreated during the interval of comparison. The estimated uncertainty in the average thickness change is ±5 m. which is mainly due to errors in the existing maps. Constraints on the accuracy of the maps are obtained by profiling in proglacial areas.

scholarly journals LONG-TERM MONITORING OF THE EUROPEAN ROLLER (CORACIAS GARRULUS) IN UKRAINE: IS CLIMATE BEHIND THE CHANGES?

2021 ◽  
Author(s):  
Tatiana Shupova ◽  
Volodymyr Tytar
Keyword(s):  
Spatially Explicit ◽  
Climate Data ◽  
Time Intervals ◽  
Coracias Garrulus ◽  
The Past ◽  
Historical Times ◽  
Long Term Monitoring ◽  
European Roller ◽  
Term Monitoring

Since the 1980s there has been a long-term decline in numbers and contraction of range in Europe, including Ukraine. Our specific goals were to reconstruct the climatically suitable range of the species in Ukraine before the 1980s, gain better knowledge on its requirements, compare the past and current suitable areas, infer the regional and environmental variables that best explain its occurrence, and quantify the overall range change in the country. For these purposes we created a database consisting of 347 records of the roller made ever in Ukraine. We employed a species distribution modeling (SDM) approach to hindcast changes in the suitable range of the roller during historical times across Ukraine and to derive spatially explicit predictions of climatic suitability for the species under current climate. SDMs were created for three time intervals (before 1980, 1985-2009, 2010-2021) using corresponding climate data extracted from the TerraClim database. SDMs show a decline of suitable for rollers areas in the country from 85 to 46%. Several factors, including land cover and use, human population density and climate, that could have contributed to the decline of the species in Ukraine were considered. We suggest climate change and its speed (velocity) have been responsible for shaping the contemporary home range of the European roller.

scholarly journals Simulation of climate, ice sheets and CO<sub>2</sub> evolution during the last four glacial cycles with an Earth system model of intermediate complexity

2017 ◽  
Vol 13 (12) ◽  
pp. 1695-1716 ◽  
Author(s):  
Andrey Ganopolski ◽  
Victor Brovkin
Keyword(s):  
Carbon Cycle ◽  
Ice Sheets ◽  
Co2 Concentration ◽  
System Model ◽  
Model Parameters ◽  
Orbital Forcing ◽  
Earth System ◽  
Glacial Cycles ◽  
The Past ◽  
Paleoclimate Reconstructions

Abstract. In spite of significant progress in paleoclimate reconstructions and modelling of different aspects of the past glacial cycles, the mechanisms which transform regional and seasonal variations in solar insolation into long-term and global-scale glacial–interglacial cycles are still not fully understood – in particular, in relation to CO2 variability. Here using the Earth system model of intermediate complexity CLIMBER-2 we performed simulations of the co-evolution of climate, ice sheets, and carbon cycle over the last 400 000 years using the orbital forcing as the only external forcing. The model simulates temporal dynamics of CO2, global ice volume, and other climate system characteristics in good agreement with paleoclimate reconstructions. These results provide strong support for the idea that long and strongly asymmetric glacial cycles of the late Quaternary represent a direct but strongly nonlinear response of the Northern Hemisphere ice sheets to orbital forcing. This response is strongly amplified and globalised by the carbon cycle feedbacks. Using simulations performed with the model in different configurations, we also analyse the role of individual processes and sensitivity to the choice of model parameters. While many features of simulated glacial cycles are rather robust, some details of CO2 evolution, especially during glacial terminations, are sensitive to the choice of model parameters. Specifically, we found two major regimes of CO2 changes during terminations: in the first one, when the recovery of the Atlantic meridional overturning circulation (AMOC) occurs only at the end of the termination, a pronounced overshoot in CO2 concentration occurs at the beginning of the interglacial and CO2 remains almost constant during the interglacial or even declines towards the end, resembling Eemian CO2 dynamics. However, if the recovery of the AMOC occurs in the middle of the glacial termination, CO2 concentration continues to rise during the interglacial, similar to the Holocene. We also discuss the potential contribution of the brine rejection mechanism for the CO2 and carbon isotopes in the atmosphere and the ocean during the past glacial termination.

scholarly journals 14C Variations Caused by Changes in the Global Carbon Cycle

Radiocarbon ◽  
1980 ◽  
Vol 22 (2) ◽  
pp. 177-191 ◽  
Author(s):  
Ulrich Siegenthaler ◽  
Martin Heimann ◽  
Hans Oeschger
Keyword(s):  
Carbon Cycle ◽  
Production Rate ◽  
Transition Period ◽  
Forest Biomass ◽  
Step Change ◽  
Oceanic Circulation ◽  
Short Time ◽  
Global Carbon ◽  
Carbon System

A box-diffusion model for the carbon cycle is used to estimate the magnitude of 14C variations caused by changes of reservoir sizes and exchange fluxes in the global carbon system. The influence of changes in atmospheric CO2 concentration, biomass, CO2 exchange rate between atmosphere and ocean, and ocean mixing is considered. Steady-state 14C concentrations as well as the transients are calculated. For changing biomass, atmospheric CO2 levels and 13C/12C ratios are also calculated.Carbon-cycle-induced 14C variations may have been significant in the transition period from Glacial to Postglacial when drastic changes in environmental conditions took place within short time periods, while they were probably less important during the climatically more stable Postglacial.Changes of the oceanic circulation, as supposedly occurred, are considered the most important factor, besides variations of the production rate, affecting the global distribution of 14C. 14C variations due to changes of the atmospheric CO2 level or the air-sea-exchange probably did not exceed one to a few percent. Fluctuations of the forest biomass, which may have occurred between Glacial and Postglacial, hardly affected the 14C concentration over a long term.Responses of the atmospheric 14C concentration are also calculated for variations of the 14C production rate by cosmic radiation. The following cases are considered: a step change, square-wave changes producing “wiggles”, and sinusoidal variations.

scholarly journals Orbital pacing and secular evolution of the Early Jurassic carbon cycle

2020 ◽  
Vol 117 (8) ◽  
pp. 3974-3982 ◽  
Author(s):  
Marisa S. Storm ◽  
Stephen P. Hesselbo ◽  
Hugh C. Jenkyns ◽  
Micha Ruhl ◽  
Clemens V. Ullmann ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Lower Jurassic ◽  
Early Jurassic ◽  
Oceanic Anoxic Event ◽  
Secular Evolution ◽  
Igneous Provinces ◽  
Orbital Cycles ◽  
Orbital Tuning ◽  
Comparable Amplitude

Global perturbations to the Early Jurassic environment (∼201 to ∼174 Ma), notably during the Triassic–Jurassic transition and Toarcian Oceanic Anoxic Event, are well studied and largely associated with volcanogenic greenhouse gas emissions released by large igneous provinces. The long-term secular evolution, timing, and pacing of changes in the Early Jurassic carbon cycle that provide context for these events are thus far poorly understood due to a lack of continuous high-resolution δ13C data. Here we present a δ13CTOC record for the uppermost Rhaetian (Triassic) to Pliensbachian (Lower Jurassic), derived from a calcareous mudstone succession of the exceptionally expanded Llanbedr (Mochras Farm) borehole, Cardigan Bay Basin, Wales, United Kingdom. Combined with existing δ13CTOC data from the Toarcian, the compilation covers the entire Lower Jurassic. The dataset reproduces large-amplitude δ13CTOC excursions (>3‰) recognized elsewhere, at the Sinemurian–Pliensbachian transition and in the lower Toarcian serpentinum zone, as well as several previously identified medium-amplitude (∼0.5 to 2‰) shifts in the Hettangian to Pliensbachian interval. In addition, multiple hitherto undiscovered isotope shifts of comparable amplitude and stratigraphic extent are recorded, demonstrating that those similar features described earlier from stratigraphically more limited sections are nonunique in a long-term context. These shifts are identified as long-eccentricity (∼405-ky) orbital cycles. Orbital tuning of the δ13CTOC record provides the basis for an astrochronological duration estimate for the Pliensbachian and Sinemurian, giving implications for the duration of the Hettangian Stage. Overall the chemostratigraphy illustrates particular sensitivity of the marine carbon cycle to long-eccentricity orbital forcing.

scholarly journals Gamma-Ray Orbital Modulation of the Transitioning Millisecond Pulsar Binary XSS J12270–4859

2022 ◽  
Vol 924 (2) ◽  
pp. 91
Author(s):  
Hongjun An
Keyword(s):  
Gamma Ray ◽  
Optical Data ◽  
Large Area ◽  
Time Intervals ◽  
Optical Telescope ◽  
X Ray ◽  
Low Mass ◽  
Orbital Modulation ◽  
Short Time

Abstract We report on gamma-ray orbital modulation of the transitioning MSP binary XSS J12270–4859 detected in the Fermi Large Area Telescope (LAT) data. We use long-term optical data taken with the XMM-Newton OM and the Swift UltraViolet Optical Telescope to inspect radio timing solutions that are limited to relatively short time intervals and find that extrapolation of the solutions aligns well with the phasing of the optical data over 15 yr. The Fermi-LAT data folded on the timing solutions exhibit significant modulation (p = 5 × 10−6) with a gamma-ray minimum at the inferior conjunction of the pulsar. Intriguingly, the source seems to show similar modulation in both the low-mass X-ray binary and the MSP states, implying that mechanisms for gamma-ray emission in the two states are similar. We discuss these findings and their implications using an intrabinary shock scenario.

scholarly journals The 405 kyr and 2.4 Myr eccentricity components in Cenozoic carbon isotope records

2018 ◽  
Author(s):  
Ilja J. Kocken ◽  
Margot J. Cramwinckel ◽  
Richard E. Zeebe ◽  
Jack J. Middelburg ◽  
Appy Sluijs
Keyword(s):  
Carbon Cycle ◽  
Dissolved Inorganic Carbon ◽  
Low Frequency ◽  
Orbital Forcing ◽  
Ice Dynamics ◽  
Ice Volume ◽  
Low Frequency Oscillations ◽  
Amplitude Modulator ◽  
Sediment Carbon

Abstract. Cenozoic stable carbon (δ13C) and oxygen (δ18O) isotope ratios of deep-sea foraminiferal calcite co-vary with the 405 kyr eccentricity cycle, suggesting a link between orbital forcing, the climate system, and the carbon cycle. Variations in δ18O are partly forced by ice-volume changes that have mostly occurred since the Oligocene. The cyclic δ13C–δ18O co-variations are found in both ice-free and glaciated climate states, however. Consequently, there should be a mechanism that forces the δ13C cycles independently of ice-dynamics. In search of this mechanism, we simulate the response of several key components of the carbon cycle to orbital forcing in the Long-term Ocean-atmosphere-Sediment CArbon cycle Reservoir model (LOSCAR). We force the model by changing the burial of organic carbon in the ocean with various astronomical solutions and noise, and study the response of the main carbon cycle tracers. Consistent with previous work, the simulations reveal that low frequency oscillations in the forcing are preferentially amplified relative to higher frequencies. However, while oceanic δ13C mainly varies with a 405 kyr period in the model, the dynamics of dissolved inorganic carbon in the oceans and of atmospheric CO2 are dominated by the 2.4 Myr cycle of eccentricity. This implies that the total ocean and atmosphere carbon inventory is strongly influenced by carbon cycle variability that exceeds the time scale of the 405 kyr period (such as silicate weathering). To test the applicability of the model results, we assemble a long (~ 22 Myr) δ13C and δ18O composite record spanning the Eocene to Miocene (34 to 12 Ma) and perform spectral analysis to assess the presence of the 2.4 Myr cycle. We find that, while the 2.4 Myr cycle appears to be overshadowed by long-term changes in the composite record, it is is present as an amplitude modulator of the 405 and 100 kyr eccentricity cycles.

scholarly journals The 405 kyr and 2.4 Myr eccentricity components in Cenozoic carbon isotope records

2019 ◽  
Vol 15 (1) ◽  
pp. 91-104 ◽  
Author(s):  
Ilja J. Kocken ◽  
Margot J. Cramwinckel ◽  
Richard E. Zeebe ◽  
Jack J. Middelburg ◽  
Appy Sluijs
Keyword(s):  
Carbon Cycle ◽  
Dissolved Inorganic Carbon ◽  
Low Frequency ◽  
Orbital Forcing ◽  
Ice Dynamics ◽  
Ice Volume ◽  
Low Frequency Oscillations ◽  
Amplitude Modulator ◽  
Sediment Carbon

Abstract. Cenozoic stable carbon (δ13C) and oxygen (δ18O) isotope ratios of deep-sea foraminiferal calcite co-vary with the 405 kyr eccentricity cycle, suggesting a link between orbital forcing, the climate system, and the carbon cycle. Variations in δ18O are partly forced by ice-volume changes that have mostly occurred since the Oligocene. The cyclic δ13C–δ18O co-variation is found in both ice-free and glaciated climate states, however. Consequently, there should be a mechanism that forces the δ13C cycles independently of ice dynamics. In search of this mechanism, we simulate the response of several key components of the carbon cycle to orbital forcing in the Long-term Ocean-atmosphere-Sediment CArbon cycle Reservoir model (LOSCAR). We force the model by changing the burial of organic carbon in the ocean with various astronomical solutions and noise and study the response of the main carbon cycle tracers. Consistent with previous work, the simulations reveal that low-frequency oscillations in the forcing are preferentially amplified relative to higher frequencies. However, while oceanic δ13C mainly varies with a 405 kyr period in the model, the dynamics of dissolved inorganic carbon in the oceans and of atmospheric CO2 are dominated by the 2.4 Myr cycle of eccentricity. This implies that the total ocean and atmosphere carbon inventory is strongly influenced by carbon cycle variability that exceeds the timescale of the 405 kyr period (such as silicate weathering). To test the applicability of the model results, we assemble a long (∼22 Myr) δ13C and δ18O composite record spanning the Eocene to Miocene (34–12 Ma) and perform spectral analysis to assess the presence of the 2.4 Myr cycle. We find that, while the 2.4 Myr cycle appears to be overshadowed by long-term changes in the composite record, it is present as an amplitude modulator of the 405 and 100 kyr eccentricity cycles.

A review of analogues of alkaline alteration with regard to long-term barrier performance

2011 ◽  
Vol 75 (4) ◽  
pp. 2401-2418 ◽  
Author(s):  
D. Savage
Keyword(s):  
Mineral Dissolution ◽  
Time Intervals ◽  
Barrier Materials ◽  
Disturbed Zone ◽  
Natural Analogues ◽  
Zeolite Formation ◽  
Hydraulic Gradients ◽  
Short Time

AbstractCement and concrete will be used as fracture grouts, shotcrete, tunnel and borehole seals, and as matrices for waste encapsulationinter aliain geological repositories for radioactive wastes. Alteration of the host rock and/or swelling clay in waste package buffers and tunnel backfills by hyperalkaline solutions from cement/concrete may be deleterious to system performance through changes in the physicochemical properties of these barrier materials.Analogue systems (and timescales) relevant to the understanding of the alkaline disturbed zone include: industrial analogues, such as alkaline flooding of hydrocarbon reservoirs (up to 30 y), cement-aggregate reactions (up to 100 y) and the Tournemire tunnel (up to 125 y); and natural analogues, including the hyperalkaline springs at Maqarin, Jordan (more than 100,000 y), saline, alkaline lakes (more than 1,000,000 y) and certain fracture fillings in granites (more than 1,000,000 y).These systems show that alkaline alteration can be observed for thousands of years over distance scales of hundreds of metres under extreme conditions of hydraulic gradients in fractured rocks (Maqarin), but may be limited to a few centimetres over tens to a hundred years in mudstone (Tournemire). Important reaction mechanisms for retardation of alkaline fluids include: fluid mixing (alkaline oil floods, Maqarin), ion exchange (alkaline oil floods, Tournemire) and kinetic mineral dissolution-precipitation reactions (all systems studied). Qualitative and quantitative kinetic data for mineral reactions are available from cement aggregate reactions and the Searles Lake analogue, respectively. Short-term alteration observed in cement-aggregates is characterized by calcium silicate hydrate (C-S-H) minerals and incipient zeolite formation, whereas evidence from the Tournemire tunnel shows the growth of K-feldspar after relatively short time intervals (tens to a hundred years). There is a tendency for alkaline alteration to result in porosity decreases, but locally, porosity may be enhanced (e.g. near-injection well interactions in alkaline oil floods, or at fracture margins at Maqarin, Jordan). Data from industrial and natural analogues may thus supply some key data for bridging time and space scales between laboratory andin situexperiments on one hand and the requirements for safety assessment on the other.

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