Response of atmospheric carbon dioxide to the secular variation of weakening geomagnetic field in whole atmosphere simulations

Responses of atmospheric carbon dioxide(CO_(2))density to geomagnetic secular variation are investigated using the Whole Atmosphere Community Climate Model-eXtended(WACCM-X).Our ensemble simulations show that CO_(2) volume mixing ratios(VMRs)increase at high latitudes and decrease at mid and low latitudes by several ppmv in response to a 50%weakening of the geomagnetic field.Statistically significant changes in CO_(2) are mainly found above~90 km altitude and primarily redetermine the energy budget at~100-110 km.Our analysis of transformed Eulerian mean(TEM)circulation found that CO_(2) change is caused by enhanced upwelling at high latitudes and downwelling at mid and low latitudes as a result of increased Joule heating.We further analyzed the atmospheric CO_(2) response to realistic geomagnetic weakening between 1978 and 2013,and found increasing(decreasing)CO_(2) VMRs at high latitudes(mid and low latitudes)accordingly.For the first time,our simulation results demonstrate that the impact of geomagnetic variation on atmospheric CO_(2) distribution is noticeable on a time scale of decades.

Atmospheric Carbon Dioxide Reconstruction and Ocean Acidification Deduced from Carbon Isotope Variations across the Triassic–Jurassic Boundary in the Qiangtang Area, Tibetan Plateau

Objective The end-Triassic mass extinction was one of the five most profound Phanerozoic extinction events.This event was accompanied by a series of significant environmental changes,of which the most notable is the emergence of warm climate and the world-wide disappearance of carbonate platform.

Analysis of the carbon dioxide mole fraction variation and its transmission characteristics in Taiyuan

Based on the concentrations of CO2,PM2.5 and PM1.0,and conventional meteorological observation data from 2016 to 2018 at Taiyuan station,which belongs to the Shanxi greenhouse gas observation network,the CO2 concentration monthly and daily distribution characteristics,the weekend effect,and the variation characteristics on haze days and non-haze days,are analyzed.By using the Hybrid Single-Particle Lagrangian Integrated Trajectorymodel(backward trajectory model)and surface wind data,the transmission characteristics of atmospheric CO2 in Taiyuan are studied in various seasons.The results show that,in Taiyuan,the CO2 mole fraction in autumn and winter is higher than that in spring and summer,and on haze days is higher than that on non-haze days.The diurnal variation characteristic of CO2mole fraction in each season is‘single peak and single valley’with the peak value around 0700(hereafter refers to Beijing Time)and the valley value around 1600.The CO2 mole fraction on workdays is slightly higher than that on non-workdays and obviously different around 0800 of the early peak.Horizontal diffusion can reduce the CO2 mole fraction,while breezy weather is not beneficial to CO2 diffusion.The wind direction and speed in the upper levels are different from those near the surface,and the close air masses in the southwest–west–northwest sector raise the CO2 concentration in Taiyuan obviously.This indicates that the CO2 in Taiyuan is mainly contributed by local sources.

Evaluating effects of atmospheric CO_2 on stability of global climate:a cell-to-cell mapping approach

Atmospheric carbon dioxide concentration [CO2],incoming solar radiation and sea ice coverage are among the most important factors that control the global climate.By applying the simple cell-to-cell mapping technique to a simplified atmosphere-ocean-sea ice feedback climate model,effects of these factors on the stability of the climatic system are studied.The current climatic system is found to be stable but highly nonlinear.The resiliency of stability increases with [CO2] to a summit when [CO2] reaches 290 μL/L which is comparable to the pre-industrial level,suggesting carbon dioxide is essential to the stability of the global climate.With [CO2] rising further,the global climate stability decreases,the mean ocean temperature goes up and the sea ice coverage shrinks in the polar region.When the incoming solar radiation is intensified,the ice coverage gradually diminishes,but the mean ocean temperature remains relatively constant.Overall,our analysis suggests that at the current levels of three external factors the stability of global climate is highly resilient.However,there exists a possibility of extreme states of climate,such as a snow-ball earth and an ice-free earth.

New perspectives on deep carbon cycling

The proto-atmosphere serves as a crucial starting point for the carbon cycle.Estimations based on atmospheric data from Mars and Venus suggest that Earth's proto-atmosphere contained>110 bar of CO_(2)and>2.6 bar of nitrogen.The protoatmosphere had over 1000 bar of water vapor during the magma ocean stage,assuming the proto-ocean had a volume of two oceans of water.During this stage both water and carbon dioxide were in a supercritical state at the magma-atmosphere interface.Intense serpentinization reactions occurred due to rock-water interaction,producing abundant hydrogen.Consequently,nitrogen is reduced to ammonia,and carbon dioxide to methane,forming carbonate simultaneously.The proto-atmosphere dominated by methane,ammonia,and hydrogen formed a significant amount of amino acids through lightning.This process is essential not only to the origin of life,but also to the early carbon-nitrogen cycle on Earth.By the Hadean eon,a large amount of CO_(2)was sequestered as carbonate and organic material.Subsequently,it mainly entered the deep mantle through mantle overturn or subduction.In the mantle transition zone,carbonate undergoes“Redox freezing”,where carbonate is reduced to diamond through oxidation of ferrous iron in the melt.In the lower mantle,Fe^(2+)undergoes disproportionation reactions,forming Fe^(3+)and metallic iron.Among these,Fe^(3+)mainly resides in bridgmanite,thereby increasing the oxygen fugacity of the lower mantle,while metallic iron falls to the Earth's core.The distribution of carbon in the mantle is crucial for deep carbon cycling.The density curves of diamond and mantle peridotite melt intersect at the bottom of the mantle transition zone(about 660 km).This density crossover leads to the accumulation of diamond during the magma ocean stage.When materials such as subducting slabs enter the lower mantle,compensatory upwelling of lower mantle material occurs.Bridgmanite enters the upper mantle,decomposes,releasing Fe^(3+)ions and oxidizes diamond to carbonate,which under thermal disturbance from kimberlite and igneous carbonatites,moves upward.This carbonate layer may have caused significant topographic fluctuations at the 660 km boundary.Currently,diamond in this layer may still not have been completely oxidized to carbonate or carbon dioxide,serving as a redox buffering layer.This is a key factor in constraining deep carbon cycling.Subduction zones are important pathways for facilitating the cycling.Processes in the Earth's deep carbon cycle significantly influence the carbon content of surface reservoirs.The fluctuations in atmospheric CO_(2)content since the Neogene are closely linked to the uplift of the Tibetan Plateau and the subduction of the western Pacific Plate.Around 60 million years ago,the closure of the Neo-Tethys Ocean led to subduction of the Indian passive margin.The massive sediments on the Indian margin carried down large amounts of carbonate and organic material into the mantle,and the resulting volcanism released large amounts of greenhouse gases such as CO_(2)and methane into the atmosphere.The subduction of the Neo-Tethys Ocean passive margin weakened at about 51 Ma,and subduction of the western Pacific began.The depth of the western Pacific Ocean generally exceeds the carbonate compensation depth,and the amount of carbonate carried by subducting oceanic crust is minimal.Consequently,the input of subducted carbonate decreased significantly,leading to a substantial reduction in CO_(2)emissions from volcanoes.Based on volcanic data from the past12,000 years,the average rate of volcanic eruptions in subduction zones is estimated to be about 3 cubic kilometers per year.The weathering rate of volcanic ash is much higher than that of continental crust materials such as granite.The calcium,magnesium,and other ions provided by weathering of global volcanic ash are equivalent to the flux of global rivers into the oceans.The increase in volcanic ash and the decrease in CO_(2)emissions from subduction zones have led to a decrease in atmospheric CO_(2)levels,which is a key factor in the sustained global cooling since 51 million years ago.

Dynamics of Soil Organic Carbon Under Uncertain Climate Change and Elevated Atmospheric CO_2

Climate change and elevated atmospheric CO2 should affect the dynamics of soil organic carbon （SOC）. SOC dynamics under uncertain patterns of climate warming and elevated atmospheric CO2 as well as with different soil erosion extents at Nelson Farm during 1998-100 were simulated using stochastic modelling. Results based on numerous simulations showed that SOC decreased with elevated atmospheric temperature but increased with atmospheric CO2 concentration. Therefore, there was a counteract effect on SOC dynamics between climate warming and elevated CO2. For different soil erosion extents, warming 1℃ and elevated atmospheric CO2 resulted in SOC increase at least 15%, while warming 5 ℃ and elevated CO2 resulted in SOC decrease more than 29%. SOC predictions with uncertainty assessment were conducted for different scenarios of soil erosion, climate change, and elevated CO2. Statistically, SOC decreased linearly with the probability. SOC also decreased with time and the degree of soil erosion. For example, in 2100 with a probability of 50%, SOC was 1 617, 1 167, and 892 g m^-2, respectively, for no, minimum, and maximum soil erosion. Under climate warming 5 ℃ and elevated CO2, the soil carbon pools became a carbon source to the atmosphere （P 〉 95%）. The results suggested that stochastic modelling could be a useful tool to predict future SOC dynamics under uncertain climate change and elevated CO2.

Study of atmospheric CO2 and CH4 at Longfengshan WMO/GAW regional station： The variations, trends, influence of local sources/sinks, and transport

Atmospheric CO_2 and CH_4 have been continuously measured since 2009 at Longfengshan WMO/GAW station(LFS) in China. Variations of the mole fractions, influence of long-distance transport, effects of local sources/sinks and the characteristics of synoptic scale variations have been studied based on the records from 2009 to 2013. Both the CO_2 and CH_4 mole fractions display increasing trends in the last five years, with growth rates of 3.1±0.02 ppm yr.1 for CO_2 and 8±0.04 ppb yr.1(standard error, 1-σ)for CH_4. In summer, the regional CO_2 mole fractions are apparently lower than the Marine Boundary Layer reference, with the lowest value of.13.6±0.7 ppm in July, while the CH_4 values are higher than the MBL reference, with the maximum of 139±6 ppb.From 9 to 17(Local time, LT) in summer, the atmospheric CO_2 mole fractions at 10 m a.g.l. are always lower than at 80 m, with a mean difference of.1.1±0.2 ppm, indicating that the flask sampling approach deployed may underestimate the background mole fractions in summer. In winter, anthropogenic emissions dominate the regional CO_2 and CH_4 mole fractions. Cluster analysis of backward trajectories shows that atmospheric CO_2 and CH_4 at LFS are influenced by anthropogenic emissions from the southwest(Changchun and Jilin city) all year. The synoptic scale variations indicate that the northeastern China plain acts as an important source of atmospheric CO_2 and CH_4 in winter.

Greenhouse gas emissions from oilfield-produced water in Shengli Oilfield,Eastern China

Greenhouse gas（GHG） emissions from oil and gas systems are an important component of the GHG emission inventory. To assess the carbon emissions from oilfield-produced water under atmospheric conditions correctly, in situ detection and simulation experiments were developed to study the natural release of GHG into the atmosphere in the Shengli Oilfield,the second largest oilfield in China. The results showed that methane（CH4） and carbon dioxide（CO2） were the primary gases released naturally from the oilfield-produced water.The atmospheric temperature and release time played important roles in determining the CH4 and CO2emissions under atmospheric conditions. Higher temperatures enhanced the carbon emissions. The emissions of both CH4 and CO2from oilfield-produced water were highest at 27°C and lowest at 3°C. The bulk of CH4 and CO2was released from the oilfield-produced water during the first release period, 0–2 hr, for each temperature, with a maximum average emission rate of 0.415 g CH4/（m3·hr） and 3.934 g CO2/（m3·hr）, respectively. Then the carbon emissions at other time periods gradually decreased with the extension of time. The higher solubility of CO2 in water than CH4 results in a higher emission rate of CH4 than CO2over the same release duration. The simulation proved that oilfield-produced water is one of the potential emission sources that should be given great attention in oil and gas systems.