Atmospheric CO2 over the last 1000 years: A high-resolution record from the West Antarctic Ice Sheet (WAIS) Divide ice core

We report a decadally resolved record of atmospheric CO2 concentration for the last 1000 years, obtained from the West Antarctic Ice Sheet (WAIS) Divide shallow ice core. The most prominent feature of the pre‐industrial period is a rapid ∼7 ppm decrease of CO2 in a span of ∼20–50 years at ∼1600 A.D. This observation confirms the timing of an abrupt atmospheric CO2 decrease of ∼10 ppm observed for that time period in the Law Dome ice core CO2 records, but the true magnitude of the decrease remains unclear. Atmospheric CO2 variations over the time period 1000–1800 A.D. are statistically correlated with northern hemispheric climate and tropical Indo‐Pacific sea surface temperature. However, the exact relationship between CO2 and climate remains elusive due to regional climate variations and/or uneven geographical data density of paleoclimate records. We observe small differences of 0 ∼ 2% (0 ∼ 6 ppm) among the high‐precision CO2 records from the Law Dome, EPICA Dronning Maud Land and WAIS Divide Antarctic ice cores. However, those records share common trends of CO2 change on centennial to multicentennial time scales, and clearly show that atmospheric CO2 has been increasing above preindustrial levels since ∼1850 A.D

Stable isotopes provide revised global limits of aerobic methane emissions from plants

International audienceRecently Keppler et al. (2006) discovered a surprising new source of methane ? terrestrial plants under aerobic conditions, with an estimated global production of 62?236 Tg yr?1 by an unknown mechanism. This is ~10?40% of the annual total of methane entering the modern atmosphere and ~30?100% of annual methane entering the pre-industrial (0 to 1700 AD) atmosphere. Here we test this reported global production of methane from plants against ice core records of atmospheric methane concentration (CH4) and stable carbon isotope ratios (?13CH4) over the last 2000 years. Our top-down approach determines that global plant emissions must be much lower than proposed by Keppler et al. (2006) during the last 2000 years and are likely to lie in the range 0?46 Tg yr?1 and 0?176 Tg yr?1 during the pre-industrial and modern eras, respectively

Natural and anthropogenic changes in atmospheric greenhouse gases over the past 2 millennia

Millennial changes in atmospheric trace gas composition are best determined from air enclosed in ice sheets. Air extracted from the open pores in firn and the bubbles in ice is measured to derive the past concentrations and isotopic ratios of the long lived trace gases. The significant increases observed in CO2, CH4 and N2O since about 1750 and the more recent appearance of synthetic gases such as the CFCs in the atmosphere are a key feature of the anthropocene. The millennia preceding the anthropocene, the Late Pre-Industrial Holocene (LPIH), show evidence of natural changes in trace gases that can be used to constrain models and improve their ability to predict future changes under scenarios of anthropogenic emissions and climate change. Precise measurements and ice core air samples that are accurately dated and highly resolved in time are required to record the small and rapid trace gas signals of this period. The atmospheric composition records produced by CSIRO and collaborators using the Law Dome, Antarctica ice cores are widely used in models of climate, atmospheric chemistry and the carbon cycle over the anthropocene and the LPIH. Results from these studies have been influential in informing global policies, including the Montreal and Kyoto Protocols. We will present the recently revised trace gas records from Law Dome and new measurements of tracers from these and other ice sites that reveal the causes of atmospheric changes over the anthropocene and the LPIH

Electronic Structure, Pore Size Distribution, and Sorption Characterization of an Unusual MOF, {[Ni(dpbz)][Ni(CN)\u3csub\u3e4\u3c/sub\u3e]}n, dpbz = 1,4-bis(4-pyridyl)benzene

The monoclinic (Ni(L)[Ni(CN)4] (L= 1,4-Bis(4-pyridyl) benzene) compound (defined as Ni-dpbz) is a flexible metal organic framework which assumes a pillared structure with layers defined by 2D Ni[Ni(CN)4]n nets and dpbz ligands as pillars. The structure features an entrapped dpbz ligand that links between the open ends of four-fold Ni sites from two neighboring chains. This arrangement results in an unusual 5-fold pseudo square-pyramid environment for Ni and a significantly long Ni-N distance of 2.369(4) Å. Using Density Functional Theory calculations, the different bonding characteristics between the 5-fold and 6-fold Ni\u27s were determined. We found that there is weak covalent bonding between the 5-fold Ni and N in the entrapped ligand, and the 6-fold Ni-N bonds provide effective electronic conduction. The disordered dimethyl sulfoxide (DMSO) solvent molecules are not bonded to the framework. The material has a single pore with a diameter of 4.1 Å. This pore includes approximately 55% of the total free volume (based on a zero-diameter probe). The accessible pore surface area and pore volume were calculated to be 507 m2/g and 6.99 cm3/kg, respectively. The maximum amount of CO2 that can be accommodated in the pores after DMSO is removed was found to be 204 mg/g, agreeing with the results of adsorption/desorption experiments of about 220 mg/g

Phospho‐RNA‐seq: a modified small RNA‐seq method that reveals circulating mRNA and lncRNA fragments as potential biomarkers in human plasma

Extracellular RNAs (exRNAs) in biofluids have attracted great interest as potential biomarkers. Although extracellular microRNAs in blood plasma are extensively characterized, extracellular messenger RNA (mRNA) and long non‐coding RNA (lncRNA) studies are limited. We report that plasma contains fragmented mRNAs and lncRNAs that are missed by standard small RNA‐seq protocols due to lack of 5′ phosphate or presence of 3′ phosphate. These fragments were revealed using a modified protocol (“phospho‐RNA‐seq”) incorporating RNA treatment with T4‐polynucleotide kinase, which we compared with standard small RNA‐seq for sequencing synthetic RNAs with varied 5′ and 3′ ends, as well as human plasma exRNA. Analyzing phospho‐RNA‐seq data using a custom, high‐stringency bioinformatic pipeline, we identified mRNA/lncRNA transcriptome fingerprints in plasma, including tissue‐specific gene sets. In a longitudinal study of hematopoietic stem cell transplant patients, bone marrow‐ and liver‐enriched exRNA genes were tracked with bone marrow recovery and liver injury, respectively, providing proof‐of‐concept validation as a biomarker approach. By enabling access to an unexplored realm of mRNA and lncRNA fragments, phospho‐RNA‐seq opens up new possibilities for plasma transcriptomic biomarker development.SynopsisA modified RNA‐seq method (Phospho‐RNA‐seq) revealed a new population of mRNA/lncRNA fragments in plasma, including ones that track with disease. This opens up new possibilities for disease detection via RNA profiling of plasma and other biofluids.Phospho‐RNA‐seq reveals a large population of mRNA and long non‐coding RNA fragments in human plasma, which are missed by standard small RNA‐seq protocols that depend on target RNAs having a 5′ P and 3′ OH.Accurate detection of plasma mRNA and lncRNA fragments requires a stringent bioinformatic analysis pipeline to avoid false positive alignments to mRNA and lncRNA genes.Phospho‐RNA‐seq identified ensembles of tissue‐specific transcripts in plasma of hematopoietic stem cell transplant patients, which show co‐expression patterns that vary dynamically and track with pathophysiological processes.By enabling access to an unexplored space of extracellular mRNA and lncRNA fragments, phospho‐RNA‐seq opens up new possibilities for monitoring health and disease via transcriptome fragment profiling of plasma and potentially other biofluids.A modified RNA‐seq method reveals a large population of mRNA/lncRNA fragments in plasma that are missed by standard small RNA‐seq protocols including ones that are associated with disease.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149518/1/embj2019101695_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149518/2/embj2019101695-sup-0002-EVFigs.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149518/3/embj2019101695.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149518/4/embj2019101695-sup-0001-Appendix.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149518/5/embj2019101695.reviewer_comments.pd

A 60 yr record of atmospheric carbon monoxide reconstructed from Greenland firn air

We present the first reconstruction of the Northern Hemisphere (NH) high latitude atmospheric carbon monoxide (CO) mole fraction from Greenland firn air. Firn air samples were collected at three deep ice core sites in Greenland (NGRIP in 2001, Summit in 2006 and NEEM in 2008). CO records from the three sites agree well with each other as well as with recent atmospheric measurements, indicating that CO is well preserved in the firn at these sites. CO atmospheric history was reconstructed back to the year 1950 from the measurements using a combination of two forward models of gas transport in firn and an inverse model. The reconstructed history suggests that Arctic CO in 1950 was 140–150 nmol mol-1, which is higher than today's values. CO mole fractions rose by 10–15 nmol mol-1 from 1950 to the 1970s and peaked in the 1970s or early 1980s, followed by a ˜ 30 nmol mol-1 decline to today's levels. We compare the CO history with the atmospheric histories of methane, light hydrocarbons, molecular hydrogen, CO stable isotopes and hydroxyl radicals (OH), as well as with published CO emission inventories and results of a historical run from a chemistry-transport model. We find that the reconstructed Greenland CO history cannot be reconciled with available emission inventories unless unrealistically large changes in OH are assumed. We argue that the available CO emission inventories strongly underestimate historical NH emissions, and fail to capture the emission decline starting in the late 1970s, which was most likely due to reduced emissions from road transportation in North America and Europe

Extinction threshold in the spatial stochastic logistic model: space homogeneous case

We consider the extinction regime in the spatial stochastic logistic model in R^d (a.k.a. Bolker–Pacala–Dieckmann–Law model of spatial populations) using the first-order perturbation beyond the mean-field equation. In space homogeneous case (i.e. when the density is non-spatial and the covariance is translation invariant), we show that the perturbation converges as time tends to infinity; that yields the first-order approximation for the stationary density. Next, we study the critical mortality – the smallest constant death rate which ensures the extinction of the population – as a function of the mean-field scaling parameter ε>0. We find the leading term of the asymptotic expansion (as ε→0) of the critical mortality which is apparently different for the cases d≥3, d = 2, and d = 1

A revised 1000 year atmospheric δ\u3csup\u3e13\u3c/sup\u3e C-CO2 record from Law Dome and South Pole, Antarctica

We present new measurements of δ13C of CO2 extracted from a high-resolution ice core from Law Dome (East Antarctica), together with firn measurements performed at Law Dome and South Pole, covering the last 150 years. Our analysis is motivated by the need to better understand the role and feedback of the carbon (C) cycle in climate change, by advances in measurement methods, and by apparent anomalies when comparing ice core and firn air δ13C records from Law Dome and South Pole. We demonstrate improved consistency between Law Dome ice, South Pole firn, and the Cape Grim (Tasmania) atmospheric δ13C data, providing evidence that our new record reliably extends direct atmospheric measurements back in time. We also show a revised version of early δ13C measurements covering the last 1000 years, with a mean preindustrial level of -6.50‰. Finally, we use a Kalman Filter Double Deconvolution to infer net natural CO2 fluxes between atmosphere, ocean, and land, which cause small δ13C deviations from the predominant anthropogenically induced δ13C decrease. The main features found from the previous δ13C record are confirmed, including the ocean as the dominant cause for the 1940 A.D. CO2 leveling. Our new record provides a solid basis for future investigation of the causes of decadal to centennial variations of the preindustrial atmospheric CO2 concentration. Those causes are of potential significance for predicting future CO2 levels and when attempting atmospheric verification of recent and future global carbon emission mitigation measures through Coupled Climate Carbon Cycle Models. Key Points New and revised, firn and ice δ13C-CO2 measurements from Antarctica Improve consistency between ice and firn δ13C-CO2 measurements Net natural CO2 fluxes between atmosphere, ocean and land inferred ©2013. American Geophysical Union. All Rights Reserved