More Like this

1. The Impact of Orbital Precession on Air‐Sea CO ₂ Exchange in the Southern Ocean

   https://doi.org/10.1029/2023GL103820  

   Persch, Cole F.; DiNezio, Pedro; Lovenduski, Nicole S. (October 2023, Geophysical Research Letters)

   Abstract Orbital precession has been linked to glacial cycles and the atmospheric carbon dioxide (CO₂) concentration, yet the direct impact of precession on the carbon cycle is not well understood. We analyze output from an Earth system model configured under different orbital parameters to isolate the impact of precession on air‐sea CO₂flux in the Southern Ocean—a component of the global carbon cycle that is thought to play a key role on past atmospheric CO₂variations. Here, we demonstrate that periods of high precession are coincident with anomalous CO₂outgassing from the Southern Ocean. Under high precession, we find a poleward shift in the southern westerly winds, enhanced Southern Ocean meridional overturning, and an increase in the surface ocean partial pressure of CO₂along the core of the Antarctic Circumpolar Current. These results suggest that orbital precession may have played an important role in driving changes in atmospheric CO₂. 

   more » « less
2. Carbon Fluxes and Primary Magma CO ₂ Contents Along the Global Mid‐Ocean Ridge System

   https://doi.org/10.1029/2018GC007630  

   Le_Voyer, Marion; Hauri, Erik_H; Cottrell, Elizabeth; Kelley, Katherine_A; Salters, Vincent_J_M; Langmuir, Charles_H; Hilton, David_R; Barry, Peter_H; Füri, Evelyn (March 2019, Geochemistry, Geophysics, Geosystems)

   Abstract The concentration of carbon in primary mid‐ocean ridge basalts (MORBs), and the associated fluxes of CO₂outgassed at ocean ridges, is examined through new data obtained by secondary ion mass spectrometry (SIMS) on 753 globally distributed MORB glasses. MORB glasses are typically 80–90% degassed of CO₂. We thus use the limited range in CO₂/Ba (81.3 ± 23) and CO₂/Rb (991 ± 129), derived from undegassed MORB and MORB melt inclusions, to estimate primary CO₂concentrations for ridges that have Ba and/or Rb data. When combined with quality‐controlled volatile‐element data from the literature (n = 2,446), these data constrain a range of primary CO₂abundances that vary from 104 ppm to 1.90 wt%. Segment‐scale data reveal a range in MORB magma flux varying by a factor of 440 (from 6.8 × 10⁵to 3.0 × 10⁸m³/year) and an integrated global MORB magma flux of 16.5 ± 1.6 km³/year. When combined with CO₂/Ba and CO₂/Rb‐derived primary magma CO₂abundances, the calculated segment‐scale CO₂fluxes vary by more than 3 orders of magnitude (3.3 × 10⁷to 4.0 × 10¹⁰mol/year) and sum to an integrated global MORB CO₂flux of × 10¹²mol/year. Variations in ridge CO₂fluxes have a muted effect on global climate; however, because the vast majority of CO₂degassed at ridges is dissolved into seawater and enters the marine bicarbonate cycle. MORB degassing would thus only contribute to long‐term variations in climate via degassing directly into the atmosphere in shallow‐water areas or where the ridge system is exposed above sea level. 

   more » « less
3. Data for "Deep Nitrogen Fluxes and Sources Constrained by Arc Lava Phenocrysts"

   https://doi.org/10.7910/DVN/UJEGKF  

   Hudak, Michael R; Barry, Peter H; Bekaert, David V; Turner, Stephen J; Broadley, Michael W; Walowski, Kristina; Tyne, Rebecca L; Li, Kan; Nielsen, Sune G; Curtice, Joshua M; et al (October 2024, Harvard Dataverse)

   These data correspond to the article “Deep Nitrogen Fluxes and Sources Constrained by Arc Lava Phenocrysts” by Hudak et al. submitted to Geophysical Research Letters. Table S1 includes N-He-Ar data for FIs in phenocrysts from mafic are lavas and tephras. Table S2 contains the corrected N2/3He data used for volcanic arc N flux calculations and the arc-averaged mean N arc flux. Table S3 summarizes previous literature estimates of N fluxes and the data used for those calculations. Table S4 provides the N concentrations, He concentrations, N isotope compositions of the mantle, sediments, and altered oceanic crust, as well as sediment thicknesses. Finally, Table S5 gives information about the sources of the mineral separates used for these analyses. 

   more » « less
4. Primordial Helium‐3 Exchange Between Earth's Core and Mantle

   https://doi.org/10.1029/2021GC009985  

   Olson, Peter_L; Sharp, Zachary_D (March 2022, Geochemistry, Geophysics, Geosystems)

   Abstract Volatiles from the solar nebula are known to be present in Earth's deep mantle. The core also may contain solar nebula‐derived volatiles, but in unknown amounts. Here we use calculations of volatile ingassing and degassing to estimate the abundance of primordial³He now in the core and track the rate of³He exchange between the core and mantle through Earth history. We apply an ingassing model that includes a silicate magma ocean and an iron‐rich proto‐core coupled to a nebular atmosphere of solar composition to calculate the amounts of³He acquired by the mantle and core during accretion and core formation. Using experimentally determined partitioning between core‐forming metals and silicate magma, we find that dissolution from the nebular atmosphere deposits one or more petagrams of³He into the proto‐core. Following accretion,³He exchange depends on the convective history of the coupled core‐mantle system. We combine determinations of the present‐day surface³He flux with estimates of the present‐day mantle³He abundance, mantle and core heat fluxes, and our ingassed³He abundances in a convective degassing model. According to this model, the mantle³He abundance is evolving toward a statistical steady state, in which surface losses are compensated by enrichments from the core. 

   more » « less
5. A SUBLIME 3D Model for Cometary Coma Emission: The Hypervolatile-rich Comet C/2016 R2 (PanSTARRS)

   https://doi.org/10.3847/1538-4357/ac5893  

   Cordiner, M. A.; Coulson, I. M.; Garcia-Berrios, E.; Qi, C.; Lique, F.; Zołtowski, M.; de Val-Borro, M.; Kuan, Y. -J.; Ip, W. -H.; Mairs, S.; et al (April 2022, The Astrophysical Journal)

   Abstract The coma of comet C/2016 R2 (PanSTARRS) is one of the most chemically peculiar ever observed, in particular due to its extremely high CO/H₂O and ${\mathrm{N}}_2^{+}$/H₂O ratios, and unusual trace volatile abundances. However, the complex shape of its CO emission lines, as well as uncertainties in the coma structure and excitation, has lead to ambiguities in the total CO production rate. We performed high-resolution, spatially, spectrally, and temporally resolved CO observations using the James Clerk Maxwell Telescope and Submillimeter Array to elucidate the outgassing behavior of C/2016 R2. Results are analyzed using a new, time-dependent, three-dimensional radiative transfer code (SUBlimating gases in LIME; SUBLIME, based on the open-source version of the LIne Modeling Engine), incorporating for the first time, accurate state-to-state collisional rate coefficients for the CO–CO system. The total CO production rate was found to be in the range of (3.8 − 7.6) × 10²⁸s⁻¹between 2018 January 13 and February 1 (atr_H= 2.8–2.9 au), with a mean value of (5.3 ± 0.6) × 10²⁸s⁻¹. The emission is concentrated in a near-sunward jet, with a half-opening angle of ∼62° and an outflow velocity of 0.51 ± 0.01 km s⁻¹, compared to 0.25 ± 0.01 km s⁻¹in the ambient (and nightside) coma. Evidence was also found for an extended source of CO emission, possibly due to icy grain sublimation around 1.2 × 10⁵km from the nucleus. Based on the coma molecular abundances, we propose that the nucleus ices of C/2016 R2 can be divided into a rapidly sublimating apolar phase, rich in CO, CO₂, N₂, and CH₃OH, and a predominantly frozen (or less abundant), polar phase containing more H₂O, CH₄, H₂CO, and HCN. 

   more » « less