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Petrenko, VV, Smith AM, Brook EJ, Lowe D, Riedel K, Brailsford G, Hua Q, Schaefer H, Reeh N, Weiss RF, Etheridge D, Severinghaus JP.  2009.  14CH4 measurements in Greenland ice: investigating last glacial termination CH4 sources. Science. 324:506-508.   10.1126/science.1168909   AbstractWebsite

The cause of a large increase of atmospheric methane concentration during the Younger Dryas-Preboreal abrupt climatic transition (similar to 11,600 years ago) has been the subject of much debate. The carbon-14 (C-14) content of methane ((CH4)-C-14) should distinguish between wetland and clathrate contributions to this increase. We present measurements of (CH4)-C-14 in glacial ice, targeting this transition, performed by using ice samples obtained from an ablation site in west Greenland. Measured (CH4)-C-14 values were higher than predicted under any scenario. Sample (CH4)-C-14 appears to be elevated by direct cosmogenic C-14 production in ice. C-14 of CO was measured to better understand this process and correct the sample (CH4)-C-14. Corrected results suggest that wetland sources were likely responsible for the majority of the Younger Dryas-Preboreal CH4 rise.

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Li, PY, Muhle J, Montzka SA, Oram DE, Miller BR, Weiss RF, Fraser PJ, Tanhua T.  2019.  Atmospheric histories, growth rates and solubilities in seawater and other natural waters of the potential transient tracers HCFC-22, HCFC-141b, HCFC-142b, HFC-134a, HFC-125, HFC-23, PFC-14 and PFC-116. Ocean Science. 15:33-60.   10.5194/os-15-33-2019   AbstractWebsite

We present consistent annual mean atmospheric histories and growth rates for the mainly anthropogenic halogenated compounds HCFC-22, HCFC-141b, HCFC-142b, HFC-134a, HFC-125, HFC-23, PFC-14 and PFC-116, which are all potentially useful oceanic transient tracers (tracers of water transport within the ocean), for the Northern and Southern Hemisphere with the aim of providing input histories of these compounds for the equilibrium between the atmosphere and surface ocean. We use observations of these halogenated compounds made by the Advanced Global Atmospheric Gases Experiment (AGAGE), the Scripps Institution of Oceanography (SIO), the Commonwealth Scientific and Industrial Research Organization (CSIRO), the National Oceanic and Atmospheric Administration (NOAA) and the University of East Anglia (UEA). Prior to the direct observational record, we use archived air measurements, firn air measurements and published model calculations to estimate the atmospheric mole fraction histories. The results show that the atmospheric mole fractions for each species, except HCFC-14 lb and HCFC-142b, have been increasing since they were initially produced. Recently, the atmospheric growth rates have been decreasing for the HCFCs (HCFC-22, HCFC-141b and HCFC-142b), increasing for the HFCs (HFC-134a, HFC-125, HFC-23) and stable with little fluctuation for the PFCs (PFC-14 and PFC-116) investigated here. The atmospheric histories (source functions) and natural background mole fractions show that HCFC-22, HCFC-141b, HCFC-142b, HFC-134a, HFC-125 and HFC-23 have the potential to be oceanic transient tracers for the next few decades only because of the recently imposed bans on production and consumption. When the atmospheric histories of the compounds are not monotonically changing, the equilibrium atmospheric mole fraction (and ultimately the age associated with that mole fraction) calculated from their concentration in the ocean is not unique, reducing their potential as transient tracers. Moreover, HFCs have potential to be oceanic transient tracers for a longer period in the future than HCFCs as the growth rates of HFCs are increasing and those of HCFCs are decreasing in the background atmosphere. PFC-14 and PFC-116, however, have the potential to be tracers for longer periods into the future due to their extremely long lifetimes, steady atmospheric growth rates and no explicit ban on their emissions. In this work, we also derive solubility functions for HCFC-22, HCFC-14 lb, HCFC-142b, HFC-134a, HFC-125, HFC-23, PFC-14 and PFC-116 in water and seawater to facilitate their use as oceanic transient tracers. These functions are based on the Clark-Glew-Weiss (CGW) water solubility function fit and salting-out coefficients estimated by the poly-parameter linear free-energy relationships (pp-LFERs). Here we also provide three methods of seawater solubility estimation for more compounds. Even though our intention is for application in oceanic research, the work described in this paper is potentially useful for tracer studies in a wide range of natural waters, including freshwater and saline lakes, and, for the more stable compounds, groundwaters.

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Severinghaus, JP, Keeling RF, Miller BR, Weiss RF, Deck B, Broecker WS.  1997.  Feasibility of using sand dunes as archives of old air. Journal of Geophysical Research-Atmospheres. 102:16783-16792.   10.1029/97jd00525   AbstractWebsite

Large unaltered samples of the atmosphere covering the past century would complement the history of atmospheric gases obtained from bubbles in ice cores, enabling measurement of geochemically important species such as O-2, (CH4)-C-14, and (CO)-C-14. Sand dunes are a porous media with interstitial air in diffusive contact with the atmosphere, somewhat analogous to the unconsolidated layer of firn atop glaciers. Recent studies have demonstrated the value of firn as an archive of old air [Battle et al., 1996; Bender et al., 1994a]. Unlike firn, sand dunes are incompressible and so remain permeable to greater depths and may extend the firn record into the past century. To evaluate the feasibility of using sand dunes as archives of old air, we drilled 60 m deep test holes in the Algodones Dunes, Imperial Valley, California. The main objective was to see if the air in a sand dune is as old as predicted by a diffusion model, or if the dune is rapidly flushed by advective pumping during windstorms and barometric pressure changes. We dated the air with chlorofluorocarbons and krypton-85, anthropogenic tracers whose atmospheric concentrations are known and have been increasing rapidly in the past half century. These tracer data match the pure diffusion model well, showing that advection in this dune is negligible compared to diffusion as a transport mechanism and that the mean age of the air at 61 m depth is similar to 10 years. Dunes therefore do contain old air. However, dunes appear to suffer from two serious drawbacks as archives. Microbial metabolism is evident in elevated CO2 and N2O and depressed CH4 and O-2 concentrations in this dune, corrupting the signals of interest in this and probably most dunes. Second, isotopic analyses of N-2 and O-2 from the dune show that fractionation of the gases occurs due to diffusion of water vapor, complicating the interpretation of the O-2 signal beyond the point of viability for an air archive. Sand dunes may be useful for relatively inert gases with large atmospheric concentration changes such as chlorofluorocarbons.

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Xiao, X, Prinn RG, Simmonds PG, Steele LP, Novelli PC, Huang J, Langenfelds RL, O'Doherty S, Krummel PB, Fraser PJ, Porter LW, Weiss RF, Salameh P, Wang RHJ.  2007.  Optimal estimation of the soil uptake rate of molecular hydrogen from the Advanced Global Atmospheric Gases Experiment and other measurements. Journal of Geophysical Research-Atmospheres. 112   10.1029/2006jd007241   AbstractWebsite

[1] Hydrogen (H(2)), a proposed clean energy alternative, warrants detailed investigation of its global budget and future environmental impacts. The magnitudes and seasonal cycles of the major ( presumably microbial) soil sink of hydrogen have been estimated from high-frequency in situ AGAGE H(2) observations and also from more geographically extensive but low-frequency flask measurements from CSIRO and NOAA-GMD using the Kalman filter in a two-dimensional (2-D) global transport model. Hydrogen mole fractions exhibit well-defined seasonal cycles in each hemisphere with their phase difference being only about 3 months. The global production rate of H(2) is estimated to be 103 +/- 10 Tg yr(-1) with only a small estimated interannual variation. Soil uptake ( 84 +/- 8 Tg yr(-1)) represents the major loss process for H(2) and accounts for 81% of the total destruction. Strong seasonal cycles are deduced for the soil uptake of H(2). The soil sink is a maximum over the northern extratropics in summer and peaks only 2 to 3 months earlier in the Northern Hemisphere than in the Southern Hemisphere. Oxidation by tropospheric OH (18 +/- 3 Tg yr(-1)) accounts for 17% of the destruction, with the remainder due to destruction in the stratosphere. The calculated global burden is 191 +/- 29 Tg, indicating an overall atmospheric lifetime of 1.8 +/- 0.3 years. Hydrogen in the troposphere ( 149 +/- 23 Tg burden) has a lifetime of 1.4 +/- 0.2 years.

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Deeds, DA, Muhle J, Weiss RF.  2008.  Tetrafluoromethane in the deep North Pacific Ocean. Geophysical Research Letters. 35   10.1029/2008gl034355   AbstractWebsite

Dissolved tetrafluoromethane (CF(4)) has been measured for the first time in the North Pacific Ocean. Surface water collected during calm weather is near equilibrium with the modern atmosphere. Deep water, isolated from atmospheric exchange for centuries, is near equilibrium with the preindustrial atmosphere, after accounting for an expected 5% addition of this low-solubility gas due to air injection during high-latitude deep-water formation. These results strongly suggest that dissolved CF(4) is conservative in seawater and that the oceanic imprint of anthropogenic increases in atmospheric CF(4) can be used as a time-dependent tracer of ocean ventilation and subsurface circulation processes. Although the continental lithosphere is a source of natural atmospheric CF(4), we find no evidence of an oceanic lithospheric CF(4) input into deep Pacific waters. The estimated upper limit of a potential oceanic lithospheric CF(4) flux to the global atmosphere is on the order of 4% of that from the continental lithosphere.