Export 11 results:
Sort by: [ Author  (Asc)] Title Type Year
A B C D E F G H I J [K] L M N O P Q R S T U V W X Y Z   [Show ALL]
Keir, RS, Michel RL, Weiss RF.  1992.  Ocean mixing versus gas-exchange in Antarctic Shelf Waters near 150°E. Deep-Sea Research Part a-Oceanographic Research Papers. 39:97-119. AbstractWebsite

In February 1985, chlorofluoromethanes (CFMs), tritium and radiocarbon were measured in Antarctic continental shelf waters near 150-degrees-E. These distributions are used to evaluate (1) the transport of Warm Deep Water (WDW) and Antarctic Surface Water onto the shelf, and (2) the gas exchange rates across the sea surface. The time varying response of these tracers to atmospheric forcing is simulated with a box model of the water masses in this region. In the model, horizontal mixing of surface waters strongly affects the shelf radiocarbon level, but the CFMs and tritium are not affected. The observed low tritium concentrations (< 0.2 TU) in the shelf waters provide a lower limit to the transport of tritium deficient Warm Deep Water into the region, which is equivalent to a vertical flux of about 75 m y-1. This implies a maximum residence time of WDW in the basin of about 8 years. The transport of subsurface water out of the basin at the shelf break is estimated to be approximately 0.2 to 0.4 x 10(6) m3 s-1. The average annual CFM piston velocity for gas exchange is estimated to be about 200 m y-1.

Killworth, PD, Carmack EC, Weiss RF, Matear R.  1996.  Modeling deep-water renewal in Lake Baikal. Limnology and Oceanography. 41:1521-1538. AbstractWebsite

Temperature, dissolved oxygen, nutrients, and chlorofluorocarbon-12 data obtained from Lake Baikal are used to describe deep-water renewal in a deep, temperate-latitude lake. Observations are used to propose the physical mechanism governing convection and to formulate a model of deep ventilation. The key physical mechanism governing deep-water renewal is the so-called thermobaric instability. Because the temperature of maximum density decreases with depth, a lake can become conditionally unstable if the base of the cold mixed layer is displaced to a depth at which its temperature matches the local temperature of maximum density, thereby resulting in sinking plumes. An important consequence of this phenomenon is that deep temperate lakes such as Baikal do not completely mix twice yearly; instead, deep ventilation is episodic. A two-dimensional model of a wind- and buoyancy-driven lake shows many strong mixing events and a fairly realistic seasonal cycle, indicating that the hypothesis is physically realizable. A filling-box model is used to deduce the annually averaged fluxes necessary to produce a steady vertical distribution of tracers as observed. Good fits are obtained to oxygen and chlorofluorocarbon distributions by this model.

Kim, J, Fraser PJ, Li S, Muhle J, Ganesan AL, Krummel PB, Steele LP, Park S, Kim SK, Park MK, Arnold T, Harth CM, Salameh PK, Prinn RG, Weiss RF, Kim KR.  2014.  Quantifying aluminum and semiconductor industry perfluorocarbon emissions from atmospheric measurements. Geophysical Research Letters. 41:4787-4794.   10.1002/2014gl059783   AbstractWebsite

The potent anthropogenic perfluorocarbon greenhouse gases tetrafluoromethane (CF4) and hexafluoroethane (C2F6) are emitted to the atmosphere mainly by the aluminum and semiconductor industries. Global emissions of these perfluorocarbons (PFCs) calculated from atmospheric measurements are significantly greater than expected from reported national and industry-based emission inventories. In this study, in situ measurements of the two PFCs in the Advanced Global Atmospheric Gases Experiment network are used to show that their emission ratio varies according to the relative regional presence of these two industries, providing an industry-specific emission "signature" to apportion the observed emissions. Our results suggest that underestimated emissions from the global semiconductor industry during 1990-2010, as well as from China's aluminum industry after 2002, account for the observed differences between emissions based on atmospheric measurements and on inventories. These differences are significant despite the large uncertainties in emissions based on the methodologies used by these industries.

Kim, J, Li S, Kim KR, Stohl A, Muhle J, Kim SK, Park MK, Kang DJ, Lee G, Harth CM, Salameh PK, Weiss RF.  2010.  Regional atmospheric emissions determined from measurements at Jeju Island, Korea: Halogenated compounds from China. Geophysical Research Letters. 37   10.1029/2010gl043263   AbstractWebsite

High-frequency in-situ measurements of a wide range of halogenated compounds including chlorofluorocarbons (CFCs), halons, hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), perfluorinated compounds (PFCs), sulfur hexafluoride (SF(6)), and other chlorinated and brominated compounds have been made at Gosan (Jeju Island, Korea). Regional emissions of HCFC-22 (CHClF(2)) calculated from inverse modeling were combined with interspecies correlation methods to estimate national emissions for China, a major emitter of industrial halogenated gases. Our results confirm the signs of successful phase-out of primary ozone-depleting species such as CFCs, halons and many chlorinated or brominated compounds, along with substantial emissions of replacement HCFCs. Emissions derived for HFCs, PFCs, and SF6 were compared to published estimates and found to be a significant fraction of global totals. Overall, Chinese emissions of the halogenated compounds discussed here represent 19(14-17)% and 20(15-26)% of global emissions when evaluated in terms of their Ozone Depletion Potentials and 100-year Global Warming Potentials, respectively. Citation: Kim, J., et al. (2010), Regional atmospheric emissions determined from measurements at Jeju Island, Korea: Halogenated compounds from China, Geophys. Res. Lett., 37, L12801, doi: 10.1029/2010GL043263.

Kim, J, Li S, Muhle J, Stohl A, Kim SK, Park S, Park MK, Weiss RF, Kim KR.  2012.  Overview of the findings from measurements of halogenated compounds at Gosan (Jeju Island, Korea) quantifying emissions in East Asia. Journal of Integrative Environmental Sciences. 9:71-80.   10.1080/1943815x.2012.696548   AbstractWebsite

With increased economic growth in East Asia, regional emissions of many anthropogenic halogenated compounds now constitute a substantial fraction of the global totals. Here, we summarize recently reported findings from measurements of a wide range of chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF6), and other halogenated compounds at Gosan (Jeju Island, Korea) within the advanced global atmospheric gases experiment (AGAGE). General wind patterns at Gosan bring air masses from the surrounding areas, allowing the monitoring of both clean baseline and polluted air masses. We have analyzed our measurements since November 2007 both with an interspecies correlation method and with an inversion method based on the FLEXPART Lagrangian particle dispersion model to estimate these regional emissions. The results show that emissions of halogenated compounds in East Asia account for over 20% of global emissions, both in terms of ozone depletion potential (ODP) and global warming potential (GWP), and emphasize the importance of atmospheric measurements for quantifying emissions of these compounds in this region.

Kirschke, S, Bousquet P, Ciais P, Saunois M, Canadell JG, Dlugokencky EJ, Bergamaschi P, Bergmann D, Blake DR, Bruhwiler L, Cameron-Smith P, Castaldi S, Chevallier F, Feng L, Fraser A, Heimann M, Hodson EL, Houweling S, Josse B, Fraser PJ, Krummel PB, Lamarque JF, Langenfelds RL, Le Quere C, Naik V, O'Doherty S, Palmer PI, Pison I, Plummer D, Poulter B, Prinn RG, Rigby M, Ringeval B, Santini M, Schmidt M, Shindell DT, Simpson IJ, Spahni R, Steele LP, Strode SA, Sudo K, Szopa S, van der Werf GR, Voulgarakis A, van Weele M, Weiss RF, Williams JE, Zeng G.  2013.  Three decades of global methane sources and sinks. Nature Geoscience. 6:813-823.   10.1038/ngeo1955   AbstractWebsite

Methane is an important greenhouse gas, responsible for about 20% of the warming induced by long-lived greenhouse gases since pre-industrial times. By reacting with hydroxyl radicals, methane reduces the oxidizing capacity of the atmosphere and generates ozone in the troposphere. Although most sources and sinks of methane have been identified, their relative contributions to atmospheric methane levels are highly uncertain. As such, the factors responsible for the observed stabilization of atmospheric methane levels in the early 2000s, and the renewed rise after 2006, remain unclear. Here, we construct decadal budgets for methane sources and sinks between 1980 and 2010, using a combination of atmospheric measurements and results from chemical transport models, ecosystem models, climate chemistry models and inventories of anthropogenic emissions. The resultant budgets suggest that data-driven approaches and ecosystem models overestimate total natural emissions. We build three contrasting emission scenarios - which differ in fossil fuel and microbial emissions - to explain the decadal variability in atmospheric methane levels detected, here and in previous studies, since 1985. Although uncertainties in emission trends do not allow definitive conclusions to be drawn, we show that the observed stabilization of methane levels between 1999 and 2006 can potentially be explained by decreasing-to-stable fossil fuel emissions, combined with stable-to-increasing microbial emissions. We show that a rise in natural wetland emissions and fossil fuel emissions probably accounts for the renewed increase in global methane levels after 2006, although the relative contribution of these two sources remains uncertain.

Klatt, O, Roether W, Hoppema M, Bulsiewicz K, Fleischmann U, Rodehacke C, Fahrbach E, Weiss RF, Bullister JL.  2002.  Repeated CFC sections at the Greenwich Meridian in the Weddell Sea. Journal of Geophysical Research-Oceans. 107   10.1029/2000jc000731   AbstractWebsite

[1] Repeated observations of the tracer chlorofluorocarbon-11 (CFC-11) for a section along the Greenwich Meridian from Antarctica (70degreesS) to about 50 S are presented for the period 1984-1998. The CFC sections display a highly persistent pattern. A middepth CFC minimum in the central Weddell Sea is bounded laterally by elevated levels of dissolved CFCs at the southern margin of the Weddell Basin and by a column of elevated CFC concentrations around 55degreesS near to the northern margin. Part of the latter column covers waters of the Antarctic Circumpolar Current, which indicates that a moderate portion of these waters was ventilated in the Weddell Sea. Deep CFC maxima adjoining the southern and northern margins of the Weddell Basin indicate advective cores of recently ventilated waters. The southern core supports previous notions of deep water import into the Weddell Sea from the east. For all deep and bottom waters, the portions ventilated on the CFC timescale (similar to50 years) are small. Effective initial CFC saturations for these portions are estimated to be between 60 and 70%, using in part new data from off the Filchner-Ronne Ice Shelf. For various CFC features along the section (mostly advective cores), ventilated fractions and mean ages of these fractions were obtained (with error limits). The procedure was to fit an age distribution of a prescribed form to CFC-11 time series for these features, constructed from the various realizations of the CFC section. The ages are between 3 and 19 years, and the ventilated fractions range between 6 and 23%, indicating a rather limited ventilation of the interior Weddell Sea subsurface layer waters on the CFC timescale. It is shown that the concurrent CFC-12 data provide little additional information. The work demonstrates a high information content of repeated tracer observations and encourages similar approaches also in other ocean regions.

Klinkhammer, G, Bender M, Weiss RF.  1977.  Hydrothermal manganese in the Galapagos Rift. Nature. 269:319-320.   10.1038/269319a0   AbstractWebsite

HYDROTHERMAL emanations originating at mid-ocean ridges have been thought1–5 to provide a substantial source of manganese to the ocean but the evidence supporting this hypothesis has been indirect. Anomalous manganese concentrations have been measured in naturally occurring systems where seawater is in direct contact with lava flows6–8. Laboratory studies have shown that seawater tends to leach manganese from basalts at elevated temperatures and pressures9–11. Anomalously high manganese accumulation rates have also been determined for sediments adjacent to active ridge systems, most notably the East Pacific Rise12–14. No measurements of manganese concentrations in seawater near mid-ocean ridges, or in hydrothermal fluids emanating from these ridges, have yet been made, however. We report here the results of the first such direct measurements, which show that manganese is being injected into the deep sea by hydrothermal circulation of seawater through newly-formed oceanic crust.

Krishnaswami, S, Lal D, Somayajulu BLK, Weiss RF, Craig H.  1976.  Large-volume in situ filtration of deep Pacific waters: mineralogical and radioisotope studies. Earth and Planetary Science Letters. 32:420-429.   10.1016/0012-821x(76)90082-0   AbstractWebsite

The concentrations of CaCO3 and radioisotopes,234Th,230Th,239Pu,226Ra and210Pb have been measured in particles of >1.2 μm collected from ∼4000 liters of Pacific waters (33°N−33°S; 124°W−170°E) at depths 700–5500 m. The mean “ash” concentrations are found to be 5 μg/kg seawater, about 3–4 times lower than that in the surface waters. The particulate concentrations (dpm/kg seawater) of239Pu shows a peak at 700–1000 m, whereas the particulate concentration of230Th and210Pb which are produced in-situ in seawater increases with depth. These results provide an insight into certain aspects of particle dynamics relevant to modification of trace element composition of seawater due to particle transport and sedimentation flux. The salient features of the results are:(1) The mean settling velocity of particles are in the range of (0.3−2) × 10−3 cm/sec corresponding to a sedimentation rate of 0.1−0.6 cm/103 yr.(2) The rate constant for the adsorption of Th on particles is deduced to be 8 × 10−8 sec−1 assuming a first-order scavenging model.

Kroopnic.P, Weiss RF, Craig H.  1972.  Total CO2,13C, and dissolved oxygen -18O at GEOSECS II in the North Atlantic. Earth and Planetary Science Letters. 16:103-110.   10.1016/0012-821x(72)90242-7   AbstractWebsite

This paper presents profiles of ΣCO2, δ13C in ΣCO2, dissolved O2, and δ18O in dissolved O2, measured at Geosecs II in the North Atlantic. The O2 minimum at 1000 m is accompanied by a minimum in δ13C and a sharp maximum in δ18O; ΣCO2 increases downward through this layer with a slope change. All four parameters are remarkably uniform in the deep and bottom water below the O2 minimum, almost to the precision of measurement. Relative to data previously reported from this area of the Atlantic, our ΣCO2 values are 3% lower than those of Li et al. [10], and our δ13C values are up to 2‰ greater than those of Deuser and Hunt [12]. Also, our δ18O enrichments in dissolved O2 are very much less than Pacific values reported by Dole and coworkers [15]. All of these differences are attributed principally to bacterial O2 consumption during sample storage by previous workers, due to lack of, or inadequate, poisoning.In contrast to the North Atlantic, there is a very large gradient of dissolved O2 in the vertical profile of North Pacific Deep Water; however, if themean deep-water O2 concentration is compared with the uniform value in North Atlantic Deep Water, the O2 and ΣCO2 differences in North Atlantic and North Pacific Deep Water are essentially equimolar at 160 μm/kg. If 77% of deep-water O2 consumption is used for oxidation of organic carbon (the R-K-R “model plankton” value), the increase in ΣCO2 in Pacific deep water is about 25% due to dissolution of carbonate, and 75% due to oxidation of organic matter, in the vertical particulate flux. These proportions are in agreement with those estimated from alkalinity-ΣCO2 variations [10]. Our δ13C measurements in the Atlantic are quite consistent with the ΣCO2-O2-alkalinity variations between the Atlantic and Pacific deep water; thus the disagreement previously noted [14] is attributed to storage effects on δ13C measurements by previous workers, as noted above.

Kurylo, MJ, Rodriguez JM, Andreae MO, Atlas EL, Blake DR, Butler JH, Lal S, Lary DJ, Midgley PM, Montzka SA, Novelli PC, Reeves CE, Simmonds PG, Steele LP, Sturges WT, Weiss RF, Yokouchi Y.  1999.  Short-lived ozone-related compounds. Scientific assessment of ozone depletion, 1998 (World Meteorological Organization, Global Ozone Research and Monitoring Project Report 44). :56., Washington, DC: National Oceanic and Atmospheric Administration Abstract