Publications Published in 1998

1. Abyssal recipes II: energetics of tidal and wind mixing. Munk, W.; Wunsch, C..
   Deep Sea Research Part I Oceanographic Research Papers: 1998
   Notes
   Without deep mixing, the ocean would turn, within a few thousand years, into a stagnant pool of cold salty water with equilibrium maintained locally by near-surface mixing and with very weak convectively driven surface-intensified circulation. (This result follows from Sandstrom's theorem for a fluid heated and cooled at the surface.) In this context we revisit the 1966 "Abyssal Recipes", which called for a diapycnal diffusivity of 10(-4) m(2)/s (1 cgs) to maintain the abyssal stratification against global upwelling associated with 25 Sverdrups of deep water formation. Subsequent microstructure measurements gave a pelagic diffusivity (away from topography) of 10( -5) m(2)/s - a low value confirmed by dye release experiments. A new solution (without restriction to constant coefficients) leads to approximately the same values of global upwelling and diffusivity, but we reinterpret the computed diffusivity as a surrogate for a small number of concentrated sources of buoyancy flux (regions of intense mixing) from which the water masses (but not the turbulence) are exported into the ocean interior. Using the Levitus climatology we find that 2.1 TW (terawatts) are required to maintain the global abyssal density distribution against 30 Sverdrups of deep water formation. The winds and tides are the only possible source of mechanical energy to drive the interior mixing. Tidal dissipation is known from astronomy to equal 3.7 TW (2.50 +/- 0.05 TW from M-2 alone), but nearly all of this has traditionally been allocated to dissipation in the turbulent bottom boundary layers of marginal seas. However, two recent TOPEX/POSEIDON altimetric estimates combined with dynamical models suggest that 0.6-0.9 TW may be available for abyssal mixing. A recent estimate of wind-driving; suggests 1 TW of additional mixing power, All values are very uncertain. A surprising conclusion is that the equator-to-pole heat flux of 2000 TW associated with the meridional overturning circulation would not exist without the comparatively minute mechanical mixing sources. Coupled with the findings that mixing occurs at a few dominant sites, there is a host of questions concerning the maintenance of the present climate state, but also that of paleoclimates and their relation to detailed continental configurations, the history of the Earth-Moon system, and a possible great sensitivity to details of the wind system.
   
   
   
2. Carbon isotopic analysis of atmospheric methane in urban and suburban areas - fossil and non-fossil methane from local sources. Moriizumi, J.; Nagamine, K.; Iida, T.; Ikebe, Y..
   Atmospheric Environment: 1998
   Notes
   The carbon isotopic composition (C-12, C-13 and C-14) of atmospheric CH4 was studied to estimate CH4 sources in local areas. In urban areas of Nagoya, Japan (35 degrees 10'N, 136 degrees 55'E), where there is much anthropogenic influence, evidence of methane release into the atmosphere has been reported. Variations in the carbon isotopic composition were analyzed with diurnal fluctuation of atmospheric CH4 concentration, since the diurnal increase in the CH4 concentration is attributed mainly to release from local sources. In November and December 1993, the contribution of fossil CH, to local CH, released from the urban area was calculated to be 102 +/- 8%, and delta (13)C was -40.8 +/- 3.0 parts per thousand. Leakage of supplied natural gas and exhaust gas from automobiles would he important CH, sources in the urban area in late autumn to winter. In suburban areas in Japan there are many rice paddy fields, and these are one kind of major anthropogenic source of atmospheric CH4. In a suburban area of Nagoya fossil, CH4 contributed to less than 10% of local release in July and August 1994. The calculated value of
   
   
   
3. Climate change impacts on sand supply and the formation of desert sand dunes in the south-west usa. Clarke, M. L.; Rendell, H. M..
   Journal of Arid Environments: 1998
   Notes
   The formation of desert sand dunes has often been used as an indicator of periods of aridity. Application of luminescence dating techniques to determine the timing of sand dune formation in the Mojave Desert has shown that 94% of dated sands were deposited at times when pluvial lakes filled many desert basins, and floods were recorded in Arizona and Utah rivers. Climate change can trigger a supply of sediment for entrainment along sand transport corridors and subsequent accretion on dunes and sand ramps. In a supply-limited system, storm events associated with climate change and resulting in overland flow are the controlling factor for periods of sand dune formation in desert areas of the south-western U.S.A. (C)1998 Academic Press Limited.
   
   
   
4. Climate-ocean variability and ecosystem response in the northeast pacific. McGowan, J. A.; Cayan, D. R.; Dorman, L. M..
   Science: 1998
   Notes
   The role of climatic variation in regulating marine populations and communities is not well understood. To improve our knowledge, the sign, amplitude, and frequency of climatic and biotic variations should be compared as a necessary first step. it is shown that there have been large interannual and interdecadal sea- surface temperature changes off the West Coast of North America during the past 80 years. Interannual anomalies appear and disappear rather suddenly and synchronously along the entire coastline. The frequency of warm events has increased since 1977. Although extensive, serial, biological observations are often incomplete, it is clear that climate-ocean variations have disturbed and changed our coastal ecosystems.
   
   
   
5. Clouds, contrails and climate. Seinfeld, John H.
   Nature: 1998
   Notes
   Discusses research which studied the theory that cirrus clouds are formed from jet contrails. Effect of human activity on climate; Where cirrus clouds form; Impact of human emissions of aerosols; Formation of stratus clouds; Jet contrails seen as artificial cirrus; Impact of aircraft exhaust; Research in `Geophysical Research Letters'; Tie between nitric acid and cirrus clouds.
   
   
   
6. Effects of temperature, water content and nitrogen fertilisation on emissions of nitrous oxide by soils. Smith, K A; Thomson, P E; Clayton, H; McTaggart, I P; Conen, F.
   Atmospheric Environment: 1998
   Notes
   Nitrous oxide emissions were measured from several grassland and arable soils in the field, and from two of these soils and a forest soil transferred in large monoliths to a greenhouse. The effects of fertilizer N additions and of soil water content and temperature were investigated. Emissions were in the order grazed grassland> grassland cut for conservation> potatoes> cereal crops, and generally were higher than those from temperature natural ecosystems. Based on these data, agricultural soils constitute the major soil source of N2O in the U.K. The highest emission recorded was 8 kg N2O-N ha−1 over 10 months, from a grazed grassland site. Emissions varied from year to year, depending particularly on rainfall at the time of fertilization. When soil mineral N was not limiting, exponential relationships between N2O flux and both water-filled pore space (WFPS) and temperature were observed. The Q10 value for a sandy loam was 1.6, but ranged up to 12 for a clay loam soil at high WFPS. The high values were attributed to the increase in anaerobic zones where denitrification could take place, as respiratory demand for O2 increased. A forest soil (peaty gley) showed an optimum water potential for N2O emission. Diurnal fluctuations in emissions were associated with diurnal cycles in soil temperature, but with varying time lags, which could be explained by the N2O being produced at different depths.
   
   
   
7. Emission of Nitrous Oxide and other Trace Gases during Compsoting of Grass and Green Waste. Hellerbrand, H.J..
   Journal of Agricultural Engineering Research: 1998
   Notes
   The emission of trace gases during composting of green waste from land maintenance (fresh cuttings of mixed herbage from fallow land) were studied. Concentrations of nitrous oxide and other trace gases were measured in experimental compost heaps by means of an infrared gas analyser and a high-resolution FT-IR spectrometer. It was verified that the maintenance of aerobic conditions is essential to keep emissions of methane and nitrous oxide at a low rate. Estimates made using a simple air transport model, indicated that the emission of nitrous oxide during composting of green waste from land maintenance was about 0·5% of the total nitrogen content of the initial material. Carbon monoxide was also detected in the compost air and its emission during biodegradation corresponded to about 0·04% of the initial carbon content of green waste. For a detailed evaluation of the findings during field experiments, laboratory apparatus for measuring the composition of compost air was developed. The measurements were performed at a temperature of 35°C and at different ventilation rates. Moistened plant material (dry cuttings of mixed herbage from fallow land) amended with lime saltpetre was used as compost substrate. At a ventilation rate of 100 cm3/min of air per kg of substrate, the maximum emission rate of nitrous oxide was 2·2 mg/h per kg of substrate. The maximum emission rate increased to 13·3 mg/h kg, when the ventilation rate was lowered to 20 cm3/min kg. The emission rate of carbon monoxide was about 40 g/h per kg of substrate at the low ventilation rate and rose above 200g/h kg at the higher ventilation
   
   
   
8. Energy implications of future stabilization of atmospheric CO2 content. Hoffert, Martin I.; Caldeira, Ken; Jain, Atul K.; Haites, Erik F.; Harvey, L. D. Danny; Potter, Seth D.; Schlesinger, Michael E.; Schneider, Stephen H.; Watts, Robert G.; Wigley, Tom M. L.; Wuebbles, Donald J..
   Nature: 1998
   Notes
   The United Nations Framework Convention on Climate Change1 calls for "stabilization of greenhouse-gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system . . . ". A standard baseline scenario2,3 that assumes no policy intervention to limit greenhouse-gas emissions has 10 TW (10 1012 watts) of carbon-emission-free power being produced by the year 2050, equivalent to the power provided by all today's energy sources combined. Here we employ a carbon-cycle/energy model to estimate the carbon-emission-free power needed for various atmospheric CO2 stabilization scenarios. We find that CO2 stabilization with continued economic growth will require innovative, cost-effective and carbon-emission-free technologies that can provide additional tens of terawatts of primary power in the coming decades, and certainly by the middle of the twenty-first century, even with sustained improvement in the economic productivity of primary energy. At progressively lower atmospheric CO2-stabilization targets in the 750–350 p.p.m.v. range, implementing stabilization will become even more challenging because of the increasing demand for carbon-emission-free power. The magnitude of the implied infrastructure transition suggests the need for massive investments in innovative energy research.
   
   
   
9. Energy implications of future stabilization of atmospheric CO2 content. Hoffert, Martin I; Caldeira, Ken; Jain, Atul K; Haites, Erik F; Danny Harvey, L D; Potter, Seth D; Schlesinger, Michael E; Schneider, Stephen H; Watts, Robert G; Wigley, Tom M L; Wuebbles, Donald J.
   Nature: 1998
   Notes
   Presents research which used a carbon-cycle/energy model to estimate the carbon-emission-free power needed for carbon-dioxide stabilization scenarios. Greenhouse-gas emissions by 2050; Need for carbon-emission-free technologies; Challenges to implementing stabilization; Magnitude of the infrastructure transition needed.
   
   
   
10. European source strengths and northern hemisphere baseline concentrations of radiatively active trace gases at mace head, Ireland. Derwent, R G; Simmonds, P G; O'Doherty, S; Ciais, P; Ryall, D B.
    Atmospheric Environment: 1998
    Notes
    Greenhouse gas measurements have been made continuously with high frequency and precision at the remote baseline monitoring station at Mace Head on the Atlantic Ocean coastline of Ireland since 1987. By using three independent methods, the two-hourly observations have been sorted by air mass origins into those from "unpolluted" or Northern Hemisphere baseline air masses and those from"polluted" European air masses. Northern Hemisphere baseline methane, nitrous oxide and carbon dioxide concentrations have risen throughout the 10 year period and their respective mid-1996 levels are the highest mid-year levels recorded so far. For ozone, the mid-1996 annual mean concentrations was within 0.1 ppb of the highest mid-year level. The elevated greenhouse gas concentrations found in "polluted" air masses provide clear evidence for the presence of substantial emission sources in Europe. Using a simple climatological long-range transport model and a sophisticated Lagrangian dispersion model, it has been possible to estimate the magnitudes of the greenhouse gas emissions required to support the observations. Estimates of European source strengths of methane, nitrous oxide, carbon monoxide and halocarbons agree well with the available emission inventories. Using the Mace Head observations, significant addional contributions to global climate change have been identified from the trace gases: methane, nitrous oxide and tropospheric ozone, over and above that driven by carbon dioxide. The radiative forcing consequences of a range of HCFCs and HFCs will only become of significance should their emissions grow to become comparable with those of the CFCs that they have replaced.