Effect of chemical affinity on feldspar hydrolysis rates in two natural weathering systems

Recent studies of alkali-feldspar hydrolysis kinetics have shown that, in the near-neutral pH range, weathering rates in natural systems are up to three orders of magnitude slower than laboratory rates. It has been hypothesized that decelerated rates may result from lower thermodynamic affinities for the hydrolysis reaction in natural systems than in laboratory systems. However, the chemical affinities for the feldspar hydrolysis reaction in two well-constrained natural systems are significantly higher than the threshold value at which affinity would exert detectable influences on the reaction rates. Thus, the hypothesis is rejected, and closer proximity to thermodynamic equilibrium in natural weathering systems does not account for the observed discrepancy between natural and laboratory rates of feldspar hydrolysis. Differences in feldspar weathering rates between natural and laboratory systems are most likely due to a combination of experimental preparation artifacts, loss of reactive surface to the formation of etch pits in naturally weathered feldspars, and inhomogeneous access of reactive fluids to those surfaces.     

Climate and economic competitiveness: Florida freezes and the global citrus processing industry

Summary Casual observers of the impacts associated with four recent freezes in Florida's citrus producing areas might be inclined to agree with an assessment by Miami Herald reporters that these freezes had caused the king of citrus to be toppled from its throne, enabling Brazil to take its place. Research on the citrus industry, however, reveals that the impacts of these recent freezes only explain part of the story of the interaction between climate variability and the relationship between the citrus industries of Florida and Brazil. Climate characteristics and their variability have directly as well as indirectly affected the economic competitiveness of citrus producers whose output is in large measure climate-dependent. Climate variability has had direct impacts on Florida's citrus industry by adversely affecting the productivity of citrus groves in some areas, by altering growers' perceptions of freeze probabilities and, occasionally, by suddenly reducing output, thus elevating the price that consumers must pay for that commodity. Indirectly, competition can be affected by climate as a potential producer identifies a weakness in the supply system of an existing industry and seeks to fill the gap.Brazil's involvement in the toppling of King Citrus began not in the early 1980s (as a result of the four freezes in the past six years), but in 1962 as a result of a major freeze in that year, one that sharply increased FCOJ prices by reducing Florida's output. It was then that the climate had an impact on the economic competitiveness of the citrus industry. The records document the steady, almost meteoric, rise in Brazilian FCOJ production and exports. Subsequent freezes only served to abet a process that had been well underway two decades before the recent devastating freezes.As for Florida's ability to continue and perhaps expand its key role in the global citrus economy, the recent freezes do not appear to have fatally damaged that. Rather, those freezes have reawakened Florida's citrus producers to the fact that they are involved in a climate-sensitive industry and have reminded them that the potential for freeze-related problems is never far away. That reawakening has sparked interest in developing hardier citrus varieties, more effective freeze protection methods, and better ways to hedge economically against freeze impacts to the industry.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

The transport of CO2-induced warming into the ocean: an analysis of simulations by the OSU coupled atmosphere-ocean general circulation model

The OSU global coupled atmosphere-ocean general circulation model has been used to investigate a 2xCO₂-induced climate change. A previous analysis of the simulated 2xCO₂–1xCO₂ temperature differences showed that the CO₂-induced warming penetrated into the ocean and thereby caused a delay in the equilibration of the climate system with an estimatede-folding time of 50–75 years. The objective of the present study is to determine by what pathways and through which physical processes the simulated ocean general circulation produces the penetration of the CO₂-induced warming into the ocean.A global-mean oceanic heat budget analysis shows that the ocean gains heat at a rate of 3 W/m² due to the CO₂ doubling, and that this heat penetrates downward into the ocean predominantly through the reduction in the convective overturning. A zonal-mean oceanic heat budget analysis shows that the surface warming increases from the tropics toward the midlatitudes of both hemispheres and gradually penetrated into the deeper ocean, with a greater penetration in the subtropics and midlatitudes than in the equatorial region. The zonal-mean heat budget analysis also shows that the CO₂-induced warming of the ocean occurs predominantly through the down-ward transport of heat, with the meridional heat flux being only of secondary importance. In the tropics the penetration of the CO₂-induced heating is minimized by the upwelling of cold water. In the subtropics the heating is transported down-ward more readily by the downwelling existing there. In the high latitudes the suppressed convection plays the dominant role in the downward penetration of the CO₂-induced heating. The latter result should be considered as tentative, however, as the ocean component of the coupled model employed a prescribed surface salinity field and did not include the mechanism of brine rejection when sea water freezes into sea ice.     

The role of engineering geology for planning and construction of underground openings: Introduction of the symposium 19-3 “engineering geology in the utilization of underground space”, 29th Int. geological congress, Kyoto, Japan 1992

Langer, M., 1993. The Role of Engineering Geology for Planning and Construction of Underground Openings. In: M. Langer, K. Hoshino and K. Aoki (Editors), Engineering Geology in the Utilization of Underground Space.Eng. Geol., 35: 143–147.     

Climate-Volcanism Feedback and the Toba Eruption of 74,000 Years Ago

A general feedback between volcanism and climate at times of transition in the Quaternary climate record is suggested, exemplified by events accompanying the Toba eruption (74,000 yr ago), the largest known late Quaternary explosive volcanic eruption. The Toba paroxysm occurred during the δ¹⁸O stage 5a-4 transition, a period of rapid ice growth and falling global sea level, which may have been a factor in creating stresses that triggered the volcanic event. Toba is estimated to have produced between 10¹⁵ and 10¹⁶ g of fine ash and sulfur gases lofted in co-ignimbrite ash clouds to heights of at least 32 ± 5 km, which may have led to dense stratospheric dust and sulfuric acid aerosol clouds. These conditions could have created a brief, dramatic cooling or "volcanic winter," followed by estimated annual Northern Hemisphere surface-temperature decreases of 3° to 5°C caused by the longer-lived aerosols. Summer temperature decreases of 10°C at high northern latitudes, adjacent to regions already covered by snow and ice, might have increased snow cover and sea-ice extent, accelerating the global cooling already in progress. Evidence for such climate-volcanic feedback, following Milankovitch periodicities, is found at several climatic transitions.