Carbon Sequestration and Sediment Accretion in San Francisco Bay Tidal Wetlands

Tidal wetlands play an important role with respect to climate change because of both their sensitivity to sea-level rise and their ability to sequester carbon dioxide from the atmosphere. Policy-based interest in carbon sequestration has increased recently, and wetland restoration projects have potential for carbon credits through soil carbon sequestration. We measured sediment accretion, mineral and organic matter accumulation, and carbon sequestration rates using ¹³⁷Cs and ²¹⁰Pb downcore distributions at six natural tidal wetlands in the San Francisco Bay Estuary. The accretion rates were, in general, 0.2?C0.5?cm?year^?1, indicating that local wetlands are keeping pace with recent rates of sea-level rise. Mineral accumulation rates were higher in salt marshes and at low-marsh stations within individual sites. The average carbon sequestration rate based on ²¹⁰Pb dating was 79?g?C?m^?2?year^?1, with slightly higher rates based on ¹³⁷Cs dating. There was little difference in the sequestration rates among sites or across stations within sites, indicating that a single carbon sequestration rate could be used for crediting tidal wetland restoration projects within the Estuary.     

Interblock zones of the northwestern Baikal rift: results of geological and geophysical studies along the Bayandai Village–Cape Krestovskii profile

The structure of the Earth’s crust at the junction of the Siberian craton and Sayan–Baikal Fold Belt was studied along the Bayandai Village–Cape Krestovskii profile (85 km long) by a set of geological and geophysical methods: structural survey, interpretation of long-distance photographs, emanation survey, electrical prospecting with self-potential (SP) and direct-current (DC) resistivity profiling, magnetotelluric sounding, magnetic survey, and hydrogeochemical sampling of water objects. Interpretation of the data refined the main features of the tectonic structure of western Cisbaikalia and revealed the disruption pattern and hierarchic zone–block structure of the Earth’s crust. The Obruchev fault system (≈50 km wide), which is the northwestern shoulder of the Baikal Rift, is the main interblock zone of the studied region. It consists of the Morskoi, Primorskii, and Prikhrebtovyi interblock zones, traced from depths of tens of kilometers and widening near the surface owing to superior structures. The studies gave an insight into the regularities in the occurrence of interblock zones and the criteria for their identification in different geologic-geophysical fields. An efficient complex of methods for mapping the Earth’s crust zone–block structure is proposed.     

On the Development of Wave Disturbances of the Bottom Surface in Rivers and Channels

Izvestiya, Atmospheric and Oceanic Physics - On the basis of an analytical model of the flow of tractional sediments which takes into account the influence of the slopes of the bottom surface and...     

On facies belts and facies mosaics: Holocene isolated platforms,South China Sea

Although the general criteria for recognition and environmental interpretation of different carbonate facies are well‐established, a predictive understanding of the areal extent and spatial patterning of facies bodies and why they might organize into facies belts or facies mosaics is poorly constrained. To explore patterns and process dynamics of facies on isolated carbonate platforms, quantitative analysis of thematic maps derived from remote sensing images of 27 Holocene atolls of the Paracel and Spratly chains in the South China Sea explores variability within and among platforms. On these systems, most annular shelf‐margin reefs are less than 500 m wide on both chains; inboard of the reefs, reef sand aprons range up to 500 m (Spratlys) and 1000 m (Paracels) wide. Around individual platforms, Spratly Chain sand apron widths are wider to the north‐west, whereas apron widths in the Paracel Chain are more symmetrical; collectively, data indicate log‐normal width‐exceedance probability distributions. Platform‐interior patch reefs include area‐exceedance probability distributions and gap size distributions (lacunarity) consistent within chains, but distinct between the chains. To understand the processes underlying distinct distributions, simulations explored distinct growth scenarios. Results suggest that differences may represent distinct process classes: proportional growth processes with multiplicative random effects (reef sand aprons – belts), versus non‐linear, size‐proportional growth of randomly aged and distributed elements (patch reefs – mosaics). The probabilistically distinct sizes and spatial patterns of geomorphic elements within these general process classes are interpreted to represent ‘variations on themes’ related to the different impacts of tropical storms, winter cold fronts and circulation in each chain. The results highlight fundamentally different growth patterns impacting the sizes and distribution of facies belts and mosaics on isolated carbonate platforms. Because these types of bodies ultimately construct stratigraphy, the themes could be applied to understand and predict variability in the architecture of subsurface reservoir analogues.     

Evaluation of an alternative method for numerically modeling nonhydrostatic flows over irregular terrain

Modeling nonhydrostatic atmospheric flow requires the solution of the vertical equation of motion and a prognostic or diagnostic equation for pressure. If the nonhydrostatic components of the flow are relatively small, they can be approximated and incorporated into a purely hydrostatic model, which usually is conceptually simpler and computationally more efficient. A method to do this for a linear model of local thermally-induced circulations is further developed and adapted to a non-linear numerical model of the neutral atmospheric boundary layer. A hydrostatic model and the quasi-nonhydrostatic version were used to simulate neutral flow over simple terrain features. One set of observations taken over a simple change in roughness and another set taken over a change in both roughness and terrain were simulated by both models to assess the capabilities of the quasi-nonhydrostatic technique.It is found that (as expected) the pressure deviation from the hydrostatic state is negligible for the roughness change, but it is an important aspect of neutral flow over terrain. Thus, for flow encountering a simple roughness change, the hydrostatic approximation is good, even for small horizontal scales. However, the quasi-nonhydrostatic model qualitatively produces the features in the observations for flow over a terrain change that the hydrostatic model cannot produce.Journal Paper No. J-12737 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 2779.     

Forecast of convective storms evolution based on the analysis of their radar echo and wind hodograph in the troposphere in the moving coordinate system

Generalized are the results of the research carried out by the Special Service for Weather Modification of the Republic of Moldova and of the features of formation and evolution of cumulonimbus clouds Cb based on studying their radar echo in the Lagrange (moving) coordinate system. Besides the regularities proceeding from the ideas about the evolution of Cb on the sides of atmospheric mesoscale structures [16], the features of evolution of powerful Cb are revealed at the significant wind shear. The direction and evolution features of Cb can be predicted using the wind hodograph in the troposphere plotted in the moving coordinate system. Results of the research are used in the Special Service for Weather Modification of the Republic of Moldova during the operational activities on hail suppression for predicting the areas of formation of new convective cells and for optimizing the size of the areas for their seeding with the crystallizing reagent.     

Use of archaeology to date liquefaction features and seismic events in the New Madrid seismic zone,Central United States

Prehistoric earthquake-induced liquefaction features occur in association with Native American occupation horizons in the New Madrid seismic zone. Age control of these liquefaction features, including sand-blow deposits, sand-blow craters, and sand dikes, can be accomplished by extensive sampling and flotation processing of datable materials as well as archaeobotanical analysis of associated archaeological horizons and pits. This approach increases both the amount of carbon for radiocarbon dating and the precision dating of artifact assemblages. Using this approach, we dated liquefaction features at four sites northwest of Blytheville, Arkansas, and found that at least one significant earthquake occurred in the New Madrid seismic zone between A.D. 1180 and 1400, probably about A.D. 1300 ± 100 yr. In addition, we found three buried sand blows that formed between 3340 B.C. and A.D. 780. In this region where very large to great earthquakes appear to be closely timed, archaeology is helping to develop a paleoearthquake chronology for the New Madrid seismic zone. © 1996 John Wiley & Sons, Inc.