Geophysical surveys of the sediments of Loch Ness,Scotland: implications for the deglaciation of the Moray Firth Ice Stream,British–Irish Ice Sheet

We present results from three geophysical campaigns using high‐resolution sub‐bottom profiling to image sediments deposited in Loch Ness, Scotland. Sonar profiles show distinct packages of sediment, providing insight into the loch's deglacial history. A recessional moraine complex in the north of the loch indicates initial punctuated retreat. Subsequent retreat was rapid before stabilisation at Foyers Rise formed a large stillstand moraine. Here, the calving margin produced significant volumes of laminated sediments in a proglacial fjord‐like environment. Subsequent to this, ice retreated rapidly to the southern end of the loch, where it again deposited a sequence of proglacial laminated sediments. Sediment sequences were then disturbed by the deposition of a thick gravel layer and a large turbidite deposit as a result of a jökulhlaup from the Spean/Roy ice‐dammed lake. These sediments are overlain by a Holocene sheet drape. Data indicate: (i) a former tributary of the Moray Firth Ice Stream migrated back into Loch Ness as a major outlet glacier with a calving margin in a fjord‐like setting; (ii) there was significant sediment supply to the terminus of this outlet glacier in Loch Ness; and (iii) that jökulhlaups are important for sediment supply into proglacial fjord/lake environments and may compose >20% of proglacial sedimentary sequences. Copyright © 2011 John Wiley & Sons, Ltd.     

Initialization and data assimilation experiments with a primitive equation model

The process of combining models of the ocean circulation with large data sets is known in meteorology as model initialization and data assimilation. This process is new to oceanographers, who only now are on the verge of having available world-wide synoptic maps of dynamic variables. In this paper we carry out a series of idealized initialization/assimilation experiments with a primitive equation (PE) model, which constitute a first step in developing a realistic process model and data assimilation techniques for the Gulf Stream system. The PE model is used in a spin-down mode and initialized with an analytic jet profile with geostrophically balanced fields.Two major questions are addressed in the present study. The first concerns the initialization process of a PE model during which internal/inertial gravity wave noise is produced. We ask: are the initialization shocks equally crucial for ocean models as they have been for their atmospheric counterparts? The results of an extensive series of balanced versus unbalanced initializations indicate that, for a PE model with a rigid lid, a brutally unbalanced initialization is required to produce strong internal gravity wave shocks. A geostrophically balanced initialization is sufficient to ensure smooth jet evolutions, with no apparent gravity waves, over long time durations in the spin-down mode. No sophisticated initialization procedures seem, therefore, to be required.The second question addressed is: which component of the flow is the most important in data assimilation to drive the model response towards a baseline reference ocean? We specifically compare the knowledge of the depth-integrated flow only, corresponding to measurements of the total transport, with the knowledge of the density field only, or equivalently the velocity shear. The knowledge of the interior density field is much more effective in decreasing the root-mean-square (r.m.s.) errors relative to the reference ocean. If the baroclinic structure is known, coarse horizontal resolutions of data insertion can be reached before significantly worsening the model estimates. If only the depth-averaged flow is known, a decrease in the horizontal resolution of data assimilation has an immediate effect: the r.m.s. errors sharply increase and the assimilation run diverges from the reference ocean. In the assimilation of the barotropic flow alone, even with dense resolution, the errors in the deep layers always show an increasing trend. The relative effectiveness of baroclinic versus barotropic data insertion can be rationalized in the context of geostrophic adjustment theory.     

Digital data acquisition and analysis: An introduction

There is no doubt that although the price of PCs has fallen, the performance for money continues to rise. As this happens, so the suitability of using general-purpose computing platforms, especially PCs, for specific technical applications increases. This article discusses recent developments and reviews some of the systems which are currently available for data acquisition and analysis in the environmental sciences.     

The Indus-Tsangpo suture zone in Ladakh, northwest Himalaya: Further palaeomagnetic data and implications

A total of 81 samples (244 specimens) from Upper Cretaceous Indus Molasse and Middle to Upper Cretaceous Dras Flyschoids of the Indus-Tsangpo suture zone in Ladakh (northwest Himalaya) has been studied by thermal demagnetization methods.Both formations showed a characteristic magnetization component indicative for equatorial to low northern palaeolatitudes of acquisition. Similar palaeolatitudes have been obtained before from secondary magnetization components of Early Tertiary age in the Ladakh Intrusives and in the Tibetan Sedimentary Series of central Nepal. The present characteristic components are interpreted likewise as secondary magnetizations which stabilized between 50 and 60 m.y. ago, during Greater India's collision with Asia's southern margin.The Dras Flyschoids show another magnetic component which, in case of primary origin, indicates acquisition at a low southern palaeolatitude. If correct, this interpretation supports recent suggestions for Late Cretaceous obduction of an island arc on Greater India's northern margin.     

Catastrophic events reveal the dynamic nature of salt-marsh vegetation in Southern California

Recent hydrological disturbances, including flooding, dry-season streamflow, and drought, greatly altered coastal wetland habitats in sourthern California. At Tijuana Estuary, a six-year study of salt-marsh vegetation patterns during these rare conditions documented substantial temporal variability in plant growth and distribution. Important to cordgrass (Spartina foliosa Trin.) dynamics were the amount and timing of streamflows, which reduced soil salinity and alleviated stresses on plant growth. Poorest growing conditions occurred in 1984 when both river and tidal flows were lacking; soils had low moisture and extreme salinities (avg.=104‰ in September). Plant stress was documented in 1984 as high mortality (62% fewer stems than in 1983) and reduced height (19% less than in 1983). Cordgrass height was greatest in 1980 following winter flooding (20% increase over 1979); densities were greatest in 1983 with summer freshwater influxes (60% increase over 1982). A carbon allocation model is proposed to explain the varied responses.     

Determination of Carbonate Carbon in 41 International Geochemical Reference Samples by Coulometric Method

The carbonate-carbon (CO₂) content of forty-one geochemical reference samples has been determined by coulometric method following acid treatment of the sample for releasing CO₂. The method is superior to the conventional methods in speed, accuracy, sensitivity, specificity, and the coverage of CO₂ range. The results on NBS limestone samples agree well with the certified values. The precision of the method is 0.5 % r.s.d., and the practical detection limit is 10 ppm C.     

Carbon dioxide recovery from industrial processes

The ongoing human-induced emission of carbon dioxide (CO₂) threatens to change the earth's climate. One possible way of decreasing CO₂ emissions is to apply CO₂ removal, which involves recovering of carbon dioxide from energy conversion processes and storing it outside the atmosphere. Since the 1980's, the possibilities for recovering CO₂ from thermal power plants received increasing attention.In this study possible techniques of recovering CO₂ from large-scale industrial processes are assessed.In some industrial processes, e.g. ammonia production, CO₂ is recovered from the process streams to prevent it from interfering with the production process. The CO₂ thus recovered can easily be dehydrated and compressed, at low cost. In the iron and steel industry, carbon dioxide can be recovered from blast furnace gas. In the petrochemical industry CO₂ can be recovered from flue gases, using low-temperature heat for the separation process.Carbon dioxide can be recovered from large-scale industrial processes and in some cases the cost of recovery is significantly less than CO₂ recovery from thermal power plants. Therefore this option should be studied further and should be considered if carbon dioxide removal is introduced on a wide scale.