A comparison of tropical oceanic heat fluxes determined by airborne eddy correlation and shipboard bulk aerodynamic techniques

Vertical turbulent transports of latent and sensible heat through the tropical marine boundary layer were measured with ship and airborne instruments in the GATE experimental area. The measurements from the two systems are compared for cases of simultaneous sampling in the same locations during undisturbed weather and during the wakes of convective disturbances. The paired average fluxes from the airborne eddy correlation measurements and the shipboard bulk aerodynamic measurements, for undisturbed weather, are related with correlation coefficients in the range of 0.6 to 0.9; the correlations depend primarily on stratifications of the aircraft data according to sampling altitude (15–153 m msl) and flight pattern relative to the mean wind. The agreement between the two types of measurements is best for ship data paired with aircraft samples from the lowest altitudes (15 and 30 m) and from alongwind rather than crosswind flights, as is appropriate since the stationary ships monitor the alongwind characteristics of the turbulence. The use of long (1–3 hr) versus short (10 min) ship samples did not significantly affect the comparability with the aircraft samples during undisturbed periods.The good baseline comparability demonstrated by the undisturbed-weather comparisons was applied to interpret the results from the wakes behind showers. Although these paired measurements were few, not only the sensible heat, but also the latent heat flux was shown to decrease substantially with altitude from 10 m to at least 150 m in the wakes, where the mixing was relatively intense. Variations in the fluxes were much greater at the higher level than nearer the sea surface.     

The respective effects of water vapor and temperature on the turbulent fluxes of sensible and latent heat

Various aspects of the Brook correction for the effects of moisture fluctuations or gradients on atmospheric specific heat and, consequently, on the vertical flux of sensible heat are discussed, and additional forms of the complete and approximate equations are derived. Corollary expressions for the influence of temperature fluctuations or gradients on vertical latent heat flux are presented. Errors due to neglecting these temperature and moisture effects on the respective fluxes are compared in terms of the Bowen ratio. Either of these normally neglected effects can change the direction (sign) and very substantially affect the magnitude of the corresponding flux. The effects sometimes compensate in the total, sensible plus latent, heat flux. Calculations include practical examples from the very different climates of the tropical Atlantic Ocean and the Great Plains of Nebraska.     

Application of the UKCIP02 climate change scenarios: Reflections and lessons learnt

The UKCIP02 climate change scenarios have become the standard reference for climate change in the UK since their release in 2002. This paper describes and reflects on the ways in which they have been applied. It then identifies some strengths, weaknesses and barriers to their application, and extracts key lessons that may inform the development and provision of future climate change scenarios.Analysis of the application of UKCIP02 shows that the scenarios have been used primarily as a communication device, as well as for scientific research and to inform policy and decision-making on climate change. They have played a critical role in raising awareness on climate change and in engaging organisations in the need to adapt. Their presentation in an accessible style, and their availability in a variety of formats, greatly facilitated their uptake. However, analysis has also revealed weaknesses which served as barriers to their uptake. Some of these, such as file format and accessibility issues, were readily overcome through technical solutions. Others, such as the issue of how to use uncertain information in decision-making, have only been partially addressed and remain an outstanding challenge for future scenario packages. Two key lessons have emerged which may benefit the provision of future climate scenarios in the UK and elsewhere. First, it is not enough to simply make climate change scenarios available. Their provision must be accompanied by ongoing guidance and support to ensure widespread and appropriate uptake. Second, on-going dialogue between those providing scenarios and the communities using them is fundamental to constructively meet the challenges associated with delivering credible scenarios that balance user requirements and expectations with what the science can deliver.     

Carbon dioxide on the satellites of Saturn: Results from the Cassini VIMS investigation and revisions to the VIMS wavelength scale

Several of the icy satellites of Saturn show the spectroscopic signature of the asymmetric stretching mode of C-O in carbon dioxide (CO₂) at or near the nominal solid-phase laboratory wavelength of 4.2675 μm (2343.3 cm⁻¹), discovered with the Visible-Infrared Mapping Spectrometer (VIMS) on the Cassini spacecraft. We report here on an analysis of the variation in wavelength and width of the CO₂ absorption band in the spectra of Phoebe, Iapetus, Hyperion, and Dione. Comparisons are made to laboratory spectra of pure CO₂, CO₂ clathrates, ternary mixtures of CO₂ with other volatiles, implanted and adsorbed CO₂ in non-volatile materials, and ab initio theoretical calculations of CO₂ * nH₂O. At the wavelength resolution of VIMS, the CO₂ on Phoebe is indistinguishable from pure CO₂ ice (each molecule’s nearby neighbors are also CO₂) or type II clathrate of CO₂ in H₂O. In contrast, the CO₂ band on Iapetus, Hyperion, and Dione is shifted to shorter wavelengths (typically ∼4.255 μm (∼2350.2 cm⁻¹)) and broadened. These wavelengths are characteristic of complexes of CO₂ with different near-neighbor molecules that are encountered in other volatile mixtures such as with H₂O and CH₃OH, and non-volatile host materials like silicates, some clays, and zeolites. We suggest that Phoebe’s CO₂ is native to the body as part of the initial inventory of condensates and now exposed on the surface, while CO₂ on the other three satellites results at least in part from particle or UV irradiation of native H₂O plus a source of C, implantation or accretion from external sources, or redistribution of native CO₂ from the interior.The analysis presented here depends on an accurate VIMS wavelength scale. In preparation for this work, the baseline wavelength calibration for the Cassini VIMS was found to be distorted around 4.3 μm, apparently as a consequence of telluric CO₂ gas absorption in the pre-launch calibration. The effect can be reproduced by convolving a sequence of model detector response profiles with a deep atmospheric CO₂ absorption profile, producing distorted detector profile shapes and shifted central positions. In a laboratory blackbody spectrum used for radiance calibration, close examination of the CO₂ absorption profile shows a similar deviation from that expected from a model. These modeled effects appear to be sufficient to explain the distortion in the existing wavelength calibration now in use. A modification to the wavelength calibration for 13 adjacent bands is provided. The affected channels span about 0.2 μm centered on 4.28 μm. The maximum wavelength change is about 10 nm toward longer wavelength. This adjustment has implications for interpretation of some of the spectral features observed in the affected wavelength interval, such as from CO₂, as discussed in this paper.     

Late Miocene sedimentary architecture of the Ebro Continental Margin (Western Mediterranean): implications to the Messinian Salinity Crisis

The Messinian Salinity Crisis (MSC) resulted from a significant multi-phase drop and subsequent reflooding of the Mediterranean Sea from 5.96 to 5.33 Ma. Well-developed drainage networks, characterized by step-like profiles and abrasion platforms, are associated to this event. The Ebro Continental Margin (Western Mediterranean) presents an additional complexity since the capture of the drainage of the adjacent subaerial Ebro Basin took place sometime prior to the Messinian stage. Using 3D seismic reflection data, this work provides new insights into the origin of the step-like profile of the Messinian erosional surface (MES) and timing of the capture of the subaerial Ebro Basin. The results obtained indicate a sedimentary-active continental slope and delta progradation during Middle-Late Miocene, in a normal regressive context associated to a pre-Messinian proto-Ebro River. The mature development attained by the Messinian Ebro River network during the MSC corroborates that the capture of the Ebro Basin occurred prior to the MSC. The configuration of the clinoforms below the MES suggests that deltaic sediments of the Messinian Paleo-Ebro River deposited during the Tortonian and initial Messinian sea-level drawdown. The MES formed at the top of the Tortonian Highstand, where a fluvial network was deeply carved, and in the topset region of the Messinian Falling Stage Systems Tract, where minor erosion occurred. Fluvial deposits are outstandingly preserved on the main valleys of the MES. Therefore, the step-like profile of the MES was not created during Zanclean inundation, but during the latest stages of the main Messinian sea-level fall and lowstand.     

Observations on the crystal structures of lueshite

Laboratory powder XRD patterns of the perovskite-group mineral lueshite from the type locality (Lueshe, Kivu, DRC) and pure NaNbO₃ demonstrate that lueshite does not adopt the same space group (Pbma; #57) as the synthetic compound. The crystal structures of lueshite (2 samples) from Lueshe, Mont Saint-Hilaire (Quebec, Canada) and Sallanlatvi (Kola, Russia) have been determined by single-crystal CCD X-ray diffraction. These room temperature X-ray data for all single-crystal samples can be satisfactorily refined in the orthorhombic space group Pbnm (#62). Cell dimensions, atomic coordinates of the atoms, bond lengths and octahedron tilt angles are given for four crystals. Conventional neutron diffraction patterns for Lueshe lueshite recorded over the temperature range 11–1,000 K confirm that lueshite does not adopt space group Pbma within these temperatures. Neutron diffraction indicates no phase changes on cooling from room temperature to 11 K. None of these neutron diffraction data give satisfactorily refinements but suggest that this is the space group Pbnm. Time-of-flight neutron diffraction patterns for Lueshe lueshite recorded from room temperature to 700 °C demonstrate phase transitions above 550 °C from Cmcm through P4/mbm to \(Pm\overline{3} m\) above 650 °C. Cell dimensions and atomic coordinates of the atoms are given for the three high-temperature phases. The room temperature to 400 °C structures cannot be satisfactorily resolved, and it is suggested that the lueshite at room temperature consists of domains of pinned metastable phases with orthorhombic and/or monoclinic structures. However, the sequence of high-temperature phase transitions observed is similar to those determined for synthetic NaTaO₃, suggesting that the equilibrated room temperature structure of lueshite is orthorhombic Pbnm.     

210Pb dating of scottish lake sediments,afforestation and accelerated soil erosion

Changes in the rate of soil erosion in lake catchments can be identified from changes in the rate of sediment accumulation in lakes. Here we compare recently afforested sites with non-afforested sites in the Galloway area of Southwest Scotland. We show that lakes with non-afforested catchments have slow, constant sediment accumulation rates, whereas lakes with recently afforested catchments have changes in accumulation that parallel the known history of afforestation. For Loch Grannoch the sediment accumulation rate increases from 0.1 cm yr^?1 to over 2 cm yr^?2 during the disturbance period. Data from L. Skerrow, however, suggest that the rate might decline to predisturbance levels after approximately 10 years as the forest canopy closes and drainage channels stabilize.     

The evolution of the archaean crust of northeast Botswana

Some 1800 km² of Archaean terrain have been mapped (the Eastern Geotraverse of the Botswana Geological Survey, Geodynamics Project) including a part of the schist belt/granitic terrain of the Rhodesian Craton, and part of the Limpopo Mobile Belt in the south. The cratonic area includes the whole or part of four schist belts (greenstone belts) now referred to as ‘schist relics’ as they are shown to be mega-xenoliths surviving regional deformation and granitisation.The schist relics display a typical greenstone belt composition with basal ultra-mafic schist, extrusive meta-basalts, serpentinites, and meta-dacites, -andesites, -rhyolites and volcanoclastic rocks appearing up the succession. These are termed the Volcanic Group. They also contain marble, graphitic phyllite, meta-greywacke, banded ironstone and aluminous schist.The schist relics overlie thick sequences of granitised clastic sediments with intercalated volcanic and sedimentary layers which are regarded as an integral, lower part of the succession. The total sequence, including the Volcanic Group and underlying rocks is at least 30 km thick.The schist relics originally formed a more continuous and lithostratigraphically equivalent succession, which may have included some of the Rhodesian schist belts. Such a succession would be of the order of size of an island arc system in length and width.An early stage of regional folding (F1) is recognized, from preserved fabrics and structural analysis, which is tentatively proposed as nappe folding on a regional scale. This was accompanied by low-grade metamorphism. This first stage of deformation determined the regional pattern as it is still seen.Tonalite/monzonite plutons were emplaced within the Volcanic Group and probably protected the relics during regional granitisation.Regional granitisation, which isolated the schist relics, was accompanied by pyroxene hornfels metamorphism. This was followed by a regional, penetrative deformation (F2) with amphibolite facies (Barrovian type) metamorphism. This is the most prominent style of deformation which, although most intensely developed in the Limpopo Mobile Belt, is imposed throughout the whole area. The Limpopo Belt cuts across the area in the south as a large ductile shear zone and affects rocks largely similar to those of the craton, although anorthosites are not known outside it.The Limpopo Belt has its own style of deformation — interference folds, and several stages of folding related to transcurrent movement, and intense cataclasis.Metamorphism is similar throughout Limpopo Mobile Belt and Craton, each event being recognized in both domains and being of similar grades.In many respects the Botswana Eastern Geotraverse area resembles other Archaean terrains and analogies can be drawn. In attempting to find a geotectonic model into which it can be placed there is a considerable range of choices, and not enough constraints existing either within the imperfectly preserved geological record, nor within the expanding and elastic framework of Global tectonic theory.No direct evidence for subduction zones or plate boundaries has been found, nor is this surprising considering the subsequent history. On the other hand we see nothing in the rather detailed body of evidence that has been accumulated by mapping to preclude a place within Plate theory as outlined for the Phanerozoic. It allows a moderately uniformitarian interpretation rather than one supposing unique conditions preculiar to the Archaean, such as the concept of isolated volcanic depositaries, or of unique and peculiar crustal conditions.     

Viruses as potential regulators of regional brown tide blooms caused by the alga,Aureococcus anophagefferens

Blooms of the brown tide organismAureccoccus anophagefferens have recurred in the coastal bays in New Jersey since 1995 and in the coastal bays of Long Island since 1985. Intracellular viral-like particles (VLPs) were documented during 1999–2000 brown tide blooms in Little Egg Harbor, New Jersey, but it was not determined whether cells were infected during the termination of the bloom. The objective of this study was to determine if VLPs infected and lysed natural populations ofA. anophagefferens in coastal bays of New Jersey and New York in 2002 with the same frequency as in 1999–2000 and especially at the termination of the bloom. Our results confirmed that the highest percentage (37.5%) of VLP-infected cells occurred at the termination of the brown tide bloom in New Jersey in 2002. Intracellular VLPs were present throughout the bloom event. The percentage of visibly infected cells was higher at the beginning of the bloom than during the peak of the bloom. The intracellular VLPs in natural populations ofA. anophagefferens were consistent in size and shape (approximately 140 nm in diameter) and comparable to those in previous studies. Concentrated viral isolates, prepared from waters during brown tide blooms in New York and New Jersey in 2002, infected healthy laboratoryA. anophagefferens cultures in vitro. The viral isolates associated with the highest laboratory viral activity (lysis positive) were concentrated from water samples having the highest viral and bacteria concentrations. The intracellular viruses in these virally infected laboratory cultures ofA. anophagefferens were similar in size and shape to those found in natural populations. The successful isolation of a virus specific toA. anophagefferens from a brown tide bloom in the field, the similarity of ultrastructure of VLPs infecting both natural populations and laboratory infected cultures, and the pattern of VLP infection during bloom activity in combination with the observed high percentage of VLP-infected cells during bloom termination, supports, the hypothesis that viruses may be a major source of mortality for brown tide blooms in regional coastal bays of New Jersey and New York.