Modelling sensible and latent heat fluxes over sea during unstable,very close to neutral conditions

During slightly unstable but still very close to neutral conditions new results from two previous investigations have shown a significant increase of sensible and latent heat fluxes over the sea. The vertical heat transport during these conditions is dominated by detached eddies originating at the top of the boundary layer, bringing relatively cold and dry air to the surface. This effect can be described in numerical models by either enhanced heat transfer coefficients for sensible and latent heat (Stanton and Dalton numbers respectively) or with an additional roughness length, added to the original roughness lengths for heat and humidity. Such new expressions are developed using turbulence measurements from the Baltic Sea valid for wind speeds up to 14 m s⁻¹. The effect of including the increased heat fluxes is investigated using two different numerical models: a regional three-dimensional climate model covering northern Europe, and a process-oriented ocean model for the Baltic Sea. During periods of several days, the latent heat flux can be increased by as much as 100 W m⁻². The increase in sensible heat flux is significantly smaller since the process is only of importance in the very near-neutral regime where the sensible heat flux is very small. The long-term average effect over the Baltic Sea is of the order of several W m⁻².     

Large-Eddy Simulations of Surface Heterogeneity Effects on the Convective Boundary Layer During the LITFASS-2003 Experiment

We investigate the impact of observed surface heterogeneities during the LITFASS-2003 experiment on the convective boundary layer (CBL). Large-eddy simulations (LES), driven by observed near-surface sensible and latent heat fluxes, were performed for the diurnal cycle and compare well with observations. As in former studies of idealized one- and two-dimensional heterogeneities, secondary circulations developed that are superimposed on the turbulent field and that partly take over the vertical transport of heat and moisture. The secondary circulation patterns vary between local and roll-like structures, depending on the background wind conditions. For higher background wind speeds, the flow feels an effective surface heat-flux pattern that derives from the original pattern by streamwise averaging. This effective pattern generates a roll-like secondary circulation with roll axes along the mean boundary-layer wind direction. Mainly the upstream surface conditions control the secondary circulation pattern, where the fetch increases with increasing background wind speed. Unlike the entrainment flux that appears to be slightly decreased compared to the homogeneously-heated CBL, the vertical flux of sensible heat appears not to be modified in the mixed layer, while the vertical flux of latent heat shows different responses to secondary circulations. The study illustrates that sufficient time averaging and ensemble averaging is required to separate the heterogeneity-induced signals from the raw LES turbulence data. This might be an important reason why experiments over heterogeneous terrain in the past did not give any clear evidence of heterogeneity-induced effects.     

Effect of an oil spill in Spitzbergen in 1978

The oil content in the sediment and the marine life along the arctic shores of Van Mijenfjord, Spitzbergen, were investigated about two years after a spill from diesel storage tanks. High values of oil were recorded in the sediment along the shore near the tanks. The shore fauna is generally poor in these areas and the only biological effect detected was the disappearance of the amphipod Gammarus setosus from the surface layers.     

Interactive learning and localised knowledge in globalising learning economies

This article analyses the role of interactive learning and localised knowledge in globalising learning economies. Some authors argue that as a result of globalisation and codification processes the importance of local, contextual knowledge and localised learning is decreasing, and, thus, the competitive advantage of high-cost regions (and nations) are steadily being undermined. Other authors maintain that much strategic knowledge, tacit as well as codified, is disembodied (i.e., knowledge which is the result of positive externalities of the innovation process), and, thus, remains `sticky'. Important parts of the learning process continue to be localised as a result of the enabling role of geographical and social proximity in stimulating interactive learning, which taken together represent strong `untraded interdependencies' constituting important context conditions for regions to remain innovative and competitive. The article argues that learning economies should be used to conceptualise a specific historical period of capitalism in which knowledge and learning has attained an increasing importance in the economy. This period of capitalist development is also referred to as post-Fordism.     

Setting sediment quality guidelines: a simple yet effective method

Deriving sediment quality guidelines (SQGs) for marine sediments is a difficult task. It will often be a trade off between reproducibility and relevance. One of the fundamental questions in ecotoxicology is to decide what one should measure to detect response in ecosystems exposed to human disturbance. In this paper we use field data to estimate threshold levels eliciting effects on soft bottom macrobenthos collected at different sediment types and depths on the Norwegian Continental Shelf and test these against natural levels occurring levels in reference conditions. SQGs are presented from multivariate analyses based on 121 gradients (represented with Ba, THC, Cd, Cu, Pb and Zn) incorporating more than 2000 species. Clear clusters with slightly disturbed communities related to contamination loadings were evident in 35% of the gradients. We found large variations in naturally occurring contamination concentrations and in the threshold levels electing effects on the fauna at different sediment types and depths. For example, an increase in depth of only 100 m can triple the Cu and Zn concentrations that elicit effects. Lowest background and threshold levels were found in shallow, sandy sediment. Our results suggest that current SQGs are too high. We hypothesised that setting a SQG of 4-times background concentrations will give sufficient protection for the fauna from metal contamination. The overall background concentration eliciting effects on metal was 3.6x.     

Spatial and temporal variation in particle size and particulate organic matter content in suspended particulate matter from peatland‐dominated catchments in Finland

Properties of suspended particulate matter play a vital role in transport processes, but information from boreal lowland river systems with high organic loads is limited. This study analysed data from 2 years of sampling at 30 locations in Finland (204 samples in total) using suspended particulate matter samplers to determine effective and absolute particle size and organic fractions. Mean d₅₀ value was 22 and 49 µm for absolute and effective particle size, respectively. The organic fraction content ranged from 2.1% to 36% (mean 9.6%), highlighting the importance of particle organic matter for suspended particulate matter flux in the region. The results indicated that the suspended particulate matter particle size distribution and load in the study region is dominated by composite particles. There were considerable spatial and temporal variations in transport of organic fractions, effective particle size and degree of aggregation (range 1.5–93%). Headwaters and, in particular, late summer and spring flood conditions with flow peaks produced the largest composite particles, whereas agriculture‐dominated sites produced smaller but more tightly compacted particles. Organic plant fibres appeared to play a vital role in floc formation in peat‐covered catchments, whereas in agriculture‐dominated catchments, land use‐derived aggregates dominated the composition. This study provides empirical evidence of the importance of effective particle size measurement in understanding the dynamics of suspended particulate matters in boreal lowland river systems. Copyright © 2014 John Wiley & Sons, Ltd.     

Hengill,a high temperature thermal area in Iceland

The results of geological, geochemical and isotopic investigations in the Hengill thermal area in Iceland are presented. This area may be regarded as typical of the Icelandic high temperature areas. The Hengill area is mainly built up of pillow lavas and hyaloclastites, which were piled up in subglacial eruptions. Its western half is traversed by a very active NE-SW trending fault zone about 5 km broad, within which are several eruptive fissures of postglacial age. The volcanic rocks are basalts of various kinds, but minor occurrences of intermediate and rhyolitic rocks are also found. Solfataras and fumaroles occur mainly at higher altitude. Within the fault zone they have a linear distribution along faults. Hot water springs are found in the lowlands on the southern border of the thermal area. The concentrations of chlorine, tritium and deuterium in the water indicate that the hot springs on the lowland are fed by a deep lying aquifer which receives water from a recharge area situated in the western branch of the active volcanic zone upto 70 km to the northeast. The hot springs at higher altitude are the outlets of a secondary circulation system fed by local rain water. This water derives its heat partly from the heat content of the rocks penetrated and partly by steam and gas boiled off from the deeper lying aquifer. Preliminary results from other high temperature areas in Iceland indicate the presence of similar hydrological systems.     

Effects of waterlogging,salinity and light on the productivity of Bruguiera gymnorrhiza and Heritiera littoralis seedlings

This study aimed to establish the effects of waterlogging, salinity and light on the early development of mangroves. Seedlings of Bruguiera gymnorrhiza (L.) Lamk. and Heritiera littoralis Dryand were exposed to 12 weeks of waterlogging, during which time growth and photosynthesis were measured every two weeks. The salinity of the water inundation ranged from fresh water to full-strength sea water (salinity 35). Seedlings were exposed to either full sunlight of 1 500 µmol photon m^–2 s^–1 (SD 397) at midday or shade conditions of 325 µmol photon m^–2 s^–1 (SD 40) of light at midday, to explore whether the plants would be differently affected by prolonged waterlogging in increased salinities and under different light conditions. Heritiera littoralis was more sensitive to waterlogging, salinity and light, displaying a least relative growth rate of 0.127 g g^–1 week^–1 (SE 0.032) under shade, and 0.025 g g^–1 week^–1 (SE 0.021) in full light; while under shade, photosynthesis continued only in fresh water, but photosynthetic yield decreased from 0.7 to 0.4 with increasing duration of waterlogging. By 12 weeks, all H. littoralis seedlings treated with any saltwater mixture had died. Bruguiera gymnorrhiza seedlings maintained a moderate rate of photosynthesis throughout inundation in both shade and full light, with yields of 0.7 and 0.3, respectively. Furthermore, B. gymnorrhiza survived waterlogging in up to 66% seawater, and maintained comparable relative growth rates of 0.164 g g^–1 week^–1 (SE 0.066) with 0.083 g g^–1 week^–1 (SE 0.065) and 0.074 g g^–1 week^–1 (SE 0.036) with 0.052 g g^–1 week^–1 (SE 0.037) under shade and in full light between fresh water and the highest salinity conditions, respectively. These results suggest that B. gymnorrhiza is broadly tolerant, making it a potential candidate species for restoring vulnerable mangrove forests.     

Adaptive isogeometric finite element analysis of steady‐state groundwater flow

Numerical challenges occur in the simulation of groundwater flow problems because of complex boundary conditions, varying material properties, presence of sources or sinks in the flow domain, or a combination of these. In this paper, we apply adaptive isogeometric finite element analysis using locally refined (LR) B‐splines to address these types of problems. The fundamentals behind isogeometric analysis and LR B‐splines are briefly presented. Galerkin's method is applied to the standard weak formulation of the governing equation to derive the linear system of equations. A posteriori error estimates are calculated to identify which B‐splines should be locally refined. The error estimates are calculated based on recovery of the L₂‐projected solution. The adaptive analysis method is first illustrated by performing simulation of benchmark problems with analytical solutions. Numerical applications to two‐dimensional groundwater flow problems are then presented. The problems studied are flow around an impervious corner, flow around a cutoff wall, and flow in a heterogeneous medium. The convergence rates obtained with adaptive analysis using local refinement were, in general, observed to be of optimal order in contrast to simulations with uniform refinement. Copyright © 2015 John Wiley & Sons, Ltd.