Multi-factor impact analysis of agricultural production in Bangladesh with climate change

Diverse vulnerabilities of Bangladesh's agricultural sector in 16 sub-regions are assessed using experiments designed to investigate climate impact factors in isolation and in combination. Climate information from a suite of global climate models (GCMs) is used to drive models assessing the agricultural impact of changes in temperature, precipitation, carbon dioxide concentrations, river floods, and sea level rise for the 2040–2069 period in comparison to a historical baseline. Using the multi-factor impacts analysis framework developed in Yu et al. (2010), this study provides new sub-regional vulnerability analyses and quantifies key uncertainties in climate and production. Rice (aman, boro, and aus seasons) and wheat production are simulated in each sub-region using the biophysical Crop Environment REsource Synthesis (CERES) models. These simulations are then combined with the MIKE BASIN hydrologic model for river floods in the Ganges-Brahmaputra-Meghna (GBM) Basins, and the MIKE21 Two-Dimensional Estuary Model to determine coastal inundation under conditions of higher mean sea level. The impacts of each factor depend on GCM configurations, emissions pathways, sub-regions, and particular seasons and crops. Temperature increases generally reduce production across all scenarios. Precipitation changes can have either a positive or a negative impact, with a high degree of uncertainty across GCMs. Carbon dioxide impacts on crop production are positive and depend on the emissions pathway. Increasing river flood areas reduce production in affected sub-regions. Precipitation uncertainties from different GCMs and emissions scenarios are reduced when integrated across the large GBM Basins’ hydrology. Agriculture in Southern Bangladesh is severely affected by sea level rise even when cyclonic surges are not fully considered, with impacts increasing under the higher emissions scenario.     

Monitoring of heat transmission from buildings into geological environment and evaluation of soil deformation consequences in foundation engineering

In engineering geology a number of factors affecting foundation conditions are taken into consideration during engineering-geological investigations. This article deals with the factor of heat sourced from a structure (brick kiln) as a restrictive factor in foundation engineering in clay soils and introduces a documentation of soil deformation observations as an impact of the heat transmission into the geological environment. It was carried out in Southern Moravia in the Czech Republic, where the dominant foundation soils are Neogeneous clays where differential settlements of a tunnel kiln structure occurred as a result of ignoring the boundary conditions of temperature changes in the soil environment. The brick kilns caused heterogeneous spatial changes in the subsoil temperatures. This consequently resulted in differential settlements due to temperature changes originating from the kilns. The differential settlements reached as much as 150 mm. The major objective of the article is to highlight the importance of the heat transmission from buildings into the geological environment as a factor which should be considered in engineering geology and its application in planning. A new procedure for reducing or elimination of ground movements sourced from underlying clayey soils depending on the heat changes was also suggested in this context.     

Oceanography of Glacier Bay,Alaska: Implications for biological patterns in a glacial fjord estuary

Alaska, U.S.A, is one of the few remaining locations in the world that has fjords that contain temperate idewater glaciers. Studying such estuarine systems provides vital information on how deglaciation affects oceanographic onditions of fjords and surrounding coastal waters. The oceanographic system of Glacier Bay, Alaska, is of particular interest ue to the rapid deglaciation of the Bay and the resulting changes in the estuarine environment, the relatively high oncentrations of marine mammals, seabirds, fishes, and invertebrates, and the Bay’s status as a national park, where ommercial fisheries are being phased out. We describe the first comprehensive broad-scale analysis of physical and iological oceanographic conditions within Glacier Bay based on CTD measurements at 24 stations from 1993 to 2002. easonal patterns of near-surface salinity, temperature, stratification, turbidity, and euphotic depth suggest that freshwater nput was highest in summer, emphasizing the critical role of glacier and snowmelt to this system. Strong and persistent tratification of surface waters driven by freshwater input occurred from spring through fall. After accounting for seasonal nd spatial variation, several of the external physical factors (i.e., air temperature, precipitation, day length) explained a large mount of variation in the physical properties of the surface waters. Spatial patterns of phytoplankton biomass varied hroughout the year and were related to stratification levels, euphotic depth, and day length. We observed hydrographic atterns indicative of strong competing forces influencing water column stability within Glacier Bay: high levels of freshwater ischarge promoted stratification in the upper fjord, while strong tidal currents over the Bay’s shallow entrance sill enhanced ertical mixing. Where these two processes met in the central deep basins there were optimal conditions of intermediate tratification, higher light levels, and potential nutrient renewal. These conditions were associated with high and sustained hlorophylla levels observed from spring through fall in these zones of the Bay and provide a framework for understanding he abundance patterns of higher trophic levels within this estuarine system.     

High levels of site fidelity in movement patterns of Southern Rock Lobster (Jasus edwardsii) in Victoria,Australia

ABSTRACT

Movement patterns of the Southern Rock Lobster Jasus edwardsii in Victoria, Australia were investigated from 8,533 tag-recapture events across a 20-year period (1992–2012). In total, 83% of lobsters were recaptured within 1?km of their tagging site and 93% within 5?km. While largely resident, elevated movements were observed within specific regions, with the overall direction of movement being from inshore to offshore areas. Movement was not impacted by lobster sex, size, or reproductive stage. The fishery for Southern Rock Lobster within Victoria is currently managed into two zones with separate total allowable commercial catches in each area. Given the high levels of site fidelity, our findings suggest that management of the resource at this spatial scale is appropriate and that consideration of significant movement between zones is not warranted in fishery stock assessment models.     

Climatic and structural controls on Late-glacial and Holocene rockfall occurrence in high-elevated rock walls of the Mont Blanc massif (Western Alps)

In the Mont Blanc massif (European Western Alps), rockfalls are one of the main natural hazards for alpinists and infrastructure. Rockfall activity after the Little Ice Age is well documented. An increase in frequency during the last three decades is related to permafrost degradation caused by rising air temperatures. In order to understand whether climate exerts a long-term control on rockfall occurrence, a selection of paleo-rockfall scars was dated in the Glacier du Géant basin [>3200 m above sea level (a.s.l.)] using terrestrial cosmogenic nuclides. Rockfall occurrence was compared to different climatic and glacial proxies. This study presents 55 new samples (including replicates) and 25 previously-published ages from nine sampling sites. In total, 62 dated rockfall events display ages ranging from 0.03 ± 0.02 ka to 88.40 ± 7.60 ka. Holocene ages and their uncertainties were used to perform a Kernel density function into a continuous dataset displaying rockfall probability per 100 years. Results highlight four Holocene periods of enhanced rockfall occurrence: (i) c. 7–5.7 ka, related to the Holocene Warm Periods; (ii) c. 4.5–4 ka, related to the Sub-boreal Warm Period; (iii) c. 2.3–1.6 ka, related to the Roman Warm Period; and (iv) c. 0.9–0.3 ka, related to the Medieval Warm Period and beginning of the Little Ice Age. Laser and photogrammetric three-dimensional (3D) models of the rock walls were produced to reconstruct the detached volumes from the best-preserved rockfall scars (≤0.91 ± 0.12 ka). A structural study was carried out at the scale of the Glacier du Géant basin using aerial photographs, and at the scale of four selected rock walls using the 3D models. Two main vertical and one horizontal fracture sets were identified. They correspond respectively to alpine shear zones and veins opened-up during long-term exhumation of the Mont Blanc massif. Our study confirms that climate primarily controls rockfall occurrence, and that structural settings, coincident at both the massif and the rock wall scales, control the rock-wall shapes as well as the geometry and volume of the rockfall events. © 2020 John Wiley & Sons, Ltd.     

Velocity predictions for shoaling and breaking waves with a Boussinesq-type model

In this paper, the performance of a 1-D Boussinesq model is evaluated against laboratory data for its ability to predict surf zone velocity moments. Wave evolution over a plane beach and a complex bathymetry both extending into the surf-zone is examined for six cases. For the plane beach, these comprise two cases, a spilling and a plunging cnoidal wave. For the complex bathymetry, these comprise four cases of longer and short wavelengths (spilling and plunging breakers), with regular and irregular periodicity. The model evaluation places emphasis on parameters of the wave field that could be used for the prediction of sediment transport; orbital velocity, undertow, velocity skewness, kurtosis and asymmetry. It is found that, despite an overestimation of the depth-averaged horizontal velocity in the regular waves cases, the predicted higher order velocity moments and undertow are in good agreement with the laboratory data. A bispectral analysis demonstrates that the nonlinear transfers of energy amongst the low order harmonics are well reproduced, but energy exchanges with the higher harmonics are less well predicted. As a result, the model handles velocity moments better in the shorter wave tests than in the long wave cases where triad interactions are stronger. Of the four parameters describing wave breaking, the model behaviour is most sensitive to the critical wave front slope φ_B, especially with regard to velocity skewness and kurtosis predictions. It is also found that increasing the thickness of the surface roller for the case of plunging breakers improves the model's performance.     

Sedimentological criteria to differentiate submarine channel levee subenvironments: Exhumed examples from the Rosario Fm. (Upper Cretaceous) of Baja California, Mexico, and the Fort Brown Fm. (Permian), Karoo Basin, S. Africa

Two scales of levee confinement are commonly recognised from submarine channel-levee systems on the seafloor and in the subsurface. Large-scale external levees bound the entire system whilst smaller-scale internal levees bound individual thalweg channels within the channel-belt. Although thin beds are commonly identified in core and well logs, their origin, and consequently their stratigraphic significance is currently poorly understood. This knowledge gap stems, in part, from the lack of unambiguously identified outcrop analogues of channel-levees, and in particular the lack of identifiable internal and external levees. Here we report from two exhumed channel-levee systems where both scales of confinement can be recognised: the Rosario Fm. of Baja California, and the Fort Brown Fm. of South Africa. A suite of characteristic sedimentary features are recognised from internal and external levees respectively: internal levees are characterised by structures indicative of complexity in the waxing-waning style of overspill, interactions with topography and flow magnitude variability; in contrast, external levees are characterised by structures indicative of simple surge-like waning flows, relatively uniform flow directions, laterally extensive beds, and a lack of erosive events. Using these observations, together with published literature, we propose a simple nomenclatural scheme for levee sub-environments, and criteria to differentiate between levee sub-environments in core or outcrop.     

Coral extension rates in the NW Indian Ocean II: reconstruction of 20th century Indian monsoon strength and rainfall over India

To date, coral proxy studies have proved largely unsuccessful in reconstructing temporal variability of the Indian monsoon system in the NW Indian Ocean. In a recent publication in this journal, Storz and Gischler demonstrated that extension rates in corals can be used to fill this gap. Those authors found a link between decadal and interannual variations of the SW monsoon current velocities and Porites lutea extension rates in the lagoon of Rasdhoo Atoll (4°N/73°W) in the central Maldives for the period 1917–2007. This sister paper shows that this extension-rate record can be used to reconstruct decadal variations of summer monsoon rainfall over peninsular India and adjacent areas. The amount of monsoon rainfall and current velocities during summer are both affected by the strength of the Indian monsoon system. Assessments of coral extension rates and the mean May–September All India Monsoon Rainfall index, a measure of monsoon strength over the Indian subcontinent, revealed a significant spectral coherence within periods of 18–19 and 6–7 years. Almost 92% of variance is shared between both time series in the former band, and 85% in the latter. A correlation between the 5-year running mean extension rate and rainfall records from the Western Ghats (grid of 73–76°E/13–15°N) is significant especially for 1958–2006 (r = −0.82, p < 0.05). These findings imply that coral growth characteristics can serve as a new marine archive to reconstruct past variations of the Indian monsoon system on interannual to decadal timescales.     

Late Quaternary history of contourite drifts and variations in Labrador Current flow,Flemish Pass,offshore eastern Canada

Contourite drifts of alternating sand and mud, shaped by the Labrador Current, formed during the late Quaternary in Flemish Pass seaward of the Grand Banks of Newfoundland, Canada. The drifts preserve a record of Labrador Current flow variations through the last glacial maximum. A high-resolution seismic profile and a transect of four cores were collected across Beothuk drift on the southeast side of Flemish Pass. Downcore and lateral trends in grain size and sedimentation rate provide evidence that, between 16 and 13 ka, sediment was partitioned across Beothuk drift and the adjacent Flemish Pass floor by a strong current flow but, from 29 to 16 ka, sedimentation was more of a blanketing style, represented by draped reflections interpreted as being due to a weaker current. The data poorly resolve the low sedimentation rates since 13 ka, but the modern Labrador Current in Flemish Pass is the strongest it has been in at least the past 29 ka. Pre-29 ka current flow is interpreted based on reflection architecture in seismic profiles. A prominent drift on the southwestern side of Flemish Pass formed above a mid-Miocene erosion surface, but was buried by a mass-transport deposit after the penultimate glacial maximum and after drift deposition switched to eastern Flemish Pass. These findings illustrate the temporal complexity of drift sedimentation and provide the first detailed proxy for Labrador Current flow since the last glacial maximum.     

Cadmium accumulation by the blue crab, callinectes sapidus: Involvement of hemocyanin and characterization of cadmium-binding proteins

The accumulation of cadmium from seawater by the blue crab, Callinectes sapidus, was studied as a function of metal concentration and exposure time, with special emphasis on cadmium-binding proteins. Cadmium was found, in decreasing order of magnitude, in gills, digestive gland and hemolymph. When exposed to 0·5 ppm cadmium for 2–24h, virtually all of the cadmium in the cytosolic fraction of the gill was associated with a low molecular weight (LMW) cadmium-binding protein (MW 8000). However, after 48h of exposure only 50% of the cadmium in the cytosol was bound to this protein. The rest wasfound to be associated with proteins of a molecular weight of 300 000 and 60 000. This pattern of cadmium distribution did not change over a 12-day depuration period. Similar results were obtained upon exposure to 0·1 ppm cadmium. The pattern of cadmium accumulation in the cytosolic fraction of the digestive gland was in marked contrast to that observed for the gill. Initially, the cadmium was distributed over three low molecular weight fractions. During depuration the distribution of cadmium changed and all of the metal became bound to a low molecular weight protein (MW 9000). The cadmium concentrations in the gill and digestive gland remained essentially constant during depuration (12 days). The LMW cadmium-binding proteins were purified by a combination of gelpermeation and ion-exchange chromatography. Their molecular weight, spectral properties and amino acid composition are characteristic of the vertebrate metallothioneins. During exposure to cadmium the metal rapidly appeared in the hemolymph, mainly associated with hemocyanin. During depuration cadmium was transferred from the hemolymph to the digestive gland, demonstrating that hemocyanin acts as a carrier in trace metal transport.