A discussion of JEBAR/pycnobathic forcing

Recently a number of authors have analysed the importance of along-isobath density gradients in the vorticity balance governing flows along the continental shelf and slope. The interaction between density gradients and bathymetry has been termed JEBAR (Joint Effect of Baroclinicity and Relief). A recent formulation of these baroclinicity-bathymetry interactions has shown that the pycnobathic term, involving the Jacobian of the bottom density and the depth, can be a source of vorticity. This paper examines the divergence of opinion regarding the importance of pycnobathic forcing.Using a simple expansion of the JEBAR term we show that no JEBAR-type forcing arises when the flow field is geostrophic. We follow this up by allowing small deviations from geostrophy, a quasigeostrophic treatment. We find that when small slope dynamics are employed then a closed problem can be formulated without inclusion of a pycnobathic forcing term. If the dynamics are to apply to regimes characterized by strong bathymetry then the pycnobathic term must enter the formulation.     

A re-examination of the evidence for a plio-pleistocene marine transgression on the Chiltern hills. I. structures and surfaces

Borehole and surface outcrop data are used to construct sub-Chalk, sub-Upper Chalk and sub-Tertiary contour maps for the Chiltern area. The results show a southwest-northeast monocline, which coincides with the change of slope at the lower boundary of the morphological bench on the Chalk dipslope that Wooldridge and Linton attributed to Plio-Pleistocene marine erosion. Younger northwest-southeast synclines coincide with the main transverse river valleys of the Chilterns. The monoclinal flexuring casts doubt on the value of the bench as evidence for a Plio-Pleistocene transgression.     

Semi-variograms for modelling the spatial pattern of landform and soil properties

Many geomorphic properties can be treated as spatially-dependent random variables. Some are second-order stationary, others appear to vary without bound. In these circumstances their variation is best described by the semi-variogram. In most instances the semi-variogram can be modelled by a simple mathematical function, which itself is bounded for a stationary variable and unbounded otherwise. The function must be conditional negative semi-definite to be permissible. More complex variation can be represented by combining two or more permissible models. Sample semi-variograms of several landform and soil properties illustrate the common types of semi-variogram. Their form and parameters are interpreted in physical terms.     

The influence of climate, geomorphology and primary geology on the supergene migration of gold and silver

Redistribution of secondary gold and silver through the weathering profile is dependent on the nature and stability of anionic complexes present in fluids of the oxidized zone. Through their effect on groundwater composition, and profile development, external controls such as climate and geomorphology, as well as regional and ore geology, may influence the form and concentration of complexes and hence the mobility of gold and silver during secondary processes. Secondary gold and silver in the supergene zone of the Edna May gold mine at Westonia in Western Australia, and at the Upper Ridges mine near Wau, in Papua New Guinea, have been transported under contrasting chemical and physical conditions occurring in the extreme climate and topography of these regions. Consequent differences in the nature of secondary gold and silver enrichments have been noted. At Westonia secondary gold reprecipitated by reduction at the site of iron oxidation, is of higher fineness (lower silver content) than primary gold, due to the formation of soluble AgCl⁰, and AgCl₂⁻ complexes. Gold migrates as the chloride complex AuCl₄⁻, in the acid, saline groundwaters present in the near-surface iron-rich laterite profile.At the Upper Ridges mine, repeated “flushing” by heavy rainfall in a region of rugged relief, dilutes groundwater and prohibits anion concentration and/or the development of acid conditions on a regional scale. Under neutral to basic, moderately oxidizing conditions, found in the vicinity of the weathering carbonate veins, gold and silver may be complexed by thiosulphate, to form Au(S₂O₃)³⁻₂ and Ag(S₂O₃)³⁻₂ or a mixed complex. Secondary gold-silver alloy is reprecipitated by oxidation in the MnO₂ wad assemblage. Gold of low fineness (high silver content) is reprecipitated by reduction at the water table, as both gold and silver complexes destabilize under similar pH and Eh conditions. The identification of secondary enriched gold horizons, relative to primary ore, has important repercussions for the potential viability of a drilled deposit.     

Enclosure of the urban commons

This is an essay about the territorial enclosure of urban neighbourhoods. It develops the argument that the shared public realms that became regarded as normal in the cities of the 20th century are inherently unstable. More particularly, they are an unstable form of co-ownership domain (condominium). In many different cultures and economies new forms of local territorial governance are emerging to make joint consumption more sustainable. Most of the essay is devoted to exploring this evolutionary argument and is theoretically oriented and illustrated with historical examples. We end with illustrations of urban enclosure from China, a country that has had to discover almost overnight new forms of organisational, institutional and spatial order.     

3D joint inversion of Gradient and Mise-à-la-Masse borehole IP/Resistivity data and its application to magmatic sulfide mineral deposit exploration

Gradient and Mise-à-la-Masse IP/Resistivity surveys were conducted on a group of 19 boreholes in Eagle’s Nest, Eagle One magmatic sulfide deposit in northern Ontario, Canada. The surveys were conducted as a follow-up to the many drilled boreholes, some of which missed the target. The surveys were intended to map the distribution of the ore mineralization, outline the deposit hosted by mafic and ultramafic rocks and then guide the drilling of new boreholes. Joint Gradient and Mise-à-la-Masse data inversion produced 3D chargeability and conductivity models. The inverted 3D models in turn help delineate the outline of the mineralized zone, and determine the shape, size, strength and economic viability of the deposit. The Gradient array determined the direction of the mineralization with respect to the boreholes, and the Mise-à-la-Masse array examined the highly conductive subsurface bodies and their surroundings. The mapped ore zone shows close similarity to the 0.5 Cu% and 1.05 Ni% iso-surfaces that are produced from core assay result confirming the reliability of the results obtained in this study.     

Estimated calving interval for the New Zealand southern right whale (Eubalaena australis)

Southern right whales (Eubalaena australis) were widespread in New Zealand waters before commercial whaling in the nineteenth century caused drastic declines in their abundance and distribution. Following the cessation of whaling, the population has been recovering and is now slowly recolonising its former range. Estimates of population demographics, including reproductive output, are essential for predicting the trajectory of this population. We gathered photo-identification data on female southern right whales during annual field trips to the Auckland Islands, the principal calving area in New Zealand waters. Forty-five calving intervals were observed between 2006 and 2013 (mean interval?=?3.31 years, 95% CI?=?3.06–3.57). Incorporating the effects of possible missed calving events produced a plausible range of mean calving intervals from 3.17 to 3.31 years. Our results suggest that the calving interval of New Zealand southern right whales is similar to that found in populations elsewhere.     

Asian summer monsoon prediction in ECMWF System 4 and NCEP CFSv2 retrospective seasonal forecasts

The seasonal prediction skill of the Asian summer monsoon is assessed using retrospective predictions (1982–2009) from the ECMWF System 4 (SYS4) and NCEP CFS version 2 (CFSv2) seasonal prediction systems. In both SYS4 and CFSv2, a cold bias of sea-surface temperature (SST) is found over the equatorial Pacific, North Atlantic, Indian Oceans and over a broad region in the Southern Hemisphere relative to observations. In contrast, a warm bias is found over the northern part of North Pacific and North Atlantic. Excessive precipitation is found along the ITCZ, equatorial Atlantic, equatorial Indian Ocean and the maritime continent. The southwest monsoon flow and the Somali Jet are stronger in SYS4, while the south-easterly trade winds over the tropical Indian Ocean, the Somali Jet and the subtropical northwestern Pacific high are weaker in CFSv2 relative to the reanalysis. In both systems, the prediction of SST, precipitation and low-level zonal wind has greatest skill in the tropical belt, especially over the central and eastern Pacific where the influence of El Nino-Southern Oscillation (ENSO) is dominant. Both modeling systems capture the global monsoon and the large-scale monsoon wind variability well, while at the same time performing poorly in simulating monsoon precipitation. The Asian monsoon prediction skill increases with the ENSO amplitude, although the models simulate an overly strong impact of ENSO on the monsoon. Overall, the monsoon predictive skill is lower than the ENSO skill in both modeling systems but both systems show greater predictive skill compared to persistence.     

The large-scale context for the TOGA Coupled Ocean-Atmosphere Response Experiment

Summary The TOGA Coupled Ocean-Atmosphere Response Experiment (COARE) concentrated a variety of observational systems in the warm pool of the western equatorial Pacific for an Intensive Observation Period (IOP) November 1992 through February 1993. In this paper, aspects of the largescale variations of the tropical atmosphere and Pacific Ocean surrounding the observations of air-sea interaction in the Intensive Flux Array (IFA) during the IOP are described, with the objective of providing a context for the future analyses of these observations.The evolution of the 1991–1992 El Niño/Southern Oscillation event was unusual: Warm SST anomalies in the equatorial cold tongue region switched to colder than climatology in the last half of 1992, but waters warmer than 30°C remained displaced eastward just west of the dateline, coninuing to fuel anomalous convection there during the IOP. Fortunately, SST in the IFA remained warmer than 29°C during most of the IOP, and convective activity was observed over the IFA. The Southern Oscillation Index, which had relaxed to near zero prior to the experiment, decreased during the IOP, reflecting sea level presure changes associated with renewed westerly wind activity. In response to these westerly wind events, the warm pool migrated back into the central equatorial Pacific, leading to a reintensification of the ENSO warm SST anomalies east of the dateline.With 10 Figures