Interaction between local tectonics and glacial unloading on the Pacific margin of Canada

Variations in Late Quaternary coastal deformation along the Pacific margin of Canada reflect not only differences in glacial history, but also local non-glacial tectonics. A forebulge developed to the north in the Queen Charlotte Basin (QCB) from 13.2 until after 9.7 ka BP resulting in exposure of the currently submerged shelf; whereas similar exposure was not evident to the south in the Georgia Basin. A semi-quantitative effective elastic lithosphere thickness of between 10 and 20 km is estimated for the QCB. We propose that this warm, relatively thin lithosphere combined with tectonic movement influenced crustal displacement, particularly the decoupling of the North American plate along the Queen Charlotte (QC) Fault, which may have allowed the QCB to behave like a hinge in response to glacial unloading. This would explain large magnitude crustal tilting (2.1 m km⁻¹) observed adjacent to the QC Fault. The 50 m of depression observed in the early- and mid-Holocene may imply that the western edge of the North America Plate ‘flexed’ down below present elevation, producing a second wave of response to ice loading and unloading.     

Ethics and intentional climate change

In recent years the idea of geoengineering climate has begun to attract increasing attention. Although there was some discussion of manipulating regional climates throughout the 1970s and 1980s, the discussion was largely dormant. What has reawakened the conversation is the possibility that Earth may be undergoing a greenhouse-induced global warming, and the paucity of serious measures that have been taken to prevent it.In this paper I assess the ethical acceptability of ICC, based on my impressions of the conversation that is now taking place. Rather than offering a dispassionate analysis, I argue for a point of view. I propose a set of conditions that must be satisfied for an ICC project to be morally permissible and conclude that these conditions are not now satisfied. However, research on ICC should go forward so long as certain other conditions are met. I do not intend this to be the last word on the subject, but rather the first word. My hope is that others will be stimulated to think through the ethics of ICC.     

Features of the atmospheric cycle of aerosol trace elements and sulphur dioxide revealed by baseline observations in Canada

Selected applications of baseline aerosol, SO₂ and deposition chemistry observations in Canada are reviewed to illustrate how new insight can be gained into features of the atmospheric pathway of trace substances such as sources, transformation and removal. A strong annual variation in Arctic aerosol concentration is a manifestation of particle residence times that are much longer in winter than in summer. Differences in the variation of SO₄ ⁼ and V concentrations in the Arctic winter are due to SO₂ oxidation. The mean rate of oxidation between November and April ranges from 0.04 to 0.25%/h and is a minimum in December, January and February. Br measured on filters in the Arctic peaks in concentration later (March and April) than anthropogenic particulate matter suggesting photochemical production. Acidity in Arctic aerosol and in glacial ice are correlated. The relationship yields a best estimate of acidity in the absence of anthropogenic influences of 5.8 mole/l. Coincident air and precipitation measurements of sulphur oxides indicate that on average in eastern Canada 60% of SO₄ ⁼ in rain originates from SO₂ oxidation in the storm. Trends in Arctic ice core acidity and SO₂ emissions in Europe are similar, that is, little variation in the first half of the century and a marked increase since the mid 1950's. This is consistent with meteorological and chemical evidence linking Arctic air pollution with Eurasian sources.     

Electrical Resistivity Studies to Delimit Zones of Acceptable Ground Water Quality

A total of four vertical electrical soundings were conducted in a layered andesitic rock aquifer known in places to yield ground water with total dissolved solids (TDS) in excess of 2,000 milligrams per liter (mg/L). The objective of the soundings was to locate zones of moderate to high permeability but with acceptable chemical quality.
The resistivity of a geologic unit is a function that includes the quantity of total dissolved solids in the interstitial water and the distribution of the water within the unit. Thus, the resistivity of most granular soils and rocks is controlled more by porosity, water content and water quality than by the conductivity of the matrix materials.
The electrical data delimited a drill site where it was believed that ground water of acceptable chemical quality could be expected. Completion and test pumping of two exploration wells confirmed the electrical sounding results.
The first test well drilled prior to the survey yielded only small amounts of ground water with total dissolved solids in excess of 2,000 mg/L. The second exploration well drilled at the site as a result of the electrical study yielded in excess of 100 gallons per minute of ground water with total dissolved solids of 830 mg/L.     

Effects of dredging and open-water disposal on benthic macroinvertebrates in a South Carolina estuary

Approximately 28,475 m³ of muddy sediments were dredged from a shoal in a South Carolina estuarine system and released near the surface at a nearby site having high tidal current velocities. Effects at the dredged sites included decreased macrofaunal abundance and changes in species composition. These effects appeared to be short term, with substantial recovery occurring within 3 months. Rapid recovery was primarily attributed to immigration through slumping of channel wall sediments similar to those dredged. Detrimental effects on benthic macrofauna in the area of open water disposal were minimal. Most differences noted in community structure between collection dates were attributed to sampling and seasonal variability. The absence of a major longterm disruption to the benthos in the disposal area was probably due to (1) strong tidal currents, which rapidly dispersed the moderate amount of mud sediments released; (2) surface disposal, permitting wider dispersal; and (3) disposal during late autumn, a period of low faunal recruitment.     

The 2004 RAS National Astronomy Meeting

This year's RAS National Astronomy Meeting was held at the Open University's Milton Keynes campus from 29 March to 2 April. The event was organized by members of the OU Physics & Astronomy Department and Planetary & Space Science Research Institute. Around 450 people attended the meeting, at which more than 220 talks were presented, along with around 90 posters. Co-chairs of RAS NAM04, Barrie Jones and Andrew Norton , summarize.     

The upper Jovian atmosphere aerosol content determined from a satellite eclipse observation

The Galilean satellite eclipse technique for measuring the aerosol distribution in the upper Jovian atmosphere is described and applied using 30 color observations of the 13 May 1972 eclipse of Ganymede obtained with the 5-m Hale telescope. This event probes the South Temperate Zone. The observed aerosol lies above the visible cloud tops, is very tenuous and varies with altitude, increasing rapidly with downward passage through the tropopause. The aerosol extinction coefficient, κ_a (λ1.05 μm), is ～1.1 × 10^?9 cm^?1 in the lower stratosphere and ～1.1 × 10^?8 cm^?1 at the tropopause. The 1σ uncertainty in these values does not exceed 50% The observations require some aerosol above the tropopause but do not clearly determine its structure. The present analysis emphasizes an extended haze distribution, but the alternate possibility is not excluded that the stratospheric aerosol resides in a thin layer. The aerosol extinction increases with decreasing wavelength and indicates the particle radius to be ?0.2 μm. Larger radii are impossible. These overall results confirm Axel's (1972) suggestion of a small quantity of dust above the Jovian cloud tops and the optical depths are consistent with those required to explain the low uv albedo.