VUGS IN ORDINARY CHONDRITES

Large vugs occur in the ordinary chondrite, Farmington. They contain the same phases present in the body of the meteorite, either as vug wall lining or as crystals attached to linings. The morphologies of these phases indicate a history of melting and vapor deposition. These vugs are compared with vugs in the ordinary chondrites, Orvinio and Tadjera, and with published reports of vugs in Rose City and Shaw. It is concluded that although shock events may not cause heating above the liquidus for the body of the meteorite, local pockets of melting and vapor formation do occur due to inhomogenieties in the shock wave pattern. Vugs represent such pockets. Vug formation, as a consequence of shock processing, is widespread among ordinary chondrites and shows no correlation with the average temperature of shock heating, subsequent average cooling rate (as indicated by metallurgical criteria), or blackening of body color.     

Decadal fingerprints of freshwater discharge around Greenland in a multi-model ensemble

The recent increase in the rate of the Greenland ice sheet melting has raised with urgency the question of the impact of such a melting on the climate. As former model projections, based on a coarse representation of the melting, show very different sensitivity to this melting, it seems necessary to consider a multi-model ensemble to tackle this question. Here we use five coupled climate models and one ocean-only model to evaluate the impact of 0.1 Sv (1 Sv = 10⁶ m³/s) of freshwater equally distributed around the coast of Greenland during the historical era 1965–2004. The ocean-only model helps to discriminate between oceanic and coupled responses. In this idealized framework, we find similar fingerprints in the fourth decade of hosing among the models, with a general weakening of the Atlantic Meridional Overturning Circulation (AMOC). Initially, the additional freshwater spreads along the main currents of the subpolar gyre. Part of the anomaly crosses the Atlantic eastward and enters into the Canary Current constituting a freshwater leakage tapping the subpolar gyre system. As a consequence, we show that the AMOC weakening is smaller if the leakage is larger. We argue that the magnitude of the freshwater leakage is related to the asymmetry between the subpolar-subtropical gyres in the control simulations, which may ultimately be a primary cause for the diversity of AMOC responses to the hosing in the multi-model ensemble. Another important fingerprint concerns a warming in the Nordic Seas in response to the re-emergence of Atlantic subsurface waters capped by the freshwater in the subpolar gyre. This subsurface heat anomaly reaches the Arctic where it emerges and induces a positive upper ocean salinity anomaly by introducing more Atlantic waters. We found similar climatic impacts in all the coupled ocean–atmosphere models with an atmospheric cooling of the North Atlantic except in the region around the Nordic Seas and a slight warming south of the equator in the Atlantic. This meridional gradient of temperature is associated with a southward shift of the tropical rains. The free surface models also show similar sea-level fingerprints notably with a comma-shape of high sea-level rise following the Canary Current.     

Are Damped Lyα Systems Large Galactic Discs?

The hypothesis that damped Lyα systems (DLAs) are large galactic discs (Milky Way sized) is tested by confronting predictions of models of the formation and evolution of (large) disc galaxies with observations, in particular the zinc abundance distribution with neutral hydrogen column density found for DLAs. A pronounced mismatch is found, strongly hinting that the majority of DLAs may not be large galactic discs. This revised version was published online in July 2006 with corrections to the Cover Date.     

Upper Devonian tetrapod palaeoecology in the light of new discoveries in East Greenland

For the first time, new material of one of the world's oldest known tetrapods, Acanthostega, has been studied in its sedimentological context. The reported evidence suggests that Acanthostega was primarily aquatic and inhabited active fluvial channels in fluvial-dominated environments.     

Criticism from former director of fisheries

In an article published in Marine Policy a year ago, (Lynne and Brian Chatterton, ‘How much political compromise can fisheries management stand’, Vol 5, No 1, April 1981), it was argued that management of South Australian coastal fisheries reflected the political ideology of the government in power, rather than the biological and socioeconomic imperatives of the resource. In the first article below, A.M. Olsen, former Director of Fisheries, criticizes the Chattertons' conclusions, maintaining that fisheries should be managed by professionals not politicians and that many of Brian Chatterton's problems during his tenure as Minister of Fisheries were of his own making. In the Chattertons' response, they point out that by allocating management of the resource between various vested interests (including government bureaucracy) a minister is making a political decision. In the third article, R.D. Walkerden, a former Permanent Secretary to Fisheries Ministers in South Australia, offers an administrator's view of the controversy. Detailed and parochial as some of the points at issue appear, the debate provides an illuminating view of some of the ideological and organizational conflicts that can hinder the effective management of a coastal resource.     

The photometric period of 39 AY Ceti

Photoelectric photometry obtained in 1971 and 1972 is compared with that obtained in 1980–81 and 1981–82 to derive a photometric period of 77 ^d .65. JD 2444636.0 is an epoch of minimum light. The full amplitude has been as large as 0 ^m .18 inV. Curiously, the mean light level has dropped by almost 0 ^m .2 over the last ten years. This binary is additionally interesting because of the recently discovered white dwarf secondary component and because unpublished radial velocity measures of Fekel show a large (0.1) eccentricity and an orbital period (57 ^d .1) very different from our photometric period.