Formation and circulation of the cold intermediate layer in the Gulf of Saint Lawrence

[ 1] The local heat content and formation rate of the cold intermediate layer (CIL) in the Gulf of Saint Lawrence are examined using a combination of new in situ wintertime observations and a three-dimensional numerical model. The field observations consist of five moorings located throughout the gulf over the period of November 2002 to June 2003. The observations demonstrate a substantially deeper surface mixed layer in the central and northeast gulf than in regions downstream of the buoyant surface outflow from the Saint Lawrence Estuary. The mixed-layer depth in the estuary remains shallow (< 60 m) throughout winter, with the arrival of a layer of near-freezing waters between 40 and 100 m depth in April. An eddy-permitting ice-ocean model with realistic forcing is used to hindcast the period of observation. The model simulates well the seasonal evolution of mixed-layer depth and CIL heat content. Although the greatest heat losses occur in the northeast, the most significant change in CIL heat content over winter occurs in the Anticosti Trough. The observed renewal of CIL in the estuary in spring is captured by the model. The simulation highlights the role of the northwest gulf, and in particular, the separation of the Gaspe Current, in controlling the exchange of CIL between the estuary and the gulf. In order to isolate the effects of inflow through the Strait of Belle Isle on the CIL heat content, we examine a sensitivity experiment in which the strait is closed. This simulation shows that the inflow has a less important effect on the CIL than was suggested by previous studies.

Provenance of chalk tesserae from Brading Roman Villa, Isle of Wight, UK

Thin section petrographical analysis of chalk tesserae at Brading Roman Villa, Isle of Wight, England, identifies a range of planktonic foraminifera and the calcareous algal cyst Pithonella that identify the Late Cenomanian Rotalipora cushmani Biozone (BGS Foraminiferal Biozones 4iii to 7). The local chalk crop to the north of the villa includes rocks of R. cushmani Biozone age, and indicates a likely local, rather than long distance, source for the tesserae. Microfossils provide a powerful tool for identifying the provenance of artefacts in Roman Britain.

A Lateglacial archaeological site in the far north-west of Europe at Rubha Port an t-Seilich, Isle of Islay, western Scotland: Ahrensburgian-style artefacts, absolute dating and geoarchaeology

The exact pattern, process and timing of the human re-colonization of northern Europe after the end of the last Ice Age remain controversial. Recent research has provided increasingly early dates for at least pioneer explorations of latitudes above 54°N in many regions, yet the far north-west of the European landmass, Scotland, has remained an unexplained exception to this pattern. Although the recently described Hamburgian artefacts from Howburn and an assemblage belonging to the arch-backed point complex from Kilmelfort Cave have established at least a sporadic human presence during earlier stages of the Lateglacial Interstadial, we currently lack evidence for Younger Dryas/Greenland Stadial 1 (GS-1) activity other than rare stray finds that have been claimed to be of Ahrensburgian affiliation but are difficult to interpret in isolation. We here report the discovery of chipped stone artefacts with technological and typological characteristics similar to those of the continental Ahrensburgian at a locality in western Scotland. A preliminary analysis of associated tephra, pollen and phytoliths, along with microstratigraphic analysis, suggest the artefacts represent one or more episodes of human activity that fall within the second half of GS-1 and the Preboreal period