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The detection and monitoring of meltwater within firn presents a significant monitoring challenge. We explore the potential of small wireless sensors (ETracer+, ET+) to measure temperature, pressure, electrical conductivity and thus the presence or absence of meltwater within firn, through tests in the dry snow zone at the East Greenland Ice Core Project site. The tested sensor platforms are small, robust and low cost, and communicate data via a VHF radio link to surface receivers. The sensors were deployed in low-temperature firn at the centre and shear margins of an ice stream for 4 weeks, and a ‘bucket experiment’ was used to test the detection of water within otherwise dry firn. The tests showed the ET+ could log subsurface temperatures and transmit the recorded data through up to 150 m dry firn. Two VHF receivers were tested: an autonomous phase-sensitive radio-echo sounder (ApRES) and a WinRadio. The ApRES can combine high-resolution imaging of the firn layers (by radio-echo sounding) with in situ measurements from the sensors, to build up a high spatial and temporal resolution picture of the subsurface. These results indicate that wireless sensors have great potential for long-term monitoring of firn processes.
The environments underneath ice sheets are of high scientific interest. Wireless sensors offer the prospect of sustained, distributed remote sensing in the subglacial environment. Typically, wireless sensor networks use radio-frequency (RF) electromagnetic communications, but these are highly attenuated in wet environments. In such environments, acoustic communications may be more power-efficient. Here we review the literature on acoustic and RF attenuation through ice and other relevant media, and present the results of new experiments on acoustic attenuation in glacial ice. Link budgets for communications from a range of subglacial environments show that acoustic communications are a viable strategy for transmission through water and ice where RF is too highly attenuated to be detected. Acoustic communication at 30 kHz is predicted to be possible through 1 km of glacial ice, using a 1 W transmitter. Such a strategy may be appropriate for shallow ice-stream environments around the Antarctic and Greenland ice sheet margins.
The Late Neolithic pottery of the Isle of Man falls into two types: Ronaldsway and Grooved Ware. This paper focuses on the former style which is markedly different from other contemporaneous pottery styles in use in Britain and Ireland. The discussion draws upon the biographical history of Ronaldsway vessels from the choice of raw materials to the deposition of the finished pots. At each stage in this biographical history the approach adopted by Manx potters and pottery users is compared with that employed in surrounding parts of the British Isles.
Bryn Celli Ddu is one of only two developed passage tombs in Wales, and has occupied a pivotal place in narratives of this region since the publication of excavations in the 1920s by W.J. Hemp. The construction sequence at the site has been at the centre of debate on several occasions with previous models raising important issues about the sequence of major monument types (notably the henge and the passage tomb) and the inter-regional links of the tomb's builders. This paper presents a new interpretation of the site's construction history, drawing on several sources, including: the recent demonstration that the tomb is aligned on the midsummer sunrise; Hemp's unpublished archive; and the results of a radiocarbon dating programme. The result is a two phase model which shows the tomb to have been built between 3074 and 2956 calbc, and which sheds fresh light on the ritual practices of the community which built it.
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