Atmospheric response in summer linked to recent Arctic sea ice loss

Since 2007 a large decline in Arctic sea ice has been observed. The large-scale atmospheric circulation response to this decline is investigated in ERA-Interim reanalyses and HadGEM3 climate model experiments. In winter, post-2007 observed circulation anomalies over the Arctic, North Atlantic and Eurasia are small compared to interannual variability. In summer, the post-2007 observed circulation is dominated by an anticyclonic anomaly over Greenland which has a large signal-to-noise ratio. Climate model experiments driven by observed SST and sea ice anomalies are able to capture the summertime pattern of observed circulation anomalies, although the magnitude is a third of that observed. The experiments suggest high SSTs and reduced sea ice in the Labrador Sea lead to positive temperature anomalies in the lower troposphere which weaken the westerlies over North America through thermal wind balance. The experiments also capture cyclonic anomalies over Northwest Europe, which are consistent with downstream Rossby wave propagatio

Atmospheric impact of Arctic Sea ice loss in a coupled ocean–atmosphere simulation

The atmospheric response to an idealized decline in Arctic sea ice is investigated in a novel fully coupled climate model experiment. In this experiment two ensembles of single-year model integrations are performed starting on 1 April, the approximate start of the ice melt season. By perturbing the initial conditions of sea ice thickness (SIT), declines in both sea ice concentration and SIT, which result in sea ice distributions that are similar to the recent sea ice minima of 2007 and 2012, are induced. In the ice loss regions there are strong (~3 K) local increases in sea surface temperature (SST); additionally, there are remote increases in SST in the central North Pacific and subpolar gyre in the North Atlantic. Over the central Arctic there are increases in surface air temperature (SAT) of ~8 K due to increases in ocean–atmosphere heat fluxes. There are increases in SAT over continental North America that are in good agreement with recent changes as seen by reanalysis data. It is estimated that up to two-thirds of the observed increase in SAT in this region could be related to Arctic sea ice loss. In early summer there is a significant but weak atmospheric circulation response that projects onto the summer North Atlantic Oscillation (NAO). In early summer and early autumn there is an equatorward shift of the eddy-driven jet over the North Atlantic as a result of a reduction in the meridional temperature gradients. In winter there is no projection onto a particular phase of the NAO

Bridge over troubled water: The Roman finds from the River Tees at Piercebridge in context (Hella Eckardt & Philippa Walton)

This collection comprises specialist reports from Roman finds at Piercebridge, which are published in summary in the book 'Bridge over troubled water: The Roman finds from the River Tees at Piercebridge in context'. When Roman objects are discovered in rivers across the north-western provinces of the Roman Empire, they are often interpreted as the accidental losses of travellers or as rubbish deposits revealed by fluvial erosion; this is in contrast to prehistoric assemblages, which are usually seen as ritual offerings. Our project challenges these assumptions by publishing an entire riverine artefactual assemblage for the first time and placing it into its archaeological context. British material has not previously been studied at all, and on the continent only exceptional assemblages like the large vessel hoard from Neupotz or high status objects like swords have been studied. To remedy this situation, we are publishing all the finds from the Tees at Roman Piercebridge (3,619 objects) as a Britannia monograph, including objects such as fishing weights and furniture fittings as well as gold jewellery and coinage. Interpretative chapters explore the significance of the different categories of finds while the individual objects are all recorded on the Portable Antiquities Scheme website (www.finds.org.uk). We employ Correspondence Analysis to compare the composition of the riverine assemblage to those excavated at nearby sites, and demonstrate that its chronological and functional profile differs significantly from settlement sites, making ritual deposition of at least some finds highly likely. There are also chapters on Roman riverine deposition and the significance of bridges across the Roman world, as well as the archaeological context of the discovery. The book is published both in hardcopy and as an Open Access book; here you can find reports by specialists on certain categories of the Piercebridge finds, which are only published in summary in the book

An Iron Age and early Roman farmstead at Calvestone Road, Cawston, near Rugby: excavations in 2012

A programme of archaeological investigation was undertaken by Cotswold Archaeology (CA) prior to housing development to the east of Calvestone Road, Cawston, on the outskirts of Rugby. The work comprised an archaeological excavation over three areas followed by a watching brief on parts of the site not subject to excavation. In Area 1 lay an Iron Age subrectangular enclosure whose ditch had been re-cut on at least three occasions. The enclosure contained evidence for an Iron Age farmstead, including a possible roundhouse. Areas 2 and 3 also revealed evidence of occupation during the Iron Age. Later, in the 1st century AD, the site was remodelled with the laying out of a series of larger enclosures and the development of a trackway. The site was abandoned during the Roman period with no evidence for continued occupation beyond c AD 200. Medieval and post-medieval furrows indicate that later the area was laid down to arable.This report presents the results of the excavation and places them within the context of settlement, the economy and the environment of the Iron Age and Roman periods. The likely function of each feature and structure encountered is considered and compared with other Iron Age and Roman sites

Excavation of an early Bronze Age Round Barrow at Emmets Post, Shaugh Prior, Dartmoor

Oxford Archaeology carried out an excavation of an early Bronze Age barrow at Emmets Post, Dartmoor. The barrow comprised a primary turf mound and a central cairn beneath a secondary turf mound with a stone kerb. No human remains were found. A radiocarbon dating programme yielded a wide range of dates. Some derived from older material incidentally incorporated within the turves during construction, but a date of 1750-1560 cal BC for the central area of the barrow may represent the true date of construction. The landscape had been largely destroyed by modern quarrying, but present-day Lidar data and contour data from historic maps were used to reconstruct the pre-quarry topography