Strongly divided opinion has led to competing, apparently contradictory, views on the timing, extent, flow configuration and decay mechanism of the last British Ice Sheet. We review the existing literature and reconcile some of these differences using remarkable new seabed imagery. This bathymetric data provides unprecedented empirical evidence of confluence and subsequent separation of the last British and Fennoscandian Ice Sheets. Critically, it also allows a viable pattern of ice-sheet disintegration to be proposed for the first time. Covering the continental shelf around the northern United Kingdom, extensive echosounder data reveals striking geomorphic evidence -in the form of tunnel valleys and moraines -relating to the former British and Fennoscandian Ice Sheets. The pattern of tunnel valleys in the northern North Sea Basin and the presence of large moraines on the West Shetland Shelf, coupled with stratigraphic evidence from the Witch Ground Basin, all suggest that at its maximum extent a grounded ice sheet flowed from SE to NW across the northern North Sea Basin, terminating at the continental shelf edge. The zone of confluence between the British and much larger Fennoscandian Ice Sheets was probably across the northern Orkney Islands, with fast-flowing ice in the Fair Isle Channel focusing sediment delivery to the Rona and Foula Wedges. This period of maximum confluent glaciation (c. 30-25 ka BP) was followed by a remarkable period of large-scale ice-sheet re-organisation. We present evidence suggesting that as sealevel rose, a large marine embayment opened in the northern North Sea Basin, as far south as the Witch Ground Basin, forcing the two ice sheets to decouple rapidly along a north-south axis east of Shetland. As a result, both ice-sheets rapidly adjusted to new quasi-stable margin positions forming a second distinct set of moraines (c. 24-18 ka BP). The lobate overprinted morphology of these moraines on the mid-shelf west of Orkney and Shetland indicates that the re-organisation of the British Ice Sheet was extremely dynamic -probably dominated by a series of internally forced readvances. Critically, much of the ice in the low-lying North Sea Basin may have disintegrated catastrophically as decoupling progressed in response to rising sea levels. Final-stage deglaciation was marked by near-shore ice streaming and increasing topographic control on ice-flow direction. Punctuated retreat of the British Ice Sheet continued until c. 16 ka BP when, following the North Atlantic iceberg-discharge event (Heinrich-1), ice was situated at the present-day coastline in NW Scotland.

No abstract

Natural dust is often associated with hot, subtropical deserts, but significant dust events have been reported from cold, high latitudes. This review synthesizes current understanding of high‐latitude (≥50°N and ≥40°S) dust source geography and dynamics and provides a prospectus for future research on the topic. Although the fundamental processes controlling aeolian dust emissions in high latitudes are essentially the same as in temperate regions, there are additional processes specific to or enhanced in cold regions. These include low temperatures, humidity, strong winds, permafrost and niveo‐aeolian processes all of which can affect the efficiency of dust emission and distribution of sediments. Dust deposition at high latitudes can provide nutrients to the marine system, specifically by contributing iron to high‐nutrient, low‐chlorophyll oceans; it also affects ice albedo and melt rates. There have been no attempts to quantify systematically the expanse, characteristics, or dynamics of high‐latitude dust sources. To address this, we identify and compare the main sources and drivers of dust emissions in the Northern (Alaska, Canada, Greenland, and Iceland) and Southern (Antarctica, New Zealand, and Patagonia) Hemispheres. The scarcity of year‐round observations and limitations of satellite remote sensing data at high latitudes are discussed. It is estimated that under contemporary conditions high‐latitude sources cover >500,000 km2 and contribute at least 80–100 Tg yr−1 of dust to the Earth system (~5% of the global dust budget); both are projected to increase under future climate change scenarios.

Iceland's glaciers are particularly sensitive to climate change, and their margins respond to trends in air temperature. Most Icelandic glaciers have been in retreat since c. 1990, and almost all since 1995. Using ice-front measurements, photographic and geomorphological evidence, we examined the record of ice-front fluctuations of Virkisjökull-Falljökull, a steep high-mass-turnover outlet glacier in maritime SE Iceland, in order to place recent changes in a longer-term (80-year) context. Detailed geomorphological mapping identifies two suites of annual push moraines: one suite formed between c. 1935 and 1945, supported by lichenometric dating; the other between 1990 and 2004. Using moraine spacing as a proxy for ice-front retreat rates, we show that average retreat rates during the 1930s and 1940s (28 m a -1 ) were twice as high as during the period from 1990 to 2004 (14 m a -1 ). Furthermore, we show that both suites of annual moraines are associated with above-average summer temperatures. Since 2005, however, retreat rates have increased considerably -averaging 35 m a -1 -with the last 5 years representing the greatest amount of ice-front retreat (~190 m) in any 5-year period since measurements began in 1932. We propose that this recent, rapid, ice-front retreat and thinning in a decade of unusually warm summers has resulted in a glaciological threshold being breached, with subsequent large-scale stagnation of the glacier terminus (i.e. no forward movement) and the cessation of annual push-moraine formation. Breaching this threshold has, we suggest, caused further very rapid non-uniform retreat and downwasting since 2005 via a system feedback between surface melting, glacier thinning, decreased driving stress and decreased forward motion.

We constrain, in detail, fluctuations of two former ice caps in NW Scotland with multibeam seabed surveys, geomorphological mapping and cosmogenic 10 Be isotope analyses. We map a continuous sequence of 40 recessional moraines stretching from ~10 km offshore to the Wester Ross mountains. Surface-exposure ages from boulders on moraine ridges in Assynt and the Summer Isles region show that substantial, dynamic, ice caps existed in NW Scotland between 13-14 ka BP. We interpret this as strong evidence that large active glaciers probably survived throughout the Lateglacial Interstadial, and that during the Older Dryas period (c.14 ka BP) ice caps in NW Scotland were thicker and considerably more extensive than in the subsequent Younger Dryas Stadial. By inference, we suggest that Lateglacial ice-cap oscillations in Scotland reflect the complex interplay between changing temperature and precipitation regimes during this climatically unstable period (~15-11 ka BP). words

New multibeam bathymetry data, onshore high-resolution elevation data (NEXTMap) and fieldwork in the Ullapool area of NW Scotland reveal large-scale megagrooves and streamlined bedrock forms in a well-defined ~20-km wide zone. The landsystem is typical of a coherent flow corridor within a grounded ice sheet on bedrockdominated terrain. We describe the morphology of the large-scale features, discuss their likely formation, and consider the wider implications for ice-sheet dynamics. Based on the strongly convergent bedform distribution, the presence of megagrooves and highly elongate bedrock forms, we interpret the erosional landscape to be the signature of a fast-flowing tributary that once fed the The Minch palaeo-ice stream -a major artery of the last British-Irish ice sheet. The exact genesis of bedrock megagrooves remains uncertain, although focused subglacial abrasion is likely to have carved most of the shallow, strongly parallel, features; whilst glacial meltwater may have carved or modified others. Bedform morphometry is used to discriminate zones reflecting the degree of glacial streamlining (elongation ratios <5:1 or >5:1). We interpret these zones to represent the transition from potentially cold-based slow ice-sheet flow to warm-based fast flow. Based on these results, and the presence of ribbed moraines, we suggest a bedform continuum model for onset zones of palaeoice streams on rigid beds. Rapid spatial bedform evolution is suggested to reflect an increase in subglacial erosive power that may be diagnostic of palaeo-ice-sheet thermal boundaries (i.e. from cold-to warm-based), and is also consistent with the expected downstream increase in ice velocity within an ice-stream onset zone. Finally, this study speculates on the role played by basal meltwater in ice-stream initiation and the role of ice streams and their tributaries in landscape evolution.

The age of recent deposits can be determined using an intrinsic characteristic of the lichen 'population' growing on their surface. This paper presents a calibrated dating curve based on the gradient of the size-frequency distribution of yellow-green Rhizocarpon lichens. The dating potential of this new curve is tested on surfaces of known age in southeast Iceland. This particular size-frequency technique is also compared with the more traditional largest-lichen approach. The results are very encouraging and suggest that the gradient can be used as an age indicator, at least on deposits formed within the last c. 150 years -and probably within the last c. 400 years -in the maritime subpolar climate of southeast Iceland. Using both lichenometric techniques, revised dates for moraines on two glacier forelands are presented which shed new light on the exact timing of the Little Ice Age glacier maximum in Iceland.

meltwater channels, tunnel valleys, trimlines, limit of key glacigenic deposits, glaciolacustrine deposits, ice-dammed lakes, erratic dispersal patterns, shelf-edge fans, and the Loch LomondReadvance limit of the main ice cap. The GIS contains over 20000 features split into thematic layers (as above). Individual features are attributed such that they can be traced back to their published sources. Given that the published sources of information that underpin this work were derived by a piecemeal effort over 150 years then our main caveat is of data consistency and reliability. It is hoped that this compilation will stimulate greater scrutiny of published data, assist in palaeo-glaciological reconstructions, and facilitate use of field-evidence in numerical ice sheet modelling. It may also help direct field workers in their future investigations.