3D seismic imagery of mega-scale glacial lineations and flow-switching by ice streams on the Norwegian continental shelf

This is the author accepted manuscript. The final version is available from the Geological Society of London via https://doi.org/doi.org/10.1144/M46.96Streamlined glacial landforms, produced by deformation of soft sediments at glacier beds (Dowdeswell et al. 2004; Ó Cofaigh et al. 2005; King et al. 2009), provide clear evidence of the direction of ice-flow at the time of their formation (e.g. Ottesen et al., 2005; Livingstone et al. 2012). Where sets of streamlined landforms are present at or close to the seafloor, swath-bathymetric imagery enables the reconstruction of multiple phases of ice-flow (e.g. Greenwood et al. 2012). In many cases, however, key morphological evidence is buried on palaeo-shelves within the Quaternary glacial sedimentary record (Fig. 1c-d), and can only be analysed by tracing these buried horizons in 3D-seismic datasets (Dowdeswell et al. 2007)

Skjoldryggen terminal moraine on the mid-Norwegian shelf

Terminal moraines are relatively large ridges of diamictic glacial debris produced at the outermost margins of past glaciers and ice sheets. Their identification on land is important in mapping the maximum extent of Quaternary ice sheets (Svendsen et al. 2004). In marine environments where fast-flowing ice streams reach the shelf edge during full-glacial intervals, moraine ridges are not usually present and the seafloor is characterised by parallel-to-flow streamlined sediments (Ottesen & Dowdeswell 2009). Submarine terminal moraine ridges, by contrast, appear more typical of slower-flowing ice margins (Dahlgren et al. 2002; Dowdeswell & Elverhøi 2002).This is the author accepted manuscript. The final version is available from the Geological Society of London via https://doi.org/10.1144/M46.6

Landforms characteristic of inter-ice stream settings on the Norwegian and Svalbard continental margins

This is the author accepted manuscript. The final version is available from the Geological Society of London via https://doi.org/10.1144/M46.16

EB Ford revisited: assessing the long-term stability of wing-spot patterns and population genetic structure of the meadow brown butterfly on the Isles of Scilly

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.Data files of wing spot sizes and AFLP genotypes available from the Dryad Digital Repository: http://dx.doi.org/10.5061/dryad.j7v42.Understanding selection in the wild remains a major aim of evolutionary ecology and work by Ford and colleagues on the meadow brown butterfly Maniola jurtina did much to ignite this agenda. A great deal of their work was conducted during the 1950s on the Isles of Scilly. They documented island-specific wing-spot patterns that remained consistent over about a decade, but patterns on some islands changed after environmental perturbation. It was suggested that these wing-spot patterns reflected island-specific selection and that there was little migration between islands. However, genetic studies to test the underlying assumption of restricted migration are lacking and it is also unknown whether the originally described wing-spot patterns have persisted over time. We therefore collected female butterflies from five of Ford's original study locations, including three large islands (St Mary's, St Martin's and Tresco) and two small islands (Tean and St Helen's). Wing-spot patterns had not changed appreciably over time on three of the islands (two large and one small), but were significantly different on the other two. Furthermore, analysis of 176 amplified fragment length polymorphisms revealed significant genome-wide differentiation among the five islands. Our findings are consistent with Ford's conclusions that despite the close proximity of these islands, there is restricted gene flow among them.Heredity advance online publication, 2 November 2016; doi:10.1038/hdy.2016.94.We thank the Genetics Society for a fieldwork grant (to DJH) that funded the collection trip and DJH thanks Mike Johnson for sparking interest in this area. SWB is supported by the Australian Research Council and a Ramsay Fellowship, NW by a Royal Society Wolfson Fellowship and NERC and DJH by the Leverhulme Trust

Fan-like sediments on outer Haltenbanken, mid-Norwegian shelf

Subaqueous fans formed in marine and lacustrine settings have been reported from Quaternary and more ancient glacier-influenced environments (e.g. Powell 1990; Dowdeswell et al. 2015). Their presence is often taken to imply a palaeo-glacial environment abundant in sediment-rich meltwater, whose load was sourced from glacial erosion and transported in subglacial channels to the ice margin. The sedimentology of these fans sometimes exhibits bedforms indicative of high-energy water-flow, suggesting that rapid drain

A tidewater glacier landform assemblage in Belcher Inlet, Canadian Arctic

Belcher Glacier, a 35 km-long tidewater outlet glacier of the 12,000 km² ice cap on Devon Island (Dowdeswell et al. 2004), is one of the fastest-flowing glaciers in the Canadian Arctic (Van Wychen et al. 2014) (Fig. 1). Belcher Glacier and neighbouring Fitzroy Glacier to the southeast account for about 55% of the iceberg calving loss from the Devon Ice Cap (Van Wychen et al. 2014). The terminus of Belcher Glacier remained relatively stable between the 1960s (light blue dashed line in Fig. 1a) and 2000 (Landsat 7 satellite image in Fig. 1a). In contrast, the unnamed glacier immediately to the north retreated 2 km during this period (Fig. 1a). Belcher Glacier and the unnamed glacier retreated around 500 m and 250 m, respectively, between 2000 and 2014 (dark blue dashed line in Fig. 1a). The bed topography of Belcher Glacier, which is around 250 m below sea level at the present-day glacier margin (Fig. 1c) and remains below sea level in the lower 11 km of the glacier, suggests that its terminus region may become unstable in the event of future retreat. Seafloor mapping of Belcher Inlet beyond the termini of Belcher Glacier and the unnamed glacier (Fig. 1a), together with sub-bottom profiling, provide information about the dynamic behaviour of tidewater glaciers.This is the author accepted manuscript. The final version is available from Geological Society of London via https://doi.org/10.1144/M46.14

3D sedimentary architecture showing the inception of an Ice Age

Abstract: Northeast Atlantic climate shifted into the Quaternary Ice Age around 2.6 M yr ago. Until now, however, the detailed changes associated with this inception of an Ice Age have remained obscure. New high-quality three-dimensional seismic data reveal a detailed geological record of buried surfaces, landforms and sedimentary architecture over vast parts of the Norwegian North Sea. Here, we show the sequence of near-coast geological events spanning the Northeast Atlantic inception of an Ice Age. We identify the location of immediate pre-glacial fluvially derived sandy systems where rivers from the Norwegian mainland built marine deltas. The stratigraphic position of a large submarine channel, formed by enhanced meltwater from initial build-up of local glaciers, is also shown. Finally, we document the transition to full ice-sheet growth over Scandinavia from the ice sheet’s earliest position to the later pattern of debris-flow lobes reaching the present-day shelf edge

3D sedimentary architecture showing the inception of an Ice Age

Abstract: Northeast Atlantic climate shifted into the Quaternary Ice Age around 2.6 M yr ago. Until now, however, the detailed changes associated with this inception of an Ice Age have remained obscure. New high-quality three-dimensional seismic data reveal a detailed geological record of buried surfaces, landforms and sedimentary architecture over vast parts of the Norwegian North Sea. Here, we show the sequence of near-coast geological events spanning the Northeast Atlantic inception of an Ice Age. We identify the location of immediate pre-glacial fluvially derived sandy systems where rivers from the Norwegian mainland built marine deltas. The stratigraphic position of a large submarine channel, formed by enhanced meltwater from initial build-up of local glaciers, is also shown. Finally, we document the transition to full ice-sheet growth over Scandinavia from the ice sheet’s earliest position to the later pattern of debris-flow lobes reaching the present-day shelf edge

A persistent Norwegian Atlantic Current through the Pleistocene glacials

Changes in ocean‐circulation regimes in the northern North Atlantic and the Nordic Seas may affect not only the Arctic but potentially hemispheric or even global climate. Therefore, unraveling the long‐term evolution of the North Atlantic Current‐Norwegian Atlantic Current system through the Pleistocene glaciations could yield useful information and climatological context for understanding contemporary changes. In this work, ~50,000 km2 of 3‐D seismic reflection data are used to investigate the Pleistocene stratigraphy for evidence of paleo‐oceanographic regimes on the mid‐Norwegian margin since 2.58 Ma. Across 33 semicontinuous regional paleo‐seafloor surfaces ~17,500 iceberg scours have been mapped. This mapping greatly expands our spatiotemporal understanding of currents and iceberg presence in the eastern Nordic Seas. The scours display a dominant southwest‐northeast trend that complements previous sedimentological and numerical modeling studies that suggest northward‐flowing currents in the Norwegian Sea during the Pleistocene. This paleo‐oceanographic study suggests that through many of the Pleistocene glaciations, the location of surface ocean currents in the Norwegian Sea and, by extension, the eastern North Atlantic, were broadly similar to the present

Discovery of a hypersaline subglacial lake complex beneath Devon Ice Cap, Canadian Arctic.

Subglacial lakes are unique environments that, despite the extreme dark and cold conditions, have been shown to host microbial life. Many subglacial lakes have been discovered beneath the ice sheets of Antarctica and Greenland, but no spatially isolated water body has been documented as hypersaline. We use radio-echo sounding measurements to identify two subglacial lakes situated in bedrock troughs near the ice divide of Devon Ice Cap, Canadian Arctic. Modeled basal ice temperatures in the lake area are no higher than -10.5°C, suggesting that these lakes consist of hypersaline water. This implication of hypersalinity is in agreement with the surrounding geology, which indicates that the subglacial lakes are situated within an evaporite-rich sediment unit containing a bedded salt sequence, which likely act as the solute source for the brine. Our results reveal the first evidence for subglacial lakes in the Canadian Arctic and the first hypersaline subglacial lakes reported to date. We conclude that these previously unknown hypersaline subglacial lakes may represent significant and largely isolated microbial habitats, and are compelling analogs for potential ice-covered brine lakes and lenses on planetary bodies across the solar system