The Experts below are selected from a list of 399 Experts worldwide ranked by ideXlab platform
David J A Evans - One of the best experts on this subject based on the ideXlab platform.
-
concentrated pulsed axial glacier flow structural glaciological evidence from kviarjokull in se iceland
Earth Surface Processes and Landforms, 2017Co-Authors: Emrys Phillips, David J A Evans, Jez Everest, Andrew Finlayson, Marek Ewertowski, Ailsa Guild, Lee JonesAbstract:A detailed structural glaciological study carried out on Kviarjokull in SE Iceland reveals that recent flow within this maritime glacier is concentrated within a narrow corridor located along its central axis. This active corridor is responsible for feeding ice from the accumulation zone on the south-eastern side of Oraefajokull to the lower reaches of the glacier and resulted in a c. 200 m advance during the winter of 2013–2014 and the formation of a Push-Moraine. The corridor comprises a series of lobes linked by a laterally continuous zone of highly fractured ice characterised by prominent flow-parallel crevasses, separated by shear zones. The lobes form highly crevassed topographic highs on the glacier surface and occur immediately down-ice of marked constrictions caused by prominent bedrock outcrops located on the northern side of the glacier. Close to the frontal margin of Kviarjokull, the southern side of the glacier is relatively smooth and pock-marked by a number of large moulins. The boundary between this slow moving ice and the active corridor is marked by a number of ice flow-parallel strike-slip faults and a prominent dextral shear zone which resulted in the clockwise rotation and dissection of an ice-cored esker exposed on the glacier surface. It is suggested that this concentrated style of glacier flow identified within Kviarjokull has affinities with the individual flow units which operate within pulsing or surging glaciers
-
glacial geomorphology of terrestrial terminating fast flow lobes ice stream margins in the southwest laurentide ice sheet
Geomorphology, 2014Co-Authors: David J A Evans, Nathaniel J P Young, Colm O CofaighAbstract:Glacial geomorphological mapping of southern Alberta, Canada, reveals landform assemblages that are diagnostic of terrestrial-terminating ice streams/fast flowing outlet glaciers with lobate snouts. Spatial variability in features that comprise the landform assemblages reflects changes in (a) palaeo-ice stream activity (switch on/off); and (b) snout basal thermal regimes associated with climate sensitive, steady state flow. Palaeo-ice stream tracks reveal distinct inset sequences of fan-shaped flowsets indicative of receding lobate ice stream margins. Former ice lobe margins are demarcated by (a) major, often glacially overridden transverse Moraine ridges, commonly comprising glacitectonically thrust bedrock; and (b) minor, closely spaced recessional Push Moraines and hummocky Moraine arcs. Details of these landform types are well exhibited around the former southern margins of the Central Alberta Ice Stream, where larger scale, more intensive mapping identifies a complex glacial geomorphology comprising minor transverse ridges (MTR types 1–3), hummocky terrain (HT types 1–3), flutings, and meltwater channels/spillways. The MTR type 1 constitute the summit corrugation patterns of glacitectonic thrust Moraines or major transverse ridges and have been glacially overrun and moderately streamlined. The MTR type 2 sequences are recessional Push Moraines similar to those developing at modern active temperate glacier snouts. The MTR type 3 document Moraine construction by incremental stagnation because they occur in association with hummocky terrain. The close association of hummocky terrain with Push Moraine assemblages indicates that they are the products of supraglacial controlled deposition on a polythermal ice sheet margin, where the HT type 3 hummocks represent former ice-walled lake plains. The ice sheet marginal thermal regime switches indicated by the spatially variable landform assemblages in southern Alberta are consistent with palaeoglaciological reconstructions proposed for other ice stream/fast flow lobes of the southern Laurentide Ice Sheet, where alternate cold, polythermal, and temperate marginal conditions associated with climate sensitive, steady state flow sequentially gave way to more dynamic streaming and surging activity.
Jez Everest - One of the best experts on this subject based on the ideXlab platform.
-
concentrated pulsed axial glacier flow structural glaciological evidence from kviarjokull in se iceland
Earth Surface Processes and Landforms, 2017Co-Authors: Emrys Phillips, David J A Evans, Jez Everest, Andrew Finlayson, Marek Ewertowski, Ailsa Guild, Lee JonesAbstract:A detailed structural glaciological study carried out on Kviarjokull in SE Iceland reveals that recent flow within this maritime glacier is concentrated within a narrow corridor located along its central axis. This active corridor is responsible for feeding ice from the accumulation zone on the south-eastern side of Oraefajokull to the lower reaches of the glacier and resulted in a c. 200 m advance during the winter of 2013–2014 and the formation of a Push-Moraine. The corridor comprises a series of lobes linked by a laterally continuous zone of highly fractured ice characterised by prominent flow-parallel crevasses, separated by shear zones. The lobes form highly crevassed topographic highs on the glacier surface and occur immediately down-ice of marked constrictions caused by prominent bedrock outcrops located on the northern side of the glacier. Close to the frontal margin of Kviarjokull, the southern side of the glacier is relatively smooth and pock-marked by a number of large moulins. The boundary between this slow moving ice and the active corridor is marked by a number of ice flow-parallel strike-slip faults and a prominent dextral shear zone which resulted in the clockwise rotation and dissection of an ice-cored esker exposed on the glacier surface. It is suggested that this concentrated style of glacier flow identified within Kviarjokull has affinities with the individual flow units which operate within pulsing or surging glaciers
-
recent very rapid retreat of a temperate glacier in se iceland
Boreas, 2013Co-Authors: Tom Bradwell, Oddur Sigurđsson, Jez EverestAbstract: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 Virkisjokull–Falljokull, 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.
Lee Jones - One of the best experts on this subject based on the ideXlab platform.
-
concentrated pulsed axial glacier flow structural glaciological evidence from kviarjokull in se iceland
Earth Surface Processes and Landforms, 2017Co-Authors: Emrys Phillips, David J A Evans, Jez Everest, Andrew Finlayson, Marek Ewertowski, Ailsa Guild, Lee JonesAbstract:A detailed structural glaciological study carried out on Kviarjokull in SE Iceland reveals that recent flow within this maritime glacier is concentrated within a narrow corridor located along its central axis. This active corridor is responsible for feeding ice from the accumulation zone on the south-eastern side of Oraefajokull to the lower reaches of the glacier and resulted in a c. 200 m advance during the winter of 2013–2014 and the formation of a Push-Moraine. The corridor comprises a series of lobes linked by a laterally continuous zone of highly fractured ice characterised by prominent flow-parallel crevasses, separated by shear zones. The lobes form highly crevassed topographic highs on the glacier surface and occur immediately down-ice of marked constrictions caused by prominent bedrock outcrops located on the northern side of the glacier. Close to the frontal margin of Kviarjokull, the southern side of the glacier is relatively smooth and pock-marked by a number of large moulins. The boundary between this slow moving ice and the active corridor is marked by a number of ice flow-parallel strike-slip faults and a prominent dextral shear zone which resulted in the clockwise rotation and dissection of an ice-cored esker exposed on the glacier surface. It is suggested that this concentrated style of glacier flow identified within Kviarjokull has affinities with the individual flow units which operate within pulsing or surging glaciers
Colm O Cofaigh - One of the best experts on this subject based on the ideXlab platform.
-
glacial geomorphology of terrestrial terminating fast flow lobes ice stream margins in the southwest laurentide ice sheet
Geomorphology, 2014Co-Authors: David J A Evans, Nathaniel J P Young, Colm O CofaighAbstract:Glacial geomorphological mapping of southern Alberta, Canada, reveals landform assemblages that are diagnostic of terrestrial-terminating ice streams/fast flowing outlet glaciers with lobate snouts. Spatial variability in features that comprise the landform assemblages reflects changes in (a) palaeo-ice stream activity (switch on/off); and (b) snout basal thermal regimes associated with climate sensitive, steady state flow. Palaeo-ice stream tracks reveal distinct inset sequences of fan-shaped flowsets indicative of receding lobate ice stream margins. Former ice lobe margins are demarcated by (a) major, often glacially overridden transverse Moraine ridges, commonly comprising glacitectonically thrust bedrock; and (b) minor, closely spaced recessional Push Moraines and hummocky Moraine arcs. Details of these landform types are well exhibited around the former southern margins of the Central Alberta Ice Stream, where larger scale, more intensive mapping identifies a complex glacial geomorphology comprising minor transverse ridges (MTR types 1–3), hummocky terrain (HT types 1–3), flutings, and meltwater channels/spillways. The MTR type 1 constitute the summit corrugation patterns of glacitectonic thrust Moraines or major transverse ridges and have been glacially overrun and moderately streamlined. The MTR type 2 sequences are recessional Push Moraines similar to those developing at modern active temperate glacier snouts. The MTR type 3 document Moraine construction by incremental stagnation because they occur in association with hummocky terrain. The close association of hummocky terrain with Push Moraine assemblages indicates that they are the products of supraglacial controlled deposition on a polythermal ice sheet margin, where the HT type 3 hummocks represent former ice-walled lake plains. The ice sheet marginal thermal regime switches indicated by the spatially variable landform assemblages in southern Alberta are consistent with palaeoglaciological reconstructions proposed for other ice stream/fast flow lobes of the southern Laurentide Ice Sheet, where alternate cold, polythermal, and temperate marginal conditions associated with climate sensitive, steady state flow sequentially gave way to more dynamic streaming and surging activity.
Riedel Thorsten - One of the best experts on this subject based on the ideXlab platform.
-
Assessing permafrost erosion in the Canadian Beaufort Sea, Herschel Island – a biomarker approach
2017Co-Authors: Riedel ThorstenAbstract:Herschel Island is the remnant of an ice-Push Moraine, formed during the farthest advance of the Laurentide Ice Sheet in the late Wisconsin. The island is located in the Canadian Beaufort Sea, in the northwestern part of the Yukon Territory. A marine depression (Herschel Basin), southeastern adjacent to Herschel Island, acts as a sink of organic matter (OM) derived from various sources. The main objective of this master thesis was to determine the amount of OM, derived from Herschel Island, in the deposits of Herschel Basin. Rapidly increasing mean annual air temperatures (MAAT) in high latitude areas raise awareness of a changing Arctic climate and consequences for the Arctic carbon cycle. Biomarker analyses of soil and sediment samples from various study sites on and around Herschel Island show that sediments in Herschel Basin are of prevailing terrigenous origin. Approximately 60 % of the OM in the surface sediments of Herschel Basin and the adjacent nearshore area can be assigned to eroded material from Herschel Island. Investigations on a sediment core from the centre of the basin suggest enhanced erosion rates and increased supply by OM from Herschel Island in the upper section of the core. Results of biomarker analyses of this thesis corroborate a progressing change of the Arctic climate, amplified by positive carbon feedback mechanisms
-
Assessing permafrost erosion in the Canadian Beaufort Sea, Herschel Island - a biomarker approach
PANGAEA, 2017Co-Authors: Riedel ThorstenAbstract:Herschel Island is the remnant of an ice-Push Moraine, formed during the farthest advance of the Laurentide Ice Sheet in the late Wisconsin. The island is located in the Canadian Beaufort Sea, in the northwestern part of the Yukon Territory. A marine depression (Herschel Basin), southeastern adjacent to Herschel Island, acts as a sink of organic matter (OM) derived from various sources. The main objective of this master thesis was to determine the amount of OM, derived from Herschel Island, in the deposits of Herschel Basin. Rapidly increasing mean annual air temperatures (MAAT) in high latitude areas raise awareness of a changing Arctic climate and consequences for the Arctic carbon cycle. Biomarker analyses of soil and sediment samples from various study sites on and around Herschel Island show that sediments in Herschel Basin are of prevailing terrigenous origin. Approximately 60 % of the OM in the surface sediments of Herschel Basin and the adjacent nearshore area can be assigned to eroded material from Herschel Island. Investigations on a sediment core from the centre of the basin suggest enhanced erosion rates and increased supply by OM from Herschel Island in the upper section of the core. Results of biomarker analyses of this thesis corroborate a progressing change of the Arctic climate, amplified by positive carbon feedback mechanisms
