Submarine landforms produced by drifting icebergs are common on the sedimentary beds of the polar... more Submarine landforms produced by drifting icebergs are common on the sedimentary beds of the polar seas. High-resolution multibeam-bathymetric images have revealed a variety of iceberg-related landforms, ranging from 1 to 2 m high corrugation ridges (e.g. Jakobsson et al. 2011; Graham et al. 2013) to large linear to curvilinear ploughmarks several tens of kilometres long and tens of metres deep, that are often distributed chaotically on polar continental shelves (e.g. Dowdeswell et al. 2010). Extensive lateral erosion of submarine ridge-top sediments in the central Arctic Ocean has also been attributed to the impact of deep-drafted icebergs that were once much more abundant in the Arctic than they are today (Jakobsson et al. 2008). Submarine terraces with remarkably flat surfaces were observed on the crest and along the distal slope of a large terminal-moraine ridge at the mouth of the Hambergbukta (Fig. 1a, c), a fjord in southeastern Spitsbergen (Fig. 1b). The terraces were recorded at several bathymetric levels from 29–66 m in water depth with their surface areas varying from c. 0.04 km2 to >2 km2 (Fig. 1a, d). Fig. 1. ( a ) Swath-bathymetric imagery …
Sediments are incorporated into glaciers mainly by basal erosion and freeze-on, and by debris-fal... more Sediments are incorporated into glaciers mainly by basal erosion and freeze-on, and by debris-fall onto the ice surface along the slopes of adjacent mountainsides. Flow-parallel debris ridges formed at the confluence of glaciers are known as medial moraines (Benn & Evans 2010). Medial moraines have a number of different origins (Eyles & Rogerson 1978; Benn & Evans 2010), including ingestion of basal marginal debris in deep crevasses and redistribution of supra-, en- and subglacial debris in the shear zone between converging glaciers (e.g. Sharp 1988; Vere & Benn 1989; Hambrey & Glasser 2003). Medial moraines up to tens of kilometres long and tens of metres high can be preserved after glacier retreat, marking the former flow path of ice masses. Medial moraines have also been shown to exert significant control over surging glaciers by inhibiting and/or redirecting glacier flow. Locally persistent subglacial meltwater conduits located under the medial moraines can also inhibit glacier surges by draining subglacial meltwater efficiently and decreasing basal water pressure (Benn et al. 2009). Hambergbukta …
ABSTRACTObservations of subglacial landforms yielding the configuration and dynamics of former ic... more ABSTRACTObservations of subglacial landforms yielding the configuration and dynamics of former ice‐flows have for the first time been made in Rijpfjorden and Duvefjorden, Nordaustlandet, Svalbard, using sub‐bottom acoustic, swath‐bathymetric data and sediment cores. Five acoustic‐stratigraphic units were distinguished suggesting the presence of a complete glacial–postglacial succession in the central fjord basins. 14C ages from the sediments indicate that the inner Rijpfjorden and central Duvefjorden were deglaciated before ca. 10.6 cal ka BP and 11.0 cal ka BP, respectively. Maximum sediment thickness in Rijpfjorden and Duvefjorden is 26 m, resulting in sediment accumulation rates of ca. 66 cm ka−1. The landform record suggests that the ice streaming in both fjords was topographically controlled. The considerably deeper basin and higher elongation ratios of the crag‐and‐tails in Duvefjorden are linked to the faulted bedrock and possibly to somewhat larger ice stream and/or more foc...
Streamlined sedimentary and bedrock glacial landforms are widespread on high-latitude continental... more Streamlined sedimentary and bedrock glacial landforms are widespread on high-latitude continental shelves and in fjords. It has been shown that they are orientated in the direction of past ice flow and are indicative of fast motion linked to basal processes (e.g. Clark 1994). Elongation ratios of these landforms have been suggested to reflect past ice velocity, with higher elongation ratios being characteristic of faster ice flow (e.g. Clark 1993). However, the subglacial substrate has a considerable influence on ice flow and on the resulting glacial landforms (e.g. Heroy & Anderson 2005). Using the character and distribution of streamlined, subglacially produced landforms, the extent and dynamics of former ice sheets and ice streams has been successfully reconstructed (e.g. Ottesen et al. 2005; Dowdeswell et al. 2010; Hogan et al. 2010 a , b ). The seafloor of Rijpfjorden on Nordaustlandet in eastern Svalbard (Fig. 1f) is dominated by crudely streamlined bedrock with south–north to SSW–NNE long-axis …
Terrestrial glacial geomorphology has long been used to evaluate the extent, chronology and dynam... more Terrestrial glacial geomorphology has long been used to evaluate the extent, chronology and dynamics of former glaciers and ice sheets. New marine geophysical methods provide an opportunity to stud ...
Submarine landforms produced by drifting icebergs are common on the sedimentary beds of the polar... more Submarine landforms produced by drifting icebergs are common on the sedimentary beds of the polar seas. High-resolution multibeam-bathymetric images have revealed a variety of iceberg-related landforms, ranging from 1 to 2 m high corrugation ridges (e.g. Jakobsson et al. 2011; Graham et al. 2013) to large linear to curvilinear ploughmarks several tens of kilometres long and tens of metres deep, that are often distributed chaotically on polar continental shelves (e.g. Dowdeswell et al. 2010). Extensive lateral erosion of submarine ridge-top sediments in the central Arctic Ocean has also been attributed to the impact of deep-drafted icebergs that were once much more abundant in the Arctic than they are today (Jakobsson et al. 2008). Submarine terraces with remarkably flat surfaces were observed on the crest and along the distal slope of a large terminal-moraine ridge at the mouth of the Hambergbukta (Fig. 1a, c), a fjord in southeastern Spitsbergen (Fig. 1b). The terraces were recorded at several bathymetric levels from 29–66 m in water depth with their surface areas varying from c. 0.04 km2 to >2 km2 (Fig. 1a, d). Fig. 1. ( a ) Swath-bathymetric imagery …
Sediments are incorporated into glaciers mainly by basal erosion and freeze-on, and by debris-fal... more Sediments are incorporated into glaciers mainly by basal erosion and freeze-on, and by debris-fall onto the ice surface along the slopes of adjacent mountainsides. Flow-parallel debris ridges formed at the confluence of glaciers are known as medial moraines (Benn & Evans 2010). Medial moraines have a number of different origins (Eyles & Rogerson 1978; Benn & Evans 2010), including ingestion of basal marginal debris in deep crevasses and redistribution of supra-, en- and subglacial debris in the shear zone between converging glaciers (e.g. Sharp 1988; Vere & Benn 1989; Hambrey & Glasser 2003). Medial moraines up to tens of kilometres long and tens of metres high can be preserved after glacier retreat, marking the former flow path of ice masses. Medial moraines have also been shown to exert significant control over surging glaciers by inhibiting and/or redirecting glacier flow. Locally persistent subglacial meltwater conduits located under the medial moraines can also inhibit glacier surges by draining subglacial meltwater efficiently and decreasing basal water pressure (Benn et al. 2009). Hambergbukta …
ABSTRACTObservations of subglacial landforms yielding the configuration and dynamics of former ic... more ABSTRACTObservations of subglacial landforms yielding the configuration and dynamics of former ice‐flows have for the first time been made in Rijpfjorden and Duvefjorden, Nordaustlandet, Svalbard, using sub‐bottom acoustic, swath‐bathymetric data and sediment cores. Five acoustic‐stratigraphic units were distinguished suggesting the presence of a complete glacial–postglacial succession in the central fjord basins. 14C ages from the sediments indicate that the inner Rijpfjorden and central Duvefjorden were deglaciated before ca. 10.6 cal ka BP and 11.0 cal ka BP, respectively. Maximum sediment thickness in Rijpfjorden and Duvefjorden is 26 m, resulting in sediment accumulation rates of ca. 66 cm ka−1. The landform record suggests that the ice streaming in both fjords was topographically controlled. The considerably deeper basin and higher elongation ratios of the crag‐and‐tails in Duvefjorden are linked to the faulted bedrock and possibly to somewhat larger ice stream and/or more foc...
Streamlined sedimentary and bedrock glacial landforms are widespread on high-latitude continental... more Streamlined sedimentary and bedrock glacial landforms are widespread on high-latitude continental shelves and in fjords. It has been shown that they are orientated in the direction of past ice flow and are indicative of fast motion linked to basal processes (e.g. Clark 1994). Elongation ratios of these landforms have been suggested to reflect past ice velocity, with higher elongation ratios being characteristic of faster ice flow (e.g. Clark 1993). However, the subglacial substrate has a considerable influence on ice flow and on the resulting glacial landforms (e.g. Heroy & Anderson 2005). Using the character and distribution of streamlined, subglacially produced landforms, the extent and dynamics of former ice sheets and ice streams has been successfully reconstructed (e.g. Ottesen et al. 2005; Dowdeswell et al. 2010; Hogan et al. 2010 a , b ). The seafloor of Rijpfjorden on Nordaustlandet in eastern Svalbard (Fig. 1f) is dominated by crudely streamlined bedrock with south–north to SSW–NNE long-axis …
Terrestrial glacial geomorphology has long been used to evaluate the extent, chronology and dynam... more Terrestrial glacial geomorphology has long been used to evaluate the extent, chronology and dynamics of former glaciers and ice sheets. New marine geophysical methods provide an opportunity to stud ...
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