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b. 2800 year time snapshot from experiment #1, 10 cm/year marine melting, zero ice shelf accumulation.
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Citations
... Inferences on the type of ice generating these glacigenic morphologies vary from armadas of deep-draft icebergs crossing the Lomonosov Ridge (Kristoffersen et al., 2004), to the passage of singular large tabular icebergs calved off an ice shelf extending from the eastern sector of the Barents/Kara ice sheet , to the grounding of an ice shelf likely extending from the St. Anna Trough on the Barents Sea (Jakobsson et al., 2005). ...
... Determining the relationship between effective stress and void ratio that defines the critical state line requires advanced triaxial and/or shear strength analyses that are currently not available for sediments from the Yermak Plateau and Lomonosov Ridge. Eurasian Basin, Jakobsson et al. (2005) found that grounding on the Yermak Plateau of an ice shelf extending from the Barents Sea occurred under a number of basal ice melt conditions when strain rates were curtailed due to over-thickened sea ice. While this was an admittedly simple model of ice-shelf growth, it illustrates that the growth and grounding of an ice shelf from the Barents margin remains possible. ...
With the coupled use of multibeam swath bathymetry, high-resolution subbottom profiling and sediment coring from icebreakers in the Arctic Ocean, there is a growing awareness of the prevalence of Quaternary ice-grounding events on many of the topographic highs found in present water depths of <1000 m. In some regions, such as the Lomonosov Ridge and Yermak Plateau, overconsolidated sediments sampled through either drilling or coring are found beneath seismically imaged unconformities of glacigenic origin. However, there exists no comprehensive analysis of the geotechnical properties of these sediments, or how their inferred stress state may be related to different glacigenic processes or types of ice-loading. Here we combine geophysical, stratigraphic and geotechnical measurements from the Lomonosov Ridge and Yermak Plateau and discuss the glacial geological implications of overconsolidated sediments. The degree of overconsolidation, determined from measurements of porosity and shear strength, is shown to result from consolidation and/or deformation below grounded ice and, with the exception of a single region on the Lomonosov Ridge, cannot be explained by erosion of overlying sediments. We demonstrate that the amount and depth of porosity loss associated with a middle Quaternary (∼790–950 thousand years ago – ka) grounding on the Yermak Plateau is compatible with sediment consolidation under an ice sheet or ice rise. Conversely, geotechnical properties of sediments from beneath late Quaternary ice-groundings in both regions, independently dated to Marine Isotope Stage (MIS) 6, indicate a more transient event commensurate with a passing tabular iceberg calved from an ice shelf.
... Evidence for glacial erosion on top of the Lomonosov Ridge (Figure 1) (Jakobsson, 1999; Polyak et al., 2001) makes this scenario possible, provided there were synchronously growing ice shelves on both the Eurasian and Laurentide sides of the ocean. Based on preliminary, simplified numerical modeling (Jakobsson et al., 2006), the growth of an ice shelf several hundred metres thick from the Eurasian margin all the way to the Lomonosov Ridge is possible provided there is a condition that constrains the stretching of ice. Such a constraint might be provided by abnormally thick sea ice or piled-up icebergs during glacial stages, but this hypothesis needs to be tested by more refined modelling based on comprehensive, agespecific palaeogeographical reconstructions. ...
New imagery of ∼14 100 km2 of seafloor along a 640 km stretch of the Alaska and Beaufort margins (ABM) in water depths from 250 to 2800 m depicts a repetitive association of glaciogenic bedforms (lineations and iceberg scours), broad erosional bathymetric features and adjacent downslope turbidite gullies. These bedforms have styles, depths and orientations similar to features discovered earlier on the Chukchi Borderland, up to 800 km northwest of the ABM. Lineations occur across the surface of a flattened bathymetric bench interpreted to have formed by an ice shelf sliding along the continental slope and scraping the seafloor at temporary grounding locations. The glacial geology of surrounding areas suggests that an ice shelf probably flowed from the mouths of overdeepened glacial troughs in the Canadian Arctic Archipelago westward along the ABM and across the Chukchi Borderland. This curved pathway indicates an obstruction to ice flow in the central Canada Basin, possibly caused by either a basin-wide ice shelf or by a pile-up of mega-bergs originating from the Eurasian side of the Arctic Ocean. The ice shelf that affected the ABM may have formed between Oxygen Isotopic Stage 4 to 5b, possibly correlating to an inferred intra-Stage 5 widespread Beringian glaciation. Evidence for glaciogenic features on the ABM corroborates suggestions that large ice volumes and extents existed in the Arctic during Pleistocene glacial periods. These findings have far-reaching implications for Arctic climate studies, ocean circulation, sediment stratigraphy and the stability of circum-Arctic continental ice masses. Copyright © 2007 John Wiley & Sons, Ltd.
... The mechanism of calving involves the propagation of a fracture through the ice and, typically, icebergs calve from an ice shelf when the thickness has been reduced to around a couple of hundred metres (Dowdeswell and Bamber, 2007). In order to test the hypothesis that an ice shelf once grounded on the Lomonosov Ridge, a numerical ice sheet model was applied (Jakobsson et al., 2006). The experiments, albeit not including the complex dynamics of floating ice shelves, indicate that free-flowing ice emanating from the Barents–Kara shelf could not have been thick enough to ground on the Lomonosov Ridge if the ice strain rate is not reduced. ...
... The experiments, albeit not including the complex dynamics of floating ice shelves, indicate that free-flowing ice emanating from the Barents–Kara shelf could not have been thick enough to ground on the Lomonosov Ridge if the ice strain rate is not reduced. However, if this ice shelf was supported or 'buttressed' by a counter-force such as a substantially thickened sea ice, it could become grounded on the ridge in the time frame of major glacial maxima (Jakobsson et al., 2006). A circum-Arctic modelling experiment shows similar preliminary results (Ritz et al., 2007). ...
The last decade of geophysical seafloor mapping in the Arctic Ocean from nuclear submarines and icebreakers reveals a wide variety of glaciogenic geomorphic features at water depths reaching 1000 m. These findings provide new and intriguing insights into the Quaternary glacial history of the Northern Hemisphere. Here we integrate multi- and single beam bathymetric data, chirp sonar profiles and sidescan images from the Chukchi Borderland and Lomonosov Ridge to perform a comparative morphological seafloor study. This investigation aims to elucidate the nature and provenance of ice masses that impacted the Arctic Ocean sea floor during the Quaternary. Mapped glaciogenic bedforms include iceberg keel scours, most abundant at water depths shallower than ∼350–400 m, flutes and megascale glacial lineations extending as deep as ∼1000 m below the present sea level, small drumlin-like features and morainic ridges and grounding-zone wedges. The combination of these features indicates that very large glacial ice masses extended into the central Arctic Ocean from surrounding North American and Eurasian ice sheets several times during the Quaternary. Ice shelves occupied large parts of the Arctic Ocean during glacial maxima and ice rises were formed over the Chukchi Borderland and portions of the Lomonosov Ridge. More geophysical and sediment core data combined with modeling experiments are needed to reconstruct the timing and patterns of these events. Copyright © 2008 John Wiley & Sons, Ltd.
