Flume studies and field observations of the interaction of frazil ice and anchor ice with sediments

Kempema, Edward W.; Reimnitz, Erk; Hunter, Ralph E.

doi:10.3133/ofr86515

Cited by 16 publications

(8 citation statements)

References 13 publications

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“…The indicated heat flux from the subbottom explains why stormgenerated anchor ice is not preserved into winter. of sediment moving with anchor ice as bedload during storms, as suggested by observations in turbulent streams [Osterkamp and Gosink, 1982;Arden and Wigle, 1972], by flume studies [Kempema et al, 1986] and also by the sand slabs tossed by waves onto beaches, is probably larger than that rafted on the sea surface during the next summer. When wave orbital motion is superimposed on storm-driven currents of 100 cm/s, bedload transport of sediment with ice may be significant.…”

Section: Regional Settingmentioning

confidence: 89%

Anchor ice, seabed freezing, and sediment dynamics in shallow Arctic Seas

Reimnitz¹,

Kempema²,

Barnes³

1987

J. Geophys. Res.

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135

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Diving investigations confirm previous circumstantial evidence of seafloor freezing and anchor ice accretion during freeze‐up storms in the Alaskan Beaufort Sea. These related bottom types were found to be continuous from shore to 2‐m depth and spotty to 4.5‐m depth. Spotty anchor ice occurred as pillow‐shaped crystal aggregates on buried slabs of frozen sand surrounded by unfrozen sand. Considerations of required conditions for ice bonding and anchor ice growth allows regional extrapolation and suggests the possibility of anchor ice growth out to 20‐m depth, the estimated maximum depth of supercooling during fall storms. Anchor ice and seabed freezing apparently do not develop during a calm freeze‐up. Because of the abrupt growth of anchor ice during a freezing storm and its release soon after formation of a surface ice cover, this ice type has not been documented before. The concretelike nature of frozen bottom, where present, should prohibit sediment transport by any conceivable wave or current regime during the freezing storm. But elsewhere, particularly where the bonded crust is broken by grounded ice, anchor ice lifts coarse material off the bottom and incorporates it into the ice canopy, thereby leading to significant ice rafting of shallow shelf sediment and likely sediment loss to the deep sea.

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Section: Regional Settingmentioning

confidence: 89%

Anchor ice, seabed freezing, and sediment dynamics in shallow Arctic Seas

Reimnitz¹,

Kempema²,

Barnes³

1987

J. Geophys. Res.

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135

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“…Frazil ice that attaches to bottom sediments in such shelf regions forms "anchor ice," which can later break loose and carry coarser-grained bottom sediments into the forming coastal pack ice. These two processes yield turbid ice with sediment concentrations much higher than those of the ambient seawater (Kempema et al, 1986;Clayton et al, 1990;Reimnitz et al, 1992Reimnitz et al, , 1993a.…”

Section: Introductionmentioning

confidence: 99%

Transport of 137Cs And 239,240Pu with Ice-rafted Debris in the Arctic Ocean

Landa¹,

Reimnitz²,

Beals³

et al. 1998

ARCTIC

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Ice rafting is the dominant mechanism responsible for the transport of fine-grained sediments from coastal zones to the deep Arctic Basin. Therefore, the drift of ice-rafted debris (IRD) could be a significant transport mechanism from the shelf to the deep basin for radionuclides originating from nuclear fuel cycle activities and released to coastal Arctic regions of the former Soviet Union.In this study, 28 samples of IRD collected from the Arctic ice pack during expeditions in 1989 -95 were analyzed for 137 Cs by gamma spectrometry and for 239 Pu and 240 Pu by thermal ionization mass spectrometry. 137 Cs concentrations in the IRD ranged from less than 0.2 to 78 Bq·kg -1 (dry weight basis). The two samples with the highest 137 Cs concentrations were collected in the vicinity of Franz Josef Land, and their backward trajectories suggest origins in the Kara Sea. Among the lowest 137 Cs values are seven measured on sediments entrained on the North American shelf in 1989 and 1995, and sampled on the shelf less than six months later.Concentrations of 239 Pu + 240 Pu ranged from about 0.02 to 1.8 Bq·kg -1 . The two highest values came from samples collected in the central Canada Basin and near Spitsbergen; calculated backward trajectories suggest at least 14 years of circulation in the Canada Basin in the former case, and an origin near Severnaya Zemlya (at the Kara Sea/Laptev Sea boundary) in the latter case. While most of the IRD samples showed 240 Pu/ 239 Pu ratios near the mean global fallout value of 0.185, five of the samples had lower ratios, in the 0.119 to 0.166 range, indicative of mixtures of Pu from fallout and from the reprocessing of weapons-grade Pu. The backward trajectories of these five samples suggest origins in the Kara Sea or near Severnaya Zemlya.RÉSUMÉ. Le transport glaciel constitue le principal mécanisme responsable du transport des sédiments à grain fin depuis les zones côtières jusqu'à la fosse du bassin Arctique. La dérive des débris du transport glaciel pourrait constituer un important mécanisme de transport, depuis la plate-forme continentale jusqu'à la fosse marine, pour des radionucléides provenant d'activités connexes au cycle du combustible nucléaire, radionucléides qui sont éliminés vers les zones côtières arctiques de l'ancienne Union Soviétique.Dans cette étude, on a analysé 28 échantillons de débris de transport glaciel recueillis dans la glace arctique au cours d'expéditions effectuées de 1989 à 1995, en vue d'y déceler du 137 Cs par spectrométrie gamma ainsi que du 239 Pu et du 240 Pu par spectrométrie de masse réalisée par thermo-ionisation. Les concentrations de 137 Cs dans les débris de transport glaciel allaient de moins de 0,2 à 78 Bq·kg -1 (poids sec). Les deux échantillons ayant les concentrations en 137 Cs les plus élevées ont été recueillis à proximité de l'archipel François-Joseph, et leurs trajectoires régressives suggèrent qu'ils proviennent de la mer de Kara. Parmi les plus faibles valeurs de 137 Cs, sept ont été mesurées sur des sédiments arrivés sur la plate-forme ...

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“…The externally fragile crystal lattice of ice pillows obviously was a product of post-storm ice growth, as was the buildup of rippled, loose sand around the pillows. Flume studies show that such crystal lattice structures can grow by accretion of frazil ice onto an ice-bonded sediment core (Kempema, 1986).…”

Section: Discussionmentioning

confidence: 99%