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Rearic, D.M., 1986

Temporal and spatial character of newly-formed ice gouges in eastern Harrison Bay, Alaska, 1977-1978

Bibliographic Reference

Rearic, D.M., 1986, Temporal and spatial character of newly-formed ice gouges in eastern Harrison Bay, Alaska, 1977-1978: San Jose, California, San Jose State University, M.S. thesis, 80 p., illust.


Interaction between the dynamic elements of wind, water, ice, and seafloor sediment is recorded on the continental shelf of the Alaska Beaufort Sea in the form of ice gouges. Gouging of the seafloor by ice keels causes a ridge and furrow microtopography with accompanying horizontal and vertical movement of the sediments (Barnes et al., 1984). Sea-ice forces are responsible for large volumes of sediment disruption and redistribution across the shelf (Barnes et al., 1984), while hydraulic forces from waves and currents further redistribute this sediment, in many cases filling depressions and smoothing the bottom (Barnes and Reimnitz, 1979; Reimnitz and Kempema, 1982).

The sea-ice canopy formed over the inner shelf in winter is broken by zones of ice ridging caused by shear and compressional forces between permanent rotating polar pack ice and seasonal stable shore fast ice (Hibler et al., 1974; Reimnitz et al., 1978; Stringer, 1978; Prichard, 1980). The formation of ice ridges causes ice blocks to be forced under the ice surface to form ice keels, which may come into contact with the seafloor. When mobile ice keels in contact with the seafloor plow through the sediments, ice gouges are formed.

Recurrence rates for ice gouging of the seafloor as well as the yearly size variation of the features is of major importance today due to petroleum development activities now taking place in the Alaskan Beaufort Sea (Oil and Gas Journal, 1983). Development plans are dependent on knowledge of yearly gouge rates, depths, widths, and areal distributions in order to protect subsea pipelines from ice impact and bottom-founded structures from excessive point-source loads and stresses. Sea-ice also has a significant geologic effect on the seafloor through the destruction of sedimentary features such as bedding structure and biological borings, the building and/or maintaining of shoals (Reimnitz and Kempema, 1984), the bulldozing of shelf sediment onto the beaches by ice ride-up (Barnes, 1982; Kovacs, 1983, 1984), the creation of sedimentary traps by the plowing of ice gouge furrows (Reimnitz and Kempema, 1982), and the transport of sediment by actual bulldozing and resuspension of sediment during ice gouging (Barnes and Rearic, in press). Data on yearly ice-gouge characteristics is unfortunately very sparse and an increase in the understanding of this marine process will lead to greater knowledge about the environment of high-latitude continental shelves and their hazards. The presence of sea ice and extreme low winter temperatures creates an environment that is affected by forces not usually found in low-latitude marine environments. Ice contact with the seafloor, permafrost in the offshore sediments, the draining of the rivers in spring through holes in the ice canopy, and ice ride-up and piling on the beaches are dynamic conditions unique to the high-latitude environment.

Ice gouges that are dated as less than one year old have been studied in the Alaska Beaufort Sea and the results are presented here. The characteristics of these relatively newly formed ice gouges are presented and an interpretation as to the significance of the information is discussed. In some cases the data speaks for itself by allowing the reader to observe variations in the characteristics over time and between shelf environments, while in other cases further interpretation of the data in the form of graphs, figures, and discussion enhances the importance of the study in relation to sedimentary processes now occurring in the Alaska Beaufort Sea.

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