Comparative Shoreface Evolution along the Laptev Sea Coast.

Are, F.E., Grigoriev, M.N., Hubberten, H.-W., Rachold, V., Razumov, S. and Schneider, W. (2002) Comparative Shoreface Evolution along the Laptev Sea Coast. Polarforschung (70). pp. 135-150.

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Abstract

Field investigations 01' the Laptev Sea shoreface morphology were
carried out (1) off erosional shores cornposed 01' unconsolidated sediments,
(2) off the modern delta shores 01' the Lena River, and (3) off rocky shores.

It was found that profiles off erosional shores had a concave shape. This shape
is not weil described by commonly applied power functions, a feature, which
is in disagreement with the generally accepted concept 01' the equilibrium
shape 01' shoreface profiles. The position 01' the lower shoreface boundary is
determined by the elevation 01' the coastal lowland inundated during the last
transgrcssion (at -5 to -10m) and may easily be recognized by a sharp, an order
01' magnitude decrease in the mean inclination 01' the sea f1oor. The mean
shoreface inclination depends on sediment grain-size and ranges from 0.0022
to 0.033. The concave shape 01' the shoreface did not change substantially
during the last 20-30 years, which indicates that shoreline retreat did not slow
down and hence suggests continued intensive coastal erosion in the 21" century.

The underwater part 01' the Lena River delta extends up to 35 km offshore. Its
upper part is fonned by a shallow andup to 18-km wide bench, which reaches
deprhs 01' 2-3 m along the outer edge. The evolution 01' the delta was irregular.
Whereas some parts 01' the delta are advancing rapidly (58 m/year), other parts
are eroding. Comparison 01' measured profiles with older bathymetric data
gave an opportunity to evaluate the changes 01' the underwater delta over past
decades. Bathymetric surveys 01' the seabed around the delta can thus contribute
towards a quantification 01' the scdiment budget 01' the river-sea system.

In addition, sorne sections 01' the Laptev Sea coast are composed 01' bedrock
that has a comparatively low resistance to wave erosion. These sections may
supply a considerable amount 01' sediment, especially if the cliffs are high.
This source must therefore also be taken into account when assessing the contribution
01' shore erosion to the Laptev Sea sediment budget.

Document Type: Article
Keywords: shoreface evolution; Laptev Sea Coast
Refereed: Yes
Open Access Journal?: Yes
ISSN: 0032-2490
Projects: Otto Schmidt Laboratory
Date Deposited: 13 Oct 2015 07:32
Last Modified: 13 Oct 2015 07:32
URI: http://oceanrep.geomar.de/id/eprint/29274

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