The Role of Coastal Retreat for Sedimentation in the Laptev Sea
F.E.Are
St. Petersburg State University 0/ Means 0/ Communications, 9 Moskovskii, 190031 St. Petersburg, Russia
Received 29 January 1997 and accepted in revised form 31 July 1997
Abstract - According to the published data the amount of sediments supp1ied to the Laptev
Sea from shore erosion is an important component of the overall sediment balance of that
sea, but at present one can ca1culate this amount more accurately than before. Data on shore
retreat rate, height of coastal c1iffs, maximum depth of wave influence on the sea floor,
position of the lower boundary of shore face, 1itho10gy of sediments building the coast and
shore face, volumetrie ice content of these sediments and their dry bulk density are needed
for such ca1culations. All these data are available from aerial photographs, geo10gica1 and
various geographical maps and bathimetric monitoring. The methodo10gy of ca1culations is
discussed in this paper. The amount of sediment released to the sea due to erosion of
Anabar-01enyok seetion of the coast is ca1culated as an examp1e. This amount is compared
with the published data on the sediment discharge of the rivers draining into the Laptev Sea.
The results of comparison showed that (1) - the amount of sediments supplied to the Laptev
Sea by rivers and retreating shores are of the same order; (2) - the transport of sediments
into the sea by rivers is poorly studied and difficult to evaluate by means of direct
measurements. To solve this problem the amount of sediments used for the growth of
deltas must be determined by means of comparison of aerial photographs and bathymetric
profiles taken with sufficient time interval and by subtracting this amount from the river
sediment discharge.
Introduction
Thousands of kilometers of Arctic sea coast retreat 2-6 mly under the action of shore erosion
(Are, 1985; Reimnitz et al., 1988). So some tens of square kilometers of Arctic land are
consumed by the sea every year. Actually it is a special kind of sea transgression occurring with
the rather constant sea level. This process was especially intensive just after the end of the last
glacio-eustatic transgression about 5000 years ago. A few islands on the Siberian shelf
disappeared due to erosion oftheir shores during this time (Zigarev and Sovershaev, 1984).
It is evident that shore erosion has to be taken into account by various kinds of modern
human activity on the coast. For example Bykovsky settlement on the Laptev Sea .coast and
Tuktoyaktuk on the Beaufort Sea coast are in danger because of the sea offensive.
The study of shore erosion is needed for proper understanding of the transformation of
modern off-shore permafrost which was widespread on the emerged shelf before last sea
transgression. The upper tens of meters of shelf permafrost contained 60-80 % ice by volume.
The thawing of this ice leads to subsidence of the surface by up to 30-40 m. This
transformation would become especially important where oil and gas are produced offshore and
are brought across the shifting shoreline in pipes.
Looking into the future we have to consider the influence of global changes on shore erosion.
It is known that sea level was rising at a rate between 1 and 2.5 mmly during last 100 years. It
is supposed that this rise will continue in the future and most probably will reach 50 cm in the
year 2100 (Houghton et al., 1996).1t is evident that such a rise of sea level will accelerate shore
erosion considerably and may be dramatically. Special studies are needed to forecast the
consequences.
Large quantities of free gases and gas hydrates of local and hypo gene origin are preserved in
frozen sediments and rocks. The retreat of Arctic shores creates conditions necessary for release
In: Kassens, H., H.A. Bauch, I. Dmitrenko, H. Eicken, H.-W. Hubberten, M. Melles, J. Thiede and L. Timokhov (eds.)
Land-Ocean Systems in the Siberian Arctic: Dynamics and History. Springer-Verlag, Berlin, 1999, 287-295.
F.E.Are
St. Petersburg State University 0/ Means 0/ Communications, 9 Moskovskii, 190031 St. Petersburg, Russia
Received 29 January 1997 and accepted in revised form 31 July 1997
Abstract - According to the published data the amount of sediments supp1ied to the Laptev
Sea from shore erosion is an important component of the overall sediment balance of that
sea, but at present one can ca1culate this amount more accurately than before. Data on shore
retreat rate, height of coastal c1iffs, maximum depth of wave influence on the sea floor,
position of the lower boundary of shore face, 1itho10gy of sediments building the coast and
shore face, volumetrie ice content of these sediments and their dry bulk density are needed
for such ca1culations. All these data are available from aerial photographs, geo10gica1 and
various geographical maps and bathimetric monitoring. The methodo10gy of ca1culations is
discussed in this paper. The amount of sediment released to the sea due to erosion of
Anabar-01enyok seetion of the coast is ca1culated as an examp1e. This amount is compared
with the published data on the sediment discharge of the rivers draining into the Laptev Sea.
The results of comparison showed that (1) - the amount of sediments supplied to the Laptev
Sea by rivers and retreating shores are of the same order; (2) - the transport of sediments
into the sea by rivers is poorly studied and difficult to evaluate by means of direct
measurements. To solve this problem the amount of sediments used for the growth of
deltas must be determined by means of comparison of aerial photographs and bathymetric
profiles taken with sufficient time interval and by subtracting this amount from the river
sediment discharge.
Introduction
Thousands of kilometers of Arctic sea coast retreat 2-6 mly under the action of shore erosion
(Are, 1985; Reimnitz et al., 1988). So some tens of square kilometers of Arctic land are
consumed by the sea every year. Actually it is a special kind of sea transgression occurring with
the rather constant sea level. This process was especially intensive just after the end of the last
glacio-eustatic transgression about 5000 years ago. A few islands on the Siberian shelf
disappeared due to erosion oftheir shores during this time (Zigarev and Sovershaev, 1984).
It is evident that shore erosion has to be taken into account by various kinds of modern
human activity on the coast. For example Bykovsky settlement on the Laptev Sea .coast and
Tuktoyaktuk on the Beaufort Sea coast are in danger because of the sea offensive.
The study of shore erosion is needed for proper understanding of the transformation of
modern off-shore permafrost which was widespread on the emerged shelf before last sea
transgression. The upper tens of meters of shelf permafrost contained 60-80 % ice by volume.
The thawing of this ice leads to subsidence of the surface by up to 30-40 m. This
transformation would become especially important where oil and gas are produced offshore and
are brought across the shifting shoreline in pipes.
Looking into the future we have to consider the influence of global changes on shore erosion.
It is known that sea level was rising at a rate between 1 and 2.5 mmly during last 100 years. It
is supposed that this rise will continue in the future and most probably will reach 50 cm in the
year 2100 (Houghton et al., 1996).1t is evident that such a rise of sea level will accelerate shore
erosion considerably and may be dramatically. Special studies are needed to forecast the
consequences.
Large quantities of free gases and gas hydrates of local and hypo gene origin are preserved in
frozen sediments and rocks. The retreat of Arctic shores creates conditions necessary for release
In: Kassens, H., H.A. Bauch, I. Dmitrenko, H. Eicken, H.-W. Hubberten, M. Melles, J. Thiede and L. Timokhov (eds.)
Land-Ocean Systems in the Siberian Arctic: Dynamics and History. Springer-Verlag, Berlin, 1999, 287-295.