Encyclopedia of Coastal Science

Living Edition
| Editors: Charles W. Finkl, Christopher Makowski

Arctic, Coastal Geomorphology

  • H. Jesse WalkerEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-3-319-48657-4_13-2

Introduction

The Arctic, long considered a “… region of darkness and mists, where sea, land and sky were merged into a congealed mass” (Nansen 1911, p. 1), has subsequently been defined according to its astronomic, biotic, climatic, cryologic, geomorphic, and hydrologic characteristics (Walker 1983). From the standpoint of coastal morphology, it is the juncture of whichever category is used with the coastline that is important. The determinant that provides the greatest extent to the coastline is sea ice. In the Northern Hemisphere using sea ice as the limiting boundary results in the inclusion of the coastlines of Hudson Bay, Labrador, and Newfoundland, the Sea of Okhotsk and most of the Baltic and Bering Seas (See Ice-Bordered Coasts). By many other criteria, most of these coastlines do not qualify as Arctic.

In this entry, the discussion centers on those coasts that border the Arctic Ocean and surround Greenland and the islands of the Canadian Archipelago. When the lengths of these coastlines are measured on the American Geographical Society 1:5,000,000 Map of the Arctic Region, they total 82,000 km, Greenland (16,000 km), the Canadian Archipelago (26,000 km) and the other arctic islands (9000 km) (Fig. 1). Other calculations, depending on the detail used, provide larger numbers. For example, Bird (1985) states that the coastline of the islands of the Canadian Archipelago is at least 90,000 km long and Nielsen (1985) reports that that of Greenland is some 40,000 km long.
Fig. 1

Geologic base, continental shelf and sea ice distribution in the Arctic. (Compiled from numerous sources including Sater et al. (1971), Péwé (1983), and Walker (1998))

The Geologic Base

Three large, stable shields composed of Pre-Cambrian rocks form the cornerstones of the Arctic, one each in Canada, Scandinavia, and central Siberia (Fig. 1). The actual exposed lengths of these Pre-Cambrian rocks along the coast is less than what the size of the shields would lead one to believe because their margins have been buried under eroded shield materials. Between and adjacent to the shields, including their buried margins, are folded mountains (or portions of the so-called “mobile belts” of the Northern Hemisphere) some of which extend to the coast (Fig. 1).

Like the embedded coasts surrounding the Atlantic Ocean, Arctic coastal margins are affected by minimal tectonic activity. Earthquakes do occur, as on the north coast of Baffin Island, north of the Mackenzie delta and in the northwest Canadian Archipelago, but they are of low magnitude.

The most recent major event to impact most of the arctic coastal zone is glaciation. The main coastal areas not directly affected by glacial ice during the Pleistocene include the east-central Siberian lowland, a small part of the western Canadian Archipelago and the north coast of Alaska. However, even those coastal zones, though never actually covered by ice sheets, were affected by drainage across them from glacial fronts and by the changes in location of the interface between land and sea due to changes in sea level as the continental glaciers waxed and waned. Today, only a small percentage of the arctic coastline is being modified by glaciers. Major segments are found on Greenland, Ellesmere Island, Novaya Zemblya, and Spitzbergen.

In addition to the direct modifications of the coastlines by glaciers in the form of moraines, drumlins, fiords and strandflats, the rebound that followed deglaciation has (and is) converted formerly submerged coastal belts into subaerial coastal plains. Such occurrences are especially common in northern Canada, the Canadian Archipelago, Scandinavia and the islands north of Siberia. In many locations former coastal features are found today at elevations of as much as 250 m. In the Canadian Archipelago and the Hudson Bay area rebound is continuing at rates of as much as 1 m/century (Andrews 1970).

The Continental Shelf and the Coastal Plain

The two basic contrasting zones of coastal significance in the Arctic are its subaerial and subaqueous portions. These two zones are highly variable in width and in the forms and processes they possess. The continental shelf varies in width from a few kilometers, as off parts of Greenland, to more than 800 km in the East Siberian Sea. With sea-level rise and with coastal erosion, the width of the subaqueous portions of the Arctic Ocean has been increasing. Weber (1989, p. 815), for example, writes that “The Chukchi Shelf was eroded far into the continent and transects the principal mountain ranges of Northern Alaska.” Much of the continental shelf of the Arctic Ocean is flat and shallow, cut only by a few submarine valleys such as those off rivers like the Kolyma and Indigirka and off Barrow, Alaska. Most of the smaller features on the shelves are the result of ice gouging and deltaic deposition or are remnants of subaerial erosion that occurred during lower sea levels (Reimnitz et al. 1988; Weber 1989).

The coastal plain, although not as extensive as the continental shelf, possesses a greater variety of forms and processes than the shelf it borders. Although, the coastal plain of today is subaerial much of it, as in Alaska and northwestern Canada, is the “… landward edge of a continental shelf that has experienced repeated transgressions and withdrawals of the sea …” (Bird 1985, p. 243). It is comprised mainly of gravels, sands, and silts that presently are ice-bonded in the permafrost. In places it is low-lying and level. Near the Indigirka River mouth, for example, storm surges have reached as far as 30 km inland (Zenkovich 1985).

The major forms of the coastal plain that border the ocean include barrier islands and lagoons, sand and gravel beaches, mudflats and marshes, sand dunes, low coastal bluffs, deltas and lengthy rias (gubas in Russian).

Among the arctic coast’s most conspicuous and extensive features are its barrier islands and sandy spits. They are present along much of the coast of arctic Alaska and northwest Canada and along various parts of the Siberian coastline. Some barrier islands are remnants of the coastal plain whereas most are composed of gravel and sand which originated offshore.

Although, most of the deltas in the Arctic are small, they are sufficiently numerous to occupy a sizeable proportion of the coastline. For example, 135 km (or 9%) of the coastline of Alaska between Cape Lisburne and the Canadian border is deltaic (Wiseman et al. 1973).

Some arctic deltas, like the Mackenzie, Lena, Indigirka, Kolyma, and Colville, face the open ocean, whereas others, such as the Yenisey and Ob, are located at the head of lengthy and narrow gubas (Fig. 2). These two deltas, even though confined to the head of their estuaries, are the fourth and fifth largest deltas in Siberia. Among arctic deltas, that of the Lena River (Fig. 3) is unique because its structure, shape, and relief appear to be the result of tectonic activity as well as modern hydrological processes (Are and Reimnitz 2000).
Fig. 2

The Arctic illustrating the numerous factors that affect the coast. (Compiled from numerous sources including NOAA (1981), Lewis (1982), Péwé (1983), and Walker (1998))

Fig. 3

The Lena River delta, the largest at 32,000 km2 in the Arctic

The deltas of the Arctic, like those elsewhere, are relatively young in that their present-day expression stems only from the time sea-level rise reached a nearly stillstand position about 5000 BP. All of the older deltas in the Arctic contain most of the features, such as distributaries, abandoned channels, lakes, sand bars, mudflats, and sand dunes, that are typical of deltas elsewhere. However, they also possess such cryospheric forms as ice-wedges, ice-wedge polygons, pingos, and thermokarst lakes.

Conditions, Forms and Processes

The present-day appearance of the arctic’s coastline, like that of coastlines elsewhere, depends on modifications that have occurred to the geologic base it inherited. Along many coastlines, these modifications include those engineered by humans. In the case of the Arctic, however, human modifications are still minimal, although they do occur at the mouth of some rivers, adjacent to some coastal villages, and where mining operations, including petroleum exploration and production enterprises, have been developed.

Thus, most of the coastal forms in the Arctic, as is true also of the Antarctic, are the result of natural conditions and processes. Included are those conditions and processes associated with cold climates such as low temperature, snow, ice (river and sea) and permafrost with its many forms of ground ice as well as those of more universal occurrence like relief, structure, sediment type, river discharge, offshore gradient, wave action, currents, storm surges, and tides (Fig. 2).

Cold climate processes are frequently divided into two types: glacial and periglacial (French 1989). Although in the arctic of today glacial processes impact only short lengths of shore, periglacial processes are of major importance along the entire coastline (Harper 1978) including those sections most recently deglaciated.

The sine qua non of periglacial processes is the freezing and thawing of the ground, which is mainly temperature dependent. The change from one state to the other may be daily, seasonal or over longer (thousands of years in some cases) periods of time.

Permafrost

Permafrost (a condition in which ground temperature remains below 0 °C for more than 2 years) is present along most of the coastline of the Arctic from which it extends both landward and seaward (Fig. 2). Although permafrost is defined by temperature, it is water in the form of ice that is especially critical in coastal modification (Fig. 4). The included ice, which serves to bond unconsolidated sediments as long as they remain in a frozen state, makes the mass especially unstable when thawed. Ground ice is highly variable in type and quantity. In the upper few meters of permafrost it may account for more than half of the volume whereas its presence in bedrock is minimal. It can range in form from microscopic pore ice to large segregated masses (Mackay 1972).
Fig. 4

Ice complex coast on Muostakh Island facing the Laptev Sea. The cliff is about 20 m high and is retreating at a rate of about 11 m/a. (Photo courtesy of Feliks Aré)

Permafrost cliffs, which border much of the coastal plain of the Arctic, are relatively stable for 8–10 months of the year because they are protected from erosion by being in a frozen state, being covered by snowdrifts, and by facing a frozen, immobile sea. With snowmelt, an active layer (the thin layer that alternately freezes and thaws on the top of permafrost) begins to form and some surface flow is initiated. However, it is after the shore has become sufficiently free of ice that wave action can impact the base of the cliff and major erosion can occur. With wave impact, thawing at the base of the ice-bonded cliff occurs and with sediment removal a thermo-erosional niche (termoerozionaja niza in Russian) is created (Gusev 1952) (Fig. 5). The height of thermoerosional niches depends largely on the change in water level during wave attack and the depth of penetration varies with the stability of the sea cliffs.
Fig. 5

Thermoerosional niche in deltaic permafrost

The permafrost of the Arctic frequently supports other features such as pingos (Mackay 1972) and ice-wedges which often express themselves at the surface in the form of ice-wedge polygons (Lachenbruch 1962). Although their size varies, polygons are usually on the order of 10–30 m in diameter. Along the coastline, paralleling wedges serve as lines of weakness and often lead to block collapse (Figs. 6 and 7) as thermoerosional niches develop. Those wedges that are perpendicular to the shore can serve as points of more rapid retreat, especially if the matrix is dominated by peat. Such coastlines are highly irregular in detail. In addition to the large block falls that result from thermoerosional niche development, many coastlines exhibit thermokarst forms such as ground-ice slumps (creating what some have called thermocirques) and breached thermokarst lakes. Along hard rock coasts (which are in the minority in the Arctic) erosion of a cliff face appears to be mainly by frost wedging (Fig. 8).
Fig. 6

Example of block collapse and ice wedge from E. de K. Leffingwell’s classic research monograph on permafrost and coastal morphology (de Leffingwell 1919)

Fig. 7

Block collapse and erosion along permafrost coastlines

Fig. 8

Bedrock shore on the Taymyr Peninsula, Siberia. (Photo courtesy of Feliks Are)

Sub-sea permafrost (offshore permafrost, submarine permafrost) occurs beneath the seabed of the continental shelves of northwest Canada, north Alaska, and Siberia (Fig. 2). It is relic in that it formed when sea level was low and much of the present-day continental shelf was subaerial. It is of major interest today because of its importance to the petroleum industry and as a store of carbon dioxide and methane (Osterkamp 2001).

Sea Ice

Sea ice which borders virtually all of the arctic coast during winter, is present along some sections even in summer (Fig. 1). During the time it is shorefast and bottomfast marine action along the coastline is nil. Also, during summer, much of the coastline is protected from wave attack because the presence of sea ice offshore reduces the fetch available to wind and dampens wave action. However, during these periods, often in the Fall of the year when the ice pack has been removed some distance offshore, storm waves may become powerful eroding agents. In 1986, strong winds over the Chukchi and Beaufort Seas resulted in severe erosion of low coastal cliffs impacting heavily the villages of Wainwright and Barrow, Alaska. Other erosive storms also occurred along these coasts in 1954, 1956, and 1963.

Some coastal specialists consider that the passive nature of sea ice is its most important role vis-à-vis the coastline. Nonetheless, sea ice is also an active agent in coastline and offshore modification. Ice push during the periods of freeze up and to a lesser extent during breakup create highly irregular surfaces on arctic beaches. Large pressure ridges formed during freeze up help protect the coastline during breakup because they may last well into the Fall. Although some of the reworked beach forms, including mounds, ridges and kettles, may last for years, depending mainly on how high up on the beach they developed, most tend to be ephemeral because they are removed by summer wave action. Large amounts of beach material (especially sand and gravel but also, in some locations, boulders) can be bulldozed, scoured, rafted, and resuspended by sea ice. In some instances, sea ice rides up on the shore and even overtops low cliffs. If rideup is over a snow bank or an ice foot it will cause minimal modification to the frozen ground beneath.

In addition to the shoreface itself, sea ice causes ice scour out to depths of more than 20 m often several kilometers from the coastline. Deep (2–3 m) gouges or trenches are created by the keels of drifting floes.

Most floes eventually become grounded in which case current movement around them can resuspend bottom sediment and transport it elsewhere.

From the standpoint of the coastline, changes occurring to sea ice because of global warming are likely to be very important in the future. Recent data show that, not only is the ice pack thinning, but its seasonal regimen is changing (Parkinson 2000). If such a trend continues, ice-free periods along coastlines will lengthen and the fetch will increase in length. Thus, both the intensity and duration of waves impacting the shore will also increase.

Snow

Although the amount of snow that falls in the Arctic is limited, partly because of low temperatures, it is an important factor in regard to the coastal zone. It accumulates as snow drifts against irregularities such as coastal bluffs and serves as protective ramps often until late summer (Fig. 9). Snow also becomes incorporated in the icefoot in combination with seawater and freshwater ice, and organic and inorganic sediment where it becomes part of the beach (McCann and Taylor 1975). Possibly the most important role of snow insofar as the arctic coastline is concerned is its service as the main source of water for the rivers that flow with their sediment load into the Arctic Ocean.
Fig. 9

Remnant snowdrift along Beaufort Sea in western Canada in August. Note the coarse textured beach and driftwood typical of many arctic beaches

Impact of Rivers on the Arctic Coast

Four of the ten longest rivers of the world (Ob, Yenisei, Lena and Mackenzie) drain into the Arctic Ocean. In addition, there are numerous smaller rivers, some of which are confined to the zone of continuous permafrost. Many of these smaller rivers cease flow completely during winter. Even the larger rivers are highly seasonal with the major discharge of water and sediment occurring during the snowmelt season (Walker 1998). Thus, the impact of rivers on the coast is confined, like that of most other arctic coastal modifiers, to a few months of the year. Nonetheless, during that restricted season river water impacts the sea ice over and under which it flows.

Floodwater aids in earlier melting of the sea ice at the mouth of the river than otherwise would be the case. Nearshore, much of the flood water flows over the top of the bottom/shore fast ice until it finds holes, as along pressure ridges, down through which it drains. From these discharge holes, which Reimnitz and Bruder (1972) call strudel, water continues to flow seaward beneath the ice (Fig. 10). As the water pours through these holes in the ice, it creates depressions in the seafloor deposits below.
Fig. 10

Floodwater overflow and the development of a freshwater wedge beneath sea ice during breakup

As sediment-laden floodwater spreads out over the sea ice, its velocity decreases and deposition occurs. Most of the sediment deposited on this bottomfast ice becomes a part of the subaqueous delta as the sea ice melts from under it (Walker 1974). The sediment that is carried by flood-waters beneath the sea ice may be transported many tens of kilometers seaward and become incorporated in long-shore currents and therefore, lost to the deltas.

Ocean Currents, Tides, and Waves

“The Arctic Ocean, relatively isolated in terms of worldwide wind systems and partially or wholly covered with sea ice, depending on season, is a body of water in which low tides, slow-moving currents, and low-energy waves predominate” (Walker 1982, p. 61).

Although there are a few locations in the Arctic where macrotides occur (e.g., off southeast Baffin Island, Canada, and in the Mezen Gulf, Russia, where ranges are more than 10 m), along most of the arctic coast tidal ranges are less than 2 m (Fig. 2). Marshes are often associated with the high tide range locations. Despite low astronomic tidal ranges, storm “tides” occasionally result in deep intrusions of water over low coastal plain surfaces. The inner edge of surge lines are often delineated by the presence of driftwood which is a common contribution of the rivers that flow through the taiga of Asia and North America.

The dominant currents in the Arctic Ocean are the Beaufort Sea Gyre and the Transpolar Drift (Fig. 2). They are the currents that provide the general direction of flow to pack ice and the occasional ice island that breaks off of Greenland and Ellesmere Island. There are other localized currents that affect the coastal zone by transporting sediments along shore and cause sea ice to impinge the coastline. Such ice movements are affected by wind as well as by ocean currents.

Waves, even though their formation is impossible for most of the year because of the canopy of sea ice that covers the ocean, are, nonetheless, the dominant agent in shore modification along most of the arctic coastline. The length of time, waves are effective, varies greatly ranging from several months along the longest-lasting ice-free zones to only occasionally or even rarely along coasts that are often ice-bound even during summer as exampled by parts of the northwest Canadian Archipelago.

Coastal Erosion and Climate Change

Many of the coasts of the Arctic are retreating, some by tens of meters per year especially along some Siberian coastlines (Aré 1988). Along the Beaufort Sea coast of Alaska, erosional rates have been such that since the sea reached its present level 4–5000 BP, the coastline has retreated as much as 25 km (Reimnitz et al. 1988). Rates ranging from 1 to 5 m/a are common in the ice-rich permafrost bluffs bordering much of the Arctic Ocean. In areas north of the Siberian coast, erosion has resulted in the disappearance of some offshore islands.

As most of this retreat is the result of the combined effect of normal marine (wave action) erosion and the periglacial process of thermokarst collapse and thermal erosion, it appears that an increase in the rate of coastal retreat with any rise in sea level and sea-ice degradation is likely.

Such a change would increase the amount of sediment contributed to the shore from cliff erosion which by some calculations already exceeds that contributed by the rivers flowing into the Arctic Ocean (Brown and Solomon 1999). However, it is likely that the same climate changes that affect sea level and sea-ice degradation will also increase permafrost thaw and river discharge and, therefore, the sediment loads of arctic rivers. Whether the relative proportions of the two sources will change is uncertain.

Conclusion

Although a number of localized programs have been undertaken in the last four decades, some of them out of research stations such as the Naval Arctic Research Laboratory, Barrow, Alaska; the Inuvik Research Laboratory, Inuvik, Canada; and the Permafrost Research Institute, Yakutsk, Russia, Arctic coastal research has generally been neglected.

In 1998, at the International Permafrost Conference, a Working Group on Coastal and Offshore Permafrost was formed. This led to the development of an Arctic Coastal Dynamics (ACD) project which has among its objective the establishment of rates of erosion and accumulation, the development of a network of monitoring sites along the coast and the initiation of research on critical coastal processes in the Arctic. The ACD is an international undertaking that bodes well for the future of arctic coastal research.

Cross-References

Bibliography

  1. Andrews JT (1970) Present and postglacial rates of uplift for glaciated northern and eastern North America derived from postglacial uplift curves. Can J Earth Sci 7:703–715CrossRefGoogle Scholar
  2. Aré F (1988) Thermal abrasion of sea coasts. Polar Geogr Geol 12(1, 2):157Google Scholar
  3. Are F, Reimnitz E (2000) An overview of the Lena River Delta setting: geology, tectonics, geomorphology, and hydrology. J Coast Res 16(4):1083–1093Google Scholar
  4. Bird JB (1985) Arctic Canada. In: Bird ECF, Schwartz ML (eds) The world’s coastline. Van Nostand Reinhold Co, New York, pp 241–251Google Scholar
  5. Brown J, Solomon S (1999) Arctic coastal dynamics. Geological Survey of Canada Open File 3929. Natural Resources, OttawaGoogle Scholar
  6. de Leffingwell EK (1919) The Canning River region, northern Alaska. United States geological survey professional paper 109. Government Printing Office, Washington, DCGoogle Scholar
  7. French HM (1989) Cold climate processes. In: Fulton RJ (ed) Quaternary geology of Canada and Greenland, vol K-l. Geological Society of America, Boulder, pp 604–611Google Scholar
  8. Gusev AI (1952) On the methods of surveying the banks at the mouths of rivers of the Polar Basin. Trans Inst Arct 107:127–128Google Scholar
  9. Harper JR (1978) The physical processes affecting tundra cliff stability. Unpublished dissertation, Louisiana State University, Baton RougeGoogle Scholar
  10. Lachenbruch A (1962) Mechanics of thermal contraction cracks and ice-wedge polygons in permafrost. Special publication no. 70. Geological Society of America, New YorkGoogle Scholar
  11. Lewis EL (1982) The Arctic Ocean: water masses and energy exchange. In: Rey L (ed) The Arctic Ocean: the hydrographie environment and the fate of pollutants. Wiley, New York, pp 43–68CrossRefGoogle Scholar
  12. Mackay JR (1972) The world of underground ice. Ann Assoc Am Geogr 62:1–22CrossRefGoogle Scholar
  13. McCann SB, Taylor RB (1975) Beach freezeup sequence at Radstock Bay, Devon Island, Arctic Canada. Arct Alp Res 7:379–386CrossRefGoogle Scholar
  14. Nansen F (1911) Northern mists, vol I. Stokes, New YorkGoogle Scholar
  15. Nielsen N (1985) Greenland. In: Bird ECF, Schwartz ML (eds) The world’s coastline. Van Nostrand Reinhold Co, New York, pp 261–265Google Scholar
  16. NOAA (1981) United States coast pilot, vol 9. U.S. Department of Commerce, Washington, DCGoogle Scholar
  17. Osterkamp T (2001) Sub-sea permafrost. In: Encyclopedia of ocean sciences. Academic, San DiegoGoogle Scholar
  18. Parkinson CL (2000) Variability of arctic sea ice; the view from space, an 18-year record. Arctic 53(4):341–358CrossRefGoogle Scholar
  19. Péwé T (1983) Alpine permafrost in the contiguous United States. Arct Alp Res 15:145–156CrossRefGoogle Scholar
  20. Reimnitz E, Bruder KF (1972) River discharge into an ice-covered ocean and related sediment dispersal, Beaufort Sea, coast of Alaska. Bull Geol Soc Am 83(3):861–866CrossRefGoogle Scholar
  21. Reimnitz E, Graves SM, Barnes PW (1988) Beaufort Sea coastal Erosion, shoreline evolution, and the erosional shelf profile. US Geological Survey Miscellaneous Investigations Series. The Survey, RestonGoogle Scholar
  22. Sater J, Ronhovde A, Van Allen L (1971) Arctic environment and resources. The Arctic Institute of North America, Washington, DCGoogle Scholar
  23. Walker HJ (1974) The Colville River and the Beaufort Sea: some interactions. In: Reed JC, Sater JE (eds) The coast and shelf of the Beaufort Sea. The Arctic Institute of North America, Washington, DC, pp 513–540Google Scholar
  24. Walker HJ (1982) Arctic, coastal morphology. In: Schwartz M (ed) The encyclopedia of beaches and coastal environments. Van Nostrand Reinhold Co, New York, pp 57–61Google Scholar
  25. Walker HJ (1983) E pluribus unum: small landforms and the Arctic landscape. In: Gardner R, Scoging H (eds) Mega-geomor-phology. Clarendon Press, OxfordGoogle Scholar
  26. Walker HJ (1998) Arctic deltas. J Coast Res 14(3):718–738Google Scholar
  27. Weber JR (1989) Physiography and bathymetry of the Arctic Ocean seafloor. In: Herman Y (ed) The Arctic seas. Van Nostrand Reinhold Co, New York, pp 797–828CrossRefGoogle Scholar
  28. Wiseman WJ, Coleman JM, Gregory A, Hsu SA, Short AD, Suhayda JN, Walters CD, Wright LD (1973) Alaskan Arctic coastal processes and morphology. Technical report, 149. Coastal Studies Institute, Baton RougeGoogle Scholar
  29. Zenkovich VP (1985) Arctic USSR. In: Bird ECF, Schwartz ML (eds) The world’s coastline. Van Nostrand Reinhold Co, New York, pp 863–869Google Scholar

Copyright information

© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of Geography and AnthropologyLouisiana State UniversityBaton RougeUSA