The role of ice in the arctic beach environment with special reference to Cape Ricketts, southwest Devon island, Northwest Territories, Canada

ABSTRACT. The Canadian Arctic marine flora is basically a regional extension of Atlantic species. As the extreme environmental conditions of low temperature, low salinity and long periods of darkness intensify towards the western and northern parts of the Canadian Arctic, there is a marked reduction in the number of species. The protective cover of sea ice, together with the seasonal development of a low salinity layer from ice melt, hinders mixing between water layers, and nutrient replenishment is apparently a critical problem. Communities are generally small and isolated largely because of substrate limitations. A population may be extensive and dense, but this is attributed to the small number of species and the relative ineffectiveness of most of these in competing for the available space. Following seasonal ice melt, the intertidal habitat in colder regions remains unsuitable for algal growth, because of its exposure to a combination of adverse climatic and oceanographic conditions. The decreasing diversity of species, as the physical conditions become more adverse, together with the nearly complete absence of endemics, indicate a low level of adaptation, and the arctic communities are judged to be ecologically immature. RÉSUMÉ:Écologie générale des algues marines benthiques de l'Arctique canadien. Fondamentalement, la flore marine du Canada arctique est une extension régionale d'espèces atlantiques. A mesure que les conditions de basse température, de faible salinité et de longues périodes d'obscurité s'intensifient vers l'ouest et le nord de l'Arctique canadien, il se produit une réduction marquée dans le nombre des espèces. La couche protectrice de glace de mer et le développement saisonnier d'une couche de faible salinité par suite de la fonte de la glace, nuit au mélange des couches d'eau, et le renouvellement des Cléments nutritifs est apparemment un problème critique. Les communautés sont généralement petites et isolées, surtout à cause des limitations du substrat. Une population peut être étendue et dense, mais ceci est attribuable au petit nombre d'espèces et à l'inefficacité relative de la plupart d'entre elles à lutter pour l'espace disponible. Après la fonte saisonnière des glaces, le milieu intertidal des régions plus froides demeure impropre à la croissance des algues par son exposition à un complexe de conditions climatiques et océanogra-phiques adverses. La diversité décroissante des espèces à mesure que les conditions physiques deviennent plus adverses, et l'absence presque complète d'endémiques, indiquent un faible niveau d'adaptation et ces communautés algaires doivent être jugées écologiquement immatures.1Based on a paper (Lee

Section: Observations and Discussionmentioning

confidence: 99%

General Ecology of the Canadian Arctic Benthic Marine Algae

Lee¹

1973

“…The beach surface may re-thaw if temperatures rise above freezing, but Short states that in Alaska the freeze-thaw oscillations cease by early September on the Beaufort Sea coast and the northwestern Arctic coast, and by late September on the southwestern Arctic coast. Ice in beaches may act as a lower limit for wave action (Owens and McCann 1970), but the presence of water at temperatures above 0°C has a very marked effect on ice, and leads to rapid melting. Therefore, if the beach is eroded to or near the depth of thaw during storms, the presence of seawater will cause further downward movement of the thaw zone.…”

Section: Discussionmentioning

confidence: 99%

“…From studies undertaken by Rex (1964) and by Rogers et al (1975) near Barrow, Alaska, by Owens and McCann (1970) and by McCann and Hannell (1971) in the Canadian Arctic, it has been shown that permafrost exists beneath the intertidal zone. Rex (1964) showed that the thaw depth fluctuates seasonally from 0-76 cm in early summer to greater than 150 cm in late August.…”

Section: Introductionmentioning

confidence: 99%

Frost-table and Thaw Depths in the Littoral Zone near Peard Bay, Alaska

Owens¹,

Harper²

1977

ABSTRACT. Measurements were made of thaw depths and of sub-surface temperatures along four beach profiles, between late May and late August. On the upper beach levels, thaw proceeded rapidly following the disappearance of surface snow, but then became much slower. Near the water line, thaw was delayed by the presence of beach-fast ice, but thereafter increased steadily to greater depths than on the upper beach. Greater thaw depths were reached on barrier beaches than on beaches backed by tundra. On the upper beach, thaw depths and zero-degree depths did not differ significantly, but near the water line they were at variance due to the presence of saline pore waters. &UM& Table de gel et profondeurs du dkgel dans la zone du littoral, pr2s dePeard Bay, Alaska. On mesura, sur une p6riode s'Ctendant de la fin mai B la fin aofit et le long de quatre lignes trades en travers des plages, les profondeurs respectives des mnes de dCgel, ainsi que les tempiratures profondes correspondantes. A des niveaux de plage ClevCs, le d6gel se poursuivit rapidement aprBs la disparition de la neige de surface, pour ensuite se ralentir consid6rablement. Par contre, le long du rivage, le dCgel se poursuivit lentement tant qu'il restait de la glace dans la mer, mais ensuite, la profondeur du dCgel augmenta considCrablement pour atteindre des profondeurs plus grandes que celles des niveaux de plage plus ClevCs. Les zones de dCgel atteignirent des profondeurs plus importantes sur les cordons littoraux que sur les plages qui se prolongeaient par la toundra. A des niveaux de plage ClevCs, on n'enregistra pas de diffkrences significatives entre la profondeur des zones de dCgel et de celles de ziro degrC de tempkrature, alors que, prbs du rivage, elles ne co'incidaient pas, B cause de la prhence de pores d'eau salBe entre les grains de sable.

“…Ice interaction with the coast can be a disruptive process (Dionne, 1976, 1992 andreferences therein;Taylor, 1978a;Forbes and Taylor, 1994), especially along coasts exposed to long wind and wave fetches (Owens and McCann, 1970;Taylor and McCann, 1976). Ice-push processes leave a recognizable morphology, such as thrust scours and mounds.…”

Section: Arctic Gravel Beach Morphologymentioning

confidence: 99%

“…The early development of an ice layer on the beach during freeze-up commonly leads to formation of an ice foot (Owens and McCann, 1970) that can protect the beach during storms. the ice foot may persist for some time after spring break-up, protecting the beachface from early summer storms (Moign, 1976;Taylor and McCann, 1983;Barnes et al, 1993;Orford et al, 2002).…”

Section: Arctic Gravel Beach Morphologymentioning

confidence: 99%

Raised Gravel Beaches as Proxy Indicators of Past Sea-Ice and Wave Conditions, Lowther Island, Canadian Arctic Archipelago

St-Hilaire-Gravel¹,

Bell²,

Forbes³

2010

ABStRACt. this study investigates whether raised beach sequences preserved on emergent coasts of the central Canadian Arctic Archipelago contain a proxy record of past sea-ice conditions and wave intensity. We hypothesize that periods of reduced sea ice (increased open water) expose shorelines to more prolonged and higher wave energy, leading to better-developed beach ridges. Surveys of raised beach sequences on Lowther Island revealed the following patterns: a) high, wide, single-to multicrested barriers backed by deep swales or lagoons characterize both the active and lowest relict shorelines; b) small, narrow, discontinuous ridges of poorly sorted gravel extend from 1.0 to 7.5 m asl, except from 4.5 to 5.0 m asl; c) ridge morphology is similar to the active and first relict ridges between 7.5 and 11 m asl; d) a near-featureless zone with minor terraces and ridges above 11 m extends to above 30 m asl. these distinct morphological and sedimentary units are interpreted as a function of wave climate and thus of summer sea-ice conditions. this model suggests periods