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TitreCruise report 2005-305: 2005 field survey of coastal changes along Barrow Strait, Bylot and northern Baffin islands, Nunavut
TéléchargerTéléchargements
AuteurTaylor, R B; Frobel, D
SourceCommission géologique du Canada, Dossier public 5395, 2006, 89 pages; 1 CD-ROM, https://doi.org/10.4095/223021 (Accès ouvert)
Année2006
ÉditeurRessources naturelles Canada
Documentdossier public
Lang.anglais
DOIhttps://doi.org/10.4095/223021
MediaCD-ROM; numérique; en ligne
Liensreadme
Formatsdoc (Microsoft Word); pdf (Adobe® Reader® v.7.0.8, is included / est fourni); xls (Microsoft Excel)
ProvinceNunavut; Région extracotière du nord
SNRC38A/03; 38A/04; 38A/05; 38A/06; 38A/11; 38A/12; 38A/13; 38A/14; 38B; 38C; 48A; 48D; 58E; 58F; 68E
Lat/Long OENS-100.0000 -88.0000 75.0000 74.0000
Lat/Long OENS-84.0000 -74.0000 74.0000 72.0000
Sujetsétudes côtières; littoraux; variations du littoral; gestion côtière; effets climatiques; érosion côtière; accretion; plages; crêtes de plage; profils de plage; cordons littoraux; plages soulevées; îles côtières; dunes; profils massifs; glace marine; dépôts cotiers; sables; déplacement des sédiments; distribution des sédiments; tempêtes; pergélisol; glace fossile; congélation du sol; climatologie; climat arctique; échantillons carrotés; modèles; changement climatique; surveillance; géologie des dépôts meubles/géomorphologie; géologie marine; Nature et environnement; Phanérozoïque; Cénozoïque; Quaternaire
Illustrationsphotographs; sketch maps; schematic diagrams; aerial photographs; profiles; tables
ProgrammeRenforcer la résilience face aux changements climatiques
Diffusé2006 12 01
Résumé(disponible en anglais seulement)
In the 1970s and 1980s permanent markers were established on 200 cross-shore lines at 87 coastal sites within the Canadian Arctic Archipelago (Nunavut). The markers were to facilitate future repetitive surveys of shoreline changes. In August 2005 coastal changes were investigated at 21 of those sites, 14 along Barrow Strait and 7 along Eastern Bylot and Northern Baffin Islands. Shoreline markers were previously positioned using only air photos. In 2005 markers at 92 of 106 cross-shore lines at the 21 sites were positioned using GPS technology and 47 of those lines were resurveyed. Three additional coastal sites established on Cornwallis Island in 2003
were also resurveyed. Beach surveys along Barrow Strait indicated that many of the lower line markers were disturbed or removed by wave and /or sea ice action. Most change was recorded along north-facing shores since our last survey in 1992. Along northern Somerset and Lowther islands, 21 of 24 beach lines were built-up or showed little net change and 9 of the 24 had prograded seaward. Where new beach ridges were formed some had been built farther landward than the previous beach face and most were built to roughly the same elevation as older backshore ridges. Shoreline changes along west and northeast Lowther Island were the largest since our first survey in1974. Waves had overwashed the outer barrier of Irvine Beach, Somerset Island and just offshore a new island had formed as a possible precursor of a new barrier beach complex. Along Radstock Bay, Devon Island, some pebbles had been tossed higher on the more north- facing beach, one survey line was eroded and most surveys indicated slight rebuilding of the upper beach and erosion of the lower beach with little net change overall. The coastal foreland at Cape Ricketts, Devon Island was built up along its west-facing shore
between 1992 and 2005 but its end had not recovered to its more seaward position of 1981. Between 1968 and 1981, the end of the foreland had been cut back by 30 m including three beach ridges and part of a fourth. Beaches along Resolute Bay, Cornwallis Island, were reworked by waves since 2003 but the net change was very small. Closely spaced repetitive beach surveys suggest that longshore cut and fill is an important mechanism providing sediment and impacting the beach changes observed. Similar cyclic changes at a number of beaches provide insights and a model of major beach ridge development.
Since the mid-1980s when the last surveys were completed along Bylot Island only two of 10 lines along the outer coast were built-up and prograded, the rest had been eroded. The scale of horizontal beach change was +/- 20 m, much greater than along most Barrow Strait shores. Waves had overwashed and lowered many of the barrier beaches reducing backshore dune development. Beach crest migration was a maximum 11 m landward and one backbarrier shore was extended 3-4 m landward. The shores of Guys Bight, Baffin Island, experienced significant progradation since the mid 1980s. A major storm in August 1991 reworked and combed down the shore, and waves threatened a number of buildings in the community of Pond Inlet. Some beach recovery had occurred by 2005. Low sandy shore bluffs west of the community have receded an average of 0.2 to 0.3 m/a since 1981.
In mid-August 2005, beach thaw depths averaged 0.43 to 0.55 m beneath pebble-cobble beaches and averaged 0.69 m beneath sand-dominated shores along Barrow Strait. Farther east along the Bylot and Baffin islands, thaw beneath sand-dominated shores in late August averaged 0.84 to 0.88 m and extended to a maximum depth of 1.14 m. Beach thaw depths measured along Barrow Strait in 2005 were 0.12 to 0.26 m deeper than those collected from the same locations at roughly the same date in 1974. Beach thaw had also progressed earlier than in 1974. Depths in mid-August 2005 were 0.05 to 0.12 m deeper than those recorded at the same locations in late
August 1974.
Along the shores of Devon Island thaw depths recorded in 2005 were deeper than those in 1976 by a similar amount as observed along Somerset Island. However, the thaw depths were similar to, or slightly less, than depths recorded in 1981.
For Bylot and Baffin islands, it is more difficult to quantify differences in average thaw depths since most of the 1970s and 1980s recordings were made at different times of the summer. However, a comparison with depths recorded in 1979 suggested an increase in average thaw in late August 2005 of nearly 0.3 m. Differences in beach thaw between 1981 and 2005 were much less.
Repetitive thaw depth measurements beneath the same beaches indicated that the zone of thaw can shift upward or downward with changes in the modern beach surface ie. accretion or erosion. Where beaches are built-up, the position of the subsurface ice-bonded surface also shifts higher. The stratigraphic position of the ice-bonded surface can become higher despite deeper thaw. Also, we observed that the ice-bonded surface often coincided with former beach surfaces. Further analysis of our information is required to confirm the relationship between former beach surfaces and ice-bonded layers. Beneath raised beaches where the ground surface rarely
changed, depths of thaw were measured relative to the same surface; at these sites changes in depth are a less complicated indictor of climate change.
GEOSCAN ID223021