ABSTRACT: Variation in coastal marine geomorphic and biological systems and response to climate change across the Canadian Arctic.

CGRG Bibliography of Canadian Geomorphology
Search Results

Author :

Date :

Title :

Publication :

Issue :

Page(s) :

Abstract

Interactions between climate, sur? cial geology, relative sea level change, sea ice, waves, and human activities yield dramatically different outcomes for coastal marine systems across the Canadian Arctic. Rising air and ground temperatures and decreasing sea-ice cover are common though variable factors across the Arctic. We explored regional variation in the climate change response of coastal systems under varying geological and coastal landscape settings, climatic forcing, and human activities. Field studies were carried out from 2005 to 2009 in Sachs Harbour, NWT; Gjoa Haven and Arctic Bay, among other locations in Nunavut; two northern Labrador fjords, and Gilbert Bay in southern Labrador. GPS topographic surveys, remote sensing, and hazard mapping focused on coastal erosion, permafrost degradation, and natural hazards including waves, ice, marine ? ooding, runoff drainage, and slope instability. Marine biological surveys used paired drop-video camera and benthic grab sampler, coupled with either multibeam sonar bathymetry and backscatter coverage or single-beam sonar depth pro?les. Sachs Harbour, with ice-rich sur? cial deposits, unlithi?ed Cenozoic bedrock, and glacioisostatic submergence, suffers rapid coastal erosion driven by wave action, thermal erosion, thaw consolidation, and surface runoff following summer rains. Associated nearshore mobile sand sheets subject to frequent ice scour and seasonal wave action had low biodiversity of both epifauna and infauna. Gjoa Haven, an emergent site with low wave exposure on coarse ice-contact Quaternary sediments, exhibited no coastal erosion and low sedimentation rates except during spring thaw. Muddy nearshore habitats contained enough coarse gravel to support diverse macroalgal communities, as well as diverse epifauna and infauna. Arctic Bay borders a recently subsiding fjord cut into mid-Proterozoic well-indurated sedimentary rocks. Most of Arctic Bay is sediment-starved, and deep muddy environments had enough bedrock fragments to support epifauna. Sills underlain by igneous dykes supported diverse seaweed assemblages, branching and crustose coralline algae, and diverse epifauna. Localized coastal erosion, intermittent slope failure, active-layer deepening and increased geli?uction creep rates may cause sedimentation impacts on nearshore benthic biodiversity. Steep northern Labrador fjords are cut into Archaean metamorphic rocks, in a discontinuous permafrost zone. Maximum biodiversity was found in shallow water habitats in fjord heads, walls, and sills, with abundant seaweeds and diverse epifauna; deep basins often had enough coarse clasts in basinal muds to support large sessile epifauna. Farther south, Gilbert Bay is a shallow fjord in mid-Proterozoic crystalline basement rocks, with many submerged glacial features. High tannin levels in rivers draining the forested watersheds severely restrict light penetration, leaving the bay with few seaweeds or seagrasses, but dominated by branching and encrusting coralline algae, diverse epifauna, and a genetically distinct resident population of Atlantic Cod. Geological setting, especially sur? cial sediment composition and ground-ice content, interacting with varying relative sea level trends and exposure to ice and waves, exerted dominant controls on geomorphic system response. Flora and fauna at all sites exhibited depth zonation and, at most sites, differences in species composition according to sediment type. Variations in benthic biological community composition and response to climate change were largely driven by sur? cial geology, depth gradient, wave climate, and water clarity.

Bibliography of Canadian Geomorphology