ABSTRACT: Coastal response to tropical cyclones, extra-tropical storms, and the NAO in Atlantic Canada: Implications for interpretation of Quaternary marine beach sequences.

CGRG Bibliography of Canadian Geomorphology
Search Results

Author :

Date :

Title :

Publication :

Issue :

Page(s) :

Abstract

Assessment of the effects and prevalence of storm and wave conditions on Quaternary marine beach sequences is important in efforts to determine both the local depositional environment and the potential for preservation of broader regional signals. Analysis of modern beach systems, involving repetitive visitation, provides a base-line linking current atmospheric conditions, wave activity, and storm surges to morphological and sedimentological responses. It also provides insight into the preservation potential for features from larger storm events under falling sea level. Over the period 1989–2007, individual coastlines in Atlantic Canada have responded to large-scale, regional to hemispheric factors, including overall tropical cyclone and extra-tropical cyclone activity, sea ice coverage, and the NAO. The effectiveness of each factor on an individual beach depends upon aspect, angle of wave attack, number of previous events during the season, and other local factors. The effectivenessof any particular storm as a geomorphic agent, and consequently as an indicator of climate variation, does not depend on the overall indices of storm activity. The hyperactive tropical storm year of 2005 produced minimal effects on beach systems along the Gulf of St. Lawrence, and no effect on systems along the open Atlantic coastline. The effects of the NAO are similarly differentiated regionally and locally. Variations in the NAO are reflected in the amount of coastal snow and ice cover, sea ice activity, and northeasterly winds generated by enhanced meridional pressure gradients. There is a general correlation between the NAO and storm effects along the open Atlantic coastline and in the western Gulf of St. Lawrence. In contrast, beaches along the eastern Gulf of St. Lawrence do not exhibit any wave dynamic, tidal, storm surge, or geomorphic response to the NAO. Variations in the effectiveness of observed modern processes indicate that similar effects are likely in Quaternary successions, and thus should be considered in interpretations of raised beach sequences in Atlantic and Arctic Canada. No single beach can serve effectively as a proxy to assess the overall impact of climate variation during any time within the Quaternary. However, analysis of an assemblage of coastlines can be used to establish a general regime of wind, wave, and storm activity, and hence representations of Quaternary climates.

Bibliography of Canadian Geomorphology