ABSTRACT: Reconstruction of climatic conditions based on varve sedimentology at Meziadin Lake, northwestern British Columbia

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Abstract

The climate of the northern coast of British Columbia is influenced at a synoptic scale by the interaction of the Aleutian Low and the Pacific High, which give rise to warm moist and cool dry conditions respectively. The spatial patterns of 500 mb heights and surface temperatures through time has been investigated, leading to the recognition of oscillations and step-wise changes in the synoptic climate, broadly called the PDO (Pacific Decadal Oscillation). Little attention has been placed in a station or site based assessment of the relative impact of these changes through time in the terrestrial environment. The study area is climatically sensitive to shifts in the strength and position of the Aleutian Low and Pacific High. Using data from the two closest stations at Stewart (55° 56' N - 129° 59' W) and Murder Creek (55° 30' N - 127° 47' W), the strength of the PDO signal is assessed for the instrumental record. The dominant vectors of climate forcing which result from the influence of PDO will be the basis for the analysis of the sedimentological record. Twenty short and nine long cores have been collected from glacially fed Meziadin Lake (56° 10' N - 129° 20' W). It is situated in the lee of the Coast Mountains, and is a simple fiord-type basin, with a flat bottom at 128 m depth, comprising a majority of the western part of the basin. Monitoring in the summers of 1998 and 1999 indicate that the majority of the sediment is delivered to the lake during the summer from Strohn Creek, which enters at the western end of the basin. Most of the sediment input occurs as interflows, with underflow events becoming more important towards the west of the basin. Sub-bottom profiles and monitoring indicate that there is a strong proximal to distal gradient of sediment flux in the basin. Investigation of the sediments indicates that they are varved throughout. The sedimentological properties of the varve forms the basis for an assessment of climatic conditions. Changes within the varve series is related to the dominant variables of climate revealed in the station data.

Bibliography of Canadian Geomorphology