Annually laminated lake sediments as proxies of hydrometeorological behaviour at White Pass, British Columbia/Alaska.

摘要

Annually laminated (varved) clastic lacustrine sediments are useful climate proxies because their formation has been demonstrated to be strongly dependent on hydrometeorological conditions. Varved sediments from two lakes (Summit and Meadow Lakes) in White Pass, northwest British Columbia, were used to reconstruct hydroclimatic variability over the last seven centuries. The varve record from Summit Lake was divided into two subannual sedimentary series based upon the main sediment transfer controls that produce subannual sedimentary event laminae. Nival-glacial and rainfall-derived subannual laminae were isolated based on their sedimentological and stratigraphical characteristics. This separation permitted analysis of two independent types of hydroclimatic variability during the past 700 years. In particular increased rainfall at the end of the 17th Century appears to be associated with reduced solar irradiance and the advance of land-terminating glaciers in the region.; A varve chronology from an adjacent, but separate watershed correlates with the Summit Lake varve chronology at the decadal scale. The purpose of the Meadow Lake varve chronology was to test whether the regional hydroclimatic behaviour and variance reconstructed from one varve record could be reproduced by an independent chronology. Annual comparison suggests that geomorphic differences between the watersheds dominated the records. However, decadal variability was well correlated and suggests that a regional hydroclimatic signal is preserved in varve records.; This study represents one of the first attempts to evaluate paleoclimate conditions using a long subannual record of hydrometeorological variability and the two records from White Pass are the longest annually-resolved paleoclimate records from this region. These results demonstrate the potential of subannual reconstructions to evaluate seasonal hydroclimatic variability caused by changing influences of synoptic climate systems common to this part of North America (e.g. Pacific Decadal Variation. Pacific Decadal Oscillation, El Niño).