Connecting process to high resolution paleorecords: long term investigations of linked Arctic climate-hydrology-lacustrine sedimentary processes

Abstract:

High resolution lacustrine sedimentary sequences hold substantial potential for paleoenvironmental analyses, particularly in regions where few alternatives are available. Increased attention to quantifying processes that generate sedimentary facies has yielded increasingly detailed environmental interpretations but these efforts have been limited by available field data. The Cape Bounty Arctic Watershed Observatory (CBAWO) was initiated in 2003 to develop a long term site to evaluate the controls over sediment transport and the formation of clastic sedimentary records. This program in the Canadian Arctic has supported 13 years of research in paired watersheds and lakes, both of which contain clastic varves.

Results from 2003-14 demonstrate how multiple climatic factors delivery sediment in a complex manner. This comparatively simple hydroclimatic system is dominated by runoff and sediment transport from spring snowmelt, with clear associations between catchment snow water equivalence (or total runoff) and sediment yield, with discharge limited by snow exhaustion as the season progresses. Major rainfall can constitute a dominant contribution to seasonal sediment yield, but antecedent conditions can significantly reduce runoff markedly. Hence, these results indicate two primary competing hydroclimatic factors that control catchment sediment yield, both with independent climatic and hydrological factors.

Additionally, the impact of landscape disturbance on downstream sediment yield has been evaluated following a major episode of permafrost thaw in 2007. Results show that localized slope disturbances resulted in enhanced erosion but downstream fluvial storage reduced the magnitude of transport. Sediment from disturbances will be gradually released and may generate decadal-scale sediment delivery changes in the downstream record.

Collectively, this research indicates multiple controls over the formation of clastic varves. Advances in high resolution sedimentary structure and composition analysis provide methodological pathways for integrating a fuller set of controls over sediment deposition, and together with sustained process investigations, offer the opportunity for sedimentary records with the highest degree of fidelity.