ABSTRACT: Fluvial sediment delivery to Hudson Bay in a changing climate: projections and hypotheses.

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Abstract

The objectives of this presentation are: (1) to evaluate potential changes in sediment flux to Hudson Bay over decadal timescales due to environmentalchanges in the drainage basins that deliver water and sediment to Hudson Bay, and (2) to develop a framework for evaluating potential changes that mayhave occurred over timescales > 100y, in the recent past (since European colonization). Déry et al. (2005) have determined that river discharge into Hudson Bay decreased ~13% over the years 1963-2000, the period for which we have discharge data. What we do not know is whether these trends are consistent with or aberrations from pre-gauging river conditions. Such changes are important because this freshwater flux to Hudson Bay influences circulation and ice formation in the bay, as well as salinity and flow fields in the broader Northwest Atlantic. These observations of river discharge can be combined with summary climatic data to estimate sediment discharge from specific rivers into Hudson Bay over the same period, using statistical hydrologic models of Syvitski et al. (2003). Focusing on the Grande Rivière de la Baleine, which is an ArcticNet Supersite and typical of Déry et al.’s (2005) data set,combined climate and discharge changes might have resulted in a 22% decrease in sediment discharge over the period 1963-2000. If these estimates are approximately correct and are continuations of earlier trends, then such patterns should be evident in the seabed sediment record off the river mouth. In other words, submarine sediment records could be used as proxies to evaluate relative patterns in pre-hydrograph river discharge. Complications exist, such as the issue of lacustrine storage of sediment in rivers, and theapplication of the statistical steady-state models above to a time-dependent problem. However, these data sets and approaches do provide a theoreticalframework in which to evaluate fluvial and climatic patterns over longer timescales than instrument records allow.

Bibliography of Canadian Geomorphology