The Mackenzie Estuary of the Arctic Ocean

Abstract

The Mackenzie Estuary is a seasonally ice covered, deltaic estuary. It receives over 300 km3 of freshwater and 125 × 106 t of sediment annually in a strongly modulated seasonal cycle. Ice cover plays a crucial role in the physical setting by limiting air--sea interaction (energy and gas exchange), reducing mixing, and withdrawing freshwater from the estuary while leaving behind the bulk of the dissolved components. Few studies have been conducted on estuarine processes occurring in this estuary and, although we can project from temperate estuaries what the important conservative and nonconservative processes are likely to be, the winter encroachment by ice sufficiently alters the physical, chemical, and biological processes that projections from other estuaries will likely be wrong. Here we discuss how the estuary evolves through the seasonal cycles of temperature, ice cover, river inflow, particle loadings, and winds, and review what is known of the biogeochemical cycling within the estuary. Given that the Arctic is exceptionally vulnerable to change, especially in the marginal seas, it is safe to predict that remote, pristine estuaries of the Arctic are as much at risk in the future as estuaries more directly impacted by human encroachment.