Impacts of large-scale teleconnections on freshwater-ice break/freeze-up dates over Canada

Freshwater ice affects several physical, chemical, and biological processes in cold regions. Its duration and break-up also has numerous economic implications ranging from transportation, to the occurrence and severity of ice-jam flooding. Recent evidence indicates a shortening of the freshwater-ice season over much of Canada with the reduction being mainly attributable to earlier break-ups. These trends match those in surface air temperature during the last 50 years. Several studies have shown significant relationships between Canadian temperature and large-scale atmospheric and oceanic oscillations (i.e. teleconnections) particularly, during the cold season. However, no investigations have analyzed relationships between several teleconnection indices and historical freshwater-ice durations over Canada. This paper examines the impacts of Et Niho/Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), the Pacific North American (PNA) pattern, the North Pacific (NP) index, the North Atlantic Oscillation (NAO), and the Arctic Oscillation (AO) on Canadian freshwater-ice break/freeze-up dates from 1950-1999. Composite and correlation analyses reveal strongest links between the Pacific-related PDO, PNA, NP, and ENSO indices and ice dates over western Canada. Lakes have stronger and more spatially coherent results than rivers, while break-up dates have higher correlations as compared to freeze-up. The NAO/AO results are less coherent with no discernible impacts over any region of the country. Results from this analysis improve the understanding of relationships between large-scale atmospheric and oceanic oscillations and past freshwater-ice durations over Canada. They also provide insight into future regional changes to take and river ice given projected changes to teleconnection patterns. Crown Copyright (c) 2006 Published by Elsevier B.V. All rights reserved.