Coastal upwelling in Atlantic Canada [full paper published in Oceanological and Hydrobiological Studies, 49 (1): 81-87, 2020]

Abstract

The most studied upwelling systems occur on eastern ocean boundary coasts. We hereby focus on a western ocean boundary coast upwelling system located in Atlantic Canada. Using daily in-situ data on sea surface temperature (SST), we demonstrate a marked contrast in cooling between July 2014 (pronounced) and July 2015 (weak) for two locations ca. 110 km apart on the southeastern coast of Nova Scotia. Southwesterly winds blow parallel to this coast. In July 2014, such winds were common and their daily duration was negatively related to coastal SST. In July 2015, however, such winds were considerably less prevalent and unrelated to SST. These results are consistent with a marked interannual contrast in wind-driven upwelling. Independent measures of an upwelling index confirm this view, as the index was largely positive (indicative of upwelling) during July 2014 but, albeit generally positive, often lower, and sometimes even negative (indicative of downwelling), during July 2015. Both studied periods also experienced considerable differences in climatic phenomena such as the El Niño Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO). In July 2015, a strong El Niño event co-occurred with a negative NAO index, while both phenomena exhibited near-zero indices in July 2014. Influences of these phenomena on coastal winds and upwelling are known for other regions. Thus, given the relationships hereby reported for Atlantic Canada and the oceanographic and ecological importance of upwelling, it would be profitable to further investigate the nature and extent of atmospheric–oceanic links on this western ocean boundary coast.