Spatial-Temporal Ocean Variability on the northwest slope of Flemish Cap

Abstract

The Flemish Cap is a region impacted by human activities ranging from offshore petroleum exploration to international fisheries. This is an area of complex bathymetry and ocean circulation that is also characterized by vulnerable marine ecosystems within the benthic zone. This is a region with few long-term moored measurements of ocean properties due to the risks associated with bottom-trawl fisheries. In an attempt to address the need for science-based advice in this area, three oceanographic moorings placed in the region of northwest Flemish Cap from July 2013 to July 2014 gave some of the first long-term moored measurements of velocity, temperature, and salinity. These time series measurements were supplemented with two hydrographic surveys, in which stations were aligned in the cross-isobath direction about each mooring. These data allowed for a summary of the spatial variability over 10 to 200km and temporal variability from an hour to a year. The spatial analysis of velocity along the northern Flemish Cap shows an easterly intensified flow that extends throughout the water column over the slope (~ 1200-2200 m). Spectral analysis of the moored velocity measurements revealed a prominent 3-week peak. This was laterally and vertically coherent, and the power increased towards the bottom. A dynamical analysis in terms of the dispersion relationship indicates that these signatures were consistent with baroclinic topographic Rossby waves.