Change in Frontal Strength
Temperature fronts form at the interface between differing water masses, often marking the boundary of an ocean current within the ecosystem. Fronts are of biological significance because they tend to concentrate organisms at both lower and upper trophic levels. A measure of fronts is the gradient magnitude, which relates the change in SST per unit distance across a frontal feature. Frontal gradient magnitude has increased on Georges Bank and in much of the Middle Atlantic Bight, suggesting that stronger frontal features can be found in these areas over time. Frontal magnitude has decreased in much of the Gulf of Maine, suggesting an opposite trend of less well developed fronts. Time series of frontal magnitude is summarized for the four Northeast Shelf ecoregions. Magnitude has increased dramatically during the most recent decade of the time series in the Middle Atlantic Bight, Georges Bank and Scotian Shelf areas (blue line is time series smoother, dashed red line marks 2016 data). Magnitude in the Gulf of Maine does not have a well develop trend.