Extreme surface and near-bottom currents in the northwest Atlantic

• Published in: Natural Hazards
• Main Authors: Oliver, ECJ, Sheng, J, Thompson, KR, Urrego Blanco, JR
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer 2012
• Subjects: Earth Sciences; Oceanography; Physical Oceanography; Northwest Atlantic
• Online Access: https://doi.org/10.1007/s11069-012-0303-5; http://ecite.utas.edu.au/82914

This study presents a methodology for estimating extreme current speeds fromnumerical model results using extremal analysis techniques. This method is used to estimate theextreme near-surface and near-bottom current speeds of the northwest Atlantic Ocean with50-year return periods from 17 years of model output.The non-tidal currents produced by a threedimensionalocean circulation model for the 19882004 period were first used to estimate andmap the 17-year return period extreme current speeds at the surface and near the bottom. Extremalanalysis techniques (i.e., fitting the annualmaxima to the Type I probability distribution) are usedto estimate and map the 50-year extreme current speeds. Tidal currents are dominant in someparts of the northwest Atlantic, and a Monte Carlo-based methodology is developed to take intoaccount the fact that large non-tidal extrema may occur at different tidal phases. The inclusion oftidal currents in this way modifies the estimated 50-year extreme current speeds, and this isillustrated along several representative transects and depth profiles. Seasonal variations areexamined by calculating the extreme current speeds for fall-winter and springsummer. Finally,the distribution of extreme currents is interpreted taking into account (1) variability about thetime-mean current speeds, (2) wind-driven Ekman currents, and (3) flow along isobaths.