Low-frequency variability of sea level along the Mid-Atlantic Coast of South America, in 1983

Abstract

Meteorological events cause pronounced low-frequency sea level variations along the Mid-Atlantic coast of South America. Spectral analysis of hourly
sea level data during 1983 from tide gauges at Puerto Madryn and Mar del Plata, Argentina, and Cananeia and Ilha Fiscal, Brazil, yielded energetic variance peaks with
periods between 2 and 28 days, with good coherence among the four gauges. These results suggest that coherent low-frequency sea level disturbances may propagate
along the Mid-Atlantic coast of South America towards the northeast, mostly as barotropic shelf waves. The principal long waves were identified with heights up to 1 m,
periods of 7.8 and 9.0 days, with variances of 2.5-5.4 m2 and coherences in the order of 0.88 to 0.98. These long waves recur every 5-16 days, propagate towards the
equator with an average phase speed of 11 m/s, and require 77 hours to travel the 3,010 km distance from Puerto Madryn to Ilha Fiscal.