Changes in extreme wave events in the southwestern South Atlantic Ocean

Abstract

The southwestern South Atlantic (SWSA) has faced several extreme events that caused coastal and ocean hazards associated with high waves. This study aimed to investigate the extreme wave climate trends in the SWSA using percentile- and storm-based approaches to determine potential coastal impacts. Changes in extreme wave event characteristics were evaluated through distribution maps and directional density distributions. Our results showed an overall increase in the 95^{th}-percentile of the significant wave height (Hs), mostly in the northern and southern portions of the domain. There was a general increase in the area affected by the events and in their lifetimes in the austral summer. In contrast, winter events had higher maximum intensities, which were not homogeneous throughout the domain. Changes in the wave power direction affected most of the analysed locations, showing a clockwise shift of summer events and a large directional spread of events from the southern quadrant (SW–SE). These changes were related to the southwards shift of the subtropical branch of the storm track, reflecting increased cyclonic activity at 30^circ S (summer) and 45^circ S (winter). These storm track shifts allowed the development of large fetches on the southern edge of the domain, promoting the propagation of long waves.