Trends in global ocean surface wave characteristics as represented in the ERA-Interim wave reanalysis for 1979–2010

Abstract

This study uses the ERA-Interim wave reanalysis data for the period 1979–2010 to assess trends in global ocean surface characteristics, including mean wave direction, significant wave heights, mean wave period, and wave energy fluxes. The Mann–Kendall’s slope estimator is used to estimate trends in the four wave parameters. The results show that, among the four wave parameters analyzed, changes in mean wave period are most extensively significant, while changes in mean wave direction are least extensively significant. The results also show that there exist seasonal and regional differences in the trends. The changes in mean wave direction are characterized by clockwise rotation of the mean wave direction along the North America west coast in December–January–February and anticlockwise rotation in the eastern tropical Pacific in March–April–May (MAM). The trend patterns for the other three parameters (wave heights, mean wave period, and wave energy flux) share substantial similarity. Their most prominent feature is significant large increases in the southern mid-latitudes (30°S–60°S) and in the western part of the North Pacific and of the North Atlantic, which are accompanied with significant decreases in the eastern part of the tropical—North Pacific. The mean wave period in Arabian Sea and the Bay of Bengal has increased in June–July–August but decreased in MAM and September–October–November.