Trends of Atlantic Wave Extremes as Simulated in a 40-Yr Wave Hindcast Using Kinematically Reanalyzed Wind Fields

Abstract

In this study, seasonal extremes of wave height in the North Atlantic are analyzed. The analysis is based on a 40-yr (1958?97) numerical wave hindcast using an intensive kinematic reanalysis of wind fields. Changes in the ocean wave extremes are identified by performing the Mann?Kendall test, and are further related to changes in the atmospheric circulation (sea level pressure) by means of redundancy analysis. The relationship between sea level pressure and ocean wave extremes is also used to reconstruct the seasonal wave statistics for the last century (back to 1899). Consistent with previous studies, this high-resolution Atlantic wave hindcast also shows that the northeast North Atlantic Ocean has experienced significant multidecadal variations in the last century, and it has indeed roughened in winters of the last four decades. The winter wave height increases are closely related to changes in the North Atlantic oscillation during the last four decades. While showing trend patterns similar to the ones identified from a previous global wave hindcast using the NCEP reanalysis wind fields, this detailed Atlantic hindcast shows more significant increases in the region off the Canadian coast in summer and fall; and in winter it shows higher rates of increases in the region northwest of Ireland but less significant changes in the North Sea and in the region off the Scandinavian coast.