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Reliable estimates of ocean surface waves and their long-term global trends are fundamentally important for numerous ocean engineering and geophysical applications. Nonetheless, it is scientifically and technically demanding to accurately identify such relatively small trends [ O (0. 1 − 1) cm yr−1] from wave data currently available. In 2022, Young and Ribal demonstrated that by changing the calibration method, multiplatform altimeter observations yield noticeable differences in wave height estimates and their trends. In this paper, we use our global wave hindcast as a baseline and confirm that observations calibrated relative to one another (i.e., "altimeter-altimeter" calibration) ultimately outperform traditionally "altimeter-buoy" calibrated data. The former leads to more consistent mean and extreme wave heights across simultaneously operating altimeters and consequently to a more homogeneous evolution of global sea states over the past several decades. The underlying reason is hypothesized to be that temporal inhomogeneities in long-term NDBC buoy records due to changes in buoy hardware and software over time introduce comparable inhomogeneities to long-term altimeter observations when the "altimeter-buoy" calibration is adopted. It is encouraging to observe that the global trends of mean and 90th-percentile wave heights over the period 1992-2019 from our hindcast and re-calibrated altimeter data are very close: approximately 0.3 cm yr−1. Nonetheless, the altimeter-based trend of 99th-percentile wave height, H s 99 , is substantially-but-spuriously stronger mainly due to markedly growing availability of altimeter missions over time. Our work clearly demonstrates the power of third generation spectral wave models as diagnostics tools. Given the uncertainties embedded in buoy and satellite observations, wave modeling and global wave hindcasts can indeed guide these measurements. Further analysis of the underlying climate physics driving the interannual variability of ocean waves in wind-sea dominated regions is also presented. • Investigation of global wave height climatology and trends from altimeter and model. • Intercomparison of two calibration methods of altimeter wave observations. • The "altimeter-altimeter" calibration outperforms the "altimeter-buoy" calibration. • Inhomogeneity clearly exists in the long-term NDBC buoy records. • Impact of large-scale climate physics on the interannual variability of ocean waves. [ABSTRACT FROM AUTHOR]

A high-resolution third-generation wave model based on unstructured grids, WAVEWATCH III, was used to investigate the wave climate of Bass Strait and South-East Australia over the period 1981 to 2020. The model results are extensively validated against a network of coastal buoys and demonstrate that the model can capture the overall wave characteristics in this region. Analyses of model outputs across the 40-year period show that significant wave height has increased by approximately 5% and a slight counterclockwise rotation of peak wave direction has occurred with likely implications for coastal processes. Seasonal variations show higher significant wave height in winter compared to summer, which is driven by dominant Southern Ocean swell. The peak wave direction in the eastern region shifts from south-westerly in winter to south-easterly in summer. In autumn and winter, there is a statistically significant correlation between wave conditions and the Southern Annular Mode. During these seasons, a southward movement of Southern Ocean low pressure systems is associated with increased significant wave height, an increase in the peak wave period and a counterclockwise rotation of the peak wave direction. • High-resolution wave model for SE Australia validated against extensive buoy data. • Mean, seasonal, and extreme wave conditions are examined. • Trends over the last 40-years show an increasing wave climate. • Changes in Southern Ocean swell have a major impact on the local wave climate. • Sheltering in the region results in high spatial gradients in wave climate. [ABSTRACT FROM AUTHOR]