Wave heights over Canadian oceans: Tempo-spatial variations and climate-oscillation impacts based on macroscale spatially-extrapolative retrieval from altimetric ensembles

Estimation and analyses of significant wave heights (SWHs) are crucial to climate research, ocean engineering and other applications, with satellite retrieval serving as a fundamental approach. However, few studies attempt to extrapolate SWH models across buoy grids to retrieve ungauged-grid SWHs from multiple altimeters at macroscales, or examine variations of extreme SWHs in relation to climate oscillations, particularly in the Canadian context. To fill these gaps, we develop a macroscale spatially-extrapolative ensemble wave-height retrieval and analysis (MEERA) method to retrieve SWHs from multi-mission satellite altimetry and reveal tempo-spatial characteristics of SWHs means and extremes as well as their variations with climate oscillations. The method is applied across all Canadian waters. According to modeling results, MEERA significantly enhances consistency and accuracy of retrieved SWHs (especially in coastal areas), e.g., reducing biases of conventional methods by over 98%. From 1985 to 2020, waves were strongly seasonal and regional, which drop from winter (1.45 m) to summer (1.17 m) and tend to decline northward. SWHs tend to decrease in mid-eastern regions (e.g., Hudson Bay, Davis Strait and Gulf of St Lawrence) and increase in Canadian Atlantic, Pacific, and Arctic. Across all Canadian waters, climate indices regarding precipitation, e.g., the NBRA (Northeast Brazil Rainfall Anomaly) index, pose the strongest impacts on extreme SWHs compared with others. In Pacific and Atlantic, spatial patterns of winter SWH extremes are associated with negative NAO (North Atlantic Oscillation). El Niño might increase SWHs extremes over the Pacific and Arctic, while decreasing them over mid-eastern regions. This study advances macroscale SWH estimation and analysis, enhancing the understanding of SWH characteristics and their variations across Canada under climate change.