Statistical analysis of global ocean significant wave heights from satellite altimetry over the past 2 decades
Year: 2024
Type: article
Abstract: . The analysis of global ocean surface waves and of long-term changes is important to climate research and to ocean and coastal applications. Indeed, waves contribute to flooding, coastal erosion, extreme sea level events and ocean circulation. They also play a role in air-sea and sea-ice interactions. However, this analysis requires accurate time series of waves over several decades that have previously only been available from model reanalyses or from in situ observations. Altimetry provides a long series of observations of significant wave heights (SWHs) in the global ocean. The aim of this study is to analyse the climatology of wave heights and extreme wave heights derived from remote sensing in the global ocean and their long-term trends from 2002 to 2020 using different statistical approaches as the mean, the 95th percentile and the 100-year return level of SWH. The mean SWH and the 95th percentile of SWH were calculated for two seasons: January, February and March (JFM), and July, August and September (JAS) and for each year. A trend was then estimated using linear regression for each cell in the overall grid. The 100-year return levels were determined by fitting a Generalised Pareto distribution to all exceedances over a high threshold. The trend in 100-year return level was estimated using the transformed-stationary approach proposed by Mentaschi et al. (2016), which, to our knowledge, was used for the first time to draw a global map based on altimetry. Predominantly large positive trends over 2002–2020 for both SWH and extreme SWH are mostly found in the southern hemisphere, such as in the South Atlantic, the Southern Ocean and the southern Indian Ocean, which is consistent with previous studies. In the North Atlantic, SWH has increased above 45° N, corroborating what was concluded in the fifth IPCC Assessment Report, however SWH has also largely decreased below 45° N in JFM. As for 100-year return levels of SWH in the northern hemisphere, they have significantly increased in the North Atlantic and in the eastern tropical Pacific, where the cyclone tracks are located. Finally, in this study we find trends of SWH and 95th percentile of SWH for JFM and JAS over 2002–2020 to be much higher than those indicated in the literature for the period 1985–2018.
Source: State of the Planet
Authors: Alice Laloue, Malek Ghantous, Yannice Faugere, Alice Dalphinet, Lotfi Aouf
Language: English
Subfield: Oceanography
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: hybrid
OpenAlex ID: W4402984184