Global Trends of Sea Surface Gravity Wave, Wind, and Coastal Wave Setup

Abstract

Assessing trends of sea surface wave, wind, and coastal wave setup is of considerable scientific and practical importance in view of recent and projected long-term sea level rise due to global warming. Here we analyze global significant wave height (SWH) and wind data from 1993 to 2015 and a wave model to (i) calculate wave age and explain the causal, or the lack thereof, relationship between wave and wind trends; and (ii) estimate trends of coastal wave setup and its contributions to secular trends of relative sea level at coastal locations around the world. We show in-phase, increasing SWH and wind trends in regions dominated by younger waves, and decreasing SWH trends where older waves dominate and are unrelated to the local wind trends. In the central North Pacific where wave age is transitional, in-phase decreasing wave and wind trends are found over the west-northwestern region, but wave and wind trends are insignificantly correlated in the south-southeastern region; here, a reversed, upward momentum flux from wave to wind is postulated. We show that coastal wave setup depends primarily on open-ocean SWH but only weakly on wind, varying approximately like SWH/(wind speed)1/5. The wave-setup trends are shown to be increasing along many coastlines where the local relative sea level trends are also increasing: the North and Irish Seas, Mediterranean Sea, East and South Asian seas, and eastern United States, exacerbating the potential for increased floods along these populated coastlines.

New Wind-Wave Climate Records in the Western Mediterranean Sea

“…Wind and wave models often show a slight positive or negative bias changing depending on the buoy location and increasing or decreasing proportionally with WS and SWH. Consideration of error statistics of the used models allows reliable comparisons between the finding reported in different studies.Comparing the SWH_Mean trend results with the recent result obtained byDe Leo et al (2020), who analyses 40 years wave hindcast from 1979 to 2018, we notice a considerable difference.The areas characterized by a significant increasing trend of SWH_Mean shown during this study over the WMed Sea are much larger than the areas estimated by De.However, the results are in line with those observed byYuchun and Leo (2020), who estimate SWH and WS trend between 1993 and 2015 based on satellite observations and estimate a significant increase in both WS and SWH in almost the whole WMed Sea, and in all west European coasts. Moreover, as mentioned before, the annual trend in SWH_Mean between 1985 and 2018 estimated and mapped inYoung and Ribal (2019b) based on satellite observation show a significant increasing trend in almost all WMed Sea, which supports our results.…”

“…The trend results obtained in this study based on 41-year wave climate, compared to the results of previous studies (Young et al 2011;Soukissian et al 2018;Laloyaux et al 2018;Young and Ribal 2019a;Meucci et al 2020;Yuchun and Leo 2020;De Leo et al 2020) between 1979 to 2018. Overall, the European coasts and some African coasts are witnessing a worrying risk related to the wind and wave climate that requires serious mobilization for the prevention of probable catastrophic wave storm events and to ensure sustainable and economic development.…”

“…In this study, we are interested in the remarkable change in the wind-wave climate and in the new records of wave climate observed in the WMed Sea during the last decade, and we focus mainly on the spatial variation of the annual trends of Max SWH and simultaneously to the trend of the force responsible for their generation which is the WS, and those in order to understand the spatial relationship between the trends of WS and wave heights, and also the spatial connection of both parameters' trends, with respect to the new records of extreme SWH. A wave trend study based on 40-year wave data published by De Leo et al, (2020) shows that a large part of the Spanish coasts that were highly exposed to record waves during the storm Gloria did not have a significant trend of Max SWH (SWH_Max), thus, according to the results of Yuchun and Leo, (2020) an area characterized by a WS trend may not have a significant trend for SWH and vice versa; these facts led us to follow the present methodology. We assume that an increasing trend in extreme WS may also reflect an increase of SWH on the local scale.…”

Global ocean wave fields show consistent regional trends between 1980 and 2014 in a multi-product ensemble

“…Whereas ship and buoy records are useful sources of regional and/or local data, they are temporally and geographically inhomogeneous and spatially limited and therefore insufficient to offer a globally consistent quantification of historical variability and trends on their own. Satellite wave records are currently the most spatiotemporally comprehensive sources of wave height measurements and have been used to quantify variability and trends in H s over the last two decades, both globally and regionally 14,17,18 . Nevertheless, satellite altimetry-retrieved wave data are limited in time from 1985 onwards and tend to underestimate upper-percentile H s due to temporal sampling inhomogeneity 18,19 .…”

“…In the recent past, multi-decadal simulations of surface wave fields driven by atmospheric surface wind fields, developed to support a variety of climatological assessments, have been used to assess trends in H s 17,[20][21][22][23] . These simulations yield homogeneous spatial and temporal multivariate data at high resolution, a requirement for comprehensive analysis of wave fields, especially extreme wave events 24 .…”