Future Wave Climate Research Articles

Enhanced Coastal Shoreline Modeling Using an Ensemble Kalman Filter to Include Nonstationarity in Future Wave Climates

AbstractA novel approach to improve seasonal to interannual sandy shoreline predictions is presented, whereby model‐free parameters can vary in time, adjusting to potential nonstationarity in the underlying model forcing. This is achieved by adopting a suitable data assimilation technique (dual state‐parameter ensemble Kalman filter) within the established shoreline evolution model ShoreFor. The method is first tested and evaluated using synthetic scenarios, specifically designed to emulate a broad range of natural sandy shoreline behavior. This approach is then applied to a real‐world shoreline data set, revealing that time‐varying model‐free parameters are linked through physical processes to changing characteristics of the wave forcing. Greater accuracy of shoreline predictions is achieved, compared to existing stationary modeling approaches. It is anticipated that the wider application of this method can improve our understanding and prediction of future beach erosion patterns and trends in a changing wave climate.

Shelf sand supply determined by glacial-age sea-level modes, submerged coastlines and wave climate

Submerged paloeshorelines preserved on the continental shelf indicate the depths of the most frequent (modal) low sea-levels within the glacial stages of the Late Quaternary. Here we have determined the south-east Australian shelf configuration when sea level was 40 m and 60 m below present-day sea-level (depths of the most persistent paleoshorelines within the last 120 ka), and we resolve the wave climate variations influencing the sediment transport pathways over this period. We present evidence demonstrating that the combination of shelf morphological evolution, changes in sea-level and variations in wave climate is responsible for latitudinal changes in sediment transport and deposition during the interglacial states. The paleoshoreline and shelf evolution is key to understanding the distribution of present-day shelf sand deposits and the contemporary sand budget response to future wave climate changes.

The Contribution of Wind-Generated Waves to Coastal Sea-Level Changes

Surface gravity waves generated by winds are ubiquitous on our oceans and play a primordial role in the dynamics of the ocean–land–atmosphere interfaces. In particular, wind-generated waves cause fluctuations of the sea level at the coast over timescales from a few seconds (individual wave runup) to a few hours (wave-induced setup). These wave-induced processes are of major importance for coastal management as they add up to tides and atmospheric surges during storm events and enhance coastal flooding and erosion. Changes in the atmospheric circulation associated with natural climate cycles or caused by increasing greenhouse gas emissions affect the wave conditions worldwide, which may drive significant changes in the wave-induced coastal hydrodynamics. Since sea-level rise represents a major challenge for sustainable coastal management, particularly in low-lying coastal areas and/or along densely urbanized coastlines, understanding the contribution of wind-generated waves to the long-term budget of coastal sea-level changes is therefore of major importance. In this review, we describe the physical processes by which sea states may affect coastal sea level at several timescales, we present the methods currently used to estimate the wave contribution to coastal sea-level changes, we describe past and future wave climate variability, we discuss the contribution of wave to coastal sea-level changes, and we discuss the limitations and perspectives of this research field.

Future wind and wave climate projections in the Indian Ocean based on a super-high-resolution MRI-AGCM3.2S model projection

In this study, the impact of climate change on wind and wave characteristics has been assessed using super-high-resolution MRI-AGCM3.2S wind data and numerical modeling over the Indian Ocean. Wave characteristics were generated in two 25-year periods covering historical and future projections (RCP8.5), and the assessment indicated that, generally, the spatial distributions of wind speed, significant wave height (Hs) and mean spectral wave period (Tm01) will not dramatically change in the future. The assessment also indicated that the wind direction reversing pattern during monsoons will remain similar. Moreover, future westerly winds in the Southern Indian Ocean (SIO) will shift to the south and a decrease in future wind speed north of the equator will occur, espearound the equator due to cially during winter. The relative change of Hs will be less than wind speed the predominance of swells transferring from the SIO. There will be no considerable change in the future Tm01, except during autumn in the area north of the equator. A novel climate stability index is suggested showing that the semi-enclosed seas in the NIO and the western coasts of India and the Maldives will be areas with the least stability in terms of wave climate. Despite experiencing more intense wind and wave climates, the overall climate will be more stable in the SIO than the NIO.

Study on the Effect of Climate Change on Ship Responses Based on Nonlinear Simulations

Hull girder ultimate strength governs sagging and hogging failures, which is one of the most critical failure modes for a ship hull. The structural reliability analysis methodology has been used to develop common structural rules for tankers and bulk carriers. A linear model for bending moment in extreme weather with a nonlinear correction factor has been adopted in the analysis. It is difficult to conclude on the model uncertainty associated with nonlinear effects of bending moment as, until now, there are few studies addressing this topic. In this paper, the nonlinear effect on ship responses is analyzed, and the potential effect of climate change on ship responses is investigated with the improved three-dimensional (3D) Rankine Panel method using nonlinear wave input. The nonlinear wave input is generated by the higher-order spectral method (HOSM) wave model incorporating higher-order nonlinear effects, including nonlinear free-wave modulation as well as higher-order bound harmonics. The past and projected future wave climates of selected locations in the North Atlantic and North Norwegian Sea are considered.

Mid-twenty-first century global wave climate projections: Results from a dynamic CMIP5 based ensemble

Abstract Ocean surface gravity waves are part of the climate system, regulating the exchange of energy and momentum at the atmosphere-ocean interface. Besides that, waves have a direct impact on coastal erosion and sediment transport, in ship routing and offshore/ship infrastructure design, as well as in coastal management. Most future wave climate projections point out to statistically significant changes in wave height conditions in the global ocean towards the end of the 21st century. In the present study, the near future impact of a warmer climate on the global ocean wave climate towards the mid-21st century (2031–2060) is investigated through a 4-member “coherent” ensemble of wave climate projections: single-model (wave model WAM), single-forcing (EC-Earth) and single-scenario (RCP8.5). The wave model WAM was forced by wind speed and ice coverage from four Coupled Model Intercomparison Project Phase 5 (CMIP5) EC-Earth projections. The ensemble historic climate reference period has been evaluated by comparison against wave reanalysis/hindcast data, and wave in-situ observations. Statistically significant increases in the global mean wind speed, wave height, wave period and wave energy flux are to be expected towards the mid-twenty first century, in less than 50 years, these changes being more striking in the mid-to-high latitudes of the Southern Hemisphere. Due to the propagation of swell to lower latitudes, statistically significant increases in wave heights, periods and energy fluxes are also projected to occur in equatorial areas, especially along the eastern side of the main ocean basins, during the Austral winter. Comparatively, the projected changes in wave heights and energy fluxes are expected to occur more intensely during the first half of the 21st century, in several areas of the global ocean.

CMIP5-Derived Single-Forcing, Single-Model, and Single-Scenario Wind-Wave Climate Ensemble: Configuration and Performance Evaluation

A Coupled Model Intercomparison Project Phase 5 (CMIP5)-derived single-forcing, single-model, and single-scenario dynamic wind-wave climate ensemble is presented, and its historic period (1979–2005) performance in representing the present wave climate is evaluated. A single global climate model (GCM)-forcing wave climate ensemble was produced with the goal of reducing the inter GCM variability inherent in using a multi-forcing approach for the same wave model. Seven CMIP5 EC-Earth ensemble runs were used to force seven WAM wave model realizations, while future wave climate simulations, not analyzed here, were produced using a high-emission representative concentration pathway 8.5 (RCP8.5) set-up. The wave climate ensemble’s historic period was extensively compared against a set of 72 in situ wave-height observations, as well as to ERA-Interim reanalysis and Climate Forecast System Reanalysis (CFSR) hindcast. The agreement between the wave climate ensemble and the in situ measurements and reanalysis of mean and extreme wave heights, mean wave periods, and mean wave directions was good, in line with previous studies or even better in some areas of the global ocean, namely in the extratropical latitudes. These results give a good degree of confidence in the ability of the ensemble to simulate a realistic climate change signal.

CMIP5-based global wave climate projections including the entire Arctic Ocean

This study presents simulations of the global ocean wave climate corresponding to the surface winds and sea ice concentrations as simulated by five CMIP5 (Coupled Model Intercomparison Project Phase 5) climate models for the historical (1979–2005) and RCP8.5 scenario future (2081–2100) periods. To tackle the numerical complexities associated with the inclusion of the North Pole, the WAVEWATCH III (WW3) wave model was used with a customized unstructured Spherical Multi-Cell grid of ∼100 km offshore and ∼50 km along coastlines. The climate model simulated wind and sea ice data, and the corresponding WW3 simulated wave data, were evaluated against reanalysis and hindcast data. The results show that all the five sets of wave simulations projected lower waves in the North Atlantic, corresponding to decreased surface wind speeds there in the warmer climate. The selected CMIP5 models also consistently projected an increase in the surface wind speed in the Southern Hemisphere (SH) mid-high latitudes, which translates in an increase in the WW3 simulated significant wave height (Hs) there. The higher waves are accompanied with increased peak wave period and increased wave age in the East Pacific and Indian Oceans, and a significant counterclockwise rotation in the mean wave direction in the Southern Oceans. The latter is caused by more intense waves from the SH traveling equatorward and developing into swells. Future wave climate in the Arctic Ocean in summer is projected to be predominantly of mixed sea states, with the climatological mean of September maximum Hs ranging mostly 3–4 m. The new waves approaching Arctic coasts will be less fetch-limited as ice retreats since a predominantly southwards mean wave direction is projected in the surrounding seas.

A High-Resolution Future Wave Climate Projection for the Coastal Northwestern Atlantic

A high-resolution wave climate projection for the northwestern Atlantic Ocean has been conducted to help assess possible regional impacts due to global climate change. The spectral wave model NOAA WAVEWATCH III is utilized with three coupled (two-way) grids to resolve the northwestern Atlantic and coastal southern and eastern USA at approximately 21 km and 7 km respectively, and covers the periods 1979--2003 (historic) and 2075--2099 (future). Hourly wind field forcings are provided by a high-resolution AGCM (MRI-AGCM 3.2S; 21 km) and allow for better modeling of large storm events (important for extreme event statistics). Climatological (25-year) comparisons between future and historical periods indicate significant wave heights will decrease in the northwestern Atlantic Ocean (-5.7 %) and Gulf of Mexico (-4.7 %) but increase in the Caribbean Sea (2.4 %). Comparisons also indicate that large changes in mean wave direction will occur in the Gulf of Mexico (5.0{\deg}), with the largest occurring west of the Florida peninsula (over 15{\deg}).

Projected changes of the southwest Australian wave climate under two atmospheric greenhouse gas concentration pathways

Incident wave energy flux is responsible for sediment transport and coastal erosion in wave-dominated regions such as the southwestern Australian (SWA) coastal zone. To evaluate future wave climates under increased greenhouse gas concentration scenarios, past studies have forced global wave simulations with wind data sourced from global climate model (GCM) simulations. However, due to the generally coarse spatial resolution of global climate and wave simulations, the effects of changing offshore wave conditions and sea level rise on the nearshore wave climate are still relatively unknown. To address this gap of knowledge, we investigated the projected SWA offshore, shelf, and nearshore wave climate under two potential future greenhouse gas concentration trajectories (representative concentration pathways RCP4.5 and RCP8.5). This was achieved by downscaling an ensemble of global wave simulations, forced with winds from GCMs participating in the Coupled Model Inter-comparison Project (CMIP5), into two regional domains, using the Simulating WAves Nearshore (SWAN) wave model. The wave climate is modeled for a historical 20-year time slice (1986–2005) and a projected future 20-year time-slice (2081–2100) for both scenarios. Furthermore, we compare these scenarios to the effects of considering sea-level rise (SLR) alone (stationary wave climate), and to the effects of combined SLR and projected wind-wave change. Results indicated that the SWA shelf and nearshore wave climate is more sensitive to changes in offshore mean wave direction than offshore wave heights. Nearshore, wave energy flux was projected to increase by ∼10% in exposed areas and decrease by ∼10% in sheltered areas under both climate scenarios due to a change in wave directions, compared to an overall increase of 2–4% in offshore wave heights. With SLR, the annual mean wave energy flux was projected to increase by up to 20% in shallow water (< 30 m) as a result of decreased wave dissipation. In winter months, the longshore wave energy flux, which is responsible for littoral drift, is expected to increase by up to 39% (62%) under the RCP4.5 (RCP8.5) greenhouse gas concentration pathway with SLR. The study highlights the importance of using high-resolution wave simulations to evaluate future regional wave climates, since the coastal wave climate is more responsive to changes in wave direction and sea level than offshore wave heights.

Projected atoll shoreline and run-up changes in response to sea-level rise and varying large wave conditions at Wake and Midway Atolls, Northwestern Hawaiian Islands

Atoll islands are dynamic features that respond to seasonal alterations in wave conditions and sea level. It is unclear how shoreline wave run-up and erosion patterns along these low elevation islands will respond to projected sea-level rise (SLR) and changes in wave climate over the next century, hindering communities' preparation for the future. To elucidate how these processes may respond to climate change, extreme boreal winter and summer wave conditions under future sea-level rise (SLR) and wave climate scenarios were simulated at two atolls, Wake and Midway, using a shallow-water hydrodynamic model. Nearshore wave conditions were used to compute the potential longshore sediment flux along island shorelines via the CERC empirical formula and wave-driven erosion was calculated as the divergence of the longshore drift; run-up and the locations where the run-up exceed the berm elevation were also determined. SLR is projected to predominantly drive future island morphological change and flooding. Seaward shorelines (i.e., ocean fronted shorelines directly facing incident wave energy) were projected to experience greater erosion and flooding with SLR and in hypothetical scenarios where changes to deep water wave directions were altered, as informed by previous climate change forced Pacific wave modeling efforts. These changes caused nearshore waves to become more shore-normal, increasing wave attack along previously protected shorelines. With SLR, leeward shorelines (i.e., an ocean facing shoreline but sheltered from incident wave energy) became more accretive on windward islands and marginally more erosive along leeward islands. These shorelines became more accretionary and subject to more flooding with nearshore waves becoming more shore-normal. Lagoon shorelines demonstrated the greatest SLR-driven increase in erosion and run-up. They exhibited the greatest relative change with increasing wave heights where both erosion and run-up magnitudes increased. Wider reef flat-fronted seaward shorelines became more accretive as all oceanographic forcing parameters increased in magnitude and exhibited large run-up increases following increasing wave heights. Island end shorelines became subject to increased flooding, erosion at Wake, and accretion at Midway with SLR. Under future conditions, windward and leeward islands are projected to become thinner as ocean facing and lagoonal shorelines erode, with leeward islands becoming more elongate. Island shorelines will change dramatically over the next century as SLR and altered wave climates drive new erosional regimes. It is vital to the sustainability of island communities that the relative magnitudes of these effects are addressed when planning for projected future climates.

On the Role of Climate Change on Wind Waves Generated by Tropical Cyclones in the Gulf of Mexico

To generate projections of wave climate associated to tropical cyclones is a challenge due to their short historical record of events, their low occurrence, and the poor wind field resolution in General Circulation Models. Hence, synthetic tropical cyclones provide an alternative to overcome such limitations, improving robust statistics under both present and future climates. We use synthetic events to characterize present and future wave climate associated with tropical cyclones in the Gulf of Mexico. The NCEP/NCAR atmospheric reanalysis and the Coupled Model Intercomparison Project Phase 5 models NOAA/GFDL CM3 and UK Met Office HADGEM2-ES, were used to derive present and future wave climate under RCPs 4.5 and 8.5 scenarios. The GFDL model shows less bias in the present climate with respect to NCEP/NCAR results. Furthermore, the numerical results suggest an increase in wave activity for the future climate in the Caribbean Sea and Northern Gulf of Mexico, whereas some areas are expected to decrease the wave energy, as the stretch of the Gulf of Mexico between Yucatan and Southern Texas. The results have practical implications on the design of offshore structures. The 100-year design wave based on the present climate might result in under/over design of structures, owing to the lifespan of a structure that is within the future wave climate period.

Projected changes in significant wave height toward the end of the 21st century: Northeast Atlantic

AbstractWind field ensembles from six CMIP5 models force wave model time slices of the northeast Atlantic over the last three decades of the 20th and the 21st centuries. The future wave climate is investigated by considering the RCP4.5 and RCP8.5 emission scenarios. The CMIP5 model selection is based on their ability to reconstruct the present (1971–2000) extratropical cyclone activity, but increased spatial resolution has also been emphasized. In total, the study comprises 35 wave model integrations, each about 30 years long, in total more than 1000 years. Here annual statistics of significant wave height are analyzed, including mean parameters and upper percentiles. There is general agreement among all models considered that the mean significant wave height is expected to decrease by the end of the 21st century. This signal is statistically significant also for higher percentiles, but less evident for annual maxima. The RCP8.5 scenario yields the strongest reduction in wave height. The exception to this is the north western part of the Norwegian Sea and the Barents Sea, where receding ice cover gives longer fetch and higher waves. The upper percentiles are reduced less than the mean wave height, suggesting that the future wave climate has higher variance than the historical period.

Climate Change Impacts on Future Wave Climate around the UK

Understanding the changes in future storm wave climate is crucial for coastal managers and planners to make informed decisions required for sustainable coastal management and for the renewable energy industry. To investigate potential future changes to storm climate around the UK, global wave model outputs of two time slice experiments were analysed with 1979–2009 representing present conditions and 2075–2100 representing the future climate. Three WaveNet buoy sites around the United Kingdom, which represent diverse site conditions and have long datasets, were chosen for this study. A storm event definition (Dissanayake et al., 2015) was used to separate meteorologically-independent storm events from wave data, which in turn allowed storm wave characteristics to be analysed. Model outputs were validated through a comparison of the modelled storm data with observed storm data for overlapping periods. Although no consistent trends across all future clusters were observed, there were no significant increases in storm wave height, storm count or storm power in the future, at least according to the global wave projection results provided by the chosen model.

Projection of tropical cyclone-generated extreme wave climate based on CMIP5 multi-model ensemble in the Western North Pacific

Climate change impacts on future ocean wave climate have been studied using a suite of Global Climate Models (GCM). We investigated the representation of extreme (annual maximum) wave climate in the Atmosphere-Ocean GCM (AOGCM) driven wave climate projections, specifically looking at tropical cyclone (TC)-generated extreme waves in the Western North Pacific. The representation of the extreme wave climate by AOGCM driven wave climate projections was evaluated by comparing with higher-resolution AGCM driven wave climate projections, reanalysis and observations. We find better performance of AOGCM’s to simulate TCs leads to significantly improved representation of the extreme wave climate. The better performing models can produce more than $$30\hbox { ms}^{-1}$$ wind speed in TCs and the frequency of occurrence of TCs is 80 % of the observed frequency of occurrence. The projected changes in the extreme wave climate are dominated by changes in TC-generated waves. Although the projected changes in TC-generated wave heights show the coherent decreases in some models with greater TC skill, there is a large variation in the projected changes among models. The other models which are less able to resolve the TC characteristics display projected changes dominated by non-TC generated waves systems, which is the decrease in wave heights around latitudes 30 $$^{\circ }$$ N. Although there is a large variation in the projected changes in TC-generated waves, the change ratio is 2 times larger than those of non-TC waves. Therefore, appropriate interpretation of the TC-generated wave changes and its variation is important for risk assessment.

Twenty-first century wave climate projections for Ireland and surface winds in the North Atlantic Ocean

Abstract. Ireland has a highly energetic wave and wind climate, and is therefore uniquely placed in terms of its ocean renewable energy resource. The socio-economic importance of the marine resource to Ireland makes it critical to quantify how the wave and wind climate may change in the future due to global climate change. Projected changes in winds, ocean waves and the frequency and severity of extreme weather events should be carefully assessed for long-term marine and coastal planning. We derived an ensemble of future wave climate projections for Ireland using the EC-Earth global climate model and the WAVEWATCH III® wave model, by comparing the future 30-year period 2070–2099 to the period 1980–2009 for the RCP4.5 and the RCP8.5 forcing scenarios. This dataset is currently the highest resolution wave projection dataset available for Ireland. The EC-Earth ensemble predicts decreases in mean (up to 2 % for RCP4.5 and up to 3.5 % for RCP8.5) 10 m wind speeds over the North Atlantic Ocean (5–75° N, 0–80° W) by the end of the century, which will consequently affect swell generation for the Irish wave climate. The WAVEWATCH III® model predicts an overall decrease in annual and seasonal mean significant wave heights around Ireland, with the largest decreases in summer (up to 15 %) and winter (up to 10 %) for RCP8.5. Projected decreases in mean significant wave heights for spring and autumn were found to be small for both forcing scenarios (less than 5 %), with no significant decrease found for RCP4.5 off the west coast in those seasons.

Coastal and riverine ecosystems as adaptive flood defenses under a changing climate

Adaptation planning for flood risk forms a significant part of global climate change response. Engineering responses to higher water levels can be prohibitively costly. Several recent studies emphasize the potential role of ecosystems in flood protection as adaptive risk reduction measures while also contributing to carbon fixation. Here, we use a conceptual model study to illustrate the built-in adaptive capability of ecosystems to reduce a wide range of wave heights, occurring at different water levels, to a narrower range. Our model shows that wave height of waves running through a forested section is independent of initial height or of water level. Although the underlying phenomenon of non-linear wave attenuation within coastal vegetation is well studied, implications of reducing variability in wave heights for design of ecosystem and levee combinations have not yet been properly outlined. Narrowing the range of wave heights by a vegetation field generates an adaptive levee that is robust to a whole range of external conditions rather than only to a maximum wave height. This feature can substantially reduce costs for retrofitting of levees under changing future wave climates. Thereby, in wave prone areas, inclusion of ecosystems into flood defense schemes constitutes an adaptive and safe alternative to only hard engineered flood risk measures.

Variability and future decreases in winter wave heights in the Western North Pacific

AbstractOcean surface wave climate is a key consideration for a number of industrial and environmental systems, both offshore and at the coast. A dynamical spectral wave model forced with global climate models (GCMs) was used to produce an ensemble of simulations of both historical and projected future wave climate. To estimate the uncertainty of the projected wave climate, we combined a multimember ensemble experiment using MRI‐AGCM3.2H with a multimodel ensemble using eight CMIP5 GCMs. Future changes in wintertime wave heights from the end of the 20th to the 21st century were analyzed. Projected decreases in wave heights over the Western North Pacific are highly consistent among the ensemble. The future decreases in wave heights are significantly related to changes in the West Pacific pattern. Both locally generated waves and remotely generated swells are important to estimate future changes in the wave climate on a regional scale.

The Influence of the Subtropical High-Pressure Ridge on the Western Australian Wave Climate

Wandres, M., Pattiaratchi, C., Wijeratne, E.M.S., Hetzel, Y., 2016. The influence of the subtropical high-pressure ridge on the Western Australian wave climate. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 567–571. Coconut Creek (Florida), ISSN 0749-0208.Understanding the wave climate of a region is critical for its coastal zone management. The southwest Western Australian (SWWA) wave climate is dominated by waves generated in the energetic and variable Southern Ocean (SO) storm belt. The latitudinal variability of the SO storm belt can be described by the position (latitude) of the subtropical high-pressure ridge (STRP). To gain an understanding in how the SO storm belt influences the SWWA wave climate, the relationship between the STRP and the waves was examined. Wave data from three directional wave buoys along the SWWA shelf were compared to the STRP. The seasonal and interannual variability of the STRP and the wave climate indicated a significant correlation between the STRP and the SWWA wave heights with the strongest relationship during winter. A northward shift of the STRP resulted in a northward shift of the SO storm belt which led to increased wave heights in SWWA whereas a southward shift of the STRP resulted in decreased wave heights. The close relationship between the STRP and the local wave climate, suggests it could be used to estimate future wave climates in SWWA.

Wave climate projections for Ireland for the end of the 21st century including analysis of EC‐Earth winds over the North Atlantic Ocean

ABSTRACTThis study aims to quantify the potential impact of global climate change on Ireland's marine resource, which is of significant economic and social importance. Global climate models predict warming of the Earth's atmosphere and oceans, which will consequently affect mean sea levels, the frequency and severity of extreme weather events, winds and ocean waves. Such changes need to be carefully assessed for long‐term marine and coastal planning. We derived future wave climate projections for Ireland using the EC‐Earth global climate model and the WAVEWATCH III wave model, by comparing the future 30‐year period 2070–2099 to 1980–2009 for the RCP4.5 and the RCP8.5 forcing scenarios. This data set is currently the highest resolution wave projection data set available for Ireland. EC‐Earth predicts decreases in means (up to 3%) and extremes (up to 14% for the 95th percentile) of 10 m wind speeds over the North Atlantic Ocean (5–75°N, 0–80°W) by the end of the century. Similarly, the model projections show decreases in the frequency and intensity of wind storms crossing Ireland but these changes are not statistically significant. The WAVEWATCH III model predicts an overall decrease in mean (up to 15%) and extreme (up to 15% for the 95th percentile) annual, boreal winter and summer significant wave heights around Ireland.