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Oceanic biogeochemistry plays a pivotal role in regulating Earth's climate system by governing the cycling of key elements such as carbon, oxygen, and nutrients. Various metocean processes including wind, tides, currents, waves, and eddies significantly influence the dynamics of this system. In particular, ocean surface waves contribute to this intricate interplay by facilitating the exchange of heat, gas, and momentum between the atmosphere and the ocean. Although wave‐coupled effects are substantial, studies on their impacts on oceanic biogeochemistry, particularly on phytoplankton abundance are missing in present‐day research. Additionally, wave‐coupled effects cannot be disregarded in regions like the Southern Ocean (SO), where wind and waves activities are prominent. Addressing this gap, we incorporated a parameterization of surface wave mixing into a global ocean biogeochemical model to investigate its effects on upper ocean and biogeochemical parameters. Our results show that surface wave mixing has significant impacts on sea surface temperature (SST), mixed layer depth (MLD), and nutrient distribution—key factors that influence phytoplankton growth. Additionally, we observed significant improvements in model biases against the observations. During austral summer, additional mixing from surface waves can significantly lower SST by 0.5°C, deepen MLD by 13 m, and enhance Chlorophyll‐a (Chl‐a) concentration, an index of phytoplankton population, by 8% in the SO. This observed increase in Chl‐a concentration is mainly driven by enhanced dissolved iron levels resulting from wave‐induced mixing. Our findings underscore the significance of incorporating surface wave mixing in ocean biogeochemistry studies, an aspect that is currently overlooked. Plain Language Summary: Ocean biogeochemistry encompasses the complex interactions of the ocean's biological, geological, and chemical processes and affects the Earth's climate system. This system is highly impacted by various physical forcings such as wind, currents, waves, tides, and eddies. Among these forcings, surface waves play a crucial role by exchanging heat, gas, and momentum between the atmosphere and ocean. Understanding the roles of surface waves on upper ocean mixing and oceanic biogeochemistry is paramount, especially in regions like the Southern Ocean (SO), where wind and waves are prominent. However, present‐day studies lack research on wave‐coupled effects on ocean biogeochemistry, particularly in the SO. Addressing this research gap, we investigated the influence of surface wave mixing on oceanic biogeochemistry by adding a parameterization of surface wave mixing in a global ocean biogeochemical model. From the investigation, we found significant effects of wave coupling on upper ocean and biogeochemical parameters, such as cooling of sea surface temperature, deepening mixed layer depth, enhancing nutrient levels, and consequently, increasing phytoplankton distribution during austral summer in the SO. This study contributes to a deeper understanding of the complex interplay between ocean surface waves and oceanic biogeochemistry, especially in the SO. Key Points: Present‐day studies lack research on the wave‐coupled effects on ocean biogeochemistry, particularly in the Southern OceanA surface wave mixing parameterization is used to investigate the wave‐coupled effects on the upper ocean and biogeochemical parametersWave coupling influences ocean temperature, mixed layer depth, and nutrient levels which are essential for phytoplankton growth [ABSTRACT FROM AUTHOR]

Waves critically modulate the air‐sea fluxes, and upper‐ocean thermodynamics in a Tropical Cyclone (TC) system. This study improves the modeling of TC intensification by incorporating non‐breaking wave‐induced turbulence and sea spray from breaking waves into an atmosphere‐ocean‐wave coupled model. Notably, wind forecast error decreased by around 10% prior to TCs' peak intensity. The positive feedback of sea spray along with compensatory negative feedback from non‐breaking waves, overall enhanced TCs' intensity. These breaking and non‐breaking wave‐coupled processes consistently cool sea surface temperature, resulting in improvement of the modeled SST. Observed improvements in full‐year TC cases ranging from Categories I to IV in this study suggest that an accurate characterization of ocean wave‐coupled processes is crucial for improving TCs' intensity forecasts and advancing our understanding of severe weather events in both, the atmosphere and ocean. Plain Language Summary: Tropical Cyclones (TCs), such as hurricanes and typhoons, are destructive natural disasters that can cause extensive damage. Our study focused on understanding the role of ocean waves and related processes in TCs. Through numerical modeling, we found that ocean waves, specifically breaking and non‐breaking waves, have a substantial influence on TCs' intensity. Breaking waves contribute positively through the production of sea spray droplets, while non‐breaking wave‐induced turbulence has a compensatory negative effect, resulting in an enhancement in TCs' intensity. Incorporating both wave mechanisms into the models improved the accuracy of TCs' intensity and their underlying sea surface temperature. By highlighting the importance of ocean wave‐coupled physics, we aim to enhance our understanding of TCs and improve disaster preparedness to mitigate their impacts on coastal communities. Key Points: Full‐year regional hindcast of Tropical Cyclones (TCs) at the North West AustraliaInclusion of wave‐coupled processes improves TCs modeling, by reducing forecast errors and enhancing rapid intensification simulationsSea spray increases TC development while nonbreaking wave turbulence has the opposite effect with the first process dominating [ABSTRACT FROM AUTHOR]

Extreme significant wave height estimates, and their probability of exceedance, are fundamental offshore and coastal engineering design parameters. These estimates are characterized by uncertainty due to an incomplete understanding of the atmosphere‐ocean energy and momentum exchanges during intense storms. This particularly affects extreme wave statistics of ocean regions exposed to large and frequent synoptic disturbances such as Extra‐Tropical Cyclones (ETCs). In this work, we assessed the performance of global phase‐averaged spectral wave models in representing the 1 in 100‐year sea state generated by a Southern Ocean ETC in April 2021. We collected in situ and remote sensing observations, from the storm generation region to its decaying phase and the impact on South‐East Australian coastlines. We compared the observations with a suite of reanalysis and hindcast global wave model data sets. While comparing well for wind speed up to 20 m/s, the models presented differences in solving the air‐sea momentum exchange between the atmosphere and the ocean for wind speed velocities between 20 and 35 m/s, which are a distinctive characteristic of ETCs. Despite marked differences in the storm generation region, the models converged to a similar representation of the swell systems impacting the South‐East Australian coastlines, as demonstrated by a comparison with deep‐water buoy observations close to the coastlines. Furthermore, we found that the energy of the ERA5 reanalysis, which assimilates satellite wave height measurements is quickly dispersed and, as such, of little advantage in representing the 9.9 m significant wave heights that impacted the South‐East Australian coastlines on 10 April 2021. Plain Language Summary: Ocean wind‐wave extreme events are a major driver of coastal erosion and a fundamental aspect in the design of offshore and coastal structures. Engineers rely on accurate one‐in‐N‐year significant wave height return period estimates, and in a changing climate, accurate estimates of wind‐wave extremes are also crucial to implement efficient and resilient coastal climate adaptation strategies. Global wave reanalysis data sets are commonly used to estimate wind and wave statistical properties and design parameters. However, despite the impressive accuracy of such data sets in representing average significant wave height conditions, models still underestimate wind‐wave extremes. In this work, we take advantage of a well‐documented one‐in‐100‐year sea state generated by a Southern Hemisphere Extra‐Tropical Cyclone (ETC) to analyze the performance of state‐of‐the‐art global wave models in representing wind‐wave extremes. The aim is to support informed extreme value analysis statistical studies and suggest improvements to wave models to better represent extreme climate in the Northern and Southern Hemisphere ocean regions exposed to ETCs. Key Points: The performance of phase‐averaged global wave models is evaluated for a 100‐year sea state generated by a Southern Hemisphere Extra‐Tropical Cyclone (ETC)Lack of understanding of air‐sea momentum exchange at wind speed between 20 and 35 m/s challenges the modeling of ETC sea statesNovel atmosphere‐ocean coupled models and new ETC sea state in situ measurements are needed to improve air‐sea momentum exchange modeling [ABSTRACT FROM AUTHOR]

In spite of massive efforts directed to development of climate models over recent decades, accurate climate simulations and prediction remain a grand challenge. Large sea surface temperature model bias is one of the key indicators of the problem, among others. Qiao and his team suggested the concept of surface wave‐induced turbulence and elaborated the way for such coupling, through turbulent processes at both sides of the air‐ocean interface. These are the wave mixing in the ocean and wave modulation of air‐sea fluxes. This wave‐ocean coupled approach led to essential improvements of performance of ocean circulation and climate models, essentially introducing the next generation of large‐scale air‐sea interaction models. This Commentary reviews three recent JGR publications where the Qiao theory was implemented. The first paper (Huang & Qiao, 2021; https://doi.org/10.1029/2020JC016839) reported that the momentum gain by the ocean could be larger than the wind stress input, due to the ocean waves. The second paper (Chen et al., 2022; https://doi.org/10.1029/2021JC018360) demonstrated that, also due to waves, the drag coefficients in the atmospheric boundary layer have a spatial asymmetry during tropical cyclones. The third paper (Zhao et al., 2022; https://doi.org/10.1029/2022JC019015), based on combination of wave‐coupled effects on both sides of air‐sea interface, demonstrates their impact on simulation of tropical cyclone intensity. All papers are based on unique in situ measurements and their data analysis. The Commentary is further used as an opportunity to outline and review the current state of the small‐large scale coupling topic with respect to ocean, weather and climate modeling. Plain Language Summary: Understanding the nature of climate change and predicting its trends have been one of the highest priorities for scientific communities and of great importance for the public. Climate simulations, however, have been facing challenges which persist for decades, and apparently mean that some of the physical processes in their description are missing. A large set of such processes rest with the coupled nature of small‐ and large‐scale air‐sea interaction phenomena. Since the spatio‐temporal scales of surface waves, around 100 m and 10 s, are too far from those in the climate system, that is, thousands to tens thousands kilometers and years to decades, their coupling have never been incorporated by climate models due to lack of understanding of physics of such interactions and computing capabilities. Recent publications indicate that surface waves can both change the upper ocean through non‐breaking wave‐induced mixing and, on the atmospheric side, air‐sea fluxes through modulating the interface of ocean and atmosphere. As a result, ocean and climate predictions can be essentially improved by considering surface waves in climate models. The Commentary mainly discusses three recent papers dedicated to this topic. Key Points: This Commentary reviews three recent JGR publications dedicated to wave‐coupled approaches to large‐scale air‐sea systemsThis wave‐ocean coupled approach led to essential improvements of performance of ocean circulation and climate modelsThe Commentary is further used as an opportunity to outline and review the current state of the small‐large scale coupling topic [ABSTRACT FROM AUTHOR]

Extreme marine weather enhances the production of sea spray droplets which, in turn, affect the air‐sea fluxes. Despite the ability of sea spray to modulate air‐sea interaction processes, it remains under‐represented in tropical cyclone (TC) forecasting modeling. In this study, impacts of sea spray on the atmospheric and oceanic environments of TC Olwyn are investigated. This is achieved by high‐resolution nested simulations using an air‐sea‐wave model coupled with a sea spray production model. We compared two different sea spray models: a wave‐Reynolds‐number‐dependent model, and a wave‐steepness‐dependent spray model. By including a sea spray model, the root mean square error in the simulated TC Olwyn 10 m wind and significant wave height are significantly reduced by up to 30% and 26%, respectively, in comparison to the baseline simulation without spray. This improvement is because sea spray decreases air‐sea heat fluxes at larger radii of TC, and decreases air‐sea heat fluxes at smaller radii of TC. In contrast to the simulated results without sea spray, sea spray increases the air‐sea heat (sensible + latent) energy transfer and intensifies TC Olwyn. Sea spray also triggers stronger upper‐ocean mixing and strengthens the TC‐induced sea surface temperature cooling. Our results thus imply that sea spray critically impacts the atmosphere and ocean conditions during extreme marine weather and thus needs to be considered explicitly in TC forecasting modeling. Plain Language Summary: Large quantities of sea spray droplets are generated at the ocean surface and released into the air under extreme marine weather conditions. Even though sea spray plays an important role in the transfer of heat, moisture, and momentum between the air and ocean surface, its true impact remains uncertain in tropical cyclone (TC) modeling. In this study, we include a novel description of sea spray generation into an atmosphere‐ocean‐wave coupled model to investigate the impacts of sea spray on the development of TC Olwyn. In comparison to a simulation without sea spray, the errors of wind speed and wave height of the modeled TC Olwyn are considerably reduced when sea spray is considered. This improvement is expected to be from the impacts of sea spray on the structure of the TC Olwyn. As sea spray has significant effects on the atmospheric and oceanic environments, our results suggest that sea spray generations need to be included in current TC forecasting models. Key Points: Implementation of wind‐wave dependent sea spray parameterizations into the atmosphere‐ocean‐wave coupled modelThe simulation error of U10 and Hs for tropical cyclone (TC) Olwyn is significantly reduced by introducing the sea sprayThe sea spray plays a critical role in the development and intensification of TC Olwyn, and underlying sea surface temperature cooling [ABSTRACT FROM AUTHOR]

Global wave hindcasts are developed using the third generation spectral wave model WAVEWATCH III with the observation‐based source terms (ST6) and a hybrid rectilinear‐curvilinear, irregular‐regular‐irregular grid system (approximately at 0.25°×0.25°). Three distinct global hindcasts are produced: (a) a long‐term hindcast (1979–2019) forced by the ERA5 conventional winds U10 and (b) two short‐term hindcasts (2011–2019) driven by the NCEP climate forecast system (CFS)v2 U10 and the ERA5 neutral winds U10,neu, respectively. The input field for ice is sourced from the Ocean and Sea Ice Satellite Application Facility (OSI SAF) sea‐ice concentration climate data records. These wave simulations, together with the driving wind forcing, are validated against extensive in‐situ observations and satellite altimeter records. The performance of the ST6 wave hindcasts shows promising results across multiple wave parameters, including the conventional wave characteristics (e.g., wave height Hs and wave period) and high‐order spectral moments (e.g., the surface Stokes drift and mean square slope). The ERA5‐based simulations generally present lower random errors, but the CFS‐based run represents extreme sea states (e.g., Hs>10 m) considerably better. Novel wave parameters available in our hindcasts, namely the dominant wave breaking probability, wave‐induced mixed layer depth, freak wave indexes and wave‐spreading factor, are further described and briefly discussed. Inter‐comparisons of Hs from the long‐term (41 years) wave hindcast, buoy measurements and two different calibrated altimeter data sets highlight the inconsistency in these altimeter records arising from different calibration methodology. Significant errors in the low‐frequency bins (period T>15 s) for both wave energy and directionality call for further model development. Plain Language Summary: Ocean surface waves are fundamentally important for ocean engineering design, ship navigation, air‐sea exchange of gas, heat, momentum and energy, upper ocean dynamics, and remote sensing of the ocean. Spectral wave modeling is an indispensable tool to estimate sea state information. In this study, we present new global wave hindcasts developed using the state‐of‐the‐art model physics and numerics and the modern reanalysis winds and satellite sea ice records. It is demonstrated through validation against in‐situ observations and altimeter records that the global wave hindcasts perform well across multiple parameters. Meanwhile, intercomparisons of wave height from the long‐term hindcast, buoys, and altimeters reveal inconsistency and potential inhomogeneity in these different data sets. The wave hindcasts we developed, in combination with global wave databases published previously, will form a large ensemble of realizations of historical evolution of sea states simulated with distinct wave physics and wind forcing, which will help quantify sea states in real oceans more accurately. Key Points: Global wave hindcasts using the observation‐based source terms are developed and validated against extensive observationsThe wave hindcasts show promising performance across multiple parameters, including wave height, period, and high‐order spectral momentsIntercomparisons of wave height from the hindcast, buoys, and altimeters highlight the inconsistency and inhomogeneity in these data sets [ABSTRACT FROM AUTHOR]

A new parameterization of mixing processes in the upper ocean is tested in a 1=48 resolution global ocean climate model. The parameterization represents the effect of turbulent mixing by unbroken waves as an additional turbulent shear production term in the k-epsilon mixing scheme. The results show that the inclusion of this parameterization has a noticeable effect on ocean climate, particularly in regions of high wave activity such as the Southern Ocean. Inclusion of this process also leads to some reduction in the biases of the simulated climate, including mixed layer depth, compared with available observations. [ABSTRACT FROM AUTHOR]

Tropical cyclones dissipate large amounts of energy into the upper ocean, locally enhancing vertical mixing and cooling the sea surface. In this study, we investigate how the response of the ocean to tropical cyclones is affected by additional mixing from unbroken surface waves. This ''Surface Wave Mixing'' (SWM) is represented by a novel parameterization, in which the wave orbital motion contributes directly to the production of turbulent kinetic energy. The parameterization is implemented here as a modification to the k-e turbulence scheme, used within an ocean model with 1/48 horizontal resolution (MOM5). This model is forced with idealized tropical cyclone wind fields based on observed case studies. Relative to simulations without SMW, the inclusion of SWM leads to surface temperature differences of around 0.58C near the storm track, typically with warm anomalies on the side with the strongest winds and cool anomalies in other regions. This pattern is explained by an initial wave-induced deepening of the mixed layer, which can modify the subsequent shear-induced entrainment and upwelling. The temperature anomalies from SWM could potentially influence tropical cyclone intensity and structure. [ABSTRACT FROM AUTHOR]

It is shown that Lakes Entrance, a township located at the northern end of Ninety Mile Beach in southeastern Australia, is situated in a region that may experience noticeable changes in longshore wind, wave and ocean currents compared to present day climate variability as a consequence of the southward shifting subtropical ridge (STR) predicted in global climate change models. These changes could modify sediment transport in the littoral zone and impact the coastline position. Thirty-year hindcasts of winds, coastal currents and waves are shown to agree well with available observations and provide a long-term dataset of the climate variability. Hindcasts of coastal ocean currents and waves indicate that while the annual net mean wave and current transport are in opposing directions, their seasonal adjusted monthly anomalies are positively correlated. Furthermore they are also correlated with the position of the STR location index. On seasonal to annual time scales a weak connection between the transport variables and Southern Oscillation Index (SOI) is found. It appears that during multiple years of positive (negative) SOI conditions the STR is located north (south) of its mean monthly position, resulting in anomalous eastward (westward) transport. The four climate models used in this study indicate a southward shift in the STR for most months under a high emission future. In summer months the shift in the STR results in both increased summer westward wind-driven currents and westward wave forcing. Changes in winter months are less related to the STR location and it is discussed that the contraction and increased intensity of the westerly storm belt linked to Southern Annular Mode could possibly influence the transport. The analysis is presented at the coastal scale to provide insights into how these changes may affect net transport across the littoral zone in more detailed numerical nearshore sediment transport modelling. [ABSTRACT FROM AUTHOR]