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Abstract In this work, we seek to address the validity of Monin–Obukhov similarity theory (MOST) in the wave-affected surface boundary layer of the atmosphere. While bulk flux formulas which rely on MOST have been tested with and applied to measurements and models of air/sea interaction for several decades, the influences of surface wave–mediated fluxes on MOST have not been thoroughly quantified. We assess several months of direct covariance data from a stationary tower deployed with instruments inside the wave-affected surface layer. These measurements are analyzed in the context of the turbulent kinetic energy (TKE) equation and MOST, extending previous work due to the inclusion of directly estimated wave-coherent energy fluxes. Scaled TKE dissipation rates are reduced from what is predicted by MOST during events with large wave-coherent surface fluxes, resulting in a dissipation deficit in the energy budget (roughly 30%). However, we find that shear is much less impacted by these wave events showing much smaller deviations from baselines (less than 10%). During much of the experiment, the dissipation deficit is balanced by the wave-coherent pressure work, suggesting a general understanding of the combined turbulent and wave-driven energetics. However, several large storms in the fall of 2022 yielded much larger dissipation deficits than can be explained by the wave-coherent pressure work, highlighting that more work is needed to understand energetics in the wave-affected surface layer more generally. Significance StatementThe exchanges of heat, momentum, and gases between the air and the ocean are important for weather and climate prediction, ocean simulation, and wave models that are important for safe operations at sea. A current theory for these exchanges was designed for use over land but has been applied successfully over the ocean for several decades. One reason the overland theory [Monin–Obukhov similarity theory (MOST)] may not work as well is due to ocean waves, which change the nature of the surface in comparison with unmoving overland features like hills, mountains, and other topography. In particular, ocean waves grow with the wind, which means that they must draw down momentum and energy from the air above. In this paper, we work to understand why this theory for heat and momentum exchange at the surface (MOST) works well over ocean waves despite the unique physics when compared to wind over land. We find that the influence of waves is visible in some parts of the theory but that for the majority of conditions, the predictions from MOST should work well. 

Abstract High latitudes, including the Bering Sea, are experiencing unprecedented rates of change. Long-term Bering Sea warming trends have been identified, and marine heatwaves (MHWs), event-scale elevated sea surface temperature (SST) extremes, have also increased in frequency and longevity in recent years. Recent work has shown that variability in air–sea coupling plays a dominant role in driving Bering Sea upper-ocean thermal variability and that surface forcing has driven an increase in the occurrence of positive ocean temperature anomalies since 2010. In this work, we characterize the drivers of the anomalous surface air–sea heat fluxes in the Bering Sea over the period 2010–22 using ERA5 fields. We show that the surface turbulent heat flux dominates the net surface heat flux variability from September to April and is primarily a result of near-surface air temperature and specific humidity anomalies. The airmass anomalies that account for the majority of the turbulent heat flux variability are a function of wind direction, with southerly (northerly) wind advecting anomalously warm (cool), moist (dry) air over the Bering Sea, resulting in positive (negative) surface turbulent flux anomalies. During the remaining months of the year, anomalies in the surface radiative fluxes account for the majority of the net surface heat flux variability and are a result of anomalous cloud coverage, anomalous lower-tropospheric virtual temperature, and sea ice coverage variability. Our results indicate that atmospheric variability drives much of the Bering Sea upper-ocean temperature variability through the mediation of the surface heat fluxes during the analysis period. Significance StatementA long-term ocean warming trend and a recent increase in marine heatwaves in the Bering Sea have been identified. Previous work showed that anomalies in the exchange of heat between the ocean and the atmosphere were the primary driver of Bering Sea temperature variability, but the processes responsible for the heat exchange anomalies were unknown. In this work, we show that the atmosphere is the primary driver of anomalies in the Bering Sea air–sea heat exchange and therefore plays an important role in altering the thermal state of the Bering Sea. Our results highlight the importance of understanding more about how the ocean and the atmosphere interact at high latitudes and how this relationship will be affected by future climate change. 

Abstract Surface waves grow through a mechanism in which atmospheric pressure is offset in phase from the wavy surface. A pattern of low atmospheric pressure over upward wave orbital motions (leeward side) and high pressure over downward wave orbital motions (windward side) travels with the water wave, leading to a pumping of kinetic energy from the atmospheric boundary layer into the waves. This pressure pattern persists above the air–water interface, modifying the turbulent kinetic energy in the atmospheric wave-affected boundary layer. Here, we present field measurements of wave-coherent atmospheric pressure and velocity to elucidate the transfer of energy from the atmospheric turbulence budget into waves through wave-coherent atmospheric pressure work. Measurements show that the phase between wave-coherent pressure and velocity is shifted slightly above 90° when wind speed exceeds the wave phase speed, allowing for a downward energy flux via pressure work. Although previous studies have reported wave-coherent pressure, to the authors’ knowledge, these are the first reported field measurements of wave-coherent pressure work. Measured pressure work cospectra are consistent with an existing model for atmospheric pressure work. The implications for these measurements and their importance to the turbulent kinetic energy budget are discussed. Significance StatementSurface waves grow through a pattern of atmospheric pressure that travels with the water wave, acting as a pump against the water surface. The pressure pumping, sometimes called pressure work, or the piston pressure, results in a transfer of kinetic energy from the air to the water that makes waves grow larger. To conserve energy, it is thought that the pressure work on the surface must extract energy from the mean wind profile or wind turbulence that sets the shape of the wind speed with height. In this paper, we present direct measurements of pressure work in the atmosphere above surface waves. We show that the energy extracted by atmospheric pressure work fits existing models for how waves grow and a simple model for how waves reduce energy in the turbulent kinetic energy budget. To our knowledge, these are the first reported field measurements of wave-coherent pressure work. 

Abstract The turbulent ocean surface boundary layer (OSBL) shoals during daytime solar surface heating, developing a diurnal warm layer (DWL). The DWL significantly influences OSBL dynamics by trapping momentum and heat in a shallow near‐surface layer. Therefore, DWL depth is critical for understanding OSBL transport and ocean‐atmosphere coupling. A great challenge for determining DWL depth is considering wave‐driven Langmuir turbulence (LT), which increases vertical transport. This study investigates observations with moderate wind speeds (4–7 m/s at 10 m height) and swell waves for which breaking wave effects are less pronounced. By employing turbulence‐resolving large eddy simulation experiments that cover observed wind, wave, and heating conditions based on the wave‐averaged Craik‐Lebovich equation, we develop a DWL depth scaling unifying previous approaches. This scaling closely agrees with observed DWL depths from a year‐long mooring deployment in the subtropical North Atlantic, demonstrating the critical role of LT in determining DWL depth and OSBL dynamics.