Interaction between surface gravity waves and sea-ice in the marginal ice zone is complex, and most of the prior research focus has been in deeper oceans. Here, the regional wave model Simulating WAves Nearshore (SWAN) is configured to simulate reduced wind-generation and wave dissipation in the presence of sea-ice. The wind-generation process is modified by scaling the generation terms with the open-water fraction, while wave dissipation in the presence of sea-ice is simulated as an exponential energy decay as function of ice concentration, wave frequency and empirical coefficients determined from prior experiments. Modified SWAN is used to simulate interaction between regional sea-ice and a swell event in the Barents Sea. The simulation accounting for wave-ice interaction reasonably agrees with field measured significant wave height and the energy spectral density. Additional simulations are conducted for the shallow seas of Gulf of Bothnia, located in the northernmost reach of the Baltic sea. Modeled wave dynamics in this region agrees well with satellite altimetry based measurements. This model setup is further investigated to understand fetch scaling in the marginal ice zone, and non-dimensional energy scales well with a non-dimensional fetch determined from a cumulative fetch dependent on ice concentration. Additional implications for Stokes drift and Stokes drift shear are also discussed for the Bothnian bay. Finally recommendations for including dissipation due to ice thickness, and plans for future model coupling are considered.

The retreat of Arctic sea ice coincides with increased ocean surface wave activity, and wave-ice interactions are consequently poised to have a growing influence on the Arctic climate system. Recent field campaigns have focused on rectifying the scarcity of wave measurements inside the marginal ice zone, and work is now underway to incorporate wave-ice interactions in global climate models. Here, we apply a collection of in situ wave observations spanning multiple years in the Beaufort Sea and including wave activity beyond 100 kilometers inside the sea ice edge. To better understand waves in the presence of sea ice, we connect the in situ data with satellite-derived ice concentrations across the Arctic and compare the observations with a recent global climate model experiment that includes coupled interactions between waves and a sea ice floe size distribution. We present a series of comparisons focused on wave energy and wind-wave relationships in partial ice cover. These analyses provide a framework for assessing the impact of uncertainty in wave-ice physics on the marginal ice zone in new experiments in the coupled wave-ice model. Our work guides further model development and future observational campaigns.

Cross-shore transport of larvae, pollutants, and sediment between the surf zone and the inner shelf is important for coastal water quality and ecosystems. Rip currents are known to be a dominant pathway for exchange, but the effects of horizontal temperature and salinity gradients are not well understood. Airborne visible and infrared imagery performed on the California coast show warm and cool plumes driven by rip currents in the surf zone and extending onto the shelf, with temperature differences of approximately 1$^\circ$C. The airborne imagery and modeled temperatures and tracers indicate that warm plumes exhibit more lateral spreading and transport material in a buoyant near-surface layer, whereas cool plumes move offshore in a subsurface layer. The average cross-shore extent of warm plumes at the surface is approximately one surfzone width larger than for cool plumes. Future work may explore the sensitivity of nearshore plumes to density patterns, wave forcing, and bathymetry.

Observations from six Lagrangian Surface Wave Instrument Float with Tracking (SWIFT) drifters in January-February 2020 in the northwestern tropical Atlantic during the Atlantic Tradewind Ocean-atmosphere Mesoscale Interaction Campaign (ATOMIC) are used to evaluate the influence of wave-current interactions on wave slope and momentum flux. At wind speeds of 4-12 m/s, wave mean square slopes are positively correlated with wind speed. Wave-relative surface currents varied significantly, from opposing the wave direction at 0.16 m/s to following the waves at 0.57 m/s. For a given wind speed, wave slopes are up to 20% higher when surface currents oppose the waves compared to when currents strongly follow the waves, consistent with a theoretical Doppler shift between the absolute (fixed) and intrinsic (relative) frequency. Assuming an equilibrium frequency range in the wave spectrum, wave slope is proportional to wind friction velocity and momentum flux. The observed variation in wave slope equates to up to a 40% variation in momentum flux for a given wind speed. This is 30% greater than the variation expected from current-relative winds alone, and suggests that wave-current interactions can generate significant spatial and temporal variability in momentum fluxes in this region of prevailing trade winds. Results and data from this study motivate the continued development of fully coupled atmosphere-ocean-wave models.

Alaskan Arctic coastlines are protected seasonally from ocean waves by presence of coastal and shorefast sea ice. This study presents field observations collected during the autumn freeze up of 2019 near Icy Cape, a coastal headland in the Chukchi Sea of the Western Arctic. The evolution of the coupled air-ice-ocean-wave system during a four-day wave event was monitored using drifting wave buoys, a cross-shore mooring array, and ship-based measurements. The incident wave field was attenuated by coastal pancake and frazil sea ice, reducing significant wave height by 1 m over less than 5 km of cross-shelf distance spanning water depths from 13 to 30 m. Spectral attenuation coefficients are evaluated with respect to wave and ice conditions and the proximity to the ice edge. Attenuation rates are found to be three times higher within 500 m of the ice edge, relative to values farther in the ice cover. Attenuation rates follow a power-law dependence on frequency, with an exponent in the range of (2.3,2.7) m^-1.

The science guiding the \EURECA campaign and its measurements are presented. \EURECA comprised roughly five weeks of measurements in the downstream winter trades of the North Atlantic — eastward and south-eastward of Barbados. Through its ability to characterize processes operating across a wide range of scales, \EURECA marked a turning point in our ability to observationally study factors influencing clouds in the trades, how they will respond to warming, and their link to other components of the earth system, such as upper-ocean processes or, or the life-cycle of particulate matter. This characterization was made possible by thousands (2500) of sondes distributed to measure circulations on meso (200 km) and larger (500 km) scales, roughly four hundred hours of flight time by four heavily instrumented research aircraft, four global-ocean class research vessels, an advanced ground-based cloud observatory, a flotilla of autonomous or tethered measurement devices operating in the upper ocean (nearly 10000 profiles), lower atmosphere (continuous profiling), and along the air-sea interface, a network of water stable isotopologue measurements, complemented by special programmes of satellite remote sensing and modeling with a new generation of weather/climate models. In addition to providing an outline of the novel measurements and their composition into a unified and coordinated campaign, the six distinct scientific facets that \EURECA explored — from Brazil Ring Current Eddies to turbulence induced clustering of cloud droplets and its influence on warm-rain formation — are presented along with an overview \EURECA’s outreach activities, environmental impact, and guidelines for scientific practice.

Observations of ocean surface waves at three sites along the northern coast of Alaska show a strong coupling with seasonal sea ice patterns. In the winter, ice cover is complete, and waves are absent. In the spring and early summer, sea ice retreats regionally, but landfast ice persists near the coast. The landfast ice completely attenuates waves formed farther offshore in the open water, causing up to two-month delay in the onset of waves nearshore. In autumn, landfast ice begins to reform, though the wave attenuation is only partial due to lower ice thickness compared to spring. The annual cycle in the observations is reproduced by the ERA5 reanalysis product, but the product does not resolve landfast ice. The resulting ERA5 bias in coastal wave exposure can be corrected by applying a higher resolution ice mask, and this has a significant effect on the long-term trends inferred from ERA5.

Understanding and predicting sea ice dynamics and ice-ocean feedback processes requires accurate descriptions of momentum fluxes across the ice-ocean interface. In this study, we present observations from an array of moorings in the Beaufort Sea. Using a force-balance approach, we determine ice-ocean drag coefficient values over an annual cycle and a range of ice conditions. Statistics from high resolution ice draft measurements are used to calculate expected drag coefficient values from morphology-based parameterization schemes. With both approaches, drag coefficient values ranged from approximately 1-10×10^-3, with a minimum in fall and a maximum at the end of spring, consistent with previous observations. The parameterizations do a reasonable job of predicting the observed drag values if the under ice geometry is known, and reveal that keel drag is the primary contributor to the total ice-ocean drag coefficient. When translations of bulk model outputs to ice geometry are included in the parameterizations, they overpredict drag on floe edges, leading to the inverted seasonal cycle seen in prior models. Using these results to investigate the efficiency of total momentum flux across the atmosphere-ice-ocean interface suggests an inter-annual trend of increasing coupling between the atmosphere and the ocean.