The development of the Community Earth System Model, version 3 (CESM3) is underway and a significant advance under consideration for the sea ice component is the inclusion of wave-ice interactions. In order to explore this, we are using the Roach et al (2018) floe-size distribution (FSD) model incorporated into the CICE model. This is coupled to wave information from WAVEWATCH III (WW3), with WW3 run on a coarser 3-degree (gx3) model grid. We have implemented a new wave fracturing scheme following Tremblay and Roach (2025) that allows for better fracturing in the sea ice across a wider range of wavelengths. We have also implemented enhanced numerics for sea ice covered regions in WW3 following ideas from C. Bitz. Here we will show results from simulations comparing the new fracturing scheme versus the Horvat and Tziperman (2015) scheme. We find that the floe sizes are generally larger overall and more evenly distributed across the floe size distribution. However, there are remaining challenges with the interplay between fracturing and welding. The new wave fracturing and floe size distribution will be included in CESM3 and used in coupled earth system simulations.

Ocean surface waves play a crucial role in Earth system models, influencing momentum transfer, ice breakup, CO2 fluxes, and mixed-layer dynamics. Unlike third-generation spectral models, wave information needed for mixing, air-sea, and wave-ice coupling is minimal, relying mainly on dominant frequency, direction, and energy. Given that modest errors in sea state have limited impact, the high computational cost of spectral models is a concern for next-generation Earth System Models (ESMs). We here describe an alternative, cost-efficient wave modeling framework for air-sea interaction to enable the routine use of sea state-dependent air-sea flux parameterization in ESMs. In contrast to spectral models, the Particle-in-Cell for Efficient Swell Wave Model (PiCLES) is constructed for coupled atmosphere-ocean-sea ice modeling. Combining Lagrangian wave growth solutions with the Particle-In-Cell method leads to a periodically meshing model on an arbitrary grid that scales in an embarrassingly parallel manner. The set of equations solves for the growth and propagation of a parametric wave spectrum's peak wavenumber and total wave energy, which reduces the state vector size by a factor of 50-200 compared to spectral models. We estimate PiCLES's computational costs about one order of magnitude faster then established wave models with sufficient accuracy for ESMs -- rivaling that of spectral models in the open ocean. We will evaluate PiCLES against WaveWatch III in efficiency and accuracy and discuss the planned coupling of this Julia-based model into the CESM/NUOPC framework.

The rapid decline of summer sea ice cover in the Western Arctic has been accompanied by a dramatic increase in the sea state of the region. Ocean waves are now more common throughout the region, including multiple energetic swell events each summer. These waves interact with the sea ice and help to both form and define the expanding Marginal Ice Zone (MIZ) of the Western Arctic. The attenuation of waves into the MIZ is well-documented, but the resulting transfers of energy and momentum are less well-constrained. This talk reviews recent observations of energy and momentum transfers in the wave-ice-ocean system, including implications for sea ice retreat and coastal morphology.

Observations of waves-in-sea ice support advances in coupled modeling both by improving process understanding of attenuation mechanisms, as well as providing datasets for model comparison and validation. Both benefit from high-fidelity contextual information of sea ice conditions, while process understanding especially requires high-resolution spatial and temporal coverage to identify mechanisms and feedbacks. Conventional methods for measuring waves typically have trade-offs in these aspects. Distributed acoustic sensing (DAS) provides a novel opportunity to turn coastal seafloor telecommunication and other fiber optic cables into high-resolution surface wave measurements. Laser reflections off impurities in the fiber provide measurement of strain or strain-rate, which is responsive to variations in seafloor pressure (as well as acoustic and other waveforms in the water column). This allows each channel to act like a seafloor pressure mooring such that a fiber tens of kilometers in length with channel spacing of meters acts like a series of thousands of virtual wave buoys. Thus, it provides a particularly appealing method for observing spatial and temporal changes in seasonally ice-covered coastal environments with high spatial gradients. Results from interrogation of a telecommunication cable in the Alaskan Arctic have been used to obtain measurements of wave attenuation rates in new, partial sea ice cover. The rapid evolution of the location and strength of attenuation serves as proxy for the evolution of ice coverage and thickness, especially during rapidly evolving events. Such measurements provide notably higher spatial resolution of wave statistics than achievable by other in situ methods, with less logistical effort, providing new opportunities for process understanding and model development.

As sea ice extent decreases in the Arctic, surface ocean waves have more time and space to develop and grow, exposing the Marginal Ice Zone (MIZ) to more frequent and energetic wave events. Waves can fragment the ice cover over tens of kilometres, with the potential to strongly affect sea ice dynamics in the MIZ. To assess this impact—which remains largely unknown—we have developed a coupled wave-ice model framework, combining the spectral wave model WAVEWATCH III with the sea ice model neXtSIM. This model allows us to represent the effects of wave-induced fragmentation on sea ice mobility. We find this effect to be significant when waves propagate far enough to break thick and compact ice, which occurs regularly in the Barents and Greenland Seas. Our results indicate that wave impact on sea ice primarily depends on the distance over which waves can break the ice—that is, the MIZ extent—which remains poorly constrained due to limited observations. However, this constraint may soon be alleviated thanks to new MIZ retrieval products derived from satellite altimeters likes ICESat-2, along with the increasing deployment of affordable wave buoys in the Arctic Ocean. Leveraging these observations, we assess our model’s ability to capture the evolution of the MIZ extent. The model performs reasonably well, enabling us to investigate MIZ variability and trends related to wave activity over the past three decades. We find that the evolution of the wave-affected MIZ contrasts with the MIZ extent derived from sea ice concentration thresholds, showing a clear increasing trend in most seasons—seemingly driven by increased fetch.

Gaps (or leads) between sea ice cover create unique systems where air-sea interaction and associated mixing occurs within a sub-region of open ocean, surrounded by more quiescent ice-bound ocean. We use numerical simulations to explore how the propagation of surface waves along leads can change ocean dynamics within and around summertime leads, where the surrounding sea ice is melting. Waves significantly alter the upper-ocean turbulence regime through the development of Langmuir turbulence, and they modify the intensity and symmetry of the cross-lead circulation, with implications for ice-evolution near the lead edge. We will discuss the effects of changing system parameters and propose scalings for the wave-affected turbulence and circulation.

Ocean surface waves strongly modulate vertical turbulent mixing in the ocean surface boundary layer. When they are aligned with wind-driven shear, Craik-Leibovich instability occurs, generating Langmuir turbulence that strongly enhances vertical mixing. By the same mechanism, they can also stabilize the water column and suppress boundary layer turbulence when they are in opposite direction as the Eulerian current. In this talk, I will demonstrate this stabilizing wave-induced stratification in large eddy simulations under idealized conditions and discuss its effect on vertical mixing. In particular, I will show that a combination of destabilizing surface cooling and stabilizing wave-induced stratification leads to rolls of convective cells aligned perpendicular to Stokes drift. The turbulence intensity in this case is significantly reduced as compared to the case of pure convection. Such stabilizing effect of wave-induced stratification can also be seen under other more realistic conditions, but is missing in existing wave-driven mixing parameterizations. Ideas to incorporate this effect into an ocean vertical mixing parameterization will be discussed.

This talk will cover three relevant aspects of marginal ice dynamics. First, I’ll report on recent field campaigns held in the Saguenay fjord and the St. Lawrence Estuary, Canada, to measure sea ice mechanical properties using non-destructive seismic wave analysis, and in one instance prior to the full characterization of a wave-induced fracture event generated by an icebreaker. I’ll then report on mostly qualitative observations of frazil ice behaviour in the presence of waves and discuss its representation in models. I’ll finally present the design of an empirical floe size-dependent rheology and preliminary results of sea ice thickening and deformation using an idealized CICE configuration.