The work contained within this thesis is a field and laboratory study of snowpack and sea-ice optical and physical properties, and a computation modelling study of photochemical reaction rates within snowpack. The contribution of snow photochemistry to snow and atmospheric oxidative capacity is controlled in part by snow albedo and e-folding depths in snow. Albedo and e-folding depths (and thus snow photochemistry) are a function of black carbon mass ratio in snow. The work contained within this thesis demonstrates the complicated response of albedo, e-folding depth (wavelengths 300-600 run) and depth-integrated production rates of N02 and OH radicals to increasing black carbon mass ratio in well-characterised snowpacks of the Barrow OASIS campaign, Alaska. All snowpacks were reworked layered windpacks and were found to have similar responses to changes in black carbon mass ratio. The radiative-transfer calculations demonstrate two light absorption regimes: ice-dominated and black carbon dominated. The ice-dominated and black carbon dominated behaviour of albedo, e-folding depth and depth-integrated production rates with increasing black carbon mass ratios are presented. For black carbon mass ratios greater than 20 ng g-I (wavelength range of 300---600 nm), e-folding depth and depth integrated production rate have an inverse power law relationship with black carbon mass ratio. Doubling the black carbon mass ratio decreases the e-folding depth to -70% of the initial value and for solar zenith angles greater than 60°, doubling the black carbon mass ratio decreases depth-integrated production rates of N02 and OH to - 70% and - 65% of their original values respectively.

La banquise, qui couvre de larges étendues de l’océan près des pôles, est une composante majeure du climat. Le réchauffement de la planète entraîne sa fonte massive, en particulier en Arctique.Là où l’extension de la banquise diminue, l’augmentation du fetch est associée à une élévation de la hauteur des vagues, laissant penser que les effets liés aux interactions vagues-glace pourraient s’accroître dans le futur. L’évolution rapide de la banquise associée à l’intensification des activités humaines dans les régions polaires pressent à améliorer notre connaissance de ces interactions.La banquise atténue les vagues. Elles peuvent néanmoins s’y propager et briser la glace sur de longues distances. L’atténuation dépend des propriétés de la glace comme l’épaisseur, la taille des plaques... Les plaques de glace une fois cassées sont plus susceptibles de dériver et de fondre. En outre, lors de l’atténuation, les plaques sont poussées dans la direction de propagation des vagues.Une représentation simple de la banquise dans un modèle de vagues intégrant une distribution de la taille des plaques nous a permis de montrer l’importance des mécanismes dissipatifs dans l’atténuation, notamment ceux induits par la flexion de la glace.Après avoir été validé, ce modèle a été couplé à un modèle de glace. La taille des plaques est échangée et utilisée dans le calcul de la fonte latérale. La force exercée par les vagues sur la banquise est également envoyée depuis le modèle de vagues. En été, cette force compacte la glace et tend à diminuer la fonte, augmentant significativement la température et la salinité des eaux de surface au bord de la banquise. / Sea ice, which covers most of the ocean near the poles, is a key component of the climate system. Global warming is driving its massive melting, especially in the Arctic. Where sea ice cover decreases, fetch increases leading to more energetic sea states. This means potentially enhanced wavesice interactions effects in the future. The quick evolution of sea ice extent and volume combined with the intensification of human activities in polar regions urge us to improve our understanding of waves-ice interactions.Sea ice attenuates waves. They can however propagate through it and break it far into the ice cover. Attenuation depends on ice properties such as floe size, thickness, etc. Once broken, resulting floes are more likely to drift and melt. In addition, wave attenuation yields a force which pushes the floes in the direction of wave propagation.A simplified representation of sea ice, including a floe size distribution, has been incorporated in a wave model.It allows us to show the important contribution of dissipative mechanisms in the wave attenuation, especially those induced by the bending of the ice plates. After validation, the modified wave model is coupled to an ice model. The floe size distribution is exchanged in the coupled framework and used in ice lateral melt computation. The force exerted by the waves on the ice floes is sent from the wave model and is shown to compact sea ice in summer. This reduces the melting and significantly increases the temperature and salinity in the surface ocean close to the ice edge.