A synthesis of thermodynamic ablation at ice–ocean interfaces from theory, observations and models. (October 2020)

• Record Type: Journal Article
• Authors: Malyarenko, Alena; Wells, Andrew J.; Langhorne, Patricia J.; Robinson, Natalie J.; Williams, Michael J.M.; Nicholls, Keith W.
• Is Part Of: Ocean modelling. Volume 154(2020)
• Publication Date: 2020-10
• Subjects: Ablation -- Ice melting -- Cryosphere -- Heat transfer -- Ice shelf cavity observations -- Ice–ocean​ modelling; Oceanography -- Periodicals; Océanographie -- Périodiques; Oceanography; Periodicals; 551.46
• DOI: 10.1016/j.ocemod.2020.101692
• Languages: English
• ISSNs: 1463-5003

Abstract

Abstract: Thermodynamic ablation of ice in contact with the ocean is an essential element of ice sheet and ocean interactions but is challenging to model and quantify. Building on earlier observations of sea ice ablation, a variety of recent theoretical, experimental and observational studies have considered ice ablation in contrasting geometries, from vertical to near-horizontal ice faces, and reveal different scaling behaviour for predicted ablation rates in different dynamical regimes. However, uncertainties remain about when the contrasting results should be applied, as existing model parameterisations do not capture all relevant regimes of ice–ocean ablation. To progress towards improved models of ice–ocean​ interaction, we synthesise current understanding into a classification of ablation types. We examine the effect of the classification on the parameterisation of turbulent fluxes from the ocean towards the ice, and identify the dominant processes next to ice interfaces of different orientation. Four ablation types are defined: melting and dissolving based on ocean temperatures, and shear-controlled and buoyancy-controlled regimes based on the dynamics of the near-ice molecular sublayer. We describe existing observational and modelling studies of sea ice, ice shelves, and glacier termini, as well as laboratory studies, to show how they fit into this classification. Two sets of observations from the Ross and Ronne Ice Shelf cavities suggest that both the buoyancy-controlled and shear-controlled regimes may be relevant under different oceanographic conditions. Overall, buoyancy-controlled dynamics are more likely when the molecular sublayer has lower Reynolds number, and shear for higher Reynolds number, although the observations suggest some variability about this trend. Highlights: Four ablation types are presented based on the ice–ocean boundary layer structure. Ice ablation parameterisations are dependent on the ablation types. Existing observations, modelling and laboratory studies of ablation are classified. Two distinct turbulent flux regimes are identified in ice shelf cavity observations.