Multiphase Reactive Transport and Platelet Ice Accretion in the Sea Ice of McMurdo Sound, Antarctica

Abstract

Sea ice seasonally to interannually forms a thermal, chemical, and physical boundary between the atmosphere and hydrosphere over tens of millions of square kilometers of ocean. Its presence affects both local and global climate and ocean dynamics, ice shelf processes, and biological communities. Accurate incorporation of sea ice growth and decay, and its associated thermal and physiochemical processes, is underrepresented in large‐scale models due to the complex physics that dictate oceanic ice formation and evolution. Two phenomena complicate sea ice simulation, particularly in the Antarctic: the multiphase physics of reactive transport brought about by the inhomogeneous solidification of seawater, and the buoyancy driven accretion of platelet ice formed by supercooled ice shelf water onto the basal surface of the overlying ice. Here a one‐dimensional finite difference model capable of simulating both processes is developed and tested against ice core data. Temperature, salinity, liquid fraction, fluid velocity, total salt content, and ice structure are computed during model runs. The model results agree well with empirical observations and simulations highlight the effect platelet ice accretion has on overall ice thickness and characteristics. Results from sensitivity studies emphasize the need to further constrain sea ice microstructure and the associated physics, particularly permeability‐porosity relationships, if a complete model of sea ice evolution is to be obtained. Additionally, implications for terrestrial ice shelves and icy moons in the solar system are discussed.

Entrainment and Dynamics of Ocean‐Derived Impurities Within Europa's Ice Shell

“…For simplicity, we assume that ϕ ξ ð Þ ¼ H ξ ð Þ, where H ξ ð Þ is the Heaviside step function. While this is indeed a simplification, as it represents the mushy layer as an infinitesimally thin regime, the general liquid fraction profile of evolving sea ice demonstrates similar structure (See Figures 5-7 of Buffo et al, 2018). Substituting ϕ ξ ð Þ ¼ H ξ ð Þ into Equation 19 results in a simplified conservation of mass equation in the moving coordinate system:…”

“…With the proximity of the 100 K surface, Europa's shallow ice shell (<1 km) and any shallow liquid water bodies emplaced at such depths within the shell will experience similarly high thermal gradients (e.g., Chivers et al, 2019Chivers et al, , 2020Michaut & Manga, 2014), suggesting high impurity uptake exceeding even that of sea ice. We have previously modeled the growth of sea ice to study its thermochemical evolution and ability to record variations in ocean characteristics through the reproduction of ice core properties (Buffo et al, 2018). This model was adapted to actively track the advancing ice-ocean interface and accommodate potentially diverse ocean chemistries.…”

Response of sub-ice platelet layer thickening rate to variations in Ice Shelf Water supercooling in McMurdo Sound, Antarctica

“…Further process studies, including the influence of vertical structure of current within the ice shelf (or sea ice) -ocean boundary layer (Jenkins 2016) could also contribute. Finally, the performance of the VM 15 model in providing reliable estimates of supercooling and frazil ice flux at the SIPL base makes it an attractive tool for coupling with sea ice models focused on microscale processes within the bottom layer of the ice (Buffo et al, 2018).…”

Responses of sub-ice platelet layer thickening rate and frazil-ice concentration to variations in ice-shelf water supercooling in McMurdo Sound, Antarctica

“…The vertical distribution of frazil concentration, in reality, much like the concentration of suspended sediment (Cheng et al, 2013(Cheng et al, , 2016, should be vertically non-uniform, with higher concentrations near the ice-shelf/sea-ice base. Considering only the balance between the buoyant-rise-induced vertical advection and turbulent diffusion terms, the governing equation for frazil concentration can be written as…”

“…where w i is the frazil-ice rise velocity, determined by ice crystal size. K is the vertical frazil concentration diffusion coefficient, which can be parameterized as vertically constant (Cheng et al, 2013(Cheng et al, , 2016:…”