Representing Salinity and Isotopic Properties of Estuarine Sea Ice Using a Modified One-Dimensional Thermodynamic Model

As sea ice forms, it incorporates the salts and isotopic signature (δ18O, δ2H) from the underlying seawater. Coastal marine regions can be heavily influenced by river discharge, resulting in sea ice growing from seawater with spatially varying salinity and stable isotopic composition. Because current halo-thermodynamic models primarily address sea ice growth from seawater with salinities near 34 and have yet to integrate the isotopic composition, their application to reproduce sea ice forming in a heavily river-influenced marine region is limited. In this study, we extended the one-dimensional Semi-Adaptive Multi-phase Sea Ice Model (SAMSIM) to account for estuarine conditions and to compute δ18O and δ2H profiles of sea ice. Modelled bulk salinity and isotopic profiles agreed well with four ice core observations of sea ice formed in an estuarine environment. Sensitivity tests demonstrated that modelled bulk salinity and isotopic profiles vary based on the input seawater salinity and provide a means for the estimation of meteoric water content in sea ice. Model runs with fixed boundary conditions indicate that fresher seawaters lead to thinner and less porous sea ice bottom regions and a quicker transition to the quasi-steady state of the bulk salinity, and thus the stable isotopic composition, compared to higher seawater salinities. These findings improve our ability to trace source-water properties during sea ice growth and estimate the layer thickness of biologically habitable porosity within sea ice formed from brackish (freshened) waters.HighlightsA 1-D sea ice model was modified to address meteoric water influence on sea ice.Modified 1-D sea ice model predicts bulk salinity and stable isotopic composition.Experimental validation confirms the performance of the modified 1-D model.Findings improve predictions of sea ice meteoric water content and habitable porosity.