Thermohaline Preconditioning for Sea Ice Formation in the Beaufort Sea

The influence of ocean stratification and heat content on the timing of sea ice formation and its subsequent growth remains an open question. Here we investigate the thermohaline conditions prior to fall sea ice formation as well as the roles of stratification and heat content on sea ice growth rates through the analysis of in situ observations and numerical simulations from a one-dimensional ocean-ice-column model. We find that the simulated time series of sea ice concentration are highly correlated with observations. We identify two clusters of sea ice concentration growth rate, which we name Early Slow and Late-Fast. We find that cold, shallow mixed layers promote early sea ice freeze-up. Salinity stratification within the upper pycnocline slows the release of heat into the deepening mixed layer, leading to slower ice growth. However, where salinity stratification above the upper pycnocline is absent, sea ice growth occurs later and, once started, progresses faster.