In-situ measurements of the evolution of young sea ice

We present data from in situ measurements of the salinity evolution of young sea ice in the Arctic. The measurements were carried out with very high vertical and temporal resolution over the course of a few days until the ice had reached a thickness of around 20 cm. The measured bulk salinity profiles show that during ice growth, sea-ice salinity is continuous across the ice-ocean interface and that there is no instantaneous loss of salt at the advancing front. Measured salt fluxes emanating from the ice are as high as 90 g m(-2) h(-1) during the first few hours of new ice formation and are roughly half as large during later stages of the experiments. The bulk salinity within the ice decreases continuously with time from the ocean water salinity to a near - steady state value of around 4 parts per thousand (ppt). These results are interpreted with ideas from mushy layer theory using a Rayleigh number to analyze gravity drainage as the driving mechanism for the observed salt loss. In our experiments, gravity drainage occurs for a critical Rayleigh number of around 10, in close agreement with earlier theoretical and experimental studies. [References: 25