Complex sentence: While freezing, water rejects its salt content (leaving pure ice) and the remaining surface, made dense by the extra salinity sinks, leading to the productions of dense water masses, such as Antarctic Bottom Water.
Split into simpler sentences: While freezing, water rejects its salt content (leaving pure ice). The remaining surface water, made dense by the extra salinity, sinks, leading to the productions of dense water masses such as Antarctic Bottom Water.