How does melting iceberg ice affect the salinity of the Southern Ocean?

Melting icebergs exert a stabilizing influence on the salinity of the Southern Ocean by acting as a source of fresh water.1

As icebergs melt, they release fresh water into the ocean, which contributes to maintaining the pycnocline—the density boundary that separates lower-salinity surface water from higher-salinity deeper water. This process helps keep the surface salinity of the Southern Ocean at its observed low value of 34 parts per thousand (ppt) or below.1

While the total annual Antarctic melt is equivalent to adding approximately 0.1 metre of fresh water per year at the surface, the resulting dilution is relatively small, amounting to a decrease of only 0.015–0.03 ppt of salt when averaged over the upper 100–200 metres of the water column. Unlike sea ice, which has a neutral effect on overall salinity because it returns to liquid during summer, icebergs provide a consistent, stabilizing input of fresh water as they drift and melt at lower latitudes.1