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How does melting sea ice affect the salinity of surrounding seawater?

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Diagram illustrating Earth's environmental spheres, with labeled sections showing the geosphere (land and crust), biosphere (living things), atmosphere (air), and hydrosphere (water), each extending vertically from the Earth's surface. — hydrosphere Earth's environment includes the atmosphere, the hydrosphere, the lithosphere, and the biosphere.

When sea ice melts during warmer months, it releases fresh water into the surrounding ocean, which decreases the salinity of the surface water.12

Because this meltwater is less dense than the surrounding saline ocean water, it creates a layer of fresher water at the surface, which stabilizes the water column and inhibits vertical mixing. This process is the inverse of what occurs during the winter; when sea ice forms, it largely excludes salt, which increases the salinity of the water beneath the ice and encourages convective overturn.12

While sea ice has a neutral effect on overall ocean salinity over the course of a full annual cycle—as it returns to liquid during the summer—the seasonal melting of sea ice is a critical factor in regulating the density and stratification of surface waters.1