The most likely occurrence in the hydrosphere if the ice caps melted would be:
B. a change in the salinity of the oceans in the hydrosphere.
Melting ice caps would contribute freshwater to the oceans, which can alter the salinity levels. Additionally, while option D might also be true (as more water would exist in liquid form rather than as ice), the most direct and significant impact immediate from the melting ice caps pertains to changes in ocean salinity.