Calculate the decrease in salinity of a 50 m deep mixed layer across the entire Arctic Ocean (14x106km2) expected during the summer as a result of melting of sea ice. Assume the Arctic ocean is fully covered in sea ice in spring at the beginning of summer and 50% covered at the end of summer, that the sea ice is 2 m thick on average, and the salinity of surface ocean in spring is 33 which is approximately equal to 33 g salt per liter of seawater. Assume that the change in volume due to melting ice is not important.