A reader writes:
"Meanwhile, billions of gallons of freshwater disappears uselessly into the ocean, the result of icebergs that break off from the ice caps of Greenland and melt into the salty mix," wrote David Zax. Are you sure that they melt uselessly? Do you consider the deep ocean currents, including the Gulfstream, to be useless? The sinking of the heavier cold fresh water into the warmer lighter salt water off Greenland is a major engine of these deep ocean currents that circle the globe, moving vast amounts of heat and delivering nutrients that many major fisheries rely on.
Update: Another says "the reader's reasoning is a little off":
The driving force behind sinking of water masses near the poles is the increase in density of cold salt water due to removal of fresh water by evaporation and the formation of sea ice. Melting of icebergs might decrease the water temperature slightly due to thermodynamic considerations, but it's really all about the salt.
The Dish 