Melting truths

A recent letter writer attempted to use the cold water of melting icebergs to douse the reality of rising sea levels from global warming (“Fallacy of a hoax,” Nov. 27).

It was the equivalent of faking and doing an end run around the facts.

As the writer said, an ocean-based iceberg displaces an amount of ocean water equal to its weight. So when the ice melts and returns its water to the ocean, the total volume of water remains the same and does not raise sea levels. (Note: The volume of water does increase slightly because the ice shed the salt as it formed, and fresh water is less dense than salt water and so takes up a bit more volume).

But the point is melting icebergs in the ocean are not the key issue in the rise of sea levels. It is land-based melting ice that poses the threat.

Land-based ice includes mountain glaciers and ice sheets in Greenland and Antarctica. As temperatures rise, this ice melts and the waters flow into the oceans. This substantially raises sea levels.

It’s important to note ocean-based ice can materially contribute to global warming in a different way. The white ice reflects the sun’s rays. When the ice melts, the darker open ocean absorbs sunlight and heats up. This raises global temperatures and causes land-based ice to melt even faster.

Let’s assess a 15-yard penalty for delay of game and move on.

Richard Harkness

Ocean Springs