Dear Tom,
When glaciers and icecaps melt, the resulting water eventually makes its way to the world’s oceans. How much would the oceans rise if all the land ice were melted?

Ron Stein, Chicago

Dear Ron,
The level of the world’s oceans is rising and it is due to the meltwater released from glaciers and icepacks, as you have stated. Ocean levels have risen nearly eight inches in the last 100 years,  and the rise continues to this day.

Icecaps in the world’s oceans do not contribute to a rising sea, but land ice (ice in glaciers and icecaps) does. Practically all the world’s land ice is contained in two places: Greenland and Antarctica. (Ice contained in glaciers is relatively insignificant; similarly for water contained in snow. Their water would add little to the level of the world’s oceans.) 
The icecap covering Greenland, if it totally melted, would release enough water to raise ocean levels by about 20 feet. The Antarctic icecap is much larger, and if totally melted would cause the oceans of the world to rise 200 feet.