Actually, it will increase, these are ANTARCTIC Glaciers, which means they are on LAND. They are not currently displacing the oceans.
Having said that, I dont know why anybody expected the earth to remain constant, it is always undergoing change..
If the Antartic Glaciers are thinning, it is due to evaporation. Just as water is evaporating from the oceans, at the same rate. Water always finds it's level, so where it is lacking, it will fill up, the sahara dessert will finally become a rain forrest.
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Actually, it will increase, these are ANTARCTIC Glaciers, which means they are on LAND. They are not currently displacing the oceans.
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Except that their weight does cause the landmass to sink. I have never seen any studies on how much the continent of Antarctica will rise when relieved of trillions and trillions of tons of ice.
Of course, the weather patterns that are causing the glaciers to flow at an increased rate may also wind up causing the snowfall over Antarctica to increase significantly as well.