North Pole Ice Melt

Environmental disasters have always been popular with filmmakers. In recent years, the trend has been toward disasters on a global scale because the public has become more aware of global environmental problems. If there is a global warming trend, there could be much ice melting at the poles of Earth. Some films have portrayed seacoasts being inundated by the rising water level. What would you predict for the sea level change if the ice only at the North Pole melted completely?

Answer

There would be no change in the sea level if all the ice at the North Pole melted. Why? Because this ice is floating on water. Upon melting, the water molecules in the ice simply occupy the space of the liquid displaced by the ice originally. Of course, we need to be more careful on defining the extent of the North Pole. If we include ice on some landmass, then this ice will add extra water molecules to the liquid seas and slightly raise the sea level. In contrast, most of the ice at the South Pole is several kilometers thick and is predominantly on the Antarctica landmass, so its melting could significantly raise the sea level. Some films depict oceans that have risen hundreds of meters from the worldwide ice melt. Simple estimates easily reveal that this conjectured amount of sea level change is ridiculous.

Another concern might be the linear expansion of water when its temperature is above 4°C of about 70 × 10^–6/°C. Even if the water temperature rose by 10°C throughout the first 10 kilometers of ocean depth, the expected water level rise for a column of water would be no more than 7 meters if the surface area remained constant. But the surface area will expand, so the actual water level will rise about 2 meters of so. For a 1°C increase in temperature, the ocean level rise will be several centimeters.

Sea level changes played major roles in the migrations of our human ancestors. Some Bushmen left their homeland and their cave dwellings about 40,000 years ago, seeking better climates and less arid lands. A mini ice age had developed, so seawater became locked into the ice at the poles. Their caves, which were originally near the sea, were now several hundred kilometers inland from the sea, and the arid climate made living off the land very difficult. So they migrated along the eastern coast of Africa all the way through the Middle East and India to Australia. The Aborigines in Australia are descended directly from these peoples from Namibia and South Africa and together with the Bushmen are the oldest civilizations on Earth.