There were several articles that popped up on global warming discussing its causes and catastrophic effects. One catastrophic effect that is seemingly counter-intuitive and overlooked is the change in the gravitational field of Earth following the glacier melting. This article focuses on how the variation in earth’s gravitational field is caused as a result of melting glaciers at poles, its origins and the effect it has on the rate at which sea level rises.
Solids of a particular chemical species is formed when the liquid molecules are crammed towards each other in such a way that the only form of motion these molecules have is vibrational i.e. the molecules vibrate around a mean point, as learnt during our H2 Physics tuition classes. Since the molecules are crammed together a given mass of a chemical species occupies less volume when it exits in solid form compared with that of the liquid form. Consequently a given mass of solid when melts occupies larger volume. This rise in the volume is the frightening part when put in the context of global warming. When a glacier melts the volume occupied by the resultant liquid water is high and hence it effects the rise in sea levels. This is the simplest link between rise in sea levels and global warming.
Now let’s discuss the often overlooked side of it, gravity. Since a glacier has large amounts of water molecules packed at one place it can exert gravitational pull. In fact this gravitational pull of glaciers hold the liquid water from reaching the equator. A glacier melting is associated with a loss of this gravitational pull. Hence the liquid water which was once held by the gravitational pull of the glacier is now free to reach the equator. To understand why this is alarming, let’s discuss an example. Imagine you are given the job of filling a tank. You turn the tap on and leave then suddenly you found a hose pipe which is another source of water. To expedite the process you redirect water from hose pipe also to the tank. There are two sources of water filling the tank now and hence the process takes less time.
Coming back to our example, initial source of liquid water reaching equator and causing sea level rise is the water that is formed following the melting of glacier. But there is also other source of water reaching the equator that is the liquid water freed from the gravitational pull of glaciers (due to their melting). Since there are two different sources of water trying to submerge, the rate of sea level rise is higher compared to that of the predictions made ignoring the gravitational variations due to glacier melting.