When land ice on Antarctica melts and flows into the sea, eventually it circulates and therefore distributes uniformly over the earth's oceans. As a result, does the earth's rotational speed increase, decrease or remain unaffected? (If it does have an effect, how does it change the length of one day?)
When land ice on Antarctica melts and flows into the sea, it does have an effect on the Earth's rotational speed, but the impact is extremely small. To understand how this works, let's break it down step by step.
1. Melting Land Ice: When land ice on Antarctica melts, it eventually flows into the sea due to gravity.
2. Redistribution of Mass: As the melted ice enters the oceans, it distributes itself uniformly throughout the Earth's oceans. This redistribution of mass causes a slight change in the Earth's moment of inertia.
3. Conservation of Angular Momentum: The Earth's rotation is governed by the principle of conservation of angular momentum. This means that the total angular momentum of the Earth remains constant unless acted upon by external forces.
4. Impact on Rotational Speed: Due to the conservation of angular momentum, when the mass distribution on Earth changes, it causes a slight change in the Earth's rotational speed.
5. Effect on Earth's Rotation: The melted ice from Antarctica, although significant in mass, is spread out over a vast area of the oceans. This dispersal of mass results in an incredibly small change in the Earth's rotational speed.
6. Length of a Day: The change in rotational speed affects the length of a day, albeit minutely. The distribution of melted ice from Antarctica can either speed up or slow down the Earth's rotation by a fraction of milliseconds.
To quantify this, it is estimated that the melting of the entire Antarctic ice sheet and its entry into the oceans would result in an increase in the length of a day by a few microseconds over many centuries. This change is incredibly small and practically indistinguishable.
In conclusion, the melting and redistribution of land ice from Antarctica do have a minimal effect on Earth's rotational speed, resulting in virtually negligible changes in the length of a day.