Final answer:
The angular speed of the Earth slightly decreases when a large mass of ice drifts toward the equator, as the moment of inertia increases because the mass moves farther from the rotational axis, conserving angular momentum.
Step-by-step explanation:
When a large mass of ice breaks off from Greenland and drifts toward the equator, according to the conservation of angular momentum, the angular speed of the Earth changes. This is because Earth's moment of inertia changes as the mass redistribution occurs. The conservation of angular momentum tells us that as the moment of inertia of an isolated system increases, the angular velocity decreases to conserve the total angular momentum, given that no external torques are applied.
In this case, when the mass of ice moves towards the equator, it is effectively moving away from the Earth's rotational axis, thus increasing the Earth's moment of inertia. Therefore, to conserve angular momentum, the Earth's angular velocity would very slightly decrease. However, this effect is minuscule and not noticeable in our day-to-day experiences due to the massive scale of the Earth compared to the ice.