Final answer:
Iceberg calving contributes the least to sea-level rise because of the displacement principle; melting icebergs, already afloat, do not change the water level when they melt. Other processes like melting ice caps, glaciers, and thermal expansion add volume to the oceans and cause more significant rises.
Step-by-step explanation:
The process that would likely contribute the least to sea-level rise among the options provided is iceberg calving. Iceberg calving is the breaking off of chunks of ice from glaciers, which then float in the ocean. However, since icebergs are already in the ocean, their melting has a minimal impact on sea level rise, thanks to the principle of displacement. The other processes listed - melting of polar ice caps, thermal expansion of seawater, and glacier retreat - all contribute more significantly to sea level rise. Melting of polar ice caps and glaciers add previously trapped freshwater into the oceans, increasing the total water volume. Thermal expansion results from increases in water temperature, which causes seawater to expand and occupy more space.