Why do icebergs usually move differently from nearby sea ice?

Icebergs typically move differently from sea ice because they possess a much larger mass per unit of sea-surface area, which makes them more strongly influenced by the Coriolis force.1

While sea ice is primarily driven by surface winds, an iceberg's trajectory is determined by a complex interaction of forces, including:

• Drag: Icebergs are affected by skin friction and form drag from the wind on their exposed surfaces, as well as the drag of ocean currents acting upon their deep, submerged portions.1
• Current Variations: Because of their significant draft, icebergs are subject to currents that change direction with depth, an effect known as the Ekman spiral.1
• Coriolis Force: This force diverts icebergs toward the right of their path in the Northern Hemisphere and toward the left in the Southern Hemisphere. Consequently, an iceberg's direction of motion relative to the surface wind is typically offset by some 40°–50°.1

Because of these factors, it is unusual for icebergs to follow the same path as surrounding sea ice.1