Why Cold War navies carried nuclear depth charges

Why might a naval task force have carried nuclear depth charges?

They offered a very large lethal area when a submarine's position was uncertain, although the account does not establish which weapons continued south from Ascension.

Reports that the Falklands task force carried nuclear depth charges lead into a discussion of what may have been removed at Ascension before the ships sailed farther south. It remains uncertain whether every weapon was offloaded. A nuclear depth charge could attack a submarine believed to be nearby even when its exact position was unknown. Its enormous lethal radius reflects Cold War anti-submarine warfare and escalation planning, and the account makes no claim that one was used.