The Charlemagne Pursuit - by Steve Berry

As a child, former Justice Department agent Cotton Malone was told his father died in a submarine disaster in the North Atlantic, but now he wants the full story and asks his ex-boss, Stephanie Nelle, to secure the military files. What he learns stuns him: His father's sub was a secret nuclear vessel lost on a highly classified mission beneath the ice shelves of Antarctica.

But Malone isn't the only one after the truth.