On a Southern California beach, an olive ridley sea turtle — a creature of tropical waters far to the south — laid eggs for the first time in recorded history, crossing a threshold that scientists say the warming Pacific made possible. The event transforms an abstract climate statistic into something you can walk up to and name: a nest, a species, a shore that was once too cold. It is a quiet but unmistakable signal that the ocean's boundaries are moving, and the life within it is moving too.