Race to the South Pole (Ranger in Time Series #4)

Ranger, the time-traveling golden retriever with search-and-rescue training, joins an early twentieth-century expedition journeying from New Zealand to Antarctica. He befriends Jack Nin, the stowaway turned cabin boy of Captain Robert Falcon Scott's ship. They're racing against a rival explorer to reach the South Pole, but with unstable ice, killer whales, and raging blizzards, the journey turns into a race against time... and a struggle to stay alive.