Books in LITTLE POLAR BEAR series

Lars, the little polar bear, loves playing in the snow but this year it has been especially warm and there are only a few hills left which are covered in snow. One day Lars discovers a submarine in the bay and a funny little Dachshund. The Dachshund explains that he and his master sail the world checking how much of the ice has melted away. The Dachshund says that two polar cubs are also aboard the submarine, bound for a zoo! Brave Lars decides sneak on board, rescue them and bring them back to their parents.