The reason that the Polar Regions were warmer is the ocean currents (21). 65 million years ago the ocean currents were able to directly come from the tropics to the poles. The warm water from the tropics helped keep Antarctica and the North Pole warm and prevented permanent ice from developing. There is evidence that the Arctic region was warm enough for at least temperate forms of sea life (22) to live there. It was probably comparable to what the Mediterranean is like today.
