So, 1300 years ago there was no glacier there. Sounds like we’ve been in a global cooling period, and the glaciers have now begun to retreat.
Some retreat, some advance. Thankfully, so far we have not started the nest ice age. I always get a kick out of scientific reports about Antarctica having a tropical climate at one time. Water covered Florida in the past, the Mediterranean Sea was probably farmland, and the Sahara had a sea.
Climate always changes, with the cycle of the Sun.
Actually it did. It had a tropical climate due to the fact it was far north at one time in a tropical region. Our continents move around over time geologic time. At one time South America and Africa were one continent as was North America and Europe. India was once attached to the East Coast of Africa and sailed North until it hit Asia.