Alaska's glaciers are favoured by the CAGW hype industry, in particular the Juneau ice field which contains 32 of them. A claim was made recently that the melting of these glaciers would add a catastrophic amount of water to the oceans – and we were in danger of drowning (or something like that). However, not all of them have been melting – one at least is actually growing, the Taku glacier. However, the Mendenhall glacier has shrunk and trees have been revealed that have been frozen under ice for some 2000 years (roughly). This suggests the Roman Warm Period was not just warm in Europe but warm eslewhere, warm enough for a forest of trees to grow in what is now an ice field. See www.frontierscientists.com/2013/09/forest-revealed-under-glacial-ice/
Basically, glaciers are rivers of ice and generally come into being when the weather is cold and snowfall at high altitudes compacts into ice. Glaciers are ruled by gravity and due to their own weight advance downslope. This is why the body of Otzi, in the Alps, frozen in around 3000BC, migrated down slope and when the river of ice within which he was buried began to melt, he was revealed to a walker in the Alpine valleys. The fact he did not melt during the Roman Warm Period only means he was trapped in the river of ice at a higher altitude to that which he was later found. This came about as prior to 3000BC the treeline in the Alps, and elsewhere in the world, was much higher than it is now. Hence, Otzi was able to traverse a much higher part of the mountains – but came to grief and was frozen in situ. It is not clear how long he lay there before become entombed in ice – but if it was a short period of time this means there was an abrupt and catastrophic drop in global temperatures around 3000BC.