Highly active glacier(s)

[Silbrulf]

Let me describe my continent (not wanting to show it quite yet...):
2000 year old world, crafted by (different legends insert entity of their choice). The North holds a glacier that is incredibly active, during winter stretching nearly 50 miles beyond its summer boundaries; while to the south, 575 mi away, a blasted desert waste straddles an impassable range of mountains (46 mi across; I know...) called the barrier. Forests and plains cover the land, with an unexplored jungle (or rainforest, still deciding) in the west. A week of deadly weather strikes both summer and winter in the form of extreme drought and blizzards respectively. A single Rome-like kingdom has built roads connecting most of the continent, despite its capitol laying within the glaciers area of reach.
The glacier itself grows, not simply an effect of winter (magical influence), and that's why showing it is so important.

Now. I have expressed most of that on my map so far. What I can't seem to do is figure a way to show the full reach of the active glacier. Its summer reach is in white, the layer set to grain merge (in Gimp), but the "tundra" the glacier would leave in its wake to be absorbed again next winter? Idk how I would show that.

Edit: I finally said forget it on the glacier for now since it doesnt look quite right and i can add that as a new layer later, but i still could use some advice on how to do glaciers/ice shelves.

[Rochnan]

Hey Silbrulf,
do I understand you correctly if I say you want to show both the reach of the glacier in it's minimized state (in summer) and in it's maximized state (winter)?

If so I'd say draw the summer state as a regular glacier as that will permanently be glacier area. How to draw that depends on your style, so I can't help with that, yet.
The simplest solution to then show the maximum reach of your glacier would be with dotted lines.
Does that help?