I've been reading a bit about alpine grades, partly because I want to see how the things I can do in my home country compares to what is in the Alps themselves.
From what I've seen, AD is more for UIAA grade III to a few pitches of IV, with snow/ice up to 45 degrees, but not a lot of objective danger and relatively short approaches and easy descents. D is UIAA IV sustained and up to a few pitches of V, longer approaches, snow/ice from 50-70 degrees, objective dangers and maybe a harder descent. Then TD is UIAA V sustained, some pitches of VI, objective dangers for a lot of the route, and ice/snow up to 70-80 degrees, and a challenging descent in its own right.
And then ED is just horrible.
So something like the North Face of Glittertind (
https://peakbook.org/gfx/images/f/e5/senfterberg_foto_gt_nordvegg.jpg/senft... ) is one or two pitches of UIAA V, the rest is III, not a lot of objective danger that I'm aware of except maybe a huge cornice over the end of the route in parts of the season, but easy approach and long and easy descent. Then the mere presence of a few V pitches doesn't mean it's a D, when the average is a IV- right? Would it be an AD+`? Length is about 300 meters I think
Another example, the North East couloir of Nordre Soleibotntind (
http://www.randopedia.net/tourimages/nordre_soleibotntind__north_east_colou... ) is a 750 meter route of snow at minimum 50 degrees, maximum 60 degrees. I think there's some rock fall there, but no rock climbing required. Pretty sure there's an easy descent route there somewhere, and the approach is a few hours on a glacier and 6 hours walk in total I think. According to the descriptions I've read the length, steepness and a bit of objective danger means it's a D.
EDIT: I've also searched on the forum btw, but didn't find any answer to this. Basically the question boils down to: How much will the difficulty of the crux rock climbing matter for the overall grade compared to how sustained it is, and how much will other factors like steepness of snow/ice matter? Will it matter how many sections there are of rock followed by ice followed by rock? Do glacial approaches matter if the bergschrund is no problem? How long does an approach need to be before it affects the grade?
Post edited at 11:19