Officially, there is no South Iceberg Peak, but the route name refers to a summit on the Continental Divide south of Iceberg Peak, and the route crosses it. “South Iceberg” is the nickname for one of the summits just north of the 7930’ saddle about 1.5 miles to the south of Iceberg.
The route follows game trails along or just beneath the Divide, sometimes cutting through the cliffs from one side to the other, from the slopes of Swiftcurrent Mountain. From Granite Park, the route is around 10 miles RT with around 3200’ of elevation gain in all. Most of it is Class 2, but there will be scrambling sections that can be kept at Class 3 if care is taken. Views are spectacular all the way.
Park at Logan Pass on Going-to-the-Sun Road if you wish to approach Granite Park via the Highline Trail (arrive early). Park at the Loop, which is about 9 miles west of Logan Pass, to use the Loop Trail. If the parking lot you wish to use is full, consider parking at one of the shuttle bus stops and using that system (free) to reach the trailhead.
To reach Granite Park, one must hike almost 8 miles along the Highline Trail from Logan Pass (but the hike is easy, with little significant elevation change) or hike the Loop Trail, a more strenuous trail that gains about 2500’ in elevation over 4 miles.
The first of the following paragraphs is a paraphrase of the route as described by J. Gordon Edwards in A Climber’s Guide to Glacier National Park. The second and third detail my personal experience with the route and a variation I took. Both accounts assume starting or finishing at Granite Park.
Hike the trail up to Swiftcurrent Pass. On the east side of the pass, at the switchback farthest north, leave the trail and scramble to the ridgetop north of the trail. Hike toward some high cliffs, and as you reach the bottom of them, look for an opening in the trees to the north. This opening is the start of a game trail that heads into the basin of North Swiftcurrent Glacier. Edwards notes that you can follow the trail across the moraines or you can cross the snow itself. North of the glacier, follow a grassy slope and look for a game trail that leads to a saddle on the Divide (this is the 7930’ saddle mentioned in the Overview section), and then head north to South Iceberg. From that peak, descend north and look for a way to scramble down to the west side, where a good game trail appears. That trail provides an easy walk for several minutes. When it ends, you face scree slopes leading to the summit area of Iceberg Peak.
The guidebook makes the route sound somewhat complicated, but it is easy and mostly intuitive. The game trails are usually visible from a distance, which helps locate their starting points when up close. Try to stay as high as possible, especially if you can’t find the trails. Atop the ridge, you can at least use route-finding and scrambling skills to make progress, and you may end up spotting the trails below. If you go too low, you will reach impassable cliffs or face exhausting scree climbs back up. When the game trail along the west side ends, do not head directly up to the ridgetop with the idea of scrambling all the way to the summit; if you do so, you will reach an unclimbable pinnacle that looks like the summit but is not (but there is a fantastic view there). Instead, keep as high as possible while doing an ascending traverse to take you just north of that pinnacle. If you do take the ridgetop to the pinnacle, you will have to lose some elevation in order to bypass it. It won’t be much, but it will be frustrating and tiring after 4+ miles of off-trail hiking and scrambling.
I used this route for my descent and had no trouble finding good passage even though I did not have the guidebook or any notes with me. As a variation, though, I decided to avoid losing and regaining the elevation associated with the traverse into and through the North Swiftcurrent Glacier basin. Instead of descending from the 7930’ saddle into the basin, I headed up for the ridgeline, bypassing a minor summit and encountering some Class 3 and easy Class 4 scrambling along the way. From the ridgetop, I could see the Highline Trail below me, and I took one of several descent options to reach it. Mine involved some fast scree sliding and some glissading that made the descent to the trail mostly easy and enjoyable. Then it was about 2 miles of easy hiking back to Granite Park.
Because there is so much scrambling and steep scree travel on this route, it is important that you have sturdy boots that offer good ankle support and whose soles can stand a beating. And because of the likelihood of snow on parts of the route, you should have an ice axe and perhaps crampons as well.