Start at the South Lake trailhead (9,820') for Bishop Pass and head south. Initially this trail will lose elevation, something you'll definately remember on the hike out ;-) In 0.8 miles from the trailhead, you'll run into junction with the trail to Treasure Lakes. Follow the trail to Treasure Lakes, however, at 10,400' (or lower) you'll want to get off trail to the right and hike up some slabs and scree over the lower part of Mount Gilbert's NW Ridge. This will get you into Gilbert basin from where Gilbert's North Couloir is reachable. Continue west Thompsons Northeast Face to climb any of it's couloirs or the North Ridge (aka Thompson Ridge).
Doing the approach on the first day and camping below the couloirs is a popular option though it's possible to do this in one day from South Lake if you are fast. This probably requires downclimbing or rappelling the couloir.
Of the three couloirs on the Northeast Face, the Harrington Couloir is the right-most one, very obvious, wide and straight. Just go straight up. There are some rock belays possible on the west side (climber's right). Secor lists the length of this couloir at 900' reaching 70° at the top. Bob Pickering measured the couloir at 600' with an angle of "38-54 degrees sustained with one bulge at 60 degrees." For the vertical, it depends on where you start measuring which can account for the discrepancy.
The descent has become the crux for some trips because there are no easy walk-offs, at least short ones. Here are several options:
- Downclimb: One popular descent for any of Thompson's ice couloirs is to downclimb the Harrington Couloir.
- Rappel: It's possible to rappel using a combination of V-threads, ice bolards, and rock anchors if you don't mind leaving some gear.
- Thompson Ridge: If you don't want to do either of the above, you can descend the class 3 Thompson Ridge, however, this route may be a bit longer than desired and coming off the ridge earlier than the class 3 route means rappeling technical terrain.
Two ice tools, crampons, and a helmet. If you want to rope up, a few ice screws and nuts are useful. As of October 2002, there was a nut and old pin up on the right side.
If you have information about this route that doesn't pertain to any of the other sections, please add it here.