Monday, June 3, 2013

Mount Arkansas - 5.28.2013

Last Tuesday, on my way back from a great weekend in the desert, I met up with my old friend Brennan Metzler to ski Mount Arkansas just southeast of Fremont Pass. With a long spell of warm and sunny weather, and everyone in CO getting after it, it seemed like the snowpack was finally approaching spring stability. As we left the Climax Mine trailhead we observed a distinct freeze as evidenced by frozen streams and a firm crust on top of the snow.

The day started with a mellow approach of a few miles through the headwaters of the Arkansas River towards Mount Arkansas' north amphitheater. Mt. Democrat's west face:


Arkansas and its north face coming into sight:

Photo: Brennan Metzler

Brennan had been up in the basin the previous week, and had ideas for a handful of lines to check off. As we traveled through the basin we had plenty of time to select a line to start with. We decided to start with Arkansas' exposed and cliffy north face, looking like a mini North Maroon just above and left of Brennan:


Having just returned from Utah I was quite unfamiliar with how the Colorado snowpack has been transitioning to spring. As we started the steep snowclimb, I started to familiarize myself with the snowpack, digging into it with my ice axe. I was surprised to find downright wet snow only 25 cms below the surface. Given this rather unsettling discovery, we decided to dig a full snow pit to further assess stability.

Lo and behold, we weren't even able to isolate a column before the snowpack failed on the wet layer we had just observed. Considering the inherent spatial variability that always plagues snow pits, we moved and tried again. This time we were able to isolate the column only to have it fail on a clean shear after only three taps from the wrist. YIKES!

Needless to say, the steep and highly exposed north face of Arkansas was immediately out of the question. Digger deeper, we found a well consolidated and stable snowpack below the weak layer. So, what could we do? We needed something that did not have the near surface weak layer that we saw, but we were already well up the north face. As the north couloir had already slid and removed the weak layer, we decided to ski it instead.

Working into the north couloir:


Getting steeper:


Almost there - steep, steep, steep!


After a few minutes at the summit, we dropped north towards the couloir. Entering the couloir itself was a bit exciting - 55 degree turns through variable snow over 300 meters of rocks and cliffs.

Photo: Brennan Metzler

The first few turns near the top of the line:


Into the couloir itself:


Brennan making it look easy:


The couloir was great with pretty good vert and sustained pitch. Too soon we were back in the basin below. It was still early in the day and we had planned to tag a couple more lines, but all these lines had the same aspect and elevation as the troublesome weak layer that we'd just found.

So, we decided to build some jumps! Which went quite well...

Photo: Brennan Metzler


Photo: Brennan Metzler

Brennan making it look easy:


Getting ready for one last good thrashing:

Photo: Brennan Metzler

Overall, an interesting and rather humbling day. Neither of us successfully forecast the weak layer that could have, at the least, ruined our day. How did we miss it? Was it because people had been getting after it for the last week? Were our avy eyes turned off because it was May? Or were we in such a hurry to skit that we didn't fully consider the evolution of the snowpack over the previous week?

In retrospect, I think a few things conspired to decrease the stability of the snowpack. 1) Some recent new snow was slowing the transition of the snowpack to spring. Not only did this new snow insulate the buried wet snow from the night's cool temperatures, buts with its high albedo it also reduced the ability of the warm spring sun to melt and consolidate the upper snowpack. 2) Why was there water high in the snowpack that had not yet drained? Because this year's wet spring produced several cold and wet layers within the upper snowpack. For water to efficiently drain through these layers they must be warmed to the freezing point. Since that had not happened, lenses of water were ponding on top of one of these layers.

Lessons learned: 1) We humans inherently overestimate snowpack stability when we are familiar or comfortable with an area. 2) Although quick miniature pits provide some insight into the near surface snowpack, a full size pit and column test must be dug to provide any level of quantifiable snowpack stability assessment.