Ice lenses are layers of ice that form within the snow. The surface of the snow warms up from the sun, melts, then drips into snow beneath it. When this water hits colder snow, it tends to freeze. When it does, it prevents more meltwater from dripping down further, since the ice is too dense for water to flow through. So the additional water has to spread out to the sides, where it too will find colder snow and freeze. This goes on throughout the day (or spring), such that wide layers of ice form within the snow. We call these ice lenses. As the snow continues to warm up, many of these lenses melt again, forming new lenses even deeper within the snow. This process of creating deeper and deeper lenses continues until either there is no more meltwater or the snow and firn layers beneath it are all warmed to the melting point, preventing new ice from forming. Over the years, lenses as thick as a meter may form, and eventually all of the layers merge into one giant layer we call the glacier. This is the process that Jason is studying, by coring (to look at the layers and track their growth), by installing thermistor strings within the layers (to look at how much energy is available for freezing), and by digging pits on the surface (to track how much water is available to melt and drip down). Thus far he’s drilled 3 cores, installed 2 thermistor strings, and dug about a dozen snow pits, and he understands the process about 10 times better than he did last week, but has 100 times more questions about it, most of which have no answers yet.
Jason, drilling holes.
Joey, wondering how he’s going to reach the top.
Glass lenses on a camera focus sunlight reflected off the glacier surface into a recognizable image. The light enters the lens and is bent to hit the digital sensor in my camera, where it is recorded. To create a seamless mosaic of hundreds of photos, the camera has to be rotated about a particular spot, which is dependent on the optical properties of the lens and how it bends the light to make an image. Each lens has a different such spot, and in the case of a zoom lens, the spot changes with the amount of zoom. To find this spot, a lot of testing has to be done, as even a millimeter of error in any of the three dimension can cause visible seams in the mosaic. So I’ve spent the past two days largely trying to determine the exact location of this spot on one of my lenses. It’s the Nikkor 18-200mm zoom lens which I used last year. This year I bought a bunch of nominally higher quality fixed focal lenses on ebay, as I wanted to take the best quality panoramas that I could this year. Unfortunately, higher quality typically means heavier (more glass) and thus more weight to carry around. So I made some comparisons in image quality between the lenses, and found that though some of them do create sharper and richer images, the differences are pretty slight, and I decided that for those times that I’m backpacking, my original zoom lens would be the best (and lightest!) choice. But it’s a complicated lens in terms of finding this magic spot and I spent the better part of a day finding it for various zoom settings, then the better part of the next day taking panoramas and stitching them to confirm that I found them. Fortunately we’ve had some great, clear sunny weather to facilitate this and even more fortunately it appears that my settings are pretty darn close, so I shouldn’t need to do this again.
The survey pole seen here in the foreground was used in the 1990s and 1970s. Survey spots almost always have nice views. You can see our GPS antenna at camp behind the pole and to the right on the skyline. (Click on the panorama and drag to look around, press Shift to zoom in, Command (Mac) or Control (PC) to zoom out.) Enlarge this panorama
This is a snapshot out of the high resolution version of this panorama.
In between testing and various other tasks (mostly phone calls and attempts at emails again to line up project components later in the summer), I took advantage of the weather to hike around our moraine here and take some spherical panoramas, documenting the transition between the true glacier moraine, and this weird knoll that we camp on. During the Little Ice Age peak, about 150 years ago, our camp site was not overlain by ice, but it was clearly affected by the glacier. I think what happened was that the glacier ice came up to nearly the same level and created a stream channel between the ice and mountain behind ice which was probably covered in a permanent snow field, and we are now camped on the remnants of that stream channel and snow field. We know that ice was not here because there is an outcrop of rock right next to us that is heavily covered by lichens, and these take hundreds of years to grow to this size. But behind this, where our tents are, there are various zones of lichen covered rock, non-lichen covered rock, and little gullies and runnels. Probably this was a snow field much of the year, and the snow melt from this hillslope and the ones further upglacier reworked a lot of the rock here in various ways, and subsequently various types of permafrost dynamics reworked it further. It would be nice to have someone out here with expertise in glacial geology to have a look at it and see what can be learned, but until then, I can have fun speculating, documenting it with panoramas, and sharing them with others who may have good ideas about them.
Some of the rocks around camp are heavily covered in black lichen, indicating that they were not covered by ice during the last advance of McCall Glacier in the 1800s. But the ice must have come quite close to this location, and probably trapped a stream between the mountain and ice which flowed through here. Visit this page to see this location in the broader context (requires a Windows PC to view). (Click on the panorama and drag to look around, press Shift to zoom in, Command (Mac) or Control (PC) to zoom out.) Enlarge this panorama
Enlarge this panorama