Comments on: Snow survey in the Soddie Watershed 2008: results

By: Brian

Brian — Mon, 14 Jul 2008 19:24:02 +0000

Hey David, ice lenses do occur parallel with the slope. In flat areas, the ice lenses would be in a shape of a typical glass lens (thick in the middle and tappered off at the edges), but on sloped areas, they would be more like a sheet of glass parallel to the slope. I don’t know how prevalent they are though, since I haven’t taken snowpit samples over a large area like Anthony has. But ice lenses would be common–of course–in snowpack with frequent thaw/freeze events like those in Northern Michigan.

By: Anthony

Anthony — Mon, 26 May 2008 20:10:26 +0000

Well, when I was digging snow pits, I usually encountered two or three ice layers (each about 1 cm thick) throughout the 1-2 m profile. I don’t know about their horizontal structure though. Sounds like that might be a job for ground penetrating radar. Perhaps Brian Seok will jump in here since he knows more about snow physics.

By: David Knochel

David Knochel — Tue, 20 May 2008 21:42:37 +0000

Thanks for the explanation. How prevalent are those ice lenses? Do they occur at an angle parallel with the slope?

By: Anthony

Anthony — Sun, 18 May 2008 18:39:13 +0000

Dave, Thanks for your comments! Also, great question about the delivery of nitrogen to soils after their buildup in the snow. Research and theory suggest that you are right about the nitrogen delivery not necessarily matching up with snow depths, but not necessarily for the reason that you propose. The reason that nitrogen will undergo less redistribution than you think is a phenomenon called the ionic pulse. During the cold winter at Niwot Ridge, the snow stays below freezing and ions including nitrogen compounds are immobile within the snowpack. However, when it warms up in spring, the snowpack goes isothermal, meaning that it becomes a consistent 0° C throughout the snow profile. At that time, water begins to trickle through the profile and it takes the ions with it, delivering them all to the soil at once. That is the ionic pulse. Subsequent melting and redistribution of snow then theoretically contains much less nitrogen. However, there is still a complicating factor. Within the snowpack, there are often ice lenses – bands of hard ice within the snow. When the trickling water hits these lenses, it can then flow horizontally, redistributing the nitrogen, just as you suggested. The way to measure this – and it wouldn't be easy – would be to do an application of ¹⁵N to the snowpack over a decent-size area (maybe 50 x 50 m) and then try to follow the ¹⁵N into the soil during melt.

By: David Knochel

David Knochel — Fri, 16 May 2008 03:34:46 +0000

Hey Anthony,
I’m impressed! What a feat to collect all those snow depths. I wonder how the N compounds held in the crystalline layers will arrive to the soil surface during melt. For example, what happens if you have a heterogeneous 0.5 ha area of 300cm krummolz drifts, then 60cm depths, then krummulz again and so on. As the snow melts (I assume from the top-down), does the N go straight down vertically to create a hotspot. I would guess that it does, but during big melting events the water is carried across the soil surface as ephemeral streams appear. Does this cause the vegetative heterogeneity to no longer matter with respect to N compounds reaching the soil?

PEACE!

By: Jaclyn

Jaclyn — Wed, 30 Apr 2008 17:58:09 +0000

Good job baby!