Glaciers in CO

[Scott P]

What area of Colorado had the last remaining significant glacial coverage? I would have thought the San Juans given the average elevation, and amount of rock glaciers around Gilpin, Dallas/West Dallas, and surrounding areas. I seem to remember reading somewhere it was the Front Range around Boulder though.

I think their placement has something to do with the amount of blowing snow that creates isolated areas of extremely deep snowpack in certain cirques.

You're on the right track. It's because the range tends north to south, which forms a perfect snow fence. On highways, we use the same thing to keep less snow on the roads. Here's a diagram of how a line of trees forms a snow fence and how the snow drifts on the downwind side:

snow-fence-diagram.jpg (68.34 KiB) Viewed 1115 times

A mountain range that tends north south acts as a really big snow fence and the same thing happens. More snow actually falls on the west side of the Indian Peaks and RMNP, but since the range works as the perfect snow fence, a good amount is deposited by wind on the east side ridges and cirques. That's why you almost never find cornices in Colorado facing west. They almost always face east (though they can face north or south on occasion).

Even if the San Juans get more snowfall than the IPW or RMNP, it takes much longer to form a glacier than it would if they formed a north to south snow barrier like the Front Range does.

A secondary reason for the glaciers in IPW and RMNP is because east facing slopes are shaded in the afternoon/hottest part of the day, but the most important reason is the "snow fence effect" (my own words for it).

[justiner]

That's pretty interesting most of that ridgeline in RMNP is pretty much a deep vertical dropoff on the east side, but the west side is much more relaxed. I'm sure a ton of snow gets dropped off on the west side, and just blown to the east.

There's some big exceptions though in the Indian Peaks- including N/S Arapaho, where the west side is also fairly steep. Same deal with everything accessed from Brainard Lake. Once past Mt Neva heading south, it has that profile again of a chill west side and a precipitous east. Kind of puzzling the Skyscraper isn't on the USGS maps. That whole area to at least Roger's Pass has some pretty impressive snow fields. Kind of cool to think I've melted water from many of these snowfields/glaciers.

Also crazy that they decided to bore a tunnel under Andrews Glacier,

CalTopo_-_Backcountry_Mapping_Evolved.jpg (278.36 KiB) Viewed 1107 times

[XterraRob]

A mountain range that tends north south acts as a really big snow fence and the same thing happens. More snow actually falls on the west side of the Indian Peaks and RMNP, but since the range works as the perfect snow fence, a good amount is deposited by wind on the east side ridges and cirques. That's why you almost never find cornices in Colorado facing west. They almost always face east (though they can face north or south on occasion).

Even if the San Juans get more snowfall than the IPW or RMNP, it takes much longer to form a glacier than it would if they formed a north to south snow barrier like the Front Range does.

A secondary reason for the glaciers in IPW and RMNP is because east facing slopes are shaded in the afternoon/hottest part of the day, but the most important reason is the "snow fence effect" (my own words for it).

How do these mountain fences impact the flow of dust across the ranges?
Would the San Juans accumulate more due to being in the vicinity of the deserty Colorado Plateau?
And with the area around RMNP being so much farther away, would that mean the snowpack would be less effected?

[seano]

That's pretty interesting most of that ridgeline in RMNP is pretty much a deep vertical dropoff on the east side, but the west side is much more relaxed.

Thanks mostly to ancient glaciers, which carve those steep-faced cirques on the north and east sides of things. This is also quite pronounced in the southern Winds, where many peaks are walkups on their unglaciated south and west sides, and 5.hard climbs to the north and east. Examples include Wind River Peak, Temple, and much of the Cirque of the Towers.

[jibler]

there is a nice youtube vid on CO geology that touches on ice age towards end - and shows rendering of glaciers around silverthorne circa 10K ago

[Eli Boardman]

What area of Colorado had the last remaining significant glacial coverage? I would have thought the San Juans given the average elevation, and amount of rock glaciers around Gilpin, Dallas/West Dallas, and surrounding areas. I seem to remember reading somewhere it was the Front Range around Boulder though.

I think their placement has something to do with the amount of blowing snow that creates isolated areas of extremely deep snowpack in certain cirques.

You're on the right track. It's because the range tends north to south, which forms a perfect snow fence. On highways, we use the same thing to keep less snow on the roads. Here's a diagram of how a line of trees forms a snow fence and how the snow drifts on the downwind side:

snow-fence-diagram.jpg

A mountain range that tends north south acts as a really big snow fence and the same thing happens. More snow actually falls on the west side of the Indian Peaks and RMNP, but since the range works as the perfect snow fence, a good amount is deposited by wind on the east side ridges and cirques. That's why you almost never find cornices in Colorado facing west. They almost always face east (though they can face north or south on occasion).

Even if the San Juans get more snowfall than the IPW or RMNP, it takes much longer to form a glacier than it would if they formed a north to south snow barrier like the Front Range does.

A secondary reason for the glaciers in IPW and RMNP is because east facing slopes are shaded in the afternoon/hottest part of the day, but the most important reason is the "snow fence effect" (my own words for it).

How strange to see one of my dissertation research areas pop up on 14ers.com. For one of my chapters, I'm studying the effects of wind redistribution of snow on seasonal snow persistence and late-summer streamflow in the Wind River Range. The only reason these small alpine glaciers can exist in the temperate climate of the central Rockies is because they're basically just glorified snow drifts. A glacier is just a snowfield that (on average) accumulates more than it melts, and the steep cirques where these glaciers live trap barely enough wind-blown snow to survive the ablation season relatively intact (for now). In fact, we can do a really good job of predicting where the glaciers are based solely on the upwind topography.

It raises the question--after these small glaciers are mostly or completely gone, what impact will it have on the late-summer water supply? A lot of research over the past few decades has suggested that the loss of glaciers in the Wind River Range (where the glaciers are a much larger part of the water balance than CO) could lead to agricultural droughts in August-September once we lose the extra water coming from melting old ice, but I'm pushing back on this theory a bit and suggesting that historic glacier zones may first transition to seasonal drift zones, melting out completely most years but still buffering the summer water supply. So, irrigation dependent on late-summer streamflow might be more resilient than we would otherwise expect if we don't assume that the loss of glaciers necessarily implies the loss of summer snow storage.

Here's a talk I gave on this research in September (LINK). I'm also presenting it remotely at AGU if any of you are attending!

[Dave B]

How strange to see one of my dissertation research areas pop up on 14ers.com. For one of my chapters, I'm studying the effects of wind redistribution of snow on seasonal snow persistence and late-summer streamflow in the Wind River Range.

Here's a talk I gave on this research in September (LINK). I'm also presenting it remotely at AGU if any of you are attending!

Nice, Eli. How are you characterizing snow persistence? Satellite or is ASO doing flights in the Winds now? Are you going to do any snowmelt modeling?

[Scott P]

It is also interesting that a slope in Colorado only has to face slightly east (especially on a north south tending ridge or range) to form a "snow fence"/collection zone.

Here's the Google Earth shot of Stanley Mountain. Notice that the slopes where snow is present actually face mostly south, but since they face slightly east and collect the snow blowing over the ridge, the snow survives on the mostly south facing slopes even though the snow on the north facing slopes is long gone.

Stanley.png (1.01 MiB) Viewed 861 times

[Eli Boardman]

How strange to see one of my dissertation research areas pop up on 14ers.com. For one of my chapters, I'm studying the effects of wind redistribution of snow on seasonal snow persistence and late-summer streamflow in the Wind River Range.

Here's a talk I gave on this research in September (LINK). I'm also presenting it remotely at AGU if any of you are attending!

Nice, Eli. How are you characterizing snow persistence? Satellite or is ASO doing flights in the Winds now? Are you going to do any snowmelt modeling?

Thanks! ASO flew the Winds in June this year, which made some really nice 3 m drift maps, but that's the only ASO flight so far. For snow persistence, I'm currently using Landsat but planning to switch to Planet imagery (daily global coverage of 3 m RGB+NIR, 5 km^2 free per month to researchers). I've developed a Bayesian logit model that performs spatial regression on terrain metrics (adapted form of the Winstral shelter indices Sx and Sb plus elevation, eastnesss, northness, slope, etc.) calibrated to a satellite timeseries of snow cover, which produces a predictive map of snow persistence, i.e. where is snow likely to linger based on the terrain. We can show that the snow persistence map (derived solely from the DEM and satellite snow cover imagery) does a good job of predicting areas of deep snow depth in the ASO map as well as areas of active glaciation, which suggests that the same wind/shelter processes are driving drift accumulation, snow persistence, and glacier activity. As far as modeling the actual snowpack, I do run snow models for other projects, but haven't deployed one in the Winds yet, partly because most of the snow models do a very poor job of handling wind redistribution. I have dreams of deploying alpine weather stations and running turbulent mixed-phase fluid dynamics models to directly model the alpine snow/wind flow, but it turns out there's a reason no one really does that.

[disentangled]

How strange to see one of my dissertation research areas pop up on 14ers.com. For one of my chapters, I'm studying the effects of wind redistribution of snow on seasonal snow persistence and late-summer streamflow in the Wind River Range.

Here's a talk I gave on this research in September (LINK). I'm also presenting it remotely at AGU if any of you are attending!

Nice, Eli. How are you characterizing snow persistence? Satellite or is ASO doing flights in the Winds now? Are you going to do any snowmelt modeling?

Thanks! ASO flew the Winds in June this year, which made some really nice 3 m drift maps, but that's the only ASO flight so far. For snow persistence, I'm currently using Landsat but planning to switch to Planet imagery (daily global coverage of 3 m RGB+NIR, 5 km^2 free per month to researchers). I've developed a Bayesian logit model that performs spatial regression on terrain metrics (adapted form of the Winstral shelter indices Sx and Sb plus elevation, eastnesss, northness, slope, etc.) calibrated to a satellite timeseries of snow cover, which produces a predictive map of snow persistence, i.e. where is snow likely to linger based on the terrain. We can show that the snow persistence map (derived solely from the DEM and satellite snow cover imagery) does a good job of predicting areas of deep snow depth in the ASO map as well as areas of active glaciation, which suggests that the same wind/shelter processes are driving drift accumulation, snow persistence, and glacier activity. As far as modeling the actual snowpack, I do run snow models for other projects, but haven't deployed one in the Winds yet, partly because most of the snow models do a very poor job of handling wind redistribution. I have dreams of deploying alpine weather stations and running turbulent mixed-phase fluid dynamics models to directly model the alpine snow/wind flow, but it turns out there's a reason no one really does that.

haha fancy pants academics.

[Dave B]

Thanks! ASO flew the Winds in June this year, which made some really nice 3 m drift maps, but that's the only ASO flight so far. For snow persistence, I'm currently using Landsat but planning to switch to Planet imagery (daily global coverage of 3 m RGB+NIR, 5 km^2 free per month to researchers). I've developed a Bayesian logit model that performs spatial regression on terrain metrics (adapted form of the Winstral shelter indices Sx and Sb plus elevation, eastnesss, northness, slope, etc.) calibrated to a satellite timeseries of snow cover, which produces a predictive map of snow persistence, i.e. where is snow likely to linger based on the terrain. We can show that the snow persistence map (derived solely from the DEM and satellite snow cover imagery) does a good job of predicting areas of deep snow depth in the ASO map as well as areas of active glaciation, which suggests that the same wind/shelter processes are driving drift accumulation, snow persistence, and glacier activity. As far as modeling the actual snowpack, I do run snow models for other projects, but haven't deployed one in the Winds yet, partly because most of the snow models do a very poor job of handling wind redistribution. I have dreams of deploying alpine weather stations and running turbulent mixed-phase fluid dynamics models to directly model the alpine snow/wind flow, but it turns out there's a reason no one really does that.

Good to know ASO is in WY now, I was excited to see the CASM project got funding to include most of the Front Range in CO now, especially the Cameron Peak burn area. Anyways, sounds like you have an awesome PhD project lined up and Adrian is a great mentor. Best of luck with your research, let me know if you're looking for a snowmelt modeling postdoc in a few years - there will be weather stations a plenty.

[Ptglhs]

Interesting to see a 5-year-old thread I started get so much recent attention. I have appreciated the well researched and learned responses on geology and glaciology. After backpacking in the winds this year and doing Gannett Peak last year, and setting foot on the toe of Jostedalsbreen, the largest glacier in Continental Europe, I'm sad for how warm it is in Colorado for the last 200 years and how many of our glaciers have melted out. Hopefully we can enjoy the few that remain for however many years they're left.