Friday, March 27, 2015

"These Glaciers Are Dying"

Lonnie Thompson presented a remarkable portrait of climate change as inferred from high-altitude tropical glaciers at last night's Frontiers of Science lecture at the University of Utah.  Aspects of the presentation that really got my attention include the following:

1. Ice cores from glaciers and ice caps provide a remarkable history of climate change extending back in some cases 800,000+ years (Antarctic ice).

2. The loss of glacial ice in the tropics is accelerating.  The race is on to obtain and preserve cores from these areas.  One of the figures presented by Lonnie derives from a recent paper by Cullen et al. (2013) who used photographs and three-dimensional visualization techniques to map the remarkable loss of ice on Mt. Kilimanjaro from 1912 to 2011.  
Source: Cullen et al. (2013)
The figure above emphasizes changes in glacial area, but there is also thinning.  Together, this results in a significant decline in ice volume.  Basically these glaciers are dying from the sides and from the top down.  This is happening across the tropics including in Papua New Guinea and the Andes (a comprehensive summary of the latter available here).

3. 98% of the worlds glaciers are currently losing mass.  Those on Papau New Guinea will likely be gone by the end of the decade.  Roughly half of the glacial ice the the alps will be gone by 2040.

I first saw Lonnie speak 10 or 15 years ago.  The changes he was documenting back then were impressive, but those described in this latest talk are jaw dropping.  Change is underway and it is starting to pick up speed.

Lonnie also shared a remarkable story.  A leader of more than 50 high altitude expeditions for scientific research, he was stricken with congestive heart failure.  He is now a heart transplant recipient.  Learn more about Lonnie's remarkable research and life in this New York Times article by Justin Gillis.

Thursday, March 26, 2015

Collins Gulch vs. Supreme: Which Is Snowier?

With no major storms in sight, we turn our attention today to the next most important question on skiers' minds.

Is it snowier in Collins Gulch or the Supreme area at Alta?  I've always argued for the former, but I know many that argue for the latter (this is for total seasonal snowfall—the winner sometimes varies within individual storms).

This fall, my students installed one of our low impact weather and snow measurement stations at 9603 feet in upper Albion Basin (special thanks to the cabin owners who are hosting the equipment) at a site we call "Top Cecret" since it is near the top of the Cecret chair (and thus in the Supreme area).  The idea was to get some experience operating this equipment in a deep snow environment. We were hoping for some challenges.  Tripods are best used in no snow or lower snow environments.  In deep snow environments, you run into two issues.  One is that the creep of the snowpack can mangle the tripod.  The other is that as the snow depth increases, at some point you need to take off the equipment, add an extender, and then remount the equipment.  That's a job that's time consuming but not too difficult in nice weather, but isn't a heck of a lot of fun in the cold.


This winter none of that has mattered as we've had the worst snow year since WWII.  As of last weekend, the tripod bases were well buried, but the observing equipment was still far enough above the snowpack to be operating effectively.


Our comparison site is the Alta-Collins snow-study station expertly maintained and operated by Alta Ski Area at 9662 feet in Collins Gulch.  This station has provided timely and reliable observations of snowfall and snowfall water equivalent for many years, greatly assisting weather forecasting and research efforts in Little Cottonwood Canyon.  


Both Top Cecret and Alta-Collins are equipped with ultrasonic snow-depth sensors that send out inaudible pulses of sound and infer the snow depth based on how long it takes for the sound to return to the sensor.

What are the current snow depths at the two sites:

Top Cecret: 82 inches
Alta-Collins: 77 inches

Looks like Supreme is the winner!

Not so fast.  These are two localized measurements of a highly variable snowpack.  We really can't make any strong conclusions one way or the other and perhaps there simply isn't a major contrast in snow between the two areas.  Let the debate rage on.  What think you?

Wednesday, March 25, 2015

Cloning or Time Travel Recommended

If you are interested in climate science and policy, there are two great opportunities for learning more tomorrow (Thursday) at talks being given in Salt Lake City.  They overlap, so clone yourself or get a time turner and get to both.

Thursday, March 26
Dr. Lonnie Thompson
Frontiers of Science Lecture
"Global Climate Change, ENSO and Black Swans: A Paleoclimate Perspective from the World’s Highest Mountains”
6:00 – 7:30 PM
220 Aline Skaggs Building
University of Utah

Dr. Lonnie Thompson.  Source: The Ohio State University
Thursday, March 26
Dr. Katharine Hayhoe 
7:00 to 8:00 pm
Clark Planetarium, 110 S 400 West, SLC

Dr. Katherine Hayhoe.  Source: http://katharinehayhoe.com/

Tuesday, March 24, 2015

Looking Back, Looking Forward

Yesterday evening, there were a few fireworks in the Salt Lake Valley, but you might have missed them if you blinked.  Some stronger cells popped up near the south shore of the Great Salt Lake just before 8 PM MDT and I saw a lightning flash or two during this period.


The band along which these cells formed moved southeastward and, although weakening, gave a final blast of snow to the central Cottonwoods.


If you are going out skiing today, I suspect you will find a large increase in snowfall from 8000 to 9000 feet.  Accumulations at 8500 feet and above in upper Little Cottonwood look to be around 6 inches.  The Big Cottonwood resorts are reporting a bit more.  At Solitude, my bet is the 10 inches they are reporting is for the summit and you'll find a lot less at the base.

A quick hitter late today through about midnight will lay down a couple more inches in the mountains and some valley showers, bringing to an end our brief flirtation with spring showers.  After that, the death ridge returns.

Monday, March 23, 2015

A Brief Flirtation with Spring Showers

Every couple of weeks Mother Nature allows a storm or two to slip through the net and give us a brief break from the death ridge.  One of those storms is here this morning as a cold front is sweeping across northern Utah bringing valley showers and mountain snow showers.  We'll then have a break later tonight and Tuesday, with another front coming in Tuesday night, after which the death ridge returns.

Two fronts sounds exciting, but this really isn't a major storm cycle by old-fashioned Utah standards. In the upper Cottonwoods, the NAM is generating about .3 inches of water and 4 inches of snow today and tonight, with another .2 water/2 inches of snow with the front on Tuesday night (see lower two panels below).

My usual approach in the winter is to use the NAM as the low-end of the forecast range for Alta, but such an approach doesn't typically do as well in the spring when storms on average feature less orographic enhancement.  In addition, this looks like a pattern where showers will be hit or miss.  In other words, if you don't like the weather, wait 5 minutes.  As such, I think a total of 3-6" today and tonight is probably reasonable, although I won't be surprised if we come in a bit below or above that given the showery nature of the pattern.  Yes, there is a chance of thunderstorms too, which would make may day.  Looks like rain for the valley, unless we get a very strong shower and then perhaps we'll mix in some graupel or ice pellets.

We'll get a little more with the second front.  Maybe in total the two events will give us something in the 5-10 inch range in the upper Cottonwoods.  Not much by old fashioned standards, but a blizzard by contemporary standards...

Sunday, March 22, 2015

Has There Ever Been a Snow Season Like This?

Photos of Mt. Superior from Alta Ski Area show the two extremes of the Wasatch snow climate on 11 June 2011 (a season with about 800 inches of snow at 9500 feet and cold weather deep into the spring) and 21 March 2015 (a season with about 250 inches of snow - so far - at 9500 feet and record warmth.  
The answer is probably not during the period of reliable snow records at Alta-Guard, which begin after WWII, but there are a few nuances to consider, especially with regards to snowpack. 

What we know is that this winter the Dec-Feb period was the warmest on record (since 1895) in the northern mountains climate zone that includes the Wasatch and Uinta Mountains.  The closest analog in the instrumented record is 1933/34, but that was before reliable snow records at Alta-Guard.  The only other Dec-Feb period with temperatures close to this winter is 1980/81.  More on that season in a minute.

Source: NCDC
What about March?  Well, the temperature records for this March are still trickling in from volunteer observers.  Through yesterday, though, we were running well above average.  In terms of where we were through from December through the end of astronomical winter on Friday, there's a good chance it was the warmest such period on record.  

With regards to snow, the Utah Avalanche Center reports that Alta-Guard has has had only 213.5 inches of snow since November.  It looks like we're going to get some snow Monday-Wednesday.  I'm not sure how much, but for the sake of argument, let's suppose it goes big and we end up with 250 inches through the end of March.  The only other winters with less than 300 inches from November –March are 1960/61 (291 inches), 1962/63 (265 inches), and 1976/77 (283.5 inches).  Let's also throw 1980/81 into the mix since it is the closest temperature analog.  In that low snow year, the November–March snowfall was 339 inches.  

But let's look at the March snowfall in those years specifically.  In 1960/61, 1962/63, and 1976/77, and 1980/81, the March snowfall was 113, 93, 129, and 110 inches, respectively.  These were drought years, but they rallied at the end, producing above average snowfalls in March.  That's not going to happen this year, even with the storms Monday–Wednesday. 

Thus, the combination of low snowfall and high temperatures for December to mid March appears to be unprecedented since record keeping began after World War II.  

However, we haven't looked at snowpack yet.  Ideally, one would look at manual snowpack water equivalent observations for which there are records at some sites in the Wasatch that extend back to before World War II.  I don't have easy access to those records, and often they are collected around April 1st, so I'm going to leave that as an assignment for you weather sleuths and instead look at shorter-term records from SNOTEL stations.  Unfortunately, these don't extend back to 1980/81, but they do go back to 1989 or so for most central Wasatch sites.  

At the Mill D North SNOTEL, the snowpack has already ripened and begun to melt (green line) this year, which is quite remarkable (green line).  We've already lost about 3 inches of water at this site to melt.  Curiously, the winter of 1991/92 has a peak snowpack water equivalent that is only slightly higher than this year, even though we are way behind in snowfall amount at Alta-Guard.  During that season, the Alta-Guard Nov-Mar snowfall was 367.5 inches.  More on this in a minute.  


The Brighton SNOTEL shows similar behavior, with 1991/92 also being the next lowest season.  


Now lets shift to Thaynes Canyon (Park City) and Snowbird.  Both of these sites are on north-facing aspects and thus the melt has yet to begin in earnest.  Again we see 1991/92 raise it's ugly head as the next lowest season.  In fact, snowpack water equivalent at Snowbird is right on top of that year as of Friday. 



So, we sort of have a mixed bag when it comes to snowpack water equivalent observations, although most are well behind 1991/92.  How to explain the snowpack observations, especially at Snowbird?  
Welcome to the world of observational uncertainty and the comparison of apples and oranges.  SNOTEL observations are affected by changes in site characteristics and instrumentation.  They are also a measurement at a single point and in any one season, wind transport and other factors can play a role. 

Such issues affect other observations we've used here.  For example, the Alta-Guard snowfall observations are affected by changes in measurement location or techniques.  In addition, we are comparing seasonal snowfall observations (the sum of new snow depth observations taken daily or even more frequently) as opposed to snow water equivalent observations.  The latter are more important for the snowpack.  It could be that we had a low snowfall year this year, but the water equivalent is not far behind 1991/92 (another issue for you weather sleuths to dig into).  

When I put all this together, I think it's pretty safe to say that the combination of warmth and snowfall for this winter are unprecedented since WWII.  It is possible (perhaps even probable) that the current Wasatch snowpack is probably about as low as it has been in mid March since WWII too, but I'd like to see some additional analysis of longer-term snowpack records to see where we stand overall.  Again, I appeal to you enterprising sleuths out there to dig into this problem further and provide comment.

PS: I would still take this year over 1976/77 which had very little snow in the early season with most falling late.  If you have to pick between snow early and snow late, the former is better.  Further, despite the low snowpack, groomers will still fun yesterday.  Plus, keep an eye on the storms for Monday-Wednesday.  Winter is returning.