Friday, June 26, 2015
Back to Quelccaya! Earlier this month we spent a couple weeks on and around the ice cap, continuing climate system research. We began the expedition as a large group with a diversity of backgrounds and interests; lots of interesting discussions ensued, while hiking and during meals. Here are some images from the adventure.
Austral winter in the Cordillera Vilcanota is typically cold and dry, with stable weather ideal for conducting fieldwork on Quelccaya. This is not how June began this year, however, as late-season snowfall during April and May continued (see 4 May entry). Here we are looking north over fresh snowcover toward Qori Kalis outlet glacier (not visible). Strong convection is already underway by 10 AM, which brought snow squalls during the afternoon. At the summit a week later we attributed ~90 cm of snow to late accumulation.
Most of the group arrived at Moraine Camp during a heavy precipitation event on the afternoon of 2 June. For more than 2 hours, large grains of graupel pelted us, driven by wind and accompanied by lightning and thunder. One lightning strike was particularly impressive (and frightening), striking a path below camp. Later we learned from our arrieros (see below) that lightning has been unusually prevalent this year, killing numerous alpaca and at least one person.
More than 40 years after his first expedition to Quelccaya Ice Cap, Lonnie Thompson was delighted to be back in 2015. Once again, he carried out a full schedule of photographing the margin, searching for old in-situ plant material emerging from beneath retreating ice, visiting Qori Kalis, and collecting snow and firn at the summit to extend his ice core record. The approach to Quelccaya is now considerably shorter than it was in 1974, yet Lonnie confirms that the partial pressure of oxygen at 5,700 m hasn't gotten any higher!
Collaborating with David Chadwell (UCSD & Scripps) we continue to quantify the magnitude of thinning at Quelccaya since 1983, when Dave worked with Henry Brecher to carefully survey the glacier. Above, Carsten Braun is making a geodetic-quality GPS measurement at one of our reference stations, prior to re-visiting numerous sites on the glacier where elevation is accurately known from the 1983-84 measurements. A manuscript detailing this work will be submitted shortly.
The majority of our time at Quelccaya was occupied by raising the AWS tower, to accommodate the summit's positive mass balance. Working together with Carsten as well as Koky Castañeda through most of 6 days we performed a complete annual service and raised everything by over 3 m. In this upward-looking view (note wind sensor), only a final trimming of guy cables and bundling of sensor leads remains to be done.
The AWS is ready for another year of measurements. One of this year's most-difficult tasks was adjusting the tower orientation to account for glacier flow. Notice how the lowest section of the tower appears tilted? It is indeed, because the tower extends another 25 m beneath the surface! Although the station is located more-or-less at the ice cap summit, where the flow vector is essentially vertical, enough differential horizontal motion has occurred since 2003 that keeping the tower plumb is not a trivial task.
Felix, Koky, and Theodoro in the snowpit, approaching 3 m depth. Here, density measurements and snow samples have been collected in the upper portion, from the shaded south-facing wall (for stable isotopes, black carbon). Just coming into view behind Theo in the deepest section is the 2014 dry-season surface. This marks the beginning of 2014-15 accumulation, and this year the 'surface' was more of a 'zone' than normal, because there was not a prolonged interval without snowfall.
Late afternoons were often spent at the glacier margin not far from camp, observing bird behavior and searching for nests used during the prior breeding season. Note the faintly-visible nest within the cavity below Koky (used by Diuca speculifera; more here). At the time this nest was occupied it was likely even more recessed from the vertical ice face, so protected from weather and relatively safe from both terrestrial predators (e.g. foxes) and from those above (e.g., Mountain Caracara, Phalcoboenus megalopterus or Aplomado Falcon, Falco femoralis).
The vicuña population near Quelccaya has increased tremendously in the past decade (Vicugna vicugna). Groups are frequently seen and heard in the area, right up to the glacier margin.
Wednesday, June 17, 2015
Fieldwork for June 2015 is now complete, and prior to posting details of our largely-successful trip, I want to first acknowledge these two guys. Through two weeks of not-always-ideal weather at Quelccaya, including six trips to the summit and 6+ meters of digging, no one could ask for more competent and enjoyable assistants/companions. Carsten loves to point out that there are very good reasons why so few automated weather stations (AWS) exist in glacier accumulation zones. This is true, and the Quelccaya AWS would almost certainly not continue functioning so well - and for so long - without the involvement of these two!
The following points provide a glimpse of the critical role played by Carsten & Koky at Quelccaya, this year and in previous field seasons.
The work. Repeatedly ascending to 5,700 meters is the fun part of our fieldwork. While at the summit - through the full spectrum of Andean winter weather - our work is strenuous and stressful. Among the tasks required in raising the entire AWS tower and electronics by 3 meters are lifting four different enclosures with >100 Ahrs of batteries, swaging dozens of cables together for structural integrity (see red tool Koky is holding), climbing and balancing on the 5 meter-tall tower while using various tools in one hand, and thinking clearly enough at 500 hPa to solve a diversity of mind-bending problems that invariably develop. In the snowpits, collecting and recording details of nearly 100 samples is laborious, while measuring density can be downright exhausting (see Snowmetrics tool Carsten is holding); for the first time, one sample this year exceeded 600 kg/m^3. Yet in all aspects of the work, these guys remain dedicated to completing every task precisely!
Being in the field. Keeping glacier fieldwork both safe and fun is not always trivial. However, Carsten and Koky's depth of experience - and their fitness - minimize the impact of problems and discomforts which arise. Both recognize that occasional frustrations are to be expected; once challenges are overcome, they move on. And although all of us would be perfectly happy working up there without Bob Marley, Koky's incredible music archive makes the effort a tiny bit more fun.
The science. Science, after all, is the raison d'être for being at Quelccaya - and this is always at the forefront of our thoughts. Despite jokes about how much easier our lives would be if we had concentrated on modeling climate rather than measuring it, we are all addicted to the process of doing science in the field - reveling in the the excitement which sometimes results, and accepting the inevitable difficult and tedious moments. In reality, many aspects of the science are done either prior to fieldwork (e.g., designing and planning measurements/sampling), or upon return when data processing and sample analyses are done. During intervals of breathlessly digging snow, or gradually freezing while making motionless observations of bird behavior while they prepare to roost inside the glacier, Carsten and Koky always persist cheerfully. With fieldwork, one never knows when an unexpected situation or observation might prove valuable, whether in interpreting a landscape feature or providing insight into the various processes by which snow accumulation is transformed into a climate record. Our science benefits by having six eyes and three brains on the job!
So, Carsten and Koky once again earn a gigantic "thank you" for their efforts this year. We also thank those behind the scenes, including our entire logistics team led by Benjamin Vicencio, the creative wizardry of modelers with whom we work (M. Vuille and J. Hurley), and others who have helped to keep this project going over the years (R. Bradley, L. Thompson). Finally, we are grateful for both financial and technical support from NOAA ATDD/GCOS as well as NSF.
Saturday, May 30, 2015
Acclimatization has gone well, and our next round of fieldwork is about to commence. Excitement is high among our group of scientists, journalists, guides and drivers pictured above, representing 7 countries of origin. Our destination today was Cerro Wanakauri (see track here). At Quelccaya, group members this year will be pursuing a variety of objectives, from anthropology to snow chemistry to artistic photography.
Monday, May 4, 2015
After modest snow accumulation during February and March, April 2015 snowfall at Quelccaya was more typical of the core wet season months. For our 11-year period of record, the median height change during April is 12 cm. However, this year's April snowfall was 460 percent of the median, at 55 cm. This is nearly three times that of the next "snowiest" April (2007) and in 2 of the 11 years there was net ablation during April.
Change in surface height only equate with accumulation in water equivalent if densities are equal, yet our experience indicates that snow density is quite consistent at Quelccaya. Next month we will be on the ice cap to measure density profiles, among other tasks, and will have a more accurate measure of accumulation.
The Landsat image above (23 April) illustrates widespread snowcover on the landscape around Quelccaya above ~4,700 m. Our fieldwork beginning later this month will focus on the area within the red ellipse shown on the image, primarily above 5,200 m. Credit: USGS EROS data center
[UPDATE 5/20: Accumulation continues! As of 18 May, a mid-month snowy interval was underway, bringing total accumulation for 2014-15 to exactly the median for the date, at 2.05 meters. One-third of the wet-season snowfall has occurred since the end of March, which is unusually late to have so much snow. We will be on the glacier at the end of the month, and will provide an update towards the end of June.]
Tuesday, January 20, 2015
Looking through images of "North Lake" recently, this one caught my eye. It was taken on 7 July 2013 while climbing up to the ice cap margin. The view is towards the NW, with ice from the north side of Qori Kalis valley visible in the upper right-hand corner. Note that much of the lake surface is frozen, which is typical during the dry season when air temperature is lower and clear sky at night allows radiational cooling. In the portion of the lake barely visible to the right, blocks of ice were strong enough (for Carsten) to walk out onto.
Prior to ~1985 this lake did not exist, having been buried beneath ice cover for 4,700 years (Thompson et al., 2013). As the margin retreated, meltwater was impounded by bedrock which is out of view to the left, and lake formation almost certainly hastened ice retreat. Now note the section of ice within the blue ellipse above, and try to find it here:
This image is a different perspective, a wider field of view (81°) from the peninsula of bedrock just beneath the blue ellipse. It was taken only 15 months later, on 13 October 2014, and a large volume of ice is gone entirely! Here is part of this section in 2012, with a person for scale. This lower image can be explored in greater detail here, and the GigaPan below provides yet another perspective on the lake, also from October 2014.
Retreat of the glacier will likely continue this year, and soon, the margin will no longer be in contact with the lake. Within the past few decades, a series of proglacial lakes have similarly formed in the area due to ice retreat, including the well-documented Qori Kalis, and several others. Efforts continue to understand the rate of ice-volume change underway, as well as the implications for natural and human systems.
Monday, November 24, 2014
Above is one of three recently-posted GigaPan images from October fieldwork at Quelccaya, with different depictions of the ice cap's western margin (available here for browsers w/o Flash plug-in).
The image above is a 92° field of view with a relatively short focal length (42 mm), looking to the south. Virtually the entire landscape visible in the panorama was covered by ice during the late Holocene (e.g., 500 years ago or less), and most of the scene was buried only ~40 years ago. For example, the lake at 5,200 m elevation on the left-hand side began forming in ~1985 (Thompson et al., 2013). Along upper portions of the margin seen here (i.e., center of image) we have measured a retreat rate of ~10 m/yr over the past decade, in addition to thinning.
This panorama illustrates the extent to which the glacier controls local hydrology, which is also the case on a regional scale. Areas of bedrock scoured by ice often contain lakes, and areas of sediment deposition (i.e., moraines) are often responsible for development of wetlands upstream. Lakes, streams, and wetlands (bofedales) are all sustained by glacier meltwater, especially through the dry season months of June-August. Without water the landscape is dry and barren, as in this image. Throughout the Cordillera Vilcanota today, runoff from glaciers supports a tremendous biodiversity - of mammals, birds, reptiles, amphibians, insects and more.
Despite lower air temperature, the transient snowline elevation at Quelccaya progressively increases during the dry season, occasionally depressed by snowfall events. These panoramas were taken during the dry-to-wet season transition, as 2014-15 accumulation was getting underway (as shown here). By late October, the transient snowline had reached approximately 5,400 m, as can be seen above or more clearly in this image. Consequently, all portions of the glacier below this elevation lost mass during 2013-14, despite above-average accumulation at the summit.
Friday, November 14, 2014
The image above isn't likely to win any contests; the beauty of this shot is that it captures a night-time moment at the automated weather station, when we were thousands of kilometers away. This is one of over 7,000 images acquired during a 15 month interval at the Quelccaya AWS by a Pentax K100D Super camera, in an early version of a Harbortronics Time-Lapse system. It nicely demonstrates one of the ways that modern automated stations can include more than sensors making basic weather measurements.
The enclosure is installed looking toward the west, with a fixed field of view. About half of each scene shows the sky (i.e., clouds and all the information they convey about the atmospheric state), while the lower half illustrates the glacier surface, providing information such as snowfall timing, magnitude, subsequent wind re-distribution, and surface texture (see above). In addition, the foreground - only 75 cm from the camera - depicts sections of the tower, a guy cable, the GOES antenna, and a solar panel. Rime ice is easily observed here, during conditions when it develops. Remarkably, both distant and nearby elements of the image are almost always in focus!
This particular photo from 19:05 on 11 July is noteworthy because the only source of light was from a nearly-full moon, rising through clear sky to the east behind the camera. Faintly visible in the western background is a band of clouds; on the right-hand side a mountain in the Cordillera Vilcanota can be seen, ~50 km distant. On the foreground snow is a shadow of the AWS, clearly showing (left to right) an ultrasonic snow sensor, the big Met One T/RH radiation shield, and the RM Young Wind Monitor. EXIF data indicate the shutter speed was 6 seconds, with the aperture at f/4.
Our initial use for this set of hourly images is in aiding quality-control of snowfall measurements. Thanks to two different ultrasonic sensors on this station, raw measurements are usually unambiguous after adjusting for air-path temperature. But sometimes, it can be difficult to assess whether measurements recording a surface height increase are due to a snowfall event, re-distribution of previously-fallen snow, or something rare and unrelated to climate (e.g., jiggling of the tower as accumulation settles).
Getting the time-lapse system to this point hasn't been without frustration, but the result is proving both useful and interesting!