Processes in opposition

Ablation of seasonal snowcover continues at Kibo's summit, while hints of the forthcoming short rain season are becoming evident. The Sentinel-2 image above shows both continuing ablation since the end of August (see previous posts), and a dusting of new snow on southeastern slopes. This is also a nice illustration of how localized snowfall can be on the mountain.

Light accumulating snowfall is common at this time of year, as is its subsequent ablation within a few days. These opposing processes are especially critical for the glaciers as the dry season concludes, because albedo reaches an annual minimum while temperature, humidity, and solar radiation are all increasing.

In today's image (not shown), partially obscured by clouds, the dusting of snow seen above has completely ablated, and snowcover within the caldera is patchier yet.

While it appears that areas of snow will endure the dry season this year, failure of the short rains - or even a delayed onset - might yet ablate much of the lingering summit snow.

What Will Gadd learned on top of Kilimanjaro

Red Bull today released a fantastic new Will Gadd film, shot with a full crew during our pre-COVID February trip. The finished product (45 minutes) is about extreme sport, but also about the science of Kilimanjaro glaciers and climate change; it is well worth watching.

Will was a joy to work with - as eager to learn and share knowledge as he is to climb ice - and clearly articulates the responsibility we all have to reduce our carbon impact. Red Bull deserves major credit for broadening the scope of their productions. And, the stuff is tasty!

Director Tom Beard and the KEO Films crew did a wonderful job of editing, and eagerly accepted ideas to insure an accurate result.

Access the film here:  <https://redbull.com/thelastascent> or here.

 

 

31 August snowcover

Snowcover continued to decrease during the last 5 days of August, as the image below reveals relative to that from 26 August (previous post). Change appears most evident in the northwest corner of the caldera. Nonetheless, the extent of snow at the summit remains more than average - with perhaps two months remaining in the extended dry season.

Tourism on the mountain remains minimal, as the new Coronavirus pandemic continues. For example, the Machame register book shows only 58 climbers departing for the normally-busy months of July and August.

Our friend Simon Mtuy and a large SENE team have been assisting in a large clean-up operation. Over just two days, SENE staff collected 45 kilos of trash from the Machame Camp area. Simon reports that this week there will be 400 crew from 16 companies helping in the clean-up, which will include the Western Breach route and the Crater Camp area. Asante sana!

 

Snowcover at the end of August

Snowcover in the caldera has been decreasing through August, and is now at roughly 75% by area. The image above was acquired by Sentinel-2 on the 26th. Although it now appears possible to reach Stella Point without ascending on snow, considerable snow remains in some places, such as to the east of the Northern Icefield.

During the boreal summer months of June-August, when the sun is in the northern hemisphere, less solar radiation is received on any slope inclined to the south. Note the extent of snowcover remaining on the mountain's southern slopes (above). This area coincides with where the Southern Icefield used to exist - illustrated below during Walter Mittelholzer's flight over the mountain in January 1930. Whereas most of the white area in 1930 is snow over glacier ice, very little ice remains on the south side in 2020.

(Preservation of seasonal snow on the south side is not solely a function of aspect. The spatial pattern of snowfall on the mountain between November 2019 and June 2020 is not known (and was likely not uniform), and snowcover retention is also governed by the seasonal distribution and extent of cloud cover.)

 Below: Mittelholzer's Fokker F.VIIb-3m "Switzerland" refueling enroute to Kilimanjaro [credit].

Meteorological gradients on Kersten Glacier

The latest Kilimanjaro AWS paper is out, in the EGU Open-Access journal "Earth System Dynamics". Collaborator Thomas Mölg at Friedrich-Alexander-Universität conceived the concept and led the analysis and writing* on Mesoscale atmospheric circulation controls of local meteorological elevation gradients on Kersten Glacier near Kilimanjaro summit.

Anchoring the analysis are measurements made at two automated weather station sites, shown as #3 and #4 on the photo above (taken July 2005 by co-author Nicolas Cullen). The stations span 270 m in elevation; both were installed and operated by the Univ. of Innsbruck team, who have coordinated numerous analyses and publications emphasizing AWS 3 (e.g., Mölg et al., 2009). This new ESD paper uses data from a four-year interval of overlapping measurements (2009-2013), including the 2010 El Niño event.

Besides the empirical knowledge provided by analysis of the AWS datasets, the paper links measured on-glacier gradients to a high-resolution atmospheric modeling data set (Emily Collier), while also considering the large-scale geostrophic flow high on the mountain (~500 hPa).

This study illustrates the importance of field measurements, especially in environments threatened by climate change. Data such as these will endure forever, available for creative new analytical approaches and model validation. Sadly, the Kersten Glacier is no longer intact, now with a large gap between AWS 3 and 4. To the west (left on image above) the Heim Glacier is essentially gone, as is the Decken Glacier to the east (right). Replication of these measurements will never again be possible, due to the loss of ice at high elevations on the mountain...

Here is a link to the article (open access).

*Authors:  Mölg, T., D.R. Hardy, E. Collier, E. Kropač, C. Schmid, N.J. Cullen, G. Kaser, R. Prinz, and M. Winkler

August snowcover

Very few climbers have been visiting Kibo's caldera lately due to the pandemic, but satellite imagery shows extensive snowcover - even as we reach the approximate mid-point of the 2020 dry season.

The Sentinel-2 image above was acquired on 1 August. Snowcover has thinned somewhat over the past couple months, revealing interesting textures of the relatively-flat ash within the caldera; note for example those between the Reusch Crater and Uhuru Peak. Might these lobate features be periglacial?

With bright snowcover on the glaciers, ablation has likely been minimal. This situation is similar to that of the 2018 dry season, when a 2 August image also shows nearly-complete snowcover within the caldera. In contrast, there was no snow at the summit last year at this time.

Another curious ablation feature is visible within the caldera, on the Reusch Crater's western slopes. The dark area of bare ground was not present during the snowy dry season two years ago, nor as the 2020 dry season began in June. The timelapse below starts towards the end of June, showing only this area west of Reusch Crater. Despite low resolution, the progressive growth of this spot is apparent. While it is tempting to speculate that enhanced, localized geothermal heat may be responsible, an explanation will require an examination of topography (e.g., aspect and slope) as well as the snow distribution pattern.

Lastly, trails are visible on the western slope (top image), between Shira Plateau and Lava Tower, then to Barranco Camp and continuing toward Karanga. Also visible - largely transverse to the trails - are stream channels which in recent years have been deepened and widened by debris flows. Look for a post soon with details on these.

AWS, long rains end, quiet mountain

Our friend Simon (SENE*) made a trip to the summit caldera recently, and has shared some photos. He kindly detoured his climb to visit the Northern Icefield AWS and inspect our instrumentation. The upper photo illustrates snowcover on the glacier at the end of February. The red circle highlights a replacement temperature/humidity sensor, which with luck is accurately measuring these important variables again.

The second image shows a net 'long-rains' snow accumulation of at least 50 cm. Aside from footprints, the surface texture suggests that a week or more has passed since the last snowfall. On the ascent, Simon estimates ~60 cm of snow beginning below the caldera rim.

Below is a Sentinel-2 timelapse of snowcover between 18 May and 7 June. The transient snowline can be seen increasing in elevation, with thinning of snow on north-facing slopes. This pattern of ablation will likely continue in the months ahead, as rarely does the 'long-rains' season extend much into June.

Simon reports that the mountain is currently devoid of people. In the lower right-hand corner of the satellite image is a light-colored, circular area, which is "Barafu Camp" at 4,700 m. This is the last camp used by most climbers, and once the dry season gets underway it is bustling with hundreds of people. The lowest photo shows Barafu this year, with not a single tent visible; only camp infrastructure buildings can be seen.

*Tourism is severely impacting Tanzania, as the case with other destinations reliant upon international tourism. In preparation for a return to something approaching normal, SENE is offering special terms for future trips booked during June - safaris as well as Kilimanjaro climbs.  #TravelTomorrow 

Tanzania's President Magufuli has taken drastic steps to reopen the country, lifting the ban on flights and removing the required quarantine. Time will tell whether this early action was responsible...