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...

 

Ski Africa!

From a satellite's perspective, Kilimanjaro emerged from thick cloud cover yesterday, revealing substantial snow blanketing the upper ~1300 m of the entire mountain (i.e., above about 4600 m / 15,100 ft). This is an area of ~50 km^2.

Distinguishing between fresh snow and thin, low clouds is difficult on this particular image - yet snowcover appears remarkably uniform. On such a big mountain, precipitation often varies spatially, reflecting interaction of the massif with regional circulation.

Not often is it possible to ski 1000+ meters at 3° south latitude. But if snow accumulation continues through May, as it typically does, this June might be a great time to ski the mountain - with appropriate COVID-19 precautions.

#seneadventures @christianpondella

April Update

Northern Icefield margin with "cloudcam" and AWS. At the edge, note the layer of seasonal snow overlying glacier ice (23 February 2020).

Mid-April is typically not a busy time on Kilimanjaro, midway through the so-called "low season" when climbers avoid what are often the wettest months, associated with widespread convection. However, April this year is unusually quiet, due to the global pandemic; as with National Parks around the world, Kilimanjaro is devoid of human visitors. Schools are closed, and residents are sheltering in place - many without employment. For a region so dependent upon tourism and foreign exchange, this is a devastating time. We empathize with guides and all the other mountain staff who eagerly await the return of clients, and the opportunity to share their mountain with visitors.

Since the short rains diminished in January, a series of snowfall events have maintained fresh snowcover on the glaciers (see images above and below). Summit caldera snowcover has varied between continuous (see 3 Feb image) and patchy (as seen on yesterday's satellite image, above). Snowcover appears to have been gradually decreasing over the past two weeks, as also occurred during February until restored by early March snow.

In most years the long rains continue through May, ending rather abruptly by early June. Precipitation between now and then will determine what climbers encounter once travel and group climbs are safe again. Although recession of the glaciers continues, seasonal snowcover creates an illusion of permanence. At some point during the dry season though (June-September), the snow is likely to completely ablate and the bright ice will again be in stark contrast to the dark volcanic ash - reminding us that the ice will likely be gone within a few decades.

Residual ice with Mawenzi in the background. Note seasonal snow layer on the ice as well as the crater surface (25 February 2020).

Stable weather returns [updated]

February weather on Kilimanjaro is often characterized by a dry interval, between the Short Rains of approximately Nov/Dec, and Long Rains within the Mar/Apr/May time period. As noted previously, the Short Rains brought considerable rain to the mountain this year, with snow up high, beginning in early October. That wet period appears to have ended.

The upper image from 2 February shows patchy snowcover on the upper 1000 meters of the mountain's south side, as viewed from above Moshi (Simon Mtuy credit). Distinguishing remnants of the former Southern Icefield from snowcover is difficult here.

The second image above was acquired today by the ESA Sentinel-2 satellite, revealing continuous snowcover within the summit caldera, and on the upper slopes. The stable-weather cumulus clouds visible here appear only slightly more extensive than those on the day before (top image).

Although telemetry of data from the Northern Icefield (NIF) weather station is not currently available (budget constraints), several recent reports from climbers confirm what the images depict. On 23 January, collaborator Sarah Konrad visited the NIF and measured a mean snowdepth of ~0.60 m around the weather station. Shortly thereafter (28 Jan.), Simon was above the Western Breach in the Furtwängler Glacier area, reporting "almost one meter of snow."

Images below show Simon's camp at Arrow Glacier on the 27th, looking south across the Western Breach, and a Furtwängler Glacier remnant near Crater Camp (Sarah Konrad credit). Finally, a photo of the NIF weather station from Sarah reveals that the equipment is overdue for a "service visit". Fortunately, planning is underway to visit the station later this month!

[UPDATE 02/04:  Our friend Timba keeps close tabs on Kilimanjaro weather from Moshi, in the interest of safety for the many guides and porters working on the mountain. It was Timba who inspired our analysis of how tropical cyclones might influence snowfall on the mountain (Collier et al., 2019).

Timba wrote today, emphasizing how wet the region has been in recent months, especially at the end of September and through most of October 2019. As he points out, this is the time when the Indian Ocean Dipole (IOD) was very strongly positive, a water temperature pattern associated with heavy rain in eastern Africa - and bushfires in Australia (read more here and here).

So, has stable weather really returned to Kilimanjaro? Although the IOD has returned to a neutral pattern, older friends of Timba's equate the current rainfall pattern with that of Oct. 1988 to June 1989 - when the two rainy seasons merged into one long wet season.]