October fieldwork!

We were back on the glaciers for fieldwork in October! As previously reported (here), the pandemic and logistical issues prevented us from visiting since February 2020, and although 'automated', our weather stations on the ice are not self-maintaining. Over the course of the ensuing three years, problems and damage occurred - so one of our objectives last month was to remove weather instrumentation and mass balance stakes. With tremendous help from the porters and staff of Summit Expeditions (SENE), we were successful. The next step is examining data we recovered, and evaluating options to continue measurements with new instrumentation!

Doug Hardy (UMass), Mike Winkler (GeoSphere Austria), and Emily Collier (Univ. Innsbruck). 

Click on any image to enlarge:

Fig. 1 (above): Kibo and 5,000 meters of relief, from Moshi. Preparing to head up again was very exciting, first time in over 3 years!

Fig. 2 (above): Our first task, led by Emily and her newly-funded research, was exploring the Kilimanjaro Mountain Club archives - in search of historical observations pertaining to the impacts of Tropical Cyclones on Kilimanjaro precipitation.

Fig. 3 (above): Morning of day two, a favorite view on the Umbwe Trail. These southern slopes were once covered by the Southern Icefield. Only fragments remain today, including sections of the Kersten Glacier (center).

Fig. 4 (above): Umbwe route passes through a recently-burned area below Barranco Camp, one of several new fire scars seen on this trip.

Fig. 5 (above): Diamond Glacier, Breach Icicle, and fragments of the Balletto Glacier. The icicle is larger than in 2020* due to meltwater drainage from above. Also note extensive rockfall onto the Balletto. (*2020 image here.)

Fig. 6 (above): Mike and Emily above Karanga Camp. Kersten Glacier remnants are visible above Mike, and the Rebmann Glacier is above Emily; between them is the vanishingly meager Decken Glacier ice.

Fig. 7 (above): Team member Mathayo Melio, preparing fresh greens (Kale) at Barafu Camp.

Fig. 8 (above): Late afternoon at Barafu, where multiple helicopter pickups are now occurring daily - typically to expedite the descent of wealthy clients.

Fig. 9 (above): Wishful thinking. Simon is testing whether he can transmit a message directly from his brain through this cable. Kilimanjaro Park authorities are testing whether they can string fiber optic cable along the trails for tourists to post on Instagram. We had no success with either. Increasing rockfall and debris flows on the mountain could make unprotected fiber maintenance difficult...

Fig. 10 (above): Riming on the Uhuru sign, as the weather clears. Northern Icefield in the distance.

Fig. 11 (above): Furtwängler Glacier from above. Since 2020 the area has decreased by seventy percent (yes, in 3 yearss); the glacier's demise is imminent.

Fig. 12 (above): Upper Kersten Glacier, October 2017; find the weather station. Zoom in, as this is a panorama. Then find the relatively thick, clean stratum and compare it's position to that in 2023 (next image).

Fig. 13 (above): Kersten Glacier upper margin, where thinning and lateral retreat continue. Where is the weather station? Occasional collapses of the wall and a marginal meltwater lake has been noted for 20+ years. However, compare the thick, clean ice layer position here with that 2017 (prior image) or in 2014, 9 years ago (with Will Gadd for scale).

Fig. 14 (above): Mike investigating ice blocks where the Kersten Glacier margin most-recently collapsed. Find the weather station (we couldn't either).

Fig. 15 (above): The largest remaining fragments of the former Eastern Icefield. The right-hand block is featured in the Red Bull film.

Fig. 16 (above): Northern Icefield margin, just west of camp. Note person for scale, just right of center - and the interesting basal stratigraphy.

Fig. 17 (above): Wonderful textures photo taken by Mike.

Fig. 18 (above): Northern Icefield margin, looking west toward camp. Compare to this similar view in February 2000.

Fig. 19 (above): Northern Icefield again... but the northern margin. As evident here, in next image, and elsewhere - the ice is fracturing to a greater extent than previously seen.

Fig. 20 (above): A fresh, curious collapse feature at the Northern Icefield margin. An ice layer associated with ponded and frozen supraglacial meltwater can be seen at the top of the fracture. These have been occasionally observed on Kibo's glaciers, always frozen at the surface.

Fig. 21 (above): A portion of AWS being carried through penitentes on the Northern Icefield. These particularly-large penitentes made walking difficult!

Fig. 22 (above): The AWS tower being carried back across the crater toward Uhuru Peak, 23 years after being brought up!

Fig. 23 (above): Doug, Emily, and Simon - along with about 20 other team members - prepare for a tree-planting ceremony honoring climate research on the mountain.

Fig. 24 (above): Final preparations for a feast celebrating safe and successful fieldwork! Much of this food was grown right on Simon's farm.
 

September fieldwork!

With great anticipation, I'm planning to be back on Kibo's glaciers next month. After 17 years of frequent observations and measurements, circumstances beyond my control have foiled research efforts in recent years. Never take high-elevation glacier fieldwork in National Parks for granted! Chief among the issues were a major storm (October 2018), postponement of two consecutive collaborative trips (July & December 2019), a collaborative-and-fun glacier visit with limited time and deep snow (February 2020), the pandemic (2 years), and most recently - failure to get above 2200 m due to logistical/permitting difficulties (September 2022). Phew... I'm ready to get back up there!

Extensive fieldwork and AWS service was conducted in October 2017, including repairs at the station and documenting changes to summit glaciers. Accompanying us on this trip - to the Roof of Africa - was Dr. Ladislaus Chang'a, currently the Acting Director of Tanzanian Meteorological Authority.

Conditions are currently very dry at the summit. Meager high-elevation precipitation during the 2023 long rains (March-May) resulted in no snow accumulation within the caldera as the dry season began in June. By then, any snowcover remaining on glacier surfaces was continuing to thin, although without telemetry or observations, recent changes in surface mass balance remain speculative. Through June, July, and August, isolated patches of snow on Kibo's flanks have been ablating, as shown in the timelapse below - from very little, to almost none!

During this next visit, extensive glacier photography will help us better understand changes at the Northern Icefield (compare with image above). Lesser Penck Glacier (compare with image below), Furtwängler Glacier (compare with image above), and what remains of the Southern Icefield (compare with image below). Glacier images from this October will be posted here after fieldwork.

September and October fieldwork will have two objectives. The first task will be to recover AWS data from the station, extending the weather record which began over 23 years ago. These data are being stored in memory on-site, even if power to the station has been lost. In addition, the weather stations and ablation stakes (photo below) will be removed from the mountain. Both stations tipped over last year, ending the interval of high-quality measurements. Continuing a trustworthy climate record would require replacing instruments and electronics, along with sufficient funding and dedicated personnel willing to perform regular inspections and service.

Stay tuned for updates!

 

Northern Icefield weather stations, and adjacent stakes to measure ablation

Lesser Penck Glacier extent, 1930 to 2008 - continuously shrinking

Southern Icefield, 2003 (GoogleEarth image)

Summit without snow

Kibo's summit is currently snow-free, towards the end of the dry season. The two images below from the ESA Sentinel-2 satellite show virtually no snow on the mountain - the typical situation at this time of year. Back in 1889 on his first ascent, Hans Meyer observed that "in October, when all the snowfields had disappeared, there was likewise comparatively little snow to be met with on the ice-cap". This was 133 years ago! These recent images below show clouds over the west and southwest flanks of Kibo, but other white areas are glacier ice.

 

Check back in mid-October to learn more about how these dry-season conditions, and why we were unable to visit the summit weather stations in September. Planning is already underway to get up there again though!

 

Stable weather at the summit

Two months into the 2022 dry season - roughly halfway through - the extent of snowcover has remained remarkably constant. The animation below runs from 12 June through 27 July at a five-day interval (22 July not shown due clouds).

Although mass loss continues, the low rate of ablation suggests cold and dry conditions at the summit, supported by the lack of convective clouds seen on these images. With such weather conditions, sublimation is the predominant mechanism of ablation, requiring eight times more energy per unit mass lost.

Typically, an increase in atmospheric moisture marks the transition between the dry season and short rains, yet for much of eastern Africa the pattern has been disrupted in recent years. David Nash details the current and forecast situation in a short article for The Conversation.

We will be back on the mountain in September! After a 2-year COVID hiatus, we are eager to observe the glaciers, recover meteorological data - and provide a new perspective on Kilimanjaro climate variability and change (stay tuned)!

 

Kibo 2022 Dry Season begins

Throughout eastern Africa the dry season is getting underway, a period of 4-5 months with minimal precipitation. June typically begins with complete snowcover on Kilimanjaro, resulting from the March-May rainy season, which in some years supplements January snowfall events as well as snow deposited during the November-December short rains. With reduced cloud cover and lower temperatures on the mountain during the dry-season months, snow gradually sublimates and melts. This annual cycle of snowcover was roughly defined by the late 19th century:

Although Kilimanjaro lies near the equator the extent of its ice and snow varies with the season. The southern summer (December to May) is also the rainy season in the Kilimanjaro region, and it is then that the accumulations of ice and snow are greatest. In the southern winter (June to November) there is a comparative dearth of moisture, the snowfall is proportionately slight, and the process of melting goes on rapidly; hence, by the end of the season, the accumulations of ice and snow are at their smallest.
    Hans Meyer, Across East African Glaciers (1891)

Snow currently blankets only about half of the summit caldera, and only the southern flanks - as illustrated on the satellite image above, from last week (2 June). Within the caldera, this pattern of accumulation has remained quite consistent through the 2022 long rains. More noteworthy is that accumulation is clearly less than normal. Compare this year's snowcover with that of 2020 and 2018 in these images:

In a larger spatial context, snowcover on Kilimanjaro following the long rains is illustrative of the "current extreme, widespread, and persistent multi-season drought (1)" affecting East Africa, particularly in Kenya, Ethiopia, and Somalia. The figure below depicts only the most-recent wet season precipitation, as the satellite images also reflect. A joint statement by the World Meteorological Organization, UN Food and Agriculture Organization, and others states that "The 2022 March-May rainy season appears likely to be the driest on record, devastating livelihoods and driving sharp increases in food, water, and nutrition insecurity" (1). In addition, East African air temperatures have been higher than normal, and these are forecast to continue through the forthcoming dry season.

source

The current drought to the north of Kilimanjaro is both a direct and indirect consequence of climate change, and climate variability. Factors include a multiyear La Niña event (2), a longterm decrease in Long rains precipitation, more intense and severe extreme events, as well as changing large-scale patterns of convection and subsidence, driven by Sea Surface Temperature (SST) anomalies in the Indian Ocean.

Decreased snowcover on Kilimanjaro during the 2022 dry season will hasten ablation of the glaciers. Comparing the current satellite image with those of snowier years dramatically illustrates the role of snowcover in determining the reflectivity of solar radiation. Without snow, the dark volcanic surface absorbs radiation, heats up, and radiates longwave radiation to the air and adjacent ice. Kilimanjaro's summit is 5000 m above the drought-stricken plains below (primarily north of the mountain), providing information on the climate system from the mid-troposphere. These shrinking glaciers serve as a constant reminder of the importance of precipitation to human and natural systems.

A glimpse of the receding south-side glaciers

Delineating Kibo's southern slope glacier margins on satellite imagery has been difficult in recent years. This is because snow cover has persisted on both the glaciers and adjacent surfaces (see one dramatic example here). While the coverage is relatively uniform following snowfall events, ablation subsequently creates a patchy mosaic, reflecting variable snow depth (e.g., due wind redistribution) as well as topographic shading, slope, and aspect.

The issue of glacier margin delineation is nicely illustrated by the image above (Sentinel-2, acquired 19 March 2022). The southwest quadrant of the image is obscured by clouds. North of the Reusch Crater, most of the white pixels depict patchy snow cover, excepting the two remaining portions of the Northern Ice Field (NIF; labeled). The NIF southern and eastern margins are partially visible due to ablation adjacent to the near-vertical ice wall, a typical situation observed days-weeks after snowfall events.

South of the crater, Furtwängler Glacier is only ice mass entirely within the caldera, shown within the red ellipse on the image above - and likely appearing slightly larger than reality, due adjacent snow. The white arc on the image south of the crater is entirely snow, extending from west of Uhuru Peak (yellow triangle) to east of Gilman's Point (green triangle). The southern margin of this arc coincides with the steep caldera rim; snow on the north side is shaded from sun during the boreal winter, yet almost entirely ablated on the south side.

The white patches high on the southern slope, above the yellow lines, are primarily glaciers:  Kersten Glacier fragments directly south of Uhuru, the tiny Decken's Glacier finger to the east, and remnants of Rebmann Glacier just left of the label. Lower on the slope, below the yellow lines, we see a mixture of both snow-covered rock, and glacier fragments with snow cover.

Although the southern glacier margins cannot be precisely located on this image, it reveals that recession has continued despite relatively snowy conditions in recent years. For example, compare the image above with this view from July 2009.

With luck, we'll be back on Kibo in September, for a first-hand look at changes since our last fieldwork in February 2020 (including a Red Bull film).

 

Caldera glimpse with decreased snowcover

Our most-recent fieldwork at Kilimanjaro summit was in February 2020, as the global pandemic began. Since then the mountain has been unusually quiet, with many guides and porters unemployed. They are as anxious as we are to get back up the mountain! Although satellite imagery allows us to assess some changes on the mountain, it is no substitute for on-site measurements and observations. Our reliable instrumentation on the Northern Icefield was functioning 18 months ago, yet the current status is unknown.

The image above was acquired by ESA's Sentinel-2 two days ago, revealing perhaps the least snowcover in several years. Such a view is especially valuable, as distinguishing between snow and ice on imagery is difficult. Clouds of course also complicate interpretation, and in this case case there are scattered clouds visible over the Northern Icefield's northern remnant, within the Breach on the west side, and over low-elevation portions of the southern glacier remnants. On visible portions of the south side, residual snow is estimated to comprise roughly half of the bright patches (i.e., non-glacier).

Noteworthy changes apparent in this image include on-going shrinkage of the Furtwängler Glacier (see above). The extent of south-side glaciers has clearly decreased, even acknowledging residual snowcover. At the Northern Icefield, the east end appears to have experienced the greatest change, due generally-thinner ice and a less-linear margin. In addition, several locations suggest that areas of anomalous geothermal heat are involved with ice loss, an ablation mechanism we have documented elsewhere at the summit. Further information on these new features will hopefully be forthcoming soon from Tanzanian collaborators.

Late April snowcover

Satellite imagery of Kilimanjaro from the European Space Agency's Sentinel-2 is available every five days. Yesterday's nearly cloud-free image (28 April, above) and that from 23 April nicely bracket the time period when Tropical Cyclone JOBO approached the coast of Tanzania. On the 23rd, thick clouds obscured the mountain - except for the crater and a pie-shaped slice to the west, which are nicely visible.

Comparing these two images suggests essentially no snow accumulation on the mountain during the 5-day interval. The pattern of snowcover yesterday resembles that on the mountain since mid-January. Depth appears to have been thin at times when the snow-covered area was greater (i.e., following snowfall events). In general however, there currently appears to be less-than-average snowcover on the mountain, with another month remaining in the long-rains wet season (March-May).

It will be interesting to learn where the highest precipitation totals were recorded during JOBO.

For reference on the image above, Kibo Hut on the Marangu Route is visible within the orange circle (above), while the yellow ellipse highlights Barafu Camp. Trails leading toward the crater rim are faintly visible in both cases.

 

Seasonal change

Snowcover within the Kibo caldera may have reached an annual minima last week. The two-image Sentinel-2 timelapse above shows the same area, five days apart.

The mostly cloud-free image on 4 November depicts the largest extent of snowfree area for calendar year 2020. Nonetheless, note the extensive snowcovered area east of the Northern Icefield and north of Reusch Crater; this was evidently an area of higher accumulation during the previous wet seasons. South of Reusch Crater, white areas within the caldera are all patches of snow - with the exception of one remaining fragment of Furtwängler Glacier, the east-west oriented body just south of the extensive snowfree area. On the caldera's south side, snowcover blankets the south-southwest facing slope and delineates the rim, closely paralleling the trail from Stella Point to Uhuru Peak. Encompassed within this area are the upper fragments of Kersten and Deckens Glaciers, with less-continuous snow around the Rebmann Glacier. Below the upper south-side glaciers is a steep, 100-150 m band without snow, then patchy snow and the snowcovered lower fragments of the Kersten and Deckens Glaciers.

Snow blankets the entire upper portion of the mountain on 9 November, as visible in the second image (despite a thin cloud veil). This snowfall event is "right on schedule" in terms of the precipitation climatology for high elevations of Kilimanjaro. This would be a fascinating time to be up there, for a survey of snow depth and spatial variability...

Fires extinguished, snowcover continues to decrease

I hear from friends in Mweka that wildfires on the mountain are now out, thanks both to some rain, and hard work by personnel. They burned quite close to the Mweka (descent) trail, just above the upper forest line, a zone which has been severely impacted by fires and climate change in recent decades (see Andreas Hemp reference within this link). A helicopter pilot from Kenya was able to provide valuable assistance to firefighters for several days.

Today's satellite image - and that of 20 October - shows considerable cloud cover on the mountain, as expected at this time of year. A "hole" in the clouds does reveal the caldera's west side, and much of the Breach, to now be snowfree.

The next clear view of the mountain will be posted here. Will any seasonal snow persist to the next period of accumulation? Stay tuned!

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.

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].

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...