Kibo Weather Stations - 23 years later

Our team is just back from difficult-but-stimulating fieldwork on summit glaciers, documenting Kibo's climate. Initial instrumentation at our weather station was installed in February 2000, then gradually supplemented and expanded. The configuration by 2013 is shown above. After near-annual maintenance and observation visits through 2017, we visited the stations for a Red Bull film in 2020 and then could not get back during the pandemic. Fieldwork in 2022 was foiled by bureaucratic miscommunication. By September of 2023, negative mass balance resulted in tipping and damage of equipment - the extent of which will soon be revealed by analysis of recorded data.

All the hardware, instrumentation, and ablation stakes have now been removed from the mountain and the National Park. As will be detailed in subsequent posts here, this was accomplished despite delays in departure, followed by high winds and riming precipitation. Removing everything required multiple trips to the summit by our accompanying crew, as well as an additional 19 porters to move equipment down the mountain.

We dedicate our 2023 mission to the hundreds of porters who have been essential to the success of this research since February 2000. They did the hard work transporting everything up - and then down - 5,000 meters of elevation, keeping us cheerful (most of the time) and productive. Perhaps most impressively, they were integral to a perfect safety record through the entire study. On this latest trip, we crossed paths with numerous porters from past trips, and spent time with one who was along on trip #1 back in February 2000; today he continues working as a respected mountain and safari guide. Also this month, one porter introduced himself as the son of a favorite porter, not yet born when his dad started helping. Asante sana to all the porters, guides, cooks, drivers, and support staff who have been involved - from Keys Hotel, Marangu Hotel, and since 2006, Summit Expeditions and Nomadic Experience (SENE).

2023 team:  Doug Hardy (UMass), Mike Winkler (GeoSphere Austria), and Emily Collier (Univ. Innsbruck)

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)!

 

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.

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).

Summit Snow

High elevations on Kibo received an early October dusting of snow, as shown in the Sentinel-2 image above, acquired Sunday. Until AWS data are recovered, we don't know whether this snow resulted from one event, or multiple; five days prior the summit was obscured by clouds, and it was snow-free ten days earlier.

This image reveals interesting information about ice, snow, and clouds. The brightest areas which are labeled are the remaining ice bodies. Increasing fragmentation of what was once the Southern Icefield is readily apparent. Within a few years the Heim and Decken Glacier will likely be gone, followed shortly thereafter by the Furtwängler.

Almost all other bright areas - of various sizes and shapes - are new snow (e.g., southeast of the Reusch Crater). In this scene, note how snowcover is distributed rather symmetrically on the mountain, which is typically not the case for individual snowfall events.

One large bright area to the southwest of Reusch Crater shows relatively-thick convective clouds rising above the Western Breach. Elsewhere, thin clouds appear darker and more variable in brightness, forming a annular pattern around Kibo. These clouds are low in elevation, as evidenced by the visible shadows. This annular pattern is quite common on Kibo, with clouds thickening during the day due to convection. Sometimes, the crater remains cloud-free yet encircled by clouds, if convection dominates over advection (which transports moisture laterally).

Early October snowcover usually persists for only days to weeks, with the short rains not getting underway for at least another month. Nonetheless, such events considerably influence mass balance, as snowcover greatly impacts radiative energy exchanges due, for example, to the higher reflectivity (albedo) of surfaces.

NIF shrinkage: 2015-2019

The right-hand image above depicts Kilimanjaro's Northern Icefield in mid-September (2 weeks ago). Although resolution is not ideal, minimal snowcover allows comparison with the same glacier four years earlier (July 2015). Note that the two images are not perfectly registered, so the following observations are qualitative.

Both the north and south remants of the icefield have decreased in area, especially relatively-thin portions at lower elevations. These include the northwest part of the north remnant, and the western margin of the southern part. A marginal meltwater lake is visible at the southern margin of the north portion on both images, and has been present for many years. At the eastern edge, we have observed shrinkage of several isolated blocks of ice over the years; these were present in 2017, but have now disappeared. On the south portion, thin areas and holes in the left-hand image are now ice free, including one location (southeast margin) where we have evidence that geothermal heat initiated hole formation.

The rate of glacier thinning was reduced during 2018, due to above-normal snow accumulation and the attendant increase in albedo. To illustrate, note the brighter, high-elevation portions of the glacier in the 2015 image; this is snow cover over old glacier ice.

We are hoping to visit the summit glaciers early in 2020 to measure ablation stakes, conduct GPS surveys, and photographically document changes to the glaciers since our last visit.

Dry-season forecast: above-average ablation

The long rains (Masika) of 2019 are concluding with virtually no snow accumulation on Kilimanjaro glaciers, in stark contrast to last year's long-rain season - demonstrating the extreme interannual variability of precipitation at the summit.

The Sentinel-2 image above from 2 days ago (14 May) reveals a largely snow-free crater. Small areas of last year's snow persist (e.g., east of the Northern Icefield, adjacent to the Furtwängler Glacier). Elsewhere, only a dusting of snow can be seen on Kibo's south side - which not coincidentally spans the elevation range and azimuth of remnant glaciers there! (Very preliminary analysis suggests that the responsible snowfall event was somewhat more extensive, yet we know that at this SSW sector of the mountain, convection enhances snowfall and clouds reduce ablation.)

During the long rains last year - extending from 27 February until this date (16 May) - net accumulation of snow on the Northern Icefield was over one meter (as discussed here). Contrast this with 2019 long rain accumulation, shown in the figure below (blue line); prior to the minor event last week the AWS recorded a net lowering (ablation) of over 30 cm. Additional long rain snowfall may still occur this year, however, the long rains rarely extend into June at the summit.

Absent a major event bringing sufficient snow to reduce solar radiation penetration (e.g., 30-50 cm), the forthcoming extended dry season will probably begin with a snow-free crater. As a result, ablation of both horizontal and vertical glacier surfaces is likely to be dramatic in the months ahead.

(The timelapse image below provides a perspective on summit snowcover since early August of 2018. Within the crater, note the persistence of long-rain accumulation through the dry season, and the ephemeral nature of spatially-extensive-but-thin accumulation during the period February to April 2019.)

2018 long rains review

Nature does not follow calendars... but yesterday marks the typical beginning of the northern Tanzania "long rains season". Coincidentally, the long rains last year (2018) began precisely on March 1st (see earlier posts, beginning with this one). Images acquired on the day prior, both last year and this year, are shown above (Sentinel-2 L1C).

Despite partial cloud cover, both images depict limited snowcover other than on glaciers (e.g., north-facing side of the Uhuru Peak summit ridge, the crater's south rim). Most important to this discussion is that the summit crater (approximately circled) is largely free of snow. The 2019 image shows some recent snow on the northern flanks, which was present to a lesser extent on mid-February images (not shown).

Even limited snowcover at the end of February (images above) is in stark contrast to the same time in 2000. Note in our prior post (link) that a snow shovel is visible; don't be fooled by this, for there was neither snow nor firn anywhere on the glacier or within the crater. Indeed, this was an exceptionally dry period which continued through the long rains of 2000 (see figure below; red line); March through May snowfall that year totaled only 26 cm, the least of any long-rain season in our period of record.

As the long rains concluded in mid-May last year, snowcover on the mountain was extensive - as depicted in a Sentinel image from the 29th (below). Indeed, the daily snowfall total at the AWS for the 2018 long rains was double the 19-year average, resulting in more than 1 m of net accumulation. The graph below shows how anomalous this accumulation (thick blue line; 2001-2017 as thin blue lines, 2000 in red).

With even an average short rains last year (typically Nov-Dec), could crater snowcover have persisted until these next, 2019 long rains? Quite possibly! Instead, the 2018 short rains included just 2-3 minor accumulation events, plus early snowfall during our late October fieldwork (link), for a total accumulation of less than 20 cm. By Christmas, crater snowcover was patchy. Then, despite a mid-January event, ablation predominated; by yesterday (see above) the crater was largely snow-free.

In contrast, the Northern Icefield surface at the AWS gained mass over the past 12 months, increasing in height by nearly 50 cm. Higher reflectivity and less re-radiated longwave energy from below (i.e., ice vs. dark volcanic soil) are among the factors.

In summary, the extent of 2018 accumulation and it's persistence demonstrates the sensitive balance of processes governing Kilimanjaro's summit glaciers. If seasonal snowcover does ever persist in the crater through an entire year, retention will be easier the next year and subsequently become even easier. This idea is explored in Kaser et al. (2010), and 2018 observations strengthen the argument!

Crater remains snowy

Ablation of 2018 snow continues, as evidenced by the 1 October image above. Nonetheless, extensive snowcover remains within Kibo crater as the extended dry season concludes (Sentinel-2 bands 4,3,2). The mountain's south side also remains snowy, making it difficult to easily distinguish between glaciers and snow on the image.

Trails up to the crater and along the rim to Uhuru Peak appear to be free of snow. However, where snowcover remains, penitentes are likely getting steadily larger.

On the Northern Icefield, telemetry of AWS measurements reveals a surface height increase of ~30 cm for the one-year period Oct. 2017 to Oct. 2018. This accumulation was concentrated in three intervals: the first half of January, the first week of March, and a week in mid-April. In contrast, ablation was especially pronounced through the entire month of February this year. 

Whether 2018 accumulation endures will depend upon October and November weather, which typically varies considerably from year to year. Since mid-May, when peak accumulation occurred, the rate of surface lowering due to ablation has been rather constant at ~12 cm/month.

Seasonal snowcover change

 

Two views of Kibo from the plains below reveal that snowcover has largely ablated from the mountain's slopes. From the northeast (upper image) dry slopes appear capped by a fringe of snow on the crater rim, while the Northern Icefield is visible in the second image.

Both images above were taken during the 2018 Kilimanjaro Stage Run, a wonderful way to experience the mountain and the diverse cultures residing on the flanks. Adventurous runners of all abilities should look into this fun event!

Below is another view of snow on the mountain, acquired one week later. Nearly complete snowcover remains within the summit crater, although it appears that the trail to Uhuru Peak is now free of snow. Lower on the mountain, trails and camps are visible in this European Space Agency image.

Despite the extent of snow within the crater, telemetry of measurements from the Northern Icefield indicate that the glacier surface lowered by 15-20 cm, likely due to sublimation, melting, and compression of long-rain snow. This snow benefits glacier mass balance by adding mass and reducing energy exchange (e.g., reflection of solar radiation) - briefly reducing the glacier recession rate.

Kibo remains snowy, as illustrated by the Sentinel-2 image above from 3 July. Over the past month, the snowline has been only slowly moving up the mountain. Accumulation at high elevation and within the crater has been ablating slightly; compare the image above with those in earlier postings.

Extensive snowcover on the glaciers and surrounding slopes is keeping the albedo high, minimizing mass loss... at least for the moment.

Kilimanjaro is not alone in being unseasonally snowy in recent months. For example, in the Karakoram Mountains (Pakistan) climbing teams on mountains such as K2 are finding dangerous avalanche conditions due to heavy snowfall, during the core climbing season. More details can be found here.

Quelccaya Ice Cap and the Cordillera Vilcanota in Peru are also unusually snowy for July, the result of La Niña accumulation during the wet season (esp. DJF) and atypical dry-season snowfall in the past couple months.

In Northeast Greenland, the winter of 2018 brought twice as much snow as the long-term average, and snowcover into early July remains so extensive that Sanderlings and other shorebirds may not even attempt nesting this year. The late snow is having large consequences for the ecosystem.

Finally, snow on portions of the Greenland Ice Sheet is resulting in the "least surface ice loss in decades". As Jason Box notes via Twitter (@climate_ice), these persistent extremes in patterns of atmospheric circulation are an expected signature of climate change.

Dry season begins

One of the most-reliable aspects of Kibo summit climate is when the extended dry season begins; typically between late May and early June. Despite considerable snow accumulation through 2018 long rains (see posts below), the dry season initiation this year appears to be right "on schedule".

Above is a view of Kibo from Moshi just after 7 am on 28 May (Simon Mtuy credit), after a long period in which the mountain was shrouded in clouds. Snowcover has changed little since March.

The timelapse below includes images every 5 days for the past month, from ESA Sentinel-2 L1C data. Note the decreasing cloud cover thickness and extent, and thinning of snowcover on the mountain flanks. Telemetry of measurements from the summit reveals little change in snowdepth on the Northern Icefield through the interval.

In the months ahead, all seasonal snow will likely sublimate and melt, exposing glacier ice to radiant and turbulent energy. Without the bright, protective snowcover, the area and thickness of the glaciers will continue to diminish.

NIF surface, mid-February

Here is the Northern Icefield surface on 15 February, courtesy of Thomas Lämmle (EXTREK-africa). Our two UMass weather stations are visible on either side of the guides, with Mt. Meru in the background.

This image is particularly useful in documenting the glacier surface. Beneath the 2 ultrasonic snow sensors the surface is uniformly flat, with minor penitentes resulting from ablation of January accumulation. Therefore, further changes in height recorded at the station should be nicely representative of accumulation/ablation changes over a larger area.

Since our fieldwork in early October, net lowering of the surface has been ~15 cm. The current glacier surface at the AWS appears to be comprised of transformed seasonal snow, which is considerably brighter (i.e., higher albedo) than the immediately underlying ice.

Further ablation and lowering of the glacier surface will be determined by when the long rains begin, which typically occurs early in March.

January snowcover [updated]

The 2017 'short rains' season brought very little snow accumulation to the summit this year. Although snowfall is often variable during the short rains (typically November and December), this year was especially dry and resulted in a net lowering of glacier surfaces.

Early January brought the first noteworthy snow accumulation to the glaciers since the dry season began in June 2017. The graph above, illustrating January snowfall, is based on snow measurements obtained from the Northern Icefield AWS by satellite telemetry. Such measurements must always be viewed cautiously, as wind redistribution of snow and other factors can complicate data interpretation - yet as average measurements from 2 sensors, their reliability is improved.

Snowfall is critically important to Kilimanjaro glaciers, primarily by controlling the amount of solar radiation reflected from the surface. When a bright snowcover exists, the reflectivity (albedo) is high; aging snow becomes gradually less reflective, and thinning snow allows radiation to penetrate through to the underlying glacier ice.

On the graph above, numbered squares correspond to a selection of natural-color images from the ESA (European Space Agency) Sentinel-2 satellite, shown below. These depict snow accumulation steadily increasing during early January, culminating in the events of 10 and 11 January. With little precipitation through the balance of the month and into early February, the mountain's snowcover then thinned and became patchier.

Here are a few notes on the Sentinel-2 images, which qualitatively demonstrate that Kilimanjaro glaciers are sensitive to the magnitude, frequency, and spatial extent of precipitation events!

Image #1, 30 December 2017:  Clouds to the west of Kibo, filling the Western Breach and obscuring the southern slope glaciers. Within the caldera and south of the crater rim, uniformly-white areas are glaciers (likely with some snowcover). No snowcover is present within the caldera, with only a light dusting on the highest northern slopes, and some accumulation on the north-facing section of the caldera rim (e.g., below Uhuru Peak).

 
Image #2, 9 January 2018:  Extensive clouds, yet uniform snowcover is visible within the caldera. Note the lack of snow on a small portion of Reusch Crater (dark area), where geothermal heat flux is probably responsible for melting any accumulation. The graph above shows that this image represents snowcover prior to the two largest snowfall events of January, on the 10th and 11th.

Image #3, 14 January:  Little or thin cloud cover is present over the Kibo caldera, in contrast to the clouds obscuring the mountain's western and southern flanks. Snowcover is extensive, as suggested by the graph above.

Image #4, 24 January:  Scattered clouds surround the mountain at elevations below ~5,000 m. Snowcover from early January has thinned within the caldera and on the glacier (see graph), and generally become patchier. Albedo of the glacier surfaces remains high, reflecting most of the incoming solar radiation. The Reusch Crater is now mostly snow-free, and limited snow remains within the Western Breach. Climbers going to the summit on this date were likely walking on snow most of the distance above Stella Point.

Image #5, 8 February:  A typical February day on Kibo, with scattered clouds concentrated to the south and west. Snowcover patches within the caldera have shrunk further. Note the almost complete lack of snow on eastern and south-facing slopes; even at only 3° south latitude, solar radiation receipt is greater on south-facing than north-facing slopes in early February!

Image #6, 18 February (not shown on graph):  Without measurable snowfall since image #5 was acquired (see above), the extent of snowcover continues to decrease, lingering primarily on steeper north-facing slopes. During this time the Northern Icefield surface decreased in height by another 10 cm, and with ablation of January snow the surface is likely bare glacier ice once again. On the southern slope of this image, distinguishing between snow and ice is difficult for those unfamiliar with the glaciers, yet these ice bodies were all contiguous only ~10 years ago. As shown below - and explained in the 21 November post - this is no longer the case, as the glaciers continue shrinking.

Sep-Oct Fieldwork

It's time for another visit to the summit glaciers!

Final planning is underway for fieldwork during late September into October, and we anticipate finding dramatic changes since August of 2016. For example, measurements at the AWS indicate that the Northern Icefield surface is more than 60 cm lower than at the time of our 2016 visit - at a location where specific mass balance remained more-or-less neutral for ~ 5 years. With this much ablation (lowering), maintaining vertical towers is difficult, as the middle image below illustrates; by February 2017 the time-lapse camera frame was already leaning, and ablation has continued since then.

Our primary tasks during fieldwork will be to recover AWS data and service the instruments. Almost all towers will probably need to be reset, due to ablation of the glacier surface. We will spend time on both the Northern Icefield, and the south-side Kersten Glacier (see second image).

We will also visit our network of ablation stakes on the glaciers (4th image), updating height change measurements last made in August 2016. Many of these stakes will require resetting, which we do by drilling new holes into the glacier surface.

Finally, we will make observations and measurements at several sites where geothermal heat is causing basal melting, as shown in the lowermost image. Previously-located sites will be visited, and we will search for new ones.

Accompanying us at the summit will be Dr. Chang'a of the Tanzania Meteorological Agency and the IPCC (Intergovernmental Panel on Climate Change). We are looking forward to interesting discussions about Kilimanjaro climate and climate change in general, as we ascend the mountain, attend to the weather stations, and document ongoing glacier retreat.

Snow

The Northern Icefield surface has received badly-needed snow accumulation since mid-February, rising 20-25 cm to approximately mid-October 2016 height. In hindsight, it appears that a minimum height occurred on 18 February, just prior to the photographs posted in the entry below. An early March snowfall event of 15-20 cm was followed by a month of predominantly ablation. A mid-April event then brought new snow, followed by 5-6 days of accumulation up until yesterday and adding 13-14 cm more accumulation. Typically the long rains continue through May, which could partially mitigate impacts of the short rain failure.

Please share recent glacier photos!

Horizontal surfaces on Kilimanjaro glaciers are ablating rapidly at the moment (i.e., melting and sublimating), largely because the 2016 short rains "failed". Typically, a short wet season occurs during November and December, when snowfall at the summit dramatically raises albedo and the associated decrease in net radiation receipt decreases the energy available to drive ablation. During the 2016 short rains, a series of minor snowfall events were sufficient to end a long dry season which began in May, yet once this new snow ablated, the dark, decades- to centuries-old ice surface was exposed again. Ablation began accelerating, and since the New Year, flat areas of the Northern Ice Field have lost ~15 cm of snow and ice.

Snowfall during January and February is usually limited, and quite variable from year to year. Therefore, a high rate of ablation is likely to continue until the long rains begin, typically in March. One wildcard at this time of year due is some tropical cyclone paths in the south-west Indian Ocean, which can result in heavy snowfall on the mountain. This year, however, there has been little cyclone activity in the SWIO region - and indeed, the period 13 December to 31 January is the first on record (since 1960) without a hurricane (cyclone) somewhere on Earth, according to a @philklotzbach tweet.

Anyone visiting Kilimanjaro during February is encouraged to submit photos of the summit area. Any glacier photos would be helpful, especially looking to the south just below Uhuru Peak or across the crater to the Northern Icefield. One weather station is visible near the summit (upper slopes of Kersten Glacier) and another on the Northern Icefield should be barely visible on images taken with a telephoto lens and/or high resolution.

Thank you!

late short-rains [updated]

New snow on Kibo! Simon Mtuy sent this photo, taken 17 December 2016. He comments:  there was considerable rain last night, bringing snow to both Kilimanjaro and Meru; the short rains have started slowly this year.

Stay tuned for an update on snow at the summit. Ablation was greater than normal during October due to the old, low-albedo surface.

[UPDATE 1/3/2017:  Telemetry from the summit indicates that snowfall during the 3-4 days prior to this image was the largest event of December. Nonetheless, only ~4 cm was measured at the AWS. Combined with minor events during both the first and last few days of the month, the net change in surface height for December was ~2 cm. The short rains essentially failed to develop during 2016 at the summit...]

Kersten Glacier margin

This month's issue of KLM's in-flight magazine iFly has some nice photographs of climber Will Gadd, shot on Kibo's summit glaciers by Christian Pondella. One of these is above, showing the upper margin of Kersten Glacier as viewed from Uhuru Peak. Many summit climbers have enjoyed this view, with Mt. Meru ~70 km to the west through very clear air.

Despite continuing shrinkage of Kilimanjaro's glaciers, the steep margins remain impressive. For scale, the climber in this image indicates that the cliff is ~18 m or 60 ft. high. The meltwater lake at the base has been present there for many years. Has anyone ever seen it not frozen?

Most interesting here is how early-morning light highlights the stratigraphy of Kersten Glacier. As other perspectives also show, there are "bands" or "layers" of ice which are darker than those above or below. Thinking back through time, these likely formed when the surface was exposed for a period of time - probably years or decades - either due to no net snow accumulation (neutral mass balance) and/or to ablation (negative mass balance). Instead, dust accumulated and was subsequently buried during an interval of snow accumulation. Now exposed at the vertical wall, the high concentration of dust absorbs more solar radiation than the surrounding, relatively-clean ice, and absorbed energy leads to melting and sublimation -- highlighting the stratigraphy. Such features provide evidence of a complex ice history on Kilimanjaro.