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)

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)

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...

 

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.]
 

19 years on the Northern Icefield

This week marks 19 years since AWS measurements began on Kilimanjaro's Northern Icefield (NIF). With enthusiastic help from our Tanzanian crew, Mathias Vuille and I installed a tower into the ice and connected the electronics. Remarkably, the same datalogger continues measurement and control functions, and the same solar panels continue to provide power. Most sensors have been swapped out for recalibration or replacement, yet the original barometric pressure sensor continues reliable measurements every hour.

Ice ablation since 2000 has substantially reduce the areal extent of all glaciers on the mountain. However, this portion of the NIF has "only" thinned by ~5 meters, because the low surface gradient retards meltwater runoff - which then refreezes in place as superimposed ice. Other portions of the NIF, and other glaciers, have thinned more dramatically. For example, ice no longer remains at February 2000 drill sites on the Furtwängler and Decken Glaciers, which were 9.5 and ~20 m thick at the time (respectively).

March snow

The first week of March brought a net snow accumulation of nearly 50 cm to the Northern Icefield, which by any measure is a snowy interval on Kilimanjaro. This precipitation follows 25-30 cm of continuous ablation during February, as illustrated in the previous post. A context for the event follows.

Figure 1 (below) shows Sentinel-2 satellite images of the exact same scene, on the last day of February and on 5 March. As detailed in another post, snowcover was primarily confined to steep north-facing slopes by the end of February. Although considerable cloud cover is present around the mountain on the 28 Feb. image, the summit caldera is mostly cloud free. Note the red squares, which are co-located on the 5 March image for orientation. High clouds partially obscure the March image, yet pervasive snowcover is visible. A sharp snowline at ~4,400 m is visible on the left-hand side of the image.

Figure 2 provides two snowy views of the mountain from the Moshi area (SENE credit). Despite low resolution of the 3 March image (upper), substantial snowfall obviously occurred since the satellite image acquired 3 days earlier. Snowcover appears to be somewhat more uniform than it was on 8 March (lower) - consistent with the timing and magnitude of snowfall recorded at the summit weather station.

At the Northern Icefield, satellite telemetry (Argos) shows ~12 cm of accumulation on 2 March, ~15 cm on the 3rd, and ~5 cm on each of the next 4 days. The precision of these daily totals will be improved when higher temporal resolution data are recovered from the automated weather station. Due to the diurnal cycle of climate on the mountain, some ablation likely also occurred on most of these days and is probably responsible for the patchier snowcover on the 8 March image.

A fascinating element of this snowfall period is provided by a depiction of regional-scale circulation (Fig. 3; Cameron Beccario credit). Here, airflow on the morning of 4 March is illustrated at the 500 hPa pressure level, equivalent to Kilimanjaro summit elevation. Airflow at this level appears to have been influenced by Tropical Cyclone Dumazile beginning on the 2nd as the storm intensified, continuing through about 7 March. The relationship between Kilimanjaro snowfall and cyclones in the southwest Indian Ocean is being investigated with collaborators Thomas Mölg and Emily Collier (Friedrich-Alexander University), along with Timba Nimrod.

On this figure, Kilimanjaro's location is shown by the green circle. Note the westerly wind, which prevailed through the snowy interval. Wind measurements at the summit (via telemetry) verify this airflow, which is atypical at the summit (only ~5% of hourly means are from 270° ±30°). Riming of the instruments appears to have occurred during the event, causing data loss particularly on the 3rd, 4th, and 6th. Nonetheless, such verification of airflow by in situ measurements is not a trivial finding - for very few continuous meteorological measurements exist from nearly 6000 m with which to compare output from numerical models.

Finally, figure 4 depicts circulation and humidity on 3 March. Here the highest humidity is shown in cyan color, suggesting a Congo basin origin for this precipitation event.

18 years!

At the summit: days #92-96 in the crater

This month we returned to Kilimanjaro's summit glaciers and automated weather stations, 14 months since our last visit (Aug. 2016). Yes, the changes were dramatic - everywhere we looked.

This post provides a few glimpses of the remaining ice, still incredibly beautiful. Once an initial inspection is done on recovered AWS data, a subsequent post will provide an overview.

Helping out on this fieldwork were Spencer and Chang'a (Fig. 1). This was both of their first times on the mountain and both brought new insights and questions, providing stimulating discussions during the ascent and in camps. Dr. Ladislaus Chang'a is Director of Research and Applied Meteorology at the Tanzania Meteorological Agency (TMA), and involved with the IPCC. He will be coordinating our new data- and information-sharing collaboration with TMA, hopefully as part of WMO's Global Cryosphere Watch.

As previous entries have mentioned, the past year has been drier than normal at the summit. Decreased albedo has resulted in considerable ablation of both vertical and horizontal surfaces. Indeed, ice loss at the surface caused an unprecedented number of ablation stakes to melt out, and the tipping of several instrument towers. With essential support from our Summit Expeditions (SENE) crew (photos here and here), the towers were reset after 4 nights camped at the summit (see Fig. 2 & 3) and everyone descended safely.

The Furtwängler Glacier provides one illustration of the speed with which glaciers are shrinking on the mountain (Fig. 6). Since February 2000, when Henry Brecher determined the glacier area from aerial photographs, more than 80 percent of this glacier has disappeared. A brief historical perspective on this glacier is available here. The linear rate of area decrease suggests that there will be nothing left of the Furtwängler by 2025.

Many thanks to longtime collaborator Thomas Mölg for helping to support this fieldwork!

Figure 1.  Spencer Hardy and Dr. Ladislaus Chang'a at Barafu Camp (4,670 m), our fifth night of the ascent.

Figure 2.  Looking west over the Northern Icefield. Visible instrumentation includes (left to right) a timelapse camera, high-accuracy temperature and radiation measurement (Climate Reference Network compatible), and the original AWS. Several ablation stakes are faintly visible in the area around the instruments. See next image for detail.

Figure 3.  Northern Icefield instrumentation site at ~noon, looking toward Uhuru Peak on left skyline (2 km distant). This cloud pattern represents typical diurnal development, with convection to the south and west, and rising up the Western Breach.

Figure 4.  Detail of Northern Icefield surface near the AWS, with small nieves penitentes formed since the 2017 long rain season. About 35 cm of the ablation stake is exposed. Between the penitentes is new snow from the previous evening. Also note the area of dirty ice to the right of the stake; the character of all glacier surfaces on Kilimanjaro is spatially heterogeneous and varies tremendously from year to year.

Figure 5.  Rapidly shrinking, east-end remnants of the Northern Icefield, likely once part of an ice body shown in image #95, here.

Figure 6.  The view north from near Uhuru Peak. Northern Icefield in the background, still 40+ meters thick, and the Furtwängler Glacier (foreground); Reusch Crater sloping up to the right. The Furtwängler ice area is 32 percent less than it was just two years ago (Sep. 2015). See image #115 here for the same view in 2013.

Figure 7.  The remaining ice of the former Eastern Icefield, ~1.5 km distant to the northeast.

Figure 8.  Upper Deckens Glacier near Uhuru Peak, one remnant of the former Southern Icefield. Compare with image #33 here from 2009, when the Decken and Kersten Glaciers were still connected. The upper sections of these dirty south-side glaciers provide dramatic evidence for the processes of both sublimation and melt.

Figure 9.  The upper Rebmann Glacier, not far from Stella Point. The recent break-up here has been rapid, associated (in part) with marginal lake formation and drainage; note several areas of buried ice. On the right-hand side of the image, note how the ice stratigraphy more-or-less parallels the slope, yet the ablation surface is nearly horizontal. Selecting sites to obtain ice samples for age dating of these glaciers, or for ice core drilling, is not a trivial issue.

Figure 10.  Looking east from camp, just after sunset. One of the views which keeps us going back!

The value of a photograph

Measurements from our Northern Icefield AWS are transmitted to us in near-real time via the Argos system, which has proven to be extremely reliable. Telemetry is especially valuable for stations such as Kilimanjaro, for safely conducting fieldwork at 5,700 m requires considerable time simply for acclimatizing. With access to data by telemetry, conditions on the glacier can be monitored remotely, which saves on logistical costs and aids in fieldwork planning.

The figure above illustrates one measurement provided by telemetry: changes in glacier surface height. Decreases in height are due to ablation, the combined impact of melting and sublimation. Height increases are due to snow accumulation. Over time, the plot reveals both seasonal fluctuations of Northern Icefield surface height, and the on-going thinning which has been underway for decades.

For the time interval since June 2015, the bimodal wet seasons are depicted in green (Vuli = 'short rains', typically November & December) and in blue (Masika = 'long rains', typically March-May). Red circles represent the times of fieldwork in September 2015 and August 2016, and a recent visit described below. On the figure, note the lack of accumulation during the 2016 short rains, discussed in prior blog entries. Without much snowfall to add mass and brighten the glacier surface, ablation resumed in January 2017 at a rate similar to the dry season; this is not normal!

The lack of 2016 short rain precipitation on Kilimanjaro was at least partially due to a temperature contrast between the eastern and western Indian Ocean - the Indian Ocean Dipole - depicted above. During the NH summer, high ocean temperatures in the east led to more evaporation and cooling of the moister atmosphere. Easterly airflow over the western Indian Ocean resulted in less convection and less moisture delivery over East Africa during the short rains. In addition to less snowfall on the glaciers, the IOD is contributing to drought and famine in East Africa to the north of Tanzania. With over 10 million people facing food insecurity or worse, the consequences are profound (e.g., see here).

Back on the Northern Icefield, an on-site image from the AWS has provided information which measurements cannot. The image above was sent by Thomas Lämmle, who is frequently on Kilimanjaro with his company "EXTREK-africa" (website and Facebook EXTREK.AFRICA). Thomas' photo confirms the extent of ablation over the past couple months following the failed short rains. With great relief, the AWS tower appears to have remained nearly plumb, despite slackening of the guy cables. Also visible in the image are 3 ablation stakes (within blue ellipses) whose heights have been measured upon every prior visit.

Compare Thomas Lämmle's image from last month with a similar perspective ~17 months earlier, in September 2015 (below). From measurements at the AWS and the ablation stakes, we know that there was little net change in surface height between Sep. 2015 and Aug. 2016. The top figure also reveals that there was indeed no net lowering between Oct. 2011 and July 2016 (see y-axis). Not coincidentally, the AWS tower last required resetting in 2011 - the previous IOD negative event which was also associated with severe famine in East Africa, claiming 260,000 lives (link here).

Combining AWS data with photogrammetric ablation stake measurements reveals a glacier surface lowering of 40-45 cm between Sep. 2015 and the end of last month. Thanks to this recent photograph, we know that the AWS remained vertical as March began. Hopefully the long rains will bring new accumulation, which is the critical control on surface ablation at the Northern Icefield.

Thank you, Thomas!

Climate measurements on the Roof of Africa [updated]

Several radiometers used on Kilimanjaro AWS are made by the Dutch company Kipp & Zonen. Coincidentally, they were all transported to Tanzania aboard Royal Dutch Airlines (KLM).

The Kipp & Zonen website has just published an overview on Kilimanjaro, our climate studies, and why it is such a great place for climate research. The article contains several images and discussion of the following plot. Intrigued? Check it out here.

[UPDATE 5/5: A more-detailed version of this overview appears in the April edition of Meteorological Technology International - a very interesting trade publication. A link to just the 4-page article with photos is available here.]

(This is blog post #100!)

2013 Fieldwork Images

A gallery of images depicting our recent fieldwork is posted here. (Viewing these requires the freely-available Adobe Flash Player web browser plug-in, which usually works consistently across browsers on a broad range of devices.)

The objectives of our work all pertain to climate and glacier research at the summit:  recovering climate data from automated weather station instrumentation; inspecting, servicing, repairing and replacing equipment; and making both observations and measurements of the summit glaciers. However, other aspects of the fieldwork are disproportionately represented by the gallery - primarily because carrying out the research objectives requires staying alive and functional for several days at an elevation of 6,000 meters (19,000 feet). Doing this necessitates ascending slowly to allow both our bodies and those of our Tanzanian helpers to acclimatize (~6 days). Once on the summit glaciers we then become too busy and/or cold to spend much time taking photos!

For 2013 work - as the images illustrate - we began in Arusha, traveled to West Kilimanjaro, ascended the Lemosho Route, slept 3 nights at the summit, and descended via Millennium Camp to Mweka. Logistical support is required of all groups on the mountain, even with research permits, and ours was provided by SENE (Summit Expeditions and Nomadic Experience). This support allows us to maximize our time preparing for and carrying out the research.

As always, we would like to thank everyone at SENE for another safe and productive round of fieldwork - and for the two-way transfer of knowledge that characterizes these experiences. We would also like to acknowledge invaluable assistance from the staff at Tanzania Wildlife Research Institute (TAWIRI) who oversee and manage all wildlife and environmental research in Tanzania, the staff at Tanzania National Parks (TANAPA), and the many wardens and other staff at Kilimanjaro National Park. Asanteni!

Monthly weather synopsis

A monthly summary of summit weather has been available here for many years. Beginning with October 2013 the mean values for air temperature and relative humidity will be from a different sensor, and thus are not strictly comparable with those from prior months. Although the difference is likely to be only a few tenths of a degree, users should be aware of the change.

The reason for the change is that we decided to remove the fan-aspirated sensor during October fieldwork. The radiation shield housing this sensor had known systematic errors, and our technique of intermittent aspiration created additional problems. So, after 3 years of overlap with the CRN-compatible shield and sensors (T and RH), the time had come to remove this instrument.