Sunday, December 18, 2016

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...]

Wednesday, September 14, 2016

2016 Fieldwork

Fieldwork! This year we were on the mountain slightly earlier than in recent years - during late July into early August, the core of the dry season. Our primary objective was recovering AWS data and servicing instrumentation, as well as measuring the network of ablation stakes. In addition, photographer Ian Van Coller (Montana State Univ.) was along to document the summit glaciers and shoot portraits of the Tanzanians joining us; check his wonderful photos on Instagram and his website. Fantastic logistical support was again provided by the SENE team (Summit Expeditions and Nomadic Experience)!

Below are some images from the fieldwork, with brief captions. Feel free to contact us with any questions.

1.  Kibo (left) and Mawenzi (lower peak to right) viewed from the highway west of Moshi, looking up 5,000 m through relatively clear air. The maize crop near Moshi was ready for harvest, much later than those in "home garden" villages at higher elevations on the mountain.

2.  Early-evening transport of freshly-harvested maize.

3.  At Mbahe Farm; young banana tree and us not-so-young mzungos.

4.  Mbahe Farm's cheerful, attentive, and unflappable host Wilson.

5.  Friendly Mbahe children, a highlight of every visit.

6.  On day 2 of our ascent up the Umbwe Route: Ian photographing one of our first Kibo views.

7.  Barranco Camp (4,000 m) is certainly worthy of the crowds, but fortunately for us it was one of the only camps we shared with other groups. And in case you are wondering, there are at least 137 tents visible in this image!

8.  Two south-side glaciers on Kibo:  Kersten on the left and Deckens on the right. Both have thinned and retreated dramatically in the past couple years. Note that seasonal snow is also visible - in addition to the ice - above ~5,500 m. 

9.  Glaciers slightly to the north of those above, along with the Western Breach on the left-hand side. Most interesting in this late-afternoon view is a small waterfall of meltwater, barely visible at the cliff base, just left of center. 

10.  Northwest of the Breach, Uhlig Glacier was depicted on the earliest maps of Kilimanjaro's glaciers. Contrary to what one might read on the web, this glacier endured until sometime within the last year. Although a minor ice body, the Uhlig hadn't changed much in recent years due to topographic shading and persistent, local cloud cover. The two images below are from slightly offset perspectives, yet the glacier is clearly now gone...

11.  Our ascent this year came up the mountain's north side from Pofu Camp. The final campsite on this dry, rather difficult route was a scenic perch at 5,200 m looking north to Amboseli National Park, with Mawenzi just barely visible in the other direction (over the ridge; see below).

12.  Simon Mtuy ascending toward the camp shown above.

13.  Summit glaciers! Reaching the crater rim on this trip was especially rewarding after our scramble up. Beautiful lighting then brought Ian's progress to a screeching halt.

14.  Our camp beside the Northern Ice Field. Dramatic retreat of the glacier continues all around the margin. Ironically, the mass balance on flat horizontal surfaces has been near-neutral for the past 5 years, and in places the ice is still 40+ m thick!

15.  Detail of the Northern Ice Field margin. This particular section provides an atypically-clear view of ice stratigraphy in the upper portion of this glacier. Except for a very thin veneer, this is all dense glacier ice, not firn.

16.  Another perspective on the Northern Ice Field margin, with Simon for scale.

17.  Upper margin of the Deckens Glacier, along with seasonal snowcover and a frozen meltwater pond. Dust accumulation - some of which is due climbers heading to Uhuru Peak - results in very low albedo on the vertical surface, leading to considerable absorption of solar radiation each morning.

18.  A distant view of steadily-shrinking Eastern Ice Field remnants, 2001-16.

19.  A fragment of Furtängler Glacier, vanishing without a trace almost before our eyes. A larger remnant is shown in this GigaPan image, which will soon be the only way to explore this glacier.

20.  Mawenzi from near Uhuru Peak, with convergence of trails at Stella Point.

Thursday, March 10, 2016

Synopsis of 2015 Short Rains


The two images above are both from the same scene, acquired by NASA's ALI sensor (Advanced Land Imager) on 2 January 2016. The upper image shows the 3 Kilimanjaro massif components; the distance between the Shira Plateau edge and the summit of Mawenzi is ~30 km, demonstrating how large the mountain is. In general, snowcover persists for more than a few days only on Kibo, as seen here in the bluish color.

The second image illustrates the difficulty in distinguishing between snow-covered ice and transient snowcover on the volcanic surface. This difficulty has created confusion even among remote sensing experts. One example is here; although the text no longer purports to show receding ice, NASA refuses to kill this deceptive pair of images.

Shown here is the result of the 2015 Short Rains, which this year were of 6 weeks duration, extending from the second week of November to mid-December. A net height change (i.e., snow accumulation) of 32 cm was recorded at the AWS for the season.

Subsequently, January and February each saw one wet interval lasting 10 and 7 days respectively, and resulting in 8 cm then 12 cm of net height change. Not much snow relative to week-long wet intervals on other mountains, yet these were cloudy and humid periods. A beautiful view of the summit crater (below) was taken just prior to the February snow, over two weeks after the January event ended. Thanks to Alex Schwap of Salzburg for sharing this! Only tiny portions of glaciers are visible in Alex's photo (on horizon), demonstrating that minor snowfall events are preserved only in areas of topographic shading and on the glaciers.

By March 1st the AWS glacier surface was ~18 cm higher than when the Short Rains began in early November. This height change is less than the sum of events due to a combination of densification of the snow and ablation by sublimation. Melting of the newer snow also likely occurred, yet some of the meltwater probably percolated through the snow and refroze upon coming in contact with the less-permeable ice.

This new snow will keep the glacier surface albedo relatively high, serving to protect it against mass loss until the Long Rains begin.