Tuesday, January 31, 2017

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!

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.

Tuesday, December 15, 2015

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.

Tuesday, December 8, 2015

Snowy November, slope glacier changes

During the month of November, net snow accumulation on the Northern Ice Field amounted to 19 cm. During this very strong El Niño year we expect additional snowfall through at least December, as the short rains continue. The image above shows fresh snowcover as seen from Moshi just after sunrise this morning (8 December 2015); thanks as always to Simon at SENE for keeping us updated.

Some readers may recall seeing other photos from Moshi posted here previously. Despite slight differences in lighting and snowline elevation, at first glance these appear quite similar. However, even at considerable distance, with thin snowcover, and a short 1-2 year timespan, changes in the glaciers are apparent upon close inspection.

Here are links to approximately the same view, one year ago (5 Dec. 2014; lower photo) and two years ago (24 Nov. 2013).

Three locations at which change is evident are labeled on today's image, including 1) Heim Glacier, a remnant of ice which was recently contiguous with ice to the left, and not long ago flowed nearly from the crater rim (as the Deckens does today); 2) Kersten Glacier, showing overall shrinkage in area with increasing separation of the upper and the slope remnants; and 3) Deckens Glacier, which will very soon become disconnected from the upper portion. All of these glaciers formerly comprised the Southern Ice Field.

Recession of other glaciers on Kilimanjaro also continues, based on annual field observations, GPS mapping, and imagery. The Furtwängler Glacier, for example, has been reduced to 4 fragments and continues to thin. At the Northern Ice Field - Kibo's largest ice body - the vertical margins continue retreating (ablating), and thinning of the glacier in some locations is creating new holes. Somewhat surprisingly however, this is not the case at the highest, flat section of the glacier. At the AWS, the 19 cm accumulation increase during November brings the ice surface to exactly the same elevation as it was on 1 Oct. 2011, meaning that the specific mass balance of that section has been neutral for 4 years! This portion of the Northern Ice Field will almost certainly be the last ice to disappear from the mountain.

Tuesday, September 29, 2015

Clouds and humidity

Here is another view of the constantly-changing clouds we watched September 13th on Kibo, ascending from Karanga to Barafu Camp (see below or here for the image posted last week).

According to our Northern Ice Field AWS measurements that morning, wind speeds were rather modest at the time (~7 m/s); data from NCEP (see below) agree reasonably well. The image above suggests a sharp boundary between small parcels of air with contrasting moisture content, and as shown by the image below - with Kibo's location indicated by the green circle - humidity at 500 hPa (summit level) was variable that morning. The humidity contrast is even more pronounced at the 700 hPa level (see image; brown color is less than approx. 20%, cyan blue is greater than ~95%).  Although wind speeds were low by all measures, direction varied with altitude. We were watching cream be added to coffee, in slow motion.

 The spell-binding display we witnessed was no doubt the result of numerous interacting factors, in addition to these. Mountain fieldwork is always interesting!

One additional image showing NCEP humidity data follows. Note the high humidity (blue) at 500 hPa over a broad area around Kilimanjaro. Interestingly, my field notes early that morning read: "Humidity increased during the night; the air feels and smells different, and both sides of the tent fly are frosty. Sky clear." Later that afternoon we experienced a snow squall which blanketed the summit crater with ~5 cm of new snow (image 5, previous post), our only precipitation of the expedition.