As of today this blog is shifting to the AGU Blogosphere. The blog has the same name and will have the same approach with two blogs a week on a the response of glaciers to climate change, one glacier at a time. If you have been a follower of this blog, please follow there. Note all the posts have been migrated there too.
Thanks for the continued support and interest.
This is a visual introduction to our 31 years of work on Lower Curtis Glacier complimented with Google Earth imagery to illustrate the changes. Each year since 1984 this glacier has received an annual checkup from us, North Cascade Glacier Climate Project. The mass balance and retreat of this glacier is reported to the World Glacier Monitoring Service. Many nights have been spent camped below this glacier. Unfortunately in the last seven years we have had mostly wet weather at this site, that hopefully will not be repeated this coming summer.
Zongo Glacier, Bolivia extends 2.9 km down the south side of Huayna Potosi from 6000 m to 4900 m. Zongo Glacier is a small valley glacier located 30 km north-east of La Paz, and its runoff is directed to an important hydraulic power station which supplies La Paz. Note Laguna Milluni in foreground of the first image. The dam is visible as is the power station to the right and below the lake. The glacier has considerable snowcover on its upper section and crevassing. This indicates a persistent accumulation zone. In 1991 a glaciological research program was established on Zongo Glacier to monitor mass balance, understand its hydrology and energy balance. The long term director of this research Bernard Francou has been called the glacier guardian. The cumlative mass balance of the glacier from 1991-2013 has been -6.5 m water equivalent. The typical Alpine glaciers undergoes a long accumulation period in winter and a short ablation season in summer. The glaciers of the tropical Andes experience snow accumulation during the wet season, austral summer on their upper regions and maximum ablation during the same season low on the glacier. In the dry season winter there is a period of low ablation over the whole glacier. Mean annual air temperature at the long term snowline at 5250 m is -1.5 °C. Mean precipitation is about 0.9 m/year.
Google Earth image-Huayna Potosi and Zongo Glacier
Since 1991 the glacier has lost more than 7 m of thickness and has retreated significantly. The mass balance loss has been most pronounced during El Nino periods. La Nina’s are associated with positive or only slightly negative mass balance. Here we examine Landsat imagery and Google Earth imagery form 1994 to 2014.
In 1994 there is no lake at the terminus of the glacier, red arrow. By 2004 the Google Earth image indicates the glacier terminating along the northeast shore of the lake, a 90 m retreat in a decade. By 2008 the glacier no longer reaches the edge of the lake, but the front is still crevassed. In 2014 the glacier terminates 100 meters from the lake. Total retreat during the 20 year period is 220 m. The current terminus in 2014 is dirtier and less crevassed than in 2004, and less crevassed than in 2008. The lower 200 m of the glacier is thin, narrow and lacks active crevassing. This relatively stagnant area will melt away in the next decade.
Zongo Glacier continues to have an accumulation zone, a necessary essential for glacier survival, and unlike the nearby Chacaltaya Glacier which disappeared in 2009, it will exist for sometime. The Chacaltaya Glacier is a small glacier, like 80% of the glaciers in this region of the Cordillera Real, and its disappearance puts more pressure on the water resources provided by the larger remaining glaciers such as Zongo Glacier. Rabatel et al (2013) note the striking rise in the freezing levels in the region due both to higher temperatures and more convective activity that is a particular threat to glacier survival.
1994 Landsat image
2004 Google Earth image
2008 Google earth image
2014 Google Earth image
2014 Landsat image
The Mahsa Icefield is at the headwaters of Takatz Creek. This is a small glacier, not an actual icefield. Five kilometers to the west is another small unnamed glacier at the headwaters of Sawmill Creek. Here we focus on changes in the two glacier using Landsat images from 1986 to 2014.
Google Earth image
In 1986 the Mahsa Icefield is a contiguous glacier that extended 5 km from east to west, red arrow indicates the mid-section of the icefield. A separate glacier in Sawmill Creek, yellow arrows, was 2.1 km long and has no lake at its terminus. In 1997 the Mahsa Icefield has separated into an east and west half, at the red arrow, and has lost all of its snowcover. The glacier in Sawmill Creek is still a single ice mass, but has lost all of its snowcover, which happened in 1998, 2003 and 2004. In 2014 the Mahsa Icefield’s east and west half are separated by 300 m, red arrow. There is very little snowcover remaining despite there is a month left in the melt season. At the headwaters of Sawmill Creek a lake has formed as the glacier has retreated, the lake is 600 m long in 2014. The glacier has also separated into a small upper and lower section. This glacier has lost half of its area since 1986. The retreat of these glaciers on Baranof Island is similar to the retreat of nearby Carbon Lake Glacier,Lemon Creek Glacier, and Sinclair Glacier. Lemon Creek Glacier has lost more than 25 m of glacier thickness during the 1953-2014 period when its mass balance has been observed by the Juneau Icefield Research Program, and has retreated more than 1 km (Pelto et al, 2014).
Landsat image 1986
Landsat Image 1997
Landsat image 2014
On Baranof Island in southeast Alaska there are a pair of unnamed glaciers at the headwaters of the Carbon Lake watershed, that then drains into Chatham Strait. Here we examine changes in these glacier from 1986 to 2014 using Landsat imagery. The blue arrow indicates the northern glacier terminus and the yellow arrow the southern glacier terminus region.
In 1986 the southern glacier terminus, yellow arrow consisted of three main tributaries combining to form a low sloped terminus region. The northern glacier had a single terminus. By 1997 a lake has formed at the southern glacier, which now has two separate termini, the red arrow indicates a new terminus area and the pink arrow the eastern portion of this glacier. The northern glacier, blue arrow, is retreating but still joined. By 2014 the southern glacier has separated into three parts. There is a terminus at the red arrow, this represents a 900 m retreat since 1986. This portion of the glacier has further separated since 1997 into two parts. The eastern glacier, pink arrow has retreated 700 m since 1986. The new alpine lake is 600 m long. The northern glacier, blue arrow, has separated into two main termini and the glacier has retreated 200 m. The retreat of these glaciers paralells the observed losses of other smaller glacier in the region most notably Lemon Creek Glacier, which is a World Glacier Monitoring Service reference glacier, 30 km west on the edge of the Juneau Icefield. Another nearby example is Sinclair Glacier. Lemon Creek Glacier has lost more than 25 m of glacier thickness during the 1953-2014 period when its mass balance has been observed by the Juneau Icefield Research Program, and has retreated more than 1 km.
1986 Landsat image Carbon Lake Glaciers
1997 Landsat image Carbon Lake Glaciers
2014 Landsat image of Carbon Glacier
Chickamin Glacier covers the north slope of Sinister Peak in the North Cascade Range of Washington. The glacier has a valley tongue that descends to an outwash plain. Here we examine retreat of the glacier from 1979 to 2012. The glacier had advanced from 1955-1975, before commencing retreat.
Chickamin Glacier (Tom Hammond)
USGS Map of Chickamin Glacier
In 1979 the glacier terminus was at the pink arrow, several hundred meters beyond a prominent buttress, red arrow, where the glacier turns west. The lowest icefall is indicated by a green arrow. In 1991 the glacier has retreated from the pink arrow, but still is turning the corner beyond the buttress. The lower icefall is still extensively crevassed. By 1998 in a Google Earth image the terminus is outlined with yellow dots and has retreated 230 m from the 1979 position. The lower icefall is still crevassed. By 2005 in a photograph from Tom Hammond (North Cascades Conservation Council), the glacier has retreated to the buttress. in a 2006 Google Earth image the terminus position is indicated by yellow dots, with a retreat of 50 m since 1998. The lower portion of the glacier has limited crevassing. In the 2012 image the glacier terminus no longer reaches the buttress and has retreated 360 m since 1979. We observed exceptional ablation conditions in the North Cascades in 2013 and 2014, which combined with exceptionally low snowpack in 2015 will lead to a continued significant retreat of this glacier. The crevassing in the lowest icefall has declined and is now superficial. All 47 glaciers observed by the North Cascade Glacier Climate Project have been retreating and four have disappeared (Pelto, 2011). This glacier is similar in size and retreat to Boston Glacier and Honeycomb Glacier.
Chickamin Glacier 1979 (Austin Post)
1991 Chickamin Glacier
1998 Google Earth image
2005 Chickamin Glacier (Tom Hammond)
2006 Google Earth image
2012 Google Earth Image