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Friday, 14 March 2014

Franz Josef Ice on the Retreat

Franz Josef Glacier 2009 - Julian Thomson GNS Science
Recently I visited the West Coast Glaciers and was interested to see their condition after my last visit 5 years ago in 2009.







Franz Josef 2009- Photo Eric Burger
These photos give and immediate comparison of Franz Josef Glacier over the last 5 years:

In 2009 the glacier filled the head of the valley with its spectacular ice falls. It was easy to walk onto the glacier with the appropriate equipment - crampons and ice axe.

Franz Josef 2014- Julian Thomson, GNS Science





2014 - a big difference! The ice is now no longer apparent on the floor of the main valley, and only the distant ice of the upper ice fall can be seen. The glacier terminus has melted back by about 500 metres.







From closer up, this is where the terminus of the glacier was in 2009. You can see that rock debris now covers the area. The exposed wall of the valley on the left shows where the ice level was in the late 1990s. The mound on the right is actually an isolated heap of 'dead' (stationary) ice that has been protected from melting by the insulating effect of rock fall debris that fell onto part of the glacier several years ago.
The hollowed out and unstable ice and rock is the reason why tourists are not allowed to go any further up the valley than this.

Some of the boulders are smoothed and rounded, having been dragged along at the base of the glacier before being dumped where the ice melted.







Huge jagged boulders like this one will have fallen onto the surface of the glacier from the adjacent cliffs. They have not been smoothed by any scraping action along the bed of the glacier.






This ridge of boulders running from the foreground into the centre distance of the image is one of several small terminal moraines left recently by the retreating ice. The glacier is now away to the left of the image.

Is this a view of the long term future of Franz Josef, or will this barren pile of debris be over-ridden again by the glacier again sometime soon?




Measuring summer melting at Franz Josef 2009
To explore this question further we need to understand a bit about the dynamics of a glacier. (For more in depth information about processes of glacier formation have a look at our GNS glacier page here.) On  top of a general understanding, we also have to consider some of the unique characteristics of Franz Josef glacier, and its sister, the Fox.

 Franz Neve,  Julian Thomson GNS Science
Lloyd Homer GNS Science
With extremely high snowfall over a large accumulation zone and a steep, narrow valley that funnels the ice quickly to a very low altitude, the Franz Josef and Fox glaciers are the most sensitive in the world to climate change. Residual snowfall at the top of the glacier at the end of the summer melt season has been measured at over 8 metres of water equivalent per year. Ice melt at the terminus is around 20m w.e./ year which is the highest annual melt rate known for any glacier. The loss of ice of the lower glacier is replaced by very rapid flow rates of up to 2.5 metres per day that transports the abundant accumulation to lower altitudes. This dynamism is the cause of the sensitivity of the glacier to changes in average snowfall or temperatures which are reflected in an adjustment of the terminus position (glacier front) in only about five to six years.

From 1890 to about 1980 the Franz has retreated by over 3.5 kilometres, interspersed with 3 or 4 re-advances of several hundred metres lasting roughly 10 years each.




However, from about 1980 to 2000, there was a more substantial re-advance of 1.5 kilometres. This has been associated with regionally wetter and cooler conditions brought about by a phase of more El Nino conditions. These in turn relate to a fluctuating climate cycle called the Inter-decadal Pacific Oscillation. However, while the Franz and Fox were re-advancing, other glaciers in the Southern Alps with longer response times,continued to lose ice as they were (and are) still responding to the general warming of the 20th Century.

Mount Cook and Hooker Valley,   J. Thomson GNS Science
Overall from the 1850s to about 2007, it has been calculated that 61% of the ice volume of the Southern Alps has been lost, and from 1977 to 2005 there was a 17% reduction in ice volume. mainly because of massive calving into lakes that have formed at the termini of the Tasman and other valley glaciers, and also the continued downwasting ( i.e. surface lowering due to high rates of melting) of these larger glaciers.

Re-advances of the Franz Josef, when they occur, have to be understood against the underlying trend of a warming climate. In the light of this, we can expect that, subject to temporary fluctuations, our cherished view of the Franz Josef's terminal ice face from the approach walk has a rocky future.




An excellent information leaflet about the Franz and Fox glaciers is available from GNS Science:

1 comment:

Juha Sompinmaeki said...

Wow, these photos really illustrate the fact how the glacier is retreating so rapidly. Better go before its gone.