Observations relating to global warming and glacier retreat in Norway
Allan Johanson 2002, Adelaide Australia 3rd draft
While travelling in Norway's Fjordland, i came across a record of glacier retreat observations dating from 1930 onwards. The record indicated a significant amount of movement over recent decades.
Boyabreen glacier in the Fjaerland region of Norway
The location and discovery
You may have heard of the Oslo to Bergen scenic railway in Norway, it is one of the world's classic train journeys across the ridge-line of Norway's Fjordland. Approximately half way it is suggested to disembark at Myrdal station and take the very steep scenic railway down to the village of Flam, a fjord level ferry terminal. From Flam a ferry boat ride via Balestrand town gets to Fjaerland village which is the starting point to visit two of the many glaciers.
At Fjaerland a fellow traveller and i bought a map and hired bicycles for the ride to Suphellabreen and Boyabreen glaciers. I guess the "breen" part of the names may be Norwegian for "glacier"?.
The picture above of Boyabreen shows a turquoise coloured lake, with the "leading edge" of the glacier half way up the mountain. While we sat and ate our lunch, ice chunks were breaking off the glacier and falling with a very loud shattering noise tumbling down the slope and ending up being pummeled into small fragments on the rocks below. It was the 13th of September and the Northern Hemisphere Summer was over, so one could assume it was the tail-end of the Summer thaw.
After a walk near the base of the glacier slope we entered a small timber hut which was serving as a kiosk and postcard store. As we were leaving it i noticed a chart on the back of the door, it was a sectional drawing showing the mountain, glacier and lake. The recession of the glacier was recorded on it from being at the lake level in 1930, through decade marked progressions up the slope. This seemed evidence enough of global warming i thought at the time, and significant recent movement at that.
An approximation of the chart (lower part of the mountain only).
Later back in Adelaide i noticed the map i had purchased had very thorough contour definitions, it showed the relative lake level and the level of the glacier at the time of printing the map (1984).
Just the Boyabreen glacier area is reproduced here.
The lake is shown at 150 metres above sea level and the 1984 edge of glacier line at the 500 metre altitude line. Measuring from the plan the distance from the lake to the glacier edge is 500 m, therefore by trigonometry the slope of that part of the mountain is 35 degrees. This gives an "along the slope length" of glacier retreat of 610 metres over the 54 years from 1930 to the map printing date. Resulting in an average figure of 11.3 metres of glacial retreat per year.
How does this compare with other glacial retreats?
An internet search using the key words "glacier+retreat" brought up the site:
Which is headed "Glacier retreat in Glacier Park Montana", by the United States Geological Survey.
They refer to an average recession of 6 metres per year between 1850 and 1920, but with figures ranging from 2 metres per year to 11 metres per year.
A query arose as to whether they also measured the "along the slope" recession.
An email to the contact point of the web site gave me the answer;
"slope angles were not accounted for, so reported measures may actually underestimate actual distances over the ground surface." Carl H Key.
Their web site is well worth a visit.
We also hear media reports recently of receding glaciers in New Zealand and icy parts of Antarctica breaking off.
What else could be contributing to the glacier recession?
Rather than the whole of the recession being due to global warming perhaps consider; " Was there less ice and snow being deposited on the glacier back when the current leading-edge ice was being formed?"
The Little Ice Age and the Medieval Warm Period
An interesting web site that also came up with the same web search was
http://www.agu.org/revgeophys/mayews01/node5.html,provided by the American Geophysical Union.
This tells of the Little Ice Age from AD 1400-AD1900 and the Medieval Warm Period a few centuries earlier than the Little Ice Age. Well worth the read.The Science Show (ABC Radio) 13/7/2002 "Antarctic Ice Cores"
http://www.abc.net.au/rn/science/ss/stories/s601030.htmDr Barbara Smith Ice Core Analyst Australian Antarctic Division Hobart says; " There is the little Ice Age for example thatís well documented and went from about say 1400 to 1850. Weíve actually been warming up ever since then, so to give a large-scale interpretation of whatís been happening over the last few hundred years you really need to understand that there was this little Ice Age period and you canít just start your discussions from about 1800 because we know that that was an anomalous era.
It was suggested to me that the glacier retreat record i had observed was not recent human intervention related, but was just the tail-end of another global warming cycle. Therefore how does the rate i calculated compare with the recession rate of ice after the last major ice age?
The Times "Concise Atlas of World History" has two pages "Man and the Ice Age". It includes one map that shows the extent of the ice sheet 20, 000 years ago, 12,000 years ago, 11,000 years ago, 10,000 years ago and 8,000 years ago. With this 8,000 year ago remnant being on the Scandinavian peninsula not far from the glaciers i visited.
When measuring distances from the map point-to-point map measurement should take into consideration the curvature of the earth. To make this easy a web site: http://www.wfu.edu/albatross/gcircle/calcfull.html was used.
This calculated actual distances between any two points on the globe. The latitude and longitude of the two locations are entered and the resultant figure is instantly given.
For example a retreat distance of 1000 km from a point in southern Wales to the bottom of the Scandinavian peninsula is shown for the 20,000-12,000 year ago period. This gives a result of 125 metres per year average of ice retreat.
Other locations give half the distance for the same period, so a range of 60 metres to 125 metres per year can be considered.
For the next time period period, 12,000 years ago to 8,000 years ago, we get about 125 metres per year of ice retreat.
These earlier ice age rates are therefore about 11 times greater than that calculated above for the Norwegian glacier.
A more specific reference to a "recently emerging from an ice age" is in the article.
"The Little Ice Age: When global cooling gripped the world" atthis is an article from the "Washington Post" Wed August 13 1997.
It says; "All agree, however, that it (Little Ice Age) lasted for centuries, and that the world began emerging from its grip between 1850 and 1900"
Ice ages may be related to "Milankovitch" cycles, which are variations in the orbit of Earth. One of these is a wobble in the Earth's axis every 23,000 years and another relates to the tilt of the Earth's orbit every 41,000 years. Others suggest ices ages may relate to changes in sun activity.
In summary so far
The author at the other glacier (Suphellabreen), standing on terminal moraine and with meltwater streaming out below the ice. The photo was only able to be taken by removing camera batteries, warming them up and replacing them.
Typical fjord scenery.
Another view of Boyabreen glacier.