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Climate research: Glacier melting

Norway’s Folgefonna glacier graces the cover of the IPCC’s Fifth Assessment Report. The report was published Friday 27 September.

Image of the Folgefonna glacier melting.
FOLGEFONNA MELTS: The picture of the Folgefonna glacier on the front page of the IPCC report is from the autumn of 2006, a year with extensive melting all over the glacier. The warm summer melted away many years of accumulated snow at the summit and the mosaic pattern in the picture shows the annual layers.
Photo:
www.yannarthusbertrand2.org

The United Nations’ Intergovernmental Panel on Climate Change (IPCC) releases its Fifth Assessment Report (AR5) with an extensive update of knowledge on the scientific, technical, and socio-economic aspects of climate change. The effects that mankind had on our climate will again be under the media spotlight.

For this particular report the IPCC has chosen to illustrate the report cover with a photograph of Folgefonna glacier, located in the county of Hordaland, Western Norway. Folgefonna is actually composed of three separate ice masses, namely Northern Folgefonna (Nordfonna), Middle Folgefonna (Midtfonna) and the third largest glacier in mainland Norway, Southern Folgefonna (Sørfonna).

Folgefonna makes for an apt illustration of the recent perturbations in our climate. The response of glaciers to climatic changes has led them to act as a sort of barometer for climate; glacier changes are especially useful for areas where few climate data exists.

Remote sensing of the Folgefonna glacier

Field measurements exist from the glacier, indicating the health of the ice mass. However these measurements are patchy, covering sporadic periods in the 1960s, 1970s and the past decade. In order to understand how the glacier has varied over the previous half century we need to have as frequent and continuous data as possible.

By collating together an array if satellite imagery, aerial photographs, and historic maps, it has been possible to assess the changes Folgefonna has undergone over the last 150 years in terms of the total area the glacier has covered, while comparing height data of the glacier allowed the change in glacier volume to similarly be determined, an often more preferable dataset than the glacier area, as many glaciers have been known to reduce in elevation, while their terminuses remain stationary. Unlike the field measurements, this remotely sensed data allows changes over the entire glacier area, over 200 km2 of ice, to be determined.

Global warming imprints the glacier

The three Folgefonna ice masses have all shown a similar trend, between the mid 1800s and the turn of the twentieth century the glacier has responded primarily to the wax and wain if the North Atlantic Oscillation (NAO), a phenomena that reflects the change in wet and warm verses cold and dry winters in Europe.

During positive phases of the NAO, that is warmer and wetter European winters, more snow falls on Folgefonna, causing the glacier to increase in size. However the last 15 years it has become apparent that despite a trend of an increasingly positive NAO index, Folgefonna has continued to retreat, suggesting that another mechanism is now more significant for the glacier.

When temperature data is compared to the remotely sensed glacier area record, it becomes apparent that the occurrence of hot summers from around 2000 onwards relate to years of dramatic glacier retreat. The climate has therefore become sufficiently warm enough in recent years to overpower the effect of the NAO. This means we are entering a new phase of climatic history, where our impacts have rewritten climatic relationships.

We need to consider the changes that the ice masses around the world are undergoing, and what that tells us about our climate. The fate of a Norwegian glacier may seem rather trivial, however in other parts of the world it is the glacier melt water that nourishes huge populations through the dry season each year. Melting glaciers also augment the risk of glacial lake outburst floods, a very serious hazard for many regions. The glaciers of the Himalayas for example are severely under sampled.

It is therefore important for scientist to continue to understand how the glaciers of the world are responding, both to further develop our understanding of the changes happening to our climate, but also how the perturbed state of the glaciers will effect the daily lives of people in many different parts of the world.

For more information about the Folgefonna glacier and current research on the glacier, please contact:

Professor Jostein Bakke, Department of Earth science/Bjerknes Centre for Climate Research, mobile phone: +4799273343.

PhD student Benjamin Robson, Department of Geography, University of Bergen.