A just-published report by the University of Zurich’s World Glacier Monitoring Service (WGMS) on glacial mass balances for 2006-2007 shows that the long-term decline trend described in its superb Global Glacier Changes: facts and figures, (this document is a must read for anyone interested in glacier advance and retreat–a very accessible text for the non-specialist) continues.
Morteratsch Glacier, 1985-2007. Recession of Morteratsch Glacier, Switzerland, between 1985 and 2007. Source: J. Alean, SwissEduc (www.swisseduc.ch) / Glaciers online (www.glaciers-online.net).
As Mauri Pelto at Real Climate explains:
The health of an alpine glacier is typically determined by monitoring the behavior of the terminus and/or its mass balance. Glacier mass balance is the difference between accumulation and ablation (melting and sublimation) and can be altered by climate change caused variations in temperature and snowfall. A glacier with a sustained negative balance is out of equilibrium and will retreat. A glacier with sustained positive balance is out of equilibrium, and will advance to reestablish equilibrium. Glacier advance increases the area of a glacier at lower elevations where ablation is highest, offsetting the increase in accumulation. Glacier retreat results in the loss of the low-elevation region of the glacier. Since higher elevations are cooler, the disappearance of the lowest portion of the glacier reduces total ablation, increasing mass balance and potentially reestablishing equilibrium. If a glacier lacks a consistent accumulation it is in disequilibrium (non-steady state) with climate and will retreat away without a climate change toward cooler wetter conditions (Pelto, 2006; Paul et al., 2007).
For a larger image, click here.
According to data from WGMS published on January 30, 2009:
Preliminary mass balance values for the observation periods 2005/06 and 2006/07 have been reported now from more than 100 and 80 glaciers worldwide, respectively. The mass balance statistics (Table 1) are calculated based on all reported values as well as on the data from the 30 reference glaciers in 9 mountain ranges (Table 2) with continuous observation series back to 1980.
The average mass balance of the glaciers with available long-term observation series around the world continues to decrease, with tentative figures indicating a further thickness reduction of 1.3 and 0.7 metres water equivalent (m w.e.) during the hydrological years 2006 and 2007, respectively. The new data continues the global trend in accelerated ice loss over the past few decades and brings the cumulative average thickness loss of the reference glaciers since 1980 at almost 11.3 m w.e. (see Figures 1 and 2).
Figure 1: Mean annual specific mass balance of reference glaciers.
Figure 2: Mean cumulative specific mass balance of all reported glaciers (black line) and the reference glaciers (red line).
To compare this recent data with 120 years worth of data dating from the end of the Little Ice Age see the chart below:
Or to view the data in a different way:
The average annual mass balance for nine sectors of the globe are shown for the decades (a) 1946–55, (b) 1956–65, (c) 1966–75, (d) 1976–85, (e) 1986–95, and (f) 1996–2005. Sectors with measurements are coloured according to the mean annual specific mass balance in metre w.e. with positive balances in blue, ice losses up to 0.25 m w.e. in orange and above that in red; sectors without data in grey. Average decadal mass balance values based on less than 100 observations (marked in italics) are less representative for the entire sector. For each decade, the global mean (gm) annual mass balance in m w.e. and the number of observations (no) are indicated. Source: Data from WGMS.
It is clear that since the end of the (last) Little Ice Age around 1850, that Glacial retreat has dominated over glacial advance. Even during the period 1965-1985 when there was an increase in advancing glaciers, retreat was still the dominant theme.
For its article on the release of the latest WGMS report Bloomberg interviewed Siwss geographer Michael Zemp:
“One year doesn’t tell us much, it’s really these long-term trends that help us to understand what’s going on,” Michael Zemp, a researcher at the University of Zurich’s Department of Geography, said in an interview. “The main thing that we can do to stop this is reduce greenhouse gases” that are blamed for global warming.
Some glaciers in the Alps, including Italy’s Calderone, have shrunk so much it’s becoming difficult to take accurate measurements, Zemp said. Such ice has not recovered from the 2003 European summer heat wave that melted the snow, revealing darker ice underneath which heats up faster than whiter surfaces.
The global average temperature has risen 0.76 degrees Celsius (1.4 degrees Fahrenheit) since pre-industrial times as humans used more fossil fuels to generate energy and power machinery, according to the UN’s Environment Program.
Ice melt is even speeding [up] in Greenland. In 2007, U.S. scientists discovered that water from melting glaciers, draining from a 5.6 square-kilometer lake on Greenland’s ice sheet, reached a peak flow exceeding that of Niagara Falls.
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Briksdalsbreen Glacier. Advance and retreat of Briksdalsbreen, an outlet glacier of Jostedalsbreen, Norway, in a photo series of the years 1989, 1995, 2001 and 2007. Source: S. Winkler, University of Würzburg, Germany.