Wednesday, December 31, 2014

Another Year and Glaciers Are Another Meter Thinner

Global glacial mass balance in the last fifty years, reported to the WGMS and NSIDC. The downward trend in the late 1980s is symptomatic of the increased rate and number of retreating glaciers. (Credit: Robert A. Rohde/ Click to Enlarge.
The world's glaciers act like frozen water towers, storing snowfall in winter before releasing meltwater in the summer.  This water flows downstream to thirsty cities such as La Paz in Bolivia.  Since 1980, the World Glacier Monitoring Service (WGMS) reports every other year on how  a sample of worldwide glaciers are doing.  They report the "annual mass balance", which tells you how much ice the glaciers have gained or lost each year, and the latest values have just been released.

Over the last 2 years, the glaciers measured lost almost a meter of thickness each year, bringing the total since 1980 to over 19 metres. ...

2013/2014 falls into 5th place for loss rate, but it continues the accelerated trend.  Since 2000, ice loss has been about 100% faster than it was between 1980-2000.  This fits with results of a scientific study by Marzeion et al. (2014) that reported that most of the recent glacier loss is due to human-caused global warming. Andy Skuce talks about this study in more detail in his report on a trip to the vanishing Athabasca glacier.

The WGMS only measure a sample because they use measurements taken by scientists on the ice, and it's slow and expensive to get enough to report on each enormous glacier. To expand these measurements further, we use satellites. Jacob et al. (2012) used the GRACE satellites which "feel" Earth's gravity to calculate that glaciers worldwide lost about 150 billion tonnes of ice each year from 2003-2010.  This meltwater flows into the oceans, and explains part of the sea level rise that's been measured by other satellites.

Read more at Another Year and Glaciers Are Another Meter Thinner

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