Umef Stock in the middle of Blüemlisalp glaciers, near Kandersteg, 11th August 2007. Photo: TonnyB via Wikimedia (CC BY-SA).
World's glaciers melting at 'unprecedented' rate
7th August 2015
Glaciers around the world are melting on a scale without precedent in recorded history, writes Alex Kirby. Measurements of over 5,000 glaciers show that they have been retreating so fast so far this century that even if climate is stablised, the ice losses will continue for years to come.
Observations show that the rates of early 21st century mass loss are without precedent on a global scale, at least for the time period observed and probably also for recorded history.
The world's glaciers are melting fast - probably faster than at any time in recorded history, according to new research.
Measurements show several hundred glaciers are losing between half and one metre of thickness every year - at least twice the average loss for the 20th century - and remote monitoring shows this rate of melting is far more widespread.
Drawing on reports from its observers in more than 30 countries, it has published in the Journal of Glaciology a comprehensive analysis of global glacier changes, which concludes that
"Glaciological and geodetic observations (~5200 since 1850) show that the rates of early 21st century mass loss are without precedent on a global scale, at least for the time period observed and probably also for recorded history, as indicated also in reconstructions from written and illustrated documents.
"This strong imbalance implies that glaciers in many regions will very likely suffer further ice loss, even if climate remains stable."
The study compares observations of the first decade of this century with all available earlier data from field, airborne and satellite observations, and with reconstructions from pictorial and written sources.
Dr Michael Zemp, director of WGMS and lead author of the study, says the current annual loss of 0.5-1 metre of ice thickness observed on "a few hundred glaciers" through direct measurement is two to three times more than the average for the last century.
"However, these results are qualitatively confirmed from field and satellite-based observations for tens of thousands of glaciers around the world", he adds.
The WGMS compiles the results of worldwide glacier observations in annual calls-for-data. The current database contains more than 5,000 measurements of glacier volume and mass changes since 1850, and more than 42,000 front variations from observations and reconstructions stretching back to the 16th century.
The researchers say the current rate of glacier melt is without precedent at the global scale - at least for the time period observed, and probably also for recorded history, as reconstructions from written and illustrated documents attest.
The study also shows that the long-term retreat of glacier tongues is a global phenomenon. Intermittent re-advance periods at regional and decadal scales are normally restricted to a smaller sample of glaciers and have not come close to achieving the Little Ice Age maximum positions reached between the 16th and 19th centuries.
Glacier tongues in Norway, for example, have retreated by some kilometres from their maximum extents in the 19th century. The intermittent re-advances of the 1990s were restricted to glaciers in coastal areas, and to a few hundred metres.
The study shows that the intense ice loss of the last two decades has resulted in what it calls "a strong imbalance of glaciers in many regions of the world". And Dr Zemp warns: "These glaciers will suffer further ice loss, even if climate remains stable."
He told Climate News Network: "Due to the strong ice loss over the past few decades, many glaciers are too big under current climatic conditions. They simply have not had enough time to react to the climatic changes of the past.
"So they will have to retreat further until they are in balance with climatic conditions again. In the European Alps, many glaciers would lose about 50% of their present surface area without further climate change."
Alex Kirby writes for Climate News Network.
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