Hanspeter Holzhauser Discusses the Great Aletsch Glacier
Emerging Research FRonts Commentary, February 2011
Article: Glacier and lake-level variations in west-central Europe over the last 3500 years
Authors: Holzhauser, H;Magny, M;Zumbuhl,
Hanspeter Holzhauser talks with ScienceWatch.com and answers a few questions about this month's Emerging Research Front paper in the field of Geosciences.
Why do you think your paper is highly cited?
I think, that first the paper is highly cited because accurate evidence of climate change is not so frequent and very important in terms of the hotly discussed subject, "global warming." Secondly, in the paper different methods come up and were combined for the first time. It points out that only a combination of different methods, an interdisciplinary approach, leads us to understand the motor of climate change.
Furthermore, almost complete records of glacier advances and retreats over the last 3,500 years have been established. The Aletsch glacier curve is the most complete and exact dated curve worldwide. It was also possible to reconstruct both minimum and maximum extents.
Does it describe a new discovery, methodology, or synthesis of knowledge?
The paper shows that glacier maximums (cold and moist periods) coincide with phases of higher lake levels. Furthermore, in agreement with previous studies, a comparison between the fluctuations of the Great Aletsch glacier and the variations in the atmospheric residual 14C (radiocarbon) records supports the hypothesis that variations in solar activity were a major forcing factor of climatic oscillations in west-central Europe during the late Holocene.
The methodology to reconstruct glacier fluctuations is not new, but the combination of glaciological data, historical and archaeological methods, and glacio-morphological method (the search for dateable organic material such as soils and crushed trees within and at the edge of glacier forefields) to reconstruct Holocene glacier fluctuations breaks new ground.
Would you summarize the significance of your paper in layman's terms?
The Great Aletsch glacier within four periods.
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Mountain glaciers are highly sensitive indicators and one of nature's clearest signals for climate changes in the Alps. The behavior of glaciers depends very much upon climatic conditions (temperature and precipitation) and they react according to the sum of complex interactions of climatic parameters. The resulting change in glacier length (advance or retreat) is an indirect, filtered, and delayed signal of these climatic fluctuations.
Hence, the fluctuations of glaciers indirectly reflect the natural variations in climatic conditions within the Holocene, i.e. the last 11,700 years. Accordingly, the reconstruction of preindustrial glacier fluctuations reveals the natural range of Holocene climate variability against which the present-day climatic situation can be judged. As consequence, glacier signals from mountain areas are key elements of early detection strategies for dealing with possible man-induced climatic change (global warming).
Lake levels are influenced by climate variables too, affecting evaporation as well as precipitation. Thus, lake-level records have been used in Europe to establish spatial patterns of Late Quaternary changes in moisture balance and atmospheric circulation.
How did you become involved in this research, and how would you describe the particular challenges, setbacks, and successes that you've encountered along the way?
My interest in geoscience was awaked early. When I was a child, my father and I would hike every summer in the Alps searching for minerals. In this context I became familiar with glaciers too and was fascinated by that apparently inanimate huge mass of ice. Later, I began to study Geography and Geology. During my studies it became obvious to me that I wanted to investigate glaciers, especially the history of glaciers because I took great interest in pictorial and written historical documents dealing with glaciers as well as in dating and dendrochronological analysis of formerly overridden and reappearing tree trunks within the glacier forefield.
A great challenge was searching such remains in pathless and sometimes dangerous areas. Often I was en route for days without success and I was sometimes frustrated. On the contrary there were days whilst I found a lot of wood and even fossilized soils. During analyzing the material in winter time some setbacks occurred. Often the remains were not in a good condition to analyze seriously or a lot of samples were indicating the same glacier advance and not as I hoped several glacier advances. Anyway, the results I achieved caused great echoes among experts and so I can say that in my research activities success exceeded setbacks.
Where do you see your research leading in the future?
The natural sensitivity of glaciers to climate change has been exploited to make a contribution to paleoclimatology in general but, more specifically, to Holocene climatology. The main questions in the moment are: Were there periods within the Holocene with little glacier extent or even without glaciers in the Alps? Is the current situation anomalous compared to Holocene warm periods? Have we reached the "warmer" threshold of Holocene climate variability or have we already exceeded this boundary?
At the moment we know very few about the climatic conditions in the first half of the Holocene and also about the whole climate variability during this time. Nearly all alpine glaciers are now in a retreat condition. The recession of the glaciers give us the unique chance to find within the glacier forefields more remainders of trees once buried indicating Holocene warm periods. The more data we have the more it allows us to give answers to these questions.
Do you foresee any social or political implications for your research?
The reconstruction of Holocene glacier fluctuations is primary basic research. The "glacier curves" also provide a very useful base for glacier modeling as well as calibration and crosschecks for glacier/climate models. They are among other paleoclimatic data very valuable data for climate models as well. Finally, at present we are very interested to anticipate the development of the climate in the future taking into account the development of greenhouse gases. Models developing climate scenarios until the end of the 21th century are very important.
My investigations in glacier history only provide data for such models and therefore have no direct social or political implications, but may very well indirectly in the discussion relating to global warming, which is ultimately a social and political affair.
Dr. Hanspeter Holzhauser
Institute of Geography
University of Berne
KEYWORDS: GALCIER FLUCTUATIONS, LAKE-LEVEL VARIATIONS, HISTORICAL DOCUMENTS, DENDROCHRONOLOGY, RADIOCARBON DATING, CLIMATE CHANGE, NEOGLACIATION, “LITTLE ICE AGE,” WEST CENTRAL EUROPE, ALPS, HOLOCENE, MAUNDER MINIMUM, YOUNGER DRYAS, CLIMATIC IMPLICATIONS, SOLAR ACTIVITY, RECONSTRUCTION, PRECIPITATION, TEMPERATURE, POLLEN.
Item 1: Aletsch curve.
Item 2: The Great Aletsch glacier within four periods: a) Iron/Roman Age Optimum (c. 200 BC – 50 AD, b) 1856 AD, c) 2000 AD and d) around 2050 AD (comparable with the Bronze Age Optimum). Photomontage: H. Holzhauser. (from Holocene 15: 789-801, November 2005).
Opening Photo: Dr. Hanspeter Holzhauser at the Great Aletsch glacier.