Montag, 10. Januar 2011

Modeling Glacier Change 2000-2100

According to a simulation by researchers of the University of Alaska (RADIC, V. & HOCK, R.) and based on various scenarios of precipitation change and a temperature increase, with a mean value of ca. 2°C, as predicted by most climate models, until the year 2100 the 120.000 glaciers located (mainly) in middle latitudes will experience a massive loss of 21% of the actual ice volume.
Observing the reactions of more than 300 glaciers to the climatic change in the period of 1963 to 2004 the models were extrapolated to simulate a significant increase in temperature and slight increase in precipitation and the effects of these variables on the mass balance of the glaciers.
The projections show in the 19 chosen glacierized regions different glacier retreat values, depending from factors like elevation, surface properties and effective temperature rise in the region.
According to the proposed scenarios, mountain ranges in temperate climatic zones will experience the most massive volume change, in the European Alps glacier will loss up to 75% of the actual ice volume, similar values to the New Zealand Alps with 72% and the Caucasus.
In contrast mountain ranges with a high average altitude, like in Asia or the Andes, will experience much lower loss percentages, with an average value of 20%.

I discussed a previous research dealing with possible effects of such glacier retreat on human society in this post.

Fig.1. Regional twenty-first-century glacier volume change expressed in per cent from initial volume in year 2000, the results are presented for 19 regions based on temperature and precipitation projections from the ten applied climatic models, after RADIC & HOCK 2011.

Fig.2. Example of glacier retreat in the Alps in the past 100 years: The Waxegg-glacier in the Zillertaler Alps at the border between Austria and Italy ca. 1900-1903 and 2006. Historic image from ROTHPLETZ, A. & PLATZ, E. (1903): Alpine Majestäten und ihre Gefolge - Die Gebirgswelt der Erde in Bildern, 268 Ansichten aus der Gebirgswelt.
For the history of glacier monitor projects see this post.

Bibliography:

RADIC, V. & HOCK, R. (2011): Regionally differentiated contribution of mountain glaciers and ice caps to future sea-level rise. Nature Geoscience doi:10.1038/ngeo1052

Kommentare:

Malcolm V L hat gesagt…

I thought the 2C increase was the minimum, and that the average is more 2.8C with an extreme model of 4C

David Bressan hat gesagt…

This is correct (I made an error not didn´t emphasize it) for a global temp rise, the authors based their projection on the A1B scenario, ranging between 1.4 to 6.4°C, however their model uses a downscale factor to account for regional climate and the positions of the glaciers (higher latitudes or high mountain ranges), were temp are rising but will remain relatively lower to other altitude or latitude:

"As GCMs are unable to represent the local subgrid-scale features and dynamics, this leads to biases in the climate variables over the local glacier scale.
Following a statistical downscaling approach, we shift the future monthly
temperature time series for each GCM grid cell containing WGI-XF glaciers by
the average bias for each month between the GCM and ERA-40 temperatures
over the period 1980-1999."