Studies on Hochjochferner – glaciological mass balance

In our, now completed, hiSNOW project the aim of the research was to compare methods of determining glacier and catchment scale runoff at a range of scales. While scientists and students in the Hydro_Climatology group of the Geography department have worked on running a catchment hydrological model called AMUNDSEN, and colleagues at EURAC have worked on determining the evolution of snow cover and glacier snowlines from satellite data, University of Innsbruck MSc students Hannah Prantl and Franz Grüsser, working within the Remote Sensing and topographic LiDAR research group, led the charge to compute geodetic mass changes of the glacier from terrestrial laser scanning and Rainer Prinz and myself (though mainly Rainer) measured the mass balance by the traditional glaciological method. You can read about the various methods of determining glacier mass balance in this UNESCO Glossary of Glacier Mass Balance and Related Terms.

Hochjochferner is a  small valley glacier close to the Italian-Austrian border. During the last expanded glacier extent during the Little Ice Age, a long glacier tongue descended the upper Rofental, but glacier recession since then has caused the glacier tongue to be lost and now a number of smaller glaciers are what is left of the disintegrated former Hochjochferner. The most south-westerly of these glaciers hosts the Kurzras ski area – accessed from Italy. The site of our study is the next glacier body to the north-east of the ski area (blue in the figure below).

HJFMap of Hochjochferner, showing the part that is being measured in this study (blue), the ski area (yellow) and the intervening debris-covered ice (orange) as well as the rest of the glacier also known as Hochjochferner (green). The map shows all the locations of stakes measured on this site (6 on the glacier, 2 on the debris-covered ice, and 1 in the lower ski area). It also shows the locations of snow pits excavated to determine snow properties, th locations from which TLS scans were made, and the reflectors used for ground control points in the TLS scans. Figure by Hannah Prandtl.

The hydrological year in this part of the world runs from 01-October until 30-September, so glaciological mass balance for this glacier is calculated over this period, with 01/10/2013-30/09/2014 being termed the mass balance year 2014, or more simply the annual mass balance for 2013/2014. We visit and measure the 6 stakes drilled into the glacier surface and measure the surface height change there as well as determining the density of the surface (fresh snow is less dense than old snow, which is less dense than ice) so that these height changes can be converted into a water equivalent depth change over the year. Then a contour map of the likely pattern of this water equivalent surface change is mapped out by hand using these stake data and photographs from the field to see where the snowline was. The mass change within fixed elevation bands on the glacier is then calculated, summed and divided by the total glacier area to get the specific glacier mass balance.

It turns out that while 2013/14 was a year when a moderate mass was lost (-244 kg m-2 … equivalent to removing a water layer of 24.4cm depth from the whole glacier surface), 2014/15 was a pretty nasty one for this glacier, with much more mass loss occurring (-2030 kg m-2 … equivalent to removing a water layer of 203cm (over 2m!) depth from the whole glacier surface). Here is the map of surface mass change (in units of mm water equivalent depth, which is numerically the same as mass units of kg m-2) for the mass balance year 2013/14 as determined from the glaciological method:

We are currently working on a paper looking at how the accuracy of the contouring used in distributing the point mass balance data affects the end value of glacier mass balance.

Now PhD student Hannah Prandtl has just published a paper on using laser scanning return signals intensity and glacier surface classification schemes to map the changing snow cover over the glacier in detail over a summer ablation season.

About lindsey

Environmental scientist. I am glaciologist specialising in glacier-climate interactions to better understand the climate system. The point of this is to understand how glaciated envionments might change in the future - how the glaciers will respond and what the impact on associated water resources and hazard potential will be.
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