JIRP surface dust studies

I’m just back from JIRP, whch was once again pretty amazing. I encourage you to have a read of the students blogs, some are about science and others about the JIRP experience, but in either case they are an enlightening view into the minds of the participating students, allowing us to see their deep reflections on what they are learning during the program.

As part of the program groups of students take on specific research projects while on the ice, with the aim of generating sufficient results to present them in a poster at the Fall AGU meeting at the end of the year. The biogeochemistry group were tasked to look at the glaciers surface nutrient loading and nutrient flux in the glacier meltwater. While  awaiting for the arrival of thier mentors Sarah Fortner and Natalie Kehrwald, we experiemented with using hand-held albedometers to measure the imact of different amounts of mineral dust and soil on the surface of the glacier.

Here are the students and APU Geologist Jen Witter setting up the experiment site and the foot of the Camp 10 nunatak (note how the dust loading compares visually to the photo of the ablation zone in my previous post):

JIF debris plotsWe levelled five 3’x3′ (yes those are American feet – Lucas Beem introduced me to the term ‘freedom units’ when we realised this was the only tape measure available …) patches of snow, left one clean, added some red-coloured green algae over the second, and then over the final 3 plots we sprinkled 848g of mafic, 848 g of felsic and 1696g of felsic material  from the local nunatak as evenly as we could. Over the next few days we measured the surface lowering using terrestrial photogrammetry to make digital models of the surface and by measuring the length of small dowels installed in the centre of each plot, and albedo using a Kipp and Zonen CNR1 held 0.5m above the surface of each plot.  Here is how they compare:

debris_plots_figureThe plots with mineral soil on them underwent more surface lowering than the clean and algae covered plots, and this is mose likely related to their lower surface albedo. The 4 days of measurement coincided with cloudly and rainy weather so the impact of the albedo diferent and resultant alteration of the absorption of incident shortwave radaition is likely a minimum – we might expect the differences in surface lowering to be greater if it had been sunny conditions.

The group found that the albedo measurements were sensitive to the position of the person holding the radiometer which is not really surprising as the CNR1 instrument captures electromagnetic radiation from a 180° hemispere in the shortwave. This means it can ‘see’ the person holding the instrument, as well as those of us nearly and the neighbouring surfaces as well. This raises issues of repeatability and accuracy of these albedo measurements, but the students will also use a more focussed field spectrometer with Allen Pope to investigate the links between available nutrients in the snowpack and surface albedo.

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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