Association of Polar Early Career Scientists
 

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Do you feel excited about your polar research? Do you want to share this excitement, but don't know how to reach the right audience? You don't have the time to write long blog posts and articles?

APECS Figure Friday is here to help. It is a bi-weekly event which gives you the opportunity to reach out and showcase your work among other polar researchers and enthusiasts. Pick a figure from your ongoing work (or published) which summarises your research or the one that looks the coolest. Include a short description, explaining the science behind it and what others can learn from it. This email address is being protected from spambots. You need JavaScript enabled to view it. your entry and we will showcase it on our website and our social media platforms. The figures will be published on a first come basis, so hurry up and get your research on the list. Based on the interest, we might make it a more frequent feature in the days to come.

4 Dec 15: Ca isotopes by Ruth Hindshaw

Hindshaw Ca

Background

Calcium (Ca) is the fifth most abundant element in the Earth’s crust and forms a key constituent of many rock-forming minerals. In addition, it is an essential nutrient for all living organisms, except perhaps fungi. Furthermore, the geochemical cycles of calcium and carbon are intimately linked (for example, through the formation of CaCO3 in the ocean). The analysis of calcium isotopes provides a powerful tool to trace and quantify fluxes within the calcium biogeochemical cycle.

Isotopes

Radiogenic isotopes trace sources and the values measured reflect mixing between different sources. Stable isotopes also reflect mixing between sources but the values can also be changed by fractionation processes, for example, by biological uptake.

What does this figure tell us?

This figure shows river water samples collected from the outlet of Leverett Glacier, Greenland and data from the local bedrock. It was expected that the river water samples would plot in the grey box defined by the isotopic compositions of the main Ca-bearing minerals as these constitute the main source of Ca to the river and there is no vegetation to fractionate Ca. However, the river points have clearly been fractionated and we think that this is due to fractionation during adsorption of Ca onto suspended sediments. If this is a common occurrence in sediment-laden rivers (not just glacial ones) then it will need to be taken into account when determining riverine stable isotope fluxes to the ocean (a key parameter in global biogeochemical cycle models).

Further Reading

Identifying weathering sources and processes in an outlet glacier of the Greenland Ice Sheet using Ca and Sr isotope ratios (Hindshaw et al. 2014)

20 Nov 15: Ice Rises by Vikram Goel

Goel ice rises

 

 

What are we doing?

Ice rises are grounded ice bodies (at least partially) surrounded by the floating ice shelf. They provide buttressing to the neighboring ice shelves and play a key role in controlling dynamics and mass balance of the Antarctic Ice Sheet. In turn, evolution of an ice rise is affected by the surrounding coastal environment. We are investigating glaciological settings, recent mass balance, and millennial evolution of Blåskimen Ice Rise, located in Dronning Maud Land. East Antarctica.

What does this figure tells us?

This figure shows a radar profile we took with a shallow sounding (400 MHz) radar across the ice rise (inset), to map the internal structure of the firn column. The radar pulse penetrates into the firn column and reflects back where the dielectric constant of firn changes (mostly by density changes for upper hundreds of meters). In this figure we see several continuous internal layers (some of them are shown with black curves), which are isochronous (deposited at the same time) by nature. To know when these layers were deposited, we drilled a firn core (location shown in the figure) and dated it, to develop a depth age relationship, and then used it to associate ages to different layers (as shown in the figure). Now, if we look at the third layer from top, we see the that it is deeper (15m) on the southern side and becomes shallow (10m) towards north, which implies that there is higher surface mass balance (accumulation + wind deposition - wind scouring) on the southern side from the northern side, in the past 10 years. By using different layers and other such radar profiles, we are able to study the surface mass balace variation over the ice rise both spatially and temporally. This understanding is later used to assess if the ice rise is growing, thinning or in balance.

Further Reading
Antarctic ice rises and rumples: Their properties and significance for ice-sheet dynamics and evolution (Matsuoka et. al.,2015)

 

 

 

 

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