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Frank Eckardt

Why Conduct Fieldwork in Places Hot, Flat, Dusty and Crusty?

Geomorphologist

Just because dust is small does not mean it does not matter. Some areas such as pans liberate thousands of tons per annum which effects regional air, water and soil quality and also plays a role in ocean productivity and global climate forcing. Despite all this, we don't seem to have global models that capture these dynamics or that understand the series of processes involved. We are only starting to grasp how and where dust is produced and why some areas are more productive than others.

Kate Vickery suggested we should put our equipment here.

We have been lucky to start doing some of the real work and getting some of the answers to our questions. Generally fieldwork is considered to be swift and easy. Grab a sample of soil or water or ask a few questions and analyse results later. In this case we are actually monitoring the processes, and often waiting and hoping for something to happen such as a high magnitude dust event. For any given location there may only be a few of these each year. Not only do you need to be at the right place, but also have to have all equipment up and running and more often than not working in a remote corner of the world.

Setting up and taking down equipment is the equivalent of moving an entire household.
Dusttrack measures suspended particles.

This required UK-NERC funding and coordinated field effort spear headed from Oxford (Richard Washington, Dave Thomas (Honorary Professor at UCT), Giles Wiggs and James King), Southampton (Jo Nield), Sheffield (Rob Bryant), UB (Stefan Coetzee) as well as UCT CSAG, UNAM and Gobabeb. We have been observing three consecutive winters on Botswana's Makgadikgadi Pan as well as Namibia's Skeleton coast and The Namib Sand Sea, requiring shipping and driving approximately 100 items across borders using trailers and Hiluxes with permits and additional paperwork in tow. It can take as much as three weeks to just set up all the kit.

Trouble Shooting the broken CIMEL on the left while installing the CSAG SODAR on the right. Fence should keep hyenas out.
DGPS survey tells us the pan is flat but sloping at 1.5m over 12km. This has implications on ground water and soil moisture.

Because you want to make sure you get dust event data, the sites need to be carefully identified. This was achieved early on, by MSc student Kathryn Vickery (UCT EGS) during her MSc who spent weeks going through thousands of satellite images looking for dust. Not only did this allow us to place our kit in the right place, but it also showed that the Kuiseb River is one of the dustiest places in Southern Africa which is currently being monitored (Vickery and Eckardt 2013).

Once the kit is up and running it records data at 11 sites with wind speed data at 6 different heights, wind direction, soil moisture at two different depths, airborne particular matter concentration, lateral sediment deposition, vertical sediment deposition, humidity, in and outgoing radiation, rainfall and sand transport activity. We also characterise all the surfaces for micro-topography and moisture using a laser scanner and sample all the sediments for later lab analyses. We also measured the optical thickness of the atmosphere and deploy differential GPS.

Current Site in The Namib Sand Sea.
Active Dust Day in the Lower Huab.

While wind is obviously important for dust emission, surfaces can also change with time and are able to produce and make it easier for the wind to liberate the fine particles in different quantities therefore understanding dust production basically requires one to also look at surface geomorphology and often soil moisture. That is the hard part to grasp but at the same time heart warming to a geomorphologist.

Roadside trailer repairs, fixing broken wheel and axel. A bad day turned out OK. Author was happy. (Photo K. Vickery)

The large team has more than 100 years of field experience, much of which gained in southern Africa. Still all of us would agree that to monitor episodic events in difficult places has been one of the most challenging undertakings we can remember.

While I write this, equipment is sitting unattended in the Lower Huab, Upper and Lower Kuiseb, and Lower Tschaub (coordinates withheld) steadily monitoring and waiting for the next big event to happen. Nevertheless Kathryn Vickery is now working on a PhD to look at dust particle chemistry from Sua and Jore von Holdt is looking at the sediment characteristics in the lower Kuiseb Valley. Come October 2013 it will be time to take it all down. And put it up again next year? Who knows? But the time to work on those papers has come.

Reference:

  • Vickery and Eckardt (2013), Corrected Proof Dust emission controls on the lower Kuiseb River valley, Central Namib, Aeolian Research, in press (link to paper)

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