FLATOCOA : Flux ATmosphérique d'Origine Continentale sur l'Océan Austral
We aim to know the amount of continental dust deposited over the Southern Ocean by atmospheric deposition as well asthe fraction that can be bioavailable for the oceanic biologic network.
The atmospheric flux and the dust concentration have been collected during 2 years at Kerguelen (49°27' S 70°05' E) and 1 year at Crozet Islands (46°22' S 51°41' E) with a sampling time ranging from 2 weeks to 1 month. These data are used in connection with a transport /deposition model in order to extent these results at a larger scale. Analyses are now underway and the first results show that the measured deposition flux of continental dust and of iron are in agreement with the higher values provided by global dust models.
This program is a component of the International SOLAS (Surface Ocean Lower Atmosphere Study) program since July 2009 (SOLAS endorsed projects)
In remote marine zones, the atmosphere is likely on the key transport ways of micro-nutrient from the continents into the ocean. Indeed, the whole Southern Ocean is HLNC (high nutrients, low chlorophyll) as shown by the figure below and its biological primary production is limited by the availability of some key micro-nutrients (trace metal and especially Fe, Co, Zn, Cd.. It is highly suspected that the atmospheric aerosols would be one the major sources of these elements for the Southern Ocean.
The principal station was setup in December 2008 at Atmosphere Mountains (Kerguelen). It is located 8 km west side of Port aux Français and run until March 2011. Duplicate total deposition sampling and aerosol filtration (thanks to a windpower generator system) are performed. A meteorological station is also in operation here.
A secondary station was running at Guillou Island, 30 km west of Port aux Français from December 2008 until January 2010. At this station, only duplicate deposition sampling is performed. Finally, a third station have been operated at Crozet Island during 2011.
Total deposition is collected using Teflon PTFE machined funnels with a 12 cm diameter. A 1L polypropylene bottle is screwed at the bottom of the funnel. This system stands 2 m high at the top of a 10 cm diameter PVC tube secured with Kevlar ropes.
Aerosol sampling is performed by using 3 parallel filters. One filter is 0.5 µm porosity and 47 mm diameter Teflon Zefluor filter, a second is 0.2 µm porosity and 47 mm polycarbonate Wattmann filter, and a third system is millipore polycarbonate 0.2µ porosity 25 mm filter. Power is supplied by a 400 W AirX wind generator coupled to 4 75Ah batteries and a 400 W power inverter. A 12 W solar panel and a circuit breaker are added in order to protect batteries from full discharge. Because of the windy general conditions, the three 1m3/h pumps can work about 80% of the time with this power generator.
Analyses and sample handling
Alnalytical facilities are located in LISA and operating in clean rooms (ISO5 and ISO1 flow hoods). A considerable effort was made to clean the bottles and sampler, including extensive washing, soaking and rinsing in successive different baths: Detergent, 10% HNO3, 10% HCl, Ultrapure 5% HCl twice. All the cleaning protocol does not last less than 6 months. At Kergelen, we have also set up a light clean-room (ISO6) in one of the building of Port aux Français.
First results are part of a master degree report, communicated in many meetings and today submitted in journals.
R. Losno, T. Wagener, F. Dulac, C. Guieu, S. Triquet and J.L. Colin, Dust size measurement over Austral Ocean, SOLAS Open Science Conference, Xiamen, China, 6-9 mars 2007.
R. Losno, S. Triquet, S. Lafon, A. Heimburger, F. Dulac, F. Montoya and A. Demaret, Deposition of trace metals and metalloids on kerguelen island the FLATOCOA program, SOLAS OSC, Barcelone, 16-15 novembre 2009
R. Losno, S. Triquet, Sandra Lafon, Alexie Heimburger, Francois Dulac, Florent Montoya and Alain Demaret, Atmospheric transport to Kerguelen and the South Indian Ocean - One year of measurements, AGU OS – Portland (OR) 22-26 February 2010 (GEOTRACES IPY session).
Heimburger, A., Losno, R. and Dulac, F, Atmospheric deposition of trace elements over the South Indian ocean: a time series at kerguelen islands, 2011 ASLO Aquatic Sciences Meeting, San Juan de Porto Rico, 14-18 février 2011
R. Losno, C. Guieu, F. Dulac, S. Triquet, J.L. Colin, N. Perron et J. Sciare, Approche du suivi du cycle atmosphérique des métaux dans l'océan austral, Deuxieme journée scientifique du comité national francais des recherches arctiques et antarctiques (CNFRA), Paris, 4-5 octobre 2005.
R. Losno, S. Triquet, F. Montoya, A. Demaret et F. Dulac, FLATOCOA: Flux de particules atmosphériques d'origine continentale au dessus de l'Océan Austral, IMBER-SOLAS-France, Paris, 22-23 juin 2009.
A. Heimburger, R. Losno, S. Triquet, E. Bon and A. Perot, Dust deposition over South Ocean measured at Crozet an Kerguelen Island. SOLAS-IGAC-France, 29-30 juin 2011, Paris
To be continued :A new program, entitled "Dust From Patagonia" and funded by CNRS/INSU (LEFE/CHAT) will measure dust emissions from Patagonia (2012-2014).