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Scientific participations

Frank Dehairs

  • language: NL, FR and/or ENG
  • e-mail: fdehairs@vub.ac.be
  • address: Frank Dehairs
    Vrije Universiteit Brussel
    Analytical and Environmental Chemistry
    Pleinlaan 2
    B-1050 Brussels
    Belgium
    Tel: 32-(0)2-629.32.60
    Fax: 32-(0)2-629.32.74
  • period: January or other (get in touch)

My research:

The climate on earth has fluctuated considerably in the past as controlled by natural processes, including variations in exchanged quantities of CO2 between the atmosphere and the ocean. Man is changing these natural cycles because of the enormous release of carbon dioxide from fossil fuel combustion and deforestation, and today the CO2 content in the atmosphere is increasing exponentially. A large part of the CO2 gas is taken up by the global ocean, of which the ocean around the Antarctic continent represents an important fraction. In order to understand and predict climate it is important to know more about how the ocean deals with the CO2 it receives from the atmosphere. There are purely physical and chemical processes involved (CO2 dissolves in seawater and reacts with water) but also biological processes, such as photosynthesis by unicellular algae (phytoplankton) and respiration by bacteria, plankton and higher organisms. Photosynthesis fixes carbon from CO2 into organic tissue (phytoplankton biomass). This biomass can then be eaten by zooplankton, fish or may simply die and sink to the deep ocean. Also zooplankton and fish excrete waste material and die, thus contributing to the flux of ‘dead’ organic carbon (detritus) to the deep sea. This process of carbon transfer to the deep sea via sinking biomass is called the biological carbon pump. It operates next to the physico-chemical carbon pump, which is related with CO2 solubilisation and the sinking of surface waters to great depths, as occurs in the very cold high latitude regions. I am interested in assessing this detritus flux and in understanding what happens to the detritus: does it reach the sediments to accumulate their (and form the fossil fuel of the future) or is it mainly respired by deep sea bacteria, which thereby turn organic carbon back into CO2? In the former case the biological pump has a negative feed-back on global warming (it substracts part of the emitted greenhouse gas from the atmosphere) while in the second case the effect is zero, because one day the deep sea waters will be returned to the surface to release this respiratory CO2 back to the atmosphere. We assess the carbon flux out of the surface waters by studying trace element and natural stable and radioactive isotopes which operate as ‘proxies’ of the carbon processing. We also want to know what the variability is of this process in space and time and which factors control it. Especially the element iron has been identified as a major control of the biological activity and therefore also of the detritus flux to the deep ocean.
We study the phytoplankton processes in surface water as well as the fluxes of carbon to the deeper ocean, and we assess spatial and seasonal variability. At the end we hope to construct the broad picture of the magnitude of these carbon fluxes in the Southern Ocean as well as the factors which are in control.

Fields of expertise:

My research belongs to the domain of marine biogeochemistry. It covers in fact the disciplines of marine biology, geology and chemistry. So you may become a marine biogeochemist being either a biologist, a chemist or a geologist.

Needs for participating in an expedition:

Before boarding for a Southern Ocean expedition you need to carefully prepare your scientific equipment (chemicals; sampling instruments; analysis instruments). You have to check that all equipment functions properly and that no chemical or equipment, whatever small, is forgotten but will be on the ship when you have to start your work. Your ship will be alone in the vastness of the ocean and nobody can bring in spare parts or forgotten items … If possible we will use a laboratory container from the Belgian oceanographic vessel, Belgica. This laboratory container is fully prepared in Belgium and is then send by cargo to some far away place such as Punta Arenas, Ushuaia, Hobart, La Réunion…There it will be put on a large vessel (mostly ice breakers) such as the Polarstern, Aurora Australis, Marion Dufresne, which are a German, Australian and French vessel, respectively. Indeed, Belgium has no ice breaking ship for operation in polar seas, and so we have to rely on foreign ships. You also have to bring some special clothing since the outside temperatures on deck will be negative and always close to zero, even during the southern hemisphere summer (December – February). However, we will not experience the tremendously cold temperatures typical for the Antarctic continent itself. Indeed, the Southern Ocean is a heat reservoir for the atmosphere and so the air temperature above the sea is higher than above the continent. Nevertheless, inside your laboratory container, if installed outside on the deck, it will also be quite cold; it is like working for hours in a fridge.

What is fascinating about Antarctica:

What fascinates me when starting on an expedition is the vastness of the ocean, the never reachable horizon and when approaching the vicinity of Antarctica the sight of huge icebergs, the pack ice and finally the ice edge the last obstacle to reach the continent. These ever changing sights are never monotonous because of changing sunlight: midnight light on a freezing ocean with icebergs floating at close distance is an unforgettable sight. There also is all the live that goes on in the ocean and on ice: albatrosses above the windy open ocean, penguins, whales and seals when approaching the continent. Oceanographers unfortunately can not spend too much time looking at all these marvelous things, they also have to get their deep sea samples and analyse these in their (cold) laboratories. But aboard the ship not all is work; there is also is some social live and opportunities to organize a party are not rare; but beware within a few hours you will have to be back at work !


 
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