Scientific participations
Frank Dehairs
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.
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.
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 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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My
research: