7. The Experiment Continues


Throughout this text, I have repeatedly emphasised my belief in the need for an intensive, trans-national, and structurally funded program of multi-disciplinary Mediterranean research. This is primarily required, because : (a) the health of the Mediterranean Sea is relevant to a great number of nation states that border it (with over 250 million people living in those nation states), amongst other things for fisheries, mariculture, and tourism; and (b) the Mediterranean as a large-scale environment may today be under threat due to its land-locked nature and the huge anthropogenic interferences it suffers. The practical application of studies of the basin’s recent geological past to assess the potential impacts of these interferences is obvious.

However, the relevance of Mediterranean studies goes even deeper than that. The Mediterranean is a marginal ocean basin with a circulation and ventilation that is as active as that in the open ocean. In fact, all major oceanic processes and interactions are represented ‘in miniature’ in the Mediterranean, except for those related to sea-ice and polar climates. This implies that the lessons learned from Mediteranean research are of relevance also to our understanding of the functioning of deep circulation in the world ocean and its relation to global climate.

The relatively small volume of the Mediterranean ensures very rapid adjustments to environmental/ climatic perturbations. At the same time, the Mediterranean’s landlocked nature imposes strong limitations on the exchanges with the open ocean through the narrow and shallow Strait of Gibraltar, causing the basin’s properties to respond in an amplified fashion to perturbations. In summary, the Mediterranean is recognised as an excellent ‘natural laboratory’ where processes and sensitivities relevant to the world ocean circulation can be studied in conveniently-reduced spatial scales and with a much better signal to noise ratio than may be expected in the open ocean. The spatial scale argument is important if we want to distinguish regional variability from basin-wide trends. In the Mediterranean this is feasible, while it is a very difficult problem when considering the entire world ocean. The rapidity of adjustments in the marginal basin also improves the potential for detailed monitoring of the processes and feedbacks involved in adjustments to perturbations. In the Mediterranean such studies require monitoring over one to several decades, whereas in the open ocean one or more centuries would be needed.

This does not imply we should stop studying world ocean! Obviously the larger spatial and time scales involved in world ocean circulation, and its full equator-to-pole extent (with the associated surface temperature gradient), cause distinct differences between conditions/responses in the world ocean and in the Mediterranean ‘natural laboratory’. In addition, interactions between the atmosphere and the world ocean  place important constraints on climate. The argument made here is simply that the natural laboratory should be exploited to it full potential for fundamental process studies with a detail in space and time that cannot be achieved in the wider oceanic context. That way, Mediterranean research will help in the formulation of testable working hypotheses regarding the responses of world ocean circulation, which can then be validated through targeted research.

For example: many scientists today are concerned about the (in)stability of the world ocean’s deep-water circulation, within the context of natural and/or anthropogenic climate perturbations. We know from marine geological studies in the open oceans that great fluctuations have occurred in this deep-water ventilation during the recent geological past. We do not know, however, exactly how these fluctuations developed, and how they affected different places in the world ocean. We also don’t know exactly what the nature and magnitude of the environmental/ climatic perturbations was that triggered these fluctuations. As seen earlier these can be so small and subtle that it is difficult to differentiate cause and effect. Studies on the recent geological past of the Mediterranean can provide direction to investigations concerned with these unknowns. After all, the Mediterranean provides a dense coverage in high-quality records of climate-driven collapses, fluctuations, and recoveries of a comparable deep-ventilation system. These records are complemented by detailed information about ongoing adjustments of the Mediterranean deep-ventilation system to environmental/ climatic perturbations. In other words, both nature and we ourselves have performed some crucial ‘experiments’ in this ‘natural laboratory’.

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I hope to have succeeded in passing on the message that sapropels are not just a scientific curiosity, with the formation of the next one a comfortable 11,000 years into the future. On the contrary, I argue that detailed investigations of sapropels are vital to our understanding of important processes, feedbacks, interactions, cyclicities, and time scales and magnitudes of the Mediterranean’s response to environmental perturbations (note 16). A thorough understanding of these fundamentals is essential if any educated prediction is to be made of the basin’s potential responses in the (near) future to the current combination of natural and man-induced perturbations. Perhaps, the next deep-ventilation catastrophe is not so far away into the future after all? Could we have broken the pacemaker’s grip on the system?