1. Project: EST.CLG.975821
2. Project title: The Role of Transport Processes on the Ventilation and Biogeochemical Cycling in the Black Sea
3. Participants:
- Prof. Oguz T., METU IMS, Turkey
- Dr. Ivanov L.I., MHI, Ukraine
- Dr. Samodurov A.S., MHI, Ukraine
- Dr. Konovalov S.K., MHI, Ukraine
- Prof. Korotaev G.K., MHI, Ukraine
- Dr. Demyshev S.G., MHI, Ukraine
4. Codirectors:
- Prof.
Oguz T.,
Institute of Marine Sciences, Middle East Technical University
P.K. 28 Erdemli - Icel 33731 Turkey
Tel: +90-324-521-2406
Fax: +90-324-521-2327
E-mail: oguz@ims.metu.edu.tr
Web: http://www.ims.metu.edu.tr/cv/oguz/main.html - Dr.
Ivanov L.I., Marine Hydrophysical Institute, National Academy of Sciences of Ukraine;
2, Kapitanskaya st., 335000
Sevastopol
Ukraine
Tel: +38 0692 41 30 99
Fax: + 38 0692 44 42 53
e-mail: leonid@alpha.mhi.iuf.net
5. Status: on going
6. Period (start/end): July 1999, during two years
7. Objecttives: The objectives of the proposed studies here is to investigate the role of transport processes on the ventilation and biogeochemical cycling in the upper layer water column of the Black Sea. They are listed below in two groups:
(1) Studying the circulation dynamics with data assimilation: The general circulation modeling studies were base on the yearly-mean and monthly climatological forcings. The proposed study constitutes an extension of these efforts aiming at predicting more realistic circulation fields in the Black Sea. We focus on the implementation and validation on an advanced data assimilation technique for our existing Princeton Ocean Model (POM) based general circulation model in hindcasting mode; i.e. using existing observations from a known, past state of the sea. The assimilation technique will be based on the Kalman Filter method witch has been recently implemented for the Black Sea by Korotaev (1999) and Demyshev (1999). The details of the method and other areas of applications are found in Fukumori and Malanotte-Rizzoli (1995) and Malanotte-Rizzoli and Young (1997). It is dynamically rigorous and powerful technique that minimizes the model-data misfits under the constraints of model dynamics. Two data sets to be assimilated are (i) the sea surface haight anomalies provided by TOPEX/POSEIDON and ERS-1 altimetres for the period of 1993-1997, (ii) the sea surface temperature distributions provided by AVHRR imagery for the same period.
(2) Ventilation and biogeochemical cycling within the upper layer water column: Because the Black Sea is a land-locked basin with very limited lateral oxygen input through the Bosphorus, and the anoxic layer is located only 100 m below the surface in its most parts, exploring the ventilation mechanisms of the upper layer water column is a critically important issue for its biogeochemical cycling. One possibility of the oxygen supply is vertical ventilation associated with the convective overturning process following intense winter atmospheric cooling episodes. The work performed by Oguz et al. (1998b), however, appears to indicate that the strong stability of the water column prevents any seasonal variability of the oxygen below 50-60 m depth due to atmospheric ventilation. The second mechanism which might contribute to the ventilation process is the onshore/offshore transport of oxygen by means of the meanders of the Rim Current and the cross-shelf transports across the Western-northwestern shelf. The last mechanism is the oxygen influx through the Mediterranean underflow entering into the basin off the Bosphorus northern opening. In addition, oxygen may be produced locally during the photosynthesis within the euphotic zone of the water column. As the ventilation mechanisms provides source of oxygen in the basin, its consumption during the organic matter decomposition and nitrification processes constitutes the loss of the oxygen from the system. The oxygen thus drops to its trace level values of the less than 5mM at depths around 60-to-75 m range in most parts of the water column. The ventilation problem is therefore tightly coupled with the modeling of the water column biogeochemical processes outlined in the previous section.