Aldo Drago
Malta Council for Science & Technology
112 West Street
Valletta 12
Malta
Introduction
A group of experts from France, Israel, Italy, Malta, Monaco and Spain met at the CIESM Headquarters in Monaco on 15 February 1996 for the preliminary planning of an operational network of tide gauge stations in the Mediterranean and Black Seas. The participants (see list in Annex) represented a broad spectrum of expertise in relation to the monitoring of sea-level by both in-situ and remote-sensing techniques.
The meeting was chaired by Prof. Frederic Briand, DG of CIESM, who welcomed the participants and outlined the initiative of CIESM\IOC to jointly support the establishment of this Network as an extension of GLOSS (Global Sea-level Observing System) in the Mediterranean region.
Prof. Briand emphasized that this proposal responded to pressing needs in the region to establish platforms for Mediterranean-wide oceanographic research, monitoring and operational programmes, and he paid tribute to the CIESM delegates of Israel and Malta for their decisive help in launching this initiative. The fact that CIESM envelopes amongst its Member States nearly all the countries of the Basin certainly favours initiatives such as MedGloss which depend directly on their geographical span for a successful implementation. In order to achieve its scientific objectives, MedGloss will in fact greatly rely on the extent to which it will succeed to bring the less developed North African and South-Eastern Mediterranean countries in closer proximity to their more technologically advanced Euro-Mediterranean neighbours for a strengthened and concrete "cooperation-through-participation" scheme. Especially in this respect, MedGloss aims to be a prototype for the launching of GOOS in the Mediterranean.
The GLOSS experience
After a brief presentation by each participant, Dr.Albert Tolkatchev, who is in charge of GLOSS at the IOC Secretariat, gave a detailed review of the GLOSS programme focussing in particular on the mechanisms and arrangements established for its implementation. Since its initiation in 1984, GLOSS has developed a global network of 308 tidal stations, thus enabling the large scale observation of sea level fluctuations and a better understanding of sea level changes in both time and space. A major outcome of GLOSS concerns the improved reliability of projections on sea level rise; in the special case of the Indo-Pacific region, GLOSS is a major component of the operational predictive system in relation to the El Nino effect.
The successful implementation of GLOSS is based on the following main ingredients:
- clear formulation of objectives
- correct geographical distribution and positioning of stations
- intensive programme of capacity building through regional training courses
- a well planned data management and dissemination structure
- provisions for value-added data products.
MedGloss should follow these lines of action. In a region like the Mediterranean where the tide is in most cases too small to affect navigational safety, it is particularly important to convince governments that sea level data are useful for many other applications (eg. salt water intrusions into aquifers, effect of sea level changes on wetland ecosystems, etc.). Following the example of GLOSS, brochures will certainly prove useful in raising awareness on MedGloss and sea-level related issues in the Mediterranean. It was also suggested to use the World Wide Web in order to provide a future bulletin of information for MedGloss over the INTERNET.
Training
A strong training component is essential both as a means of providing a visible gain to the participating countries as well as a sound investment towards ensuring high quality data in the network. Initially training should focus on optimal station maintenance, high standards of data acquisition and presentation as well as overall knowledge on state-of-the-art equipment for precise water level recording. In a second stage training can be directed more specifically to data interpretation and assimilation of sea level products into feasibility studies, ocean modelling/ forecasting and coastal environmental assessments. In both stages adequate manuals should be made available in order to achieve a common basis for compatible and precise sea level measurements. IOC is prepared to make available to MedGloss all its manuals and guidelines published for sea level measurements.
IOC is also prepared to support training courses specifically for MedGloss. Such courses should be mainly directed to the North African and Black Sea countries. In particular arrangements can be made in order to send some Mediterranean participants to the GLOSS training course planned for 1997 in the United Kingdom.
Finally Dr. Tolkatchev informed the participants on the EU-funded project entitled "Sea Level Fluctuations: geophysical interpretation and environmental impact (SELF)". This project is co-ordinated by Prof. Susanna Zerbini of the University of Bologna who has been invited to take part in the MedGloss group of experts. While this case study is not making use of any tide gauge stations outside the waters of the European Commission, the experience gained in this project could be of high value to MedGloss.
Elements and structure of MedGloss
In order to ensure network functionality and an efficient control on the data collection and management mechanisms 5 sub-regions were identified. The Western Mediterranean, the Adriatic Sea, the Central Mediterranean, the Eastern Mediterranean and the Black Sea were tentatively selected. Focal points will be established in time for each sub-region in order to address specific needs and identify the necessary programme adjustments in their respective sub-regions; focal points will be also responsible for the correct operation of the MedGloss stations and optimal flow of high quality data. However, it is important to adopt the MedGloss network on a de-centralised structure as much as possible; processing and treatment of data at source should be encouraged and supported so that local capacity building is ensured. A distributed database system should also be established in order to facilitate direct access of data sets from any point on the Network. In this context the focal points are envisaged to act only as facilitators and check-points.
Focal points will be identified at a later stage when a wider list of participants are involved in the Network. The participants at the meeting were however asked to make an analysis for the establishment of MedGloss in their sub-region.
It is also necessary to identify national contact points for MedGloss. The DG of CIESM shall contact all CIESM National Delegates for a brief on sea level monitoring activities in their respective countries and for the official designation of a national contact person.
Operational component
The question relating to the operational vs non-operational modes was discussed to some length. The general consensus was that both modes should co-exist and that this issue is strictly linked to the objectives of MedGloss.
Besides addressing global issues and meeting the needs of GOOS in general, MedGloss also aims to directly meet the demands on regional, sub-regional and national scales. The recommended strategy is that of adopting a network which serves national needs in the perspective of priorities on a Mediterranean-wide dimension. MedGloss shall therefore first concentrate to eliminate scientific and political barriers for the establishment of a strong platform for its network. In its initial phase MedGloss should focus on building a structure that benefits from existing national initiatives, provides scope for mutual support and co-ordinates individual efforts in synergy with plans for a future regional role. The short-term objectives should therefore rely on a Network that mainly handles data in delayed mode. Rescue and compilation of historical data is also an asset.
Provision of operational services by the Network will require a higher level of organisational, structural and scientific support. MedGloss aims to function in this mode in the future. The configuration of the Network will have to rely on specialised selected nodes on the Network which will relay data in real-time and merge their operations with Centres of excellence in the region for the provision of added-value products. In this respect MedGloss would become an essential component of GOOS in the Mediterranean. Amongst the operational activities envisaged within MedGloss, the use of satellite altimetry, the assimilation of data in numerical models for weather and ocean forecasting, and the need to establish warning mechanisms in vulnerable areas, were amongst the main topics highlighted during the discussion.
Station requirements
A minimum set of requirements were discussed for inclusion of stations in MedGloss. It was agreed that standards should be compatible to the GLOSS recommendations. In particular reference was made to page 28 in the IOC Technical Report Series Nos. 35 entitled "Global Sea Level Observing System (GLOSS) Implementation Plan".
The basic requirements are as follows:
- a station should provide hourly averaged water level data in digitised form
- a station should keep reliable reference elevation bench marks which will be connected by GPS techniques; geodetic measurements should be conducted on a regular basis to permanent GPS stations
- measurement of the wind vector, atmospheric pressure, air and sea temperatures are essential especially in those stations where pressure and acoustic sensors are used
- the agency responsible for a station should be in a position to guarantee a long-term commitment
- the use of automated reference level switching systems should be encouraged against the traditional zero referencing by the use of tide staffs.
It is also recommended to have more than one sensor at each station for reasons of backup and intercomparison.
Data formats and software
With regard to data formats, it was agreed to use GF3 as a standard. This data format is already well established within the UNESCO data managment community. Moreover GF3 is amenable to water level data and programmes for conversion of ASCII data into GF3 are already available.
During the meeting Dr. Dov Rosen gave a demonstration of the Meteocean Info Software ISRAMAR which was developed by the Israel Oceanographic & Limnological Research (IOLR). ISRAMAR is a package of computer programmes integrated in a unified system and providing near real-time information on meteorological and oceanographic parameters. All the participants will be receiving by mail a copy of ISRAMAR in order to provide feedback on its applicability to MEDGLOSS.
A common software for MedGloss is essential. This software should facilitate the input, validation, analysis, visual display and management of sea level data. It should also provide for conversion of ASCII files into the approved data formats of MedGloss. Dr. Rosen agreed to approach Dr. P. Woodworth, Chairman of the GLOSS Group of Experts, in order to obtain information on procedures and computer subroutines for the checking and quality control of sea level data.
Before MedGloss enters into operational mode, common data formats, standard communications software and protocols as well as appropriate network interfaces and databases implemented on a client-server architecture will have to be established for the transfer, exchange and relational databasing of measurements in quasi real-time.
Sea level measurements from space
With the advent of precise satellite altimeters, sea level can today be measured up to an accuracy of a centimetre. Since 1991, the processing of data from TOPEX POSEIDON and ERS-1 has permitted the establishment of an extensive set of synoptic maps of mean sea level (MSL) and sea level anomalies in the Mediterranean These satellite data sets have permitted the identification of strong seasonal signals in MSL which now need to be validated against in situ measurements.
Certain technical limitations pertaining in particular to the sparse coverage in time and to the shadow zone in the proximity of the land-to-sea transition were highlighted. It was also mentioned that patterns of the general circulation derived for the Mediterranean through satellite data are not at all compatible to those obtained from direct hydrographic measurements. These elements already provide enough groundwork for the study of the manner and extent to which MedGloss can contribute in such scientific endeavours.
A Working Group composed of Drs. Dov Rosen, Pierre Exertier and Agustin Sanchez-Arcilla was set up in order to tackle these matters. This group of experts agreed also to provide MedGloss with recommendations on geodetic aspects especially with regard to the determination of absolute sea level changes.
Further Dr. Exertier shall approach CNES (Centre National d'Etudes Spatiales, Toulouse) to discuss the availability of TOPEX POSEIDON data relevant to MedGloss.
Other assignments
Dov Rosen was appointed scientific co-ordinator of MedGloss. Aldo Drago was appointed as the rapporteur for MedGloss. In this capacity both will be able to represent MedGloss at the GLOSS Group of Experts.
Dr. Silvana Vallerga agreed to act as the liaison between MedGloss and MEDMARIS.
Next meeting
It was agreed to call a second MedGloss meeting towards the end of this year, possibly in November. This meeting will review the progress made by MedGloss in one year and share this experience with other interested countries in the Basin.
1. INTRODUCTION
Following forecasted sea-level rise due to the so called “greenhouse effect” a worldwide sea- level monitoring network named the Global Sea-Level Observing System (GLOSS) was initiated by the Intergovernmental Oceanographic Commission (IOC) in 1985. This network consists of about 300 major network stations, committed to conduct long-term monitoring of the sea-level according to monitoring methods and equipment as recommended by the Group of Experts of GLOSS. In its choice of the major stations the network emphasized it global character, mainly influenced by the oceans of the world and less by marginal seas. Presently a worldwide sea-level rise has been forecasted by the experts of the IPCC due to the greenhouse effect. While the report of this committee gives average global sea-level rise estimates for the whole globe, it is also recognized by its authors that regional sea-level rise may differ significantly from the globally averaged sea-level rise forecasts, due to a number of reasons. However, the GLOSS network contains only a very small number of stations in the Mediterranean, although it possesses a significant number of relatively low-lying coastal areas. Although the Mediterranean sea is relatively of small size in comparison of water masses in the oceans, it represents for millenniums a major center of dense human habitat and activity. The water balance and exchange between the Mediterranean sea with its neighboring seas and the Atlantic Ocean and with the atmosphere, can serve as a scaled model of the world water exchange processes.
In view of the latter two remarks, it becomes obvious that in order to better understand the effect of the greenhouse effect and be able to forecast future sea-level rise in the Mediterranean, one should not be satisfied with the small sea-level GLOSS stations in this marine basin.
2. RATIONAL OF THE PROPOSAL
The present proposal is forwarded in order to strengthen the original GLOSS network by creating a densified regional long-term sea-level monitoring network in the Mediterranean and its adjacent seas, network which will facilitate the performance of regional studies regarding sea- level rise and water exchange.
For this purpose it is recommended that the regional network will be composed from sea-level monitoring stations already active in the GLOSS strengthened by additional sea-level stations operational in a number of countries around the borders of the Mediterranean and its neighboring seas and by new sea-level stations to be installed on the coasts of countries willing to join the network. To enable quick availability of the regional sea-level data, a near real-time monitoring network system is proposed, based on the experience gathered in the last two years by Israel with the GLOSS station no. 80 at Hadera, Israel, and a national sea-level near real-time monitoring system under implementation in Israel.
Also, starting late 1995 Israel participates in a regional plate tectonics study together with Egypt, Jordan, Turkey and England to establish fiducial GPS stations in the former three countries, which will facilitate long-term monitoring of plate tectonics in the Eastern Mediterranean and Red Sea. The reference to the gravymetric system is performed relating the GPS measurements to the sea-level observed at monitoring stations in these countries.
It should be mentioned also, that due to the relatively small tidal range in the Mediterranean, the determination of long-term trends in sea-level changes at the coastal stations is masked by seasonal and other climatic fluctuations like the steric effect, wind set-up, wave induced superelevation, atmospheric pressure, general circulation, land subsidence or rise due to glacial rebound or overuse of groundwater, etc.
Consequently, to be able to remove the influences of these factors, and obtain the sea-level fluctuations it is of utmost importance to perform also long-term monitoring of their fluctuations with equipment leading to the same degree of accuracy and resolution in the determination of their rate from the measured sea-level.
3. PROPOSAL CONTENTS
a) A regional near real-time long-term sea-level monitoring network will be set up in the Mediterranean and its adjacent seas.
b) Initially, the network will consist of sea-level monitoring stations already operational, provided that the measurements are conducted with satisfactory equipment (digital output, good maintenance, reliable bench mark, external data output). Priority will be given to stations holding long-term records and/or answering to GLOSS recommendations.
c) The reference elevation bench marks of the network stations will be connected via GPS geodetic measurements conducted at least once/year to permanent GPS stations.
d) The monitoring stations will transfer their data via telephone lines or cellular telephone to a number of regional centers, which will disseminate and validate the data (promptly inform of malfunctioning of a monitoring station) and transfer the disseminated data via INTERNET or telephone to all members of the network as well as to the GLOSS via PSMSL.
e) New monitoring stations will be added to the network preferably using next-generation sea-level monitoring instruments. Assistance in the provision and preliminary operation of these stations will be provided by the regional centers, who will organize also a number of workshops for the education and training of the staff of the new stations.
f) Funding for the operation of the network and the set-up of new stations will be requested from IOC and from the participating countries.
g) Funding for the organization of workshops for education, training and scientific exchange will be requested from the CIESM, who will also be asked to manage these workshops.
4. DISCUSSION OF THE PROPOSAL
It is suggested that initially the set-up of this network will be discussed at the workshop organized jointly by IOC and CIESM on this issue in February in Monaco. It is proposed that regional centers will be established as follows: for the western Mediterranean in Spain or France, for the central Mediterranean in Italy or Malta, for the Eastern Mediterranean in Israel and for the Black Sea in Romania or Ukraine. The near real-time transfer of data can be performed with the aid of a computer software system developed by IOLR, requiring only the availability of ASCII data on a logging PC computer (386 and up) equipped with a modem and a telephone line or cellular telephone. Description of a multi-parameter near real-time monitoring program system based on this software (ISRAMAR) is provided as an addendum.