GLOSS The Global Sea Level Observing System Global

GLOSS - The Global Sea Level Observing System Global Level of the Sea Surface 1. Monitoring and Measuring Sea Level – Why and How? 2. The GLOSS Programme – Network and Activities 3. Sea Level Data Thorkild Aarup, GLOSS Technical Secretary t. aarup@unesco. org http: //www. pol. ac. uk/psmsl/programmes/gloss. info. html

GLOSS - The Global Sea Level Observing System • Establishment of high quality global and regional sea level networks for application to climate, oceanographic and coastal sea level research • Sea level stations around the world for long term climate change and oceanographic sea level monitoring • Coordinated by the Intergovernmental Oceanographic Commission (IOC) • Major contributor to IOC’s Global Ocean Observing System (GOOS) http: //www. pol. ac. uk/psmsl/programmes/gloss. info. html

Why Measure the Sea Level? • Scientific research – e. g. to measure long term changes in global sea level and ocean circulation • Practical applications – e. g. to predict flood risks in coastal regions How to Monitor the Sea Level? • Satellite radar altimetry • Tide gauges • In the deep ocean: bottom pressures obtained from sea bed devices http: //www. pol. ac. uk/psmsl/programmes/gloss. info. html

Measuring Sea Level Changes Altimeter System Bottom Pressure Gauge Tide Gauge (float) http: //www. pol. ac. uk/psmsl/programmes/gloss. info. html

Why Tide Gauges in the “Age of Altimetry”? • Principle of continuity, relative low cost of gauges • Long records for secular trend/acceleration studies (e. g. for input to IPCC) • Higher frequency sampling important in straits and other areas • High latitude regions of ice coverage • Altimeter calibrations (‘absolute’ and ‘relative’) • Coastal applications (GOOS Coastal Module) Acoustic Gauge in Australia http: //www. pol. ac. uk/psmsl/programmes/gloss. info. html

Sea-Level Changes Different Time-Scales • Momentary changes due to tsunamis • Daily changes due to tides and surges • Seasonal changes • Interannual changes e. g. due to ENSO • Long term changes due to climate change Causes of Sea Level Change • Local processes in river/coastal regimes • Ocean circulation changes Maldives Int. Airport • Regional and global climate changes • Geological processes http: //www. pol. ac. uk/psmsl/programmes/gloss. info. html

Long Term Changes in Sea Level Past 100 years • Most records show evidence for rising sea levels during the past century • IPCC concluded that there has been a global rise of approximately 10 -20 cm during the past 100 years http: //www. pol. ac. uk/psmsl/programmes/gloss. info. html

Long Term Changes in Sea Level Next 100 years • a rise between 9 and 88 cm • a central value of 48 cm • a rate of approx. 2. 2 - 4. 4 times that of the past 100 years Projected sea level rise, IPCC 2001 http: //www. pol. ac. uk/psmsl/programmes/gloss. info. html

The GLOSS Programme/Networks • GLOSS Core Network (GCN) • Regional Densifications of the GCN • Long Term Trends (LLT) • Altimeter calibration (GLOSS-ALT set) • Ocean Circulation (GLOSS-OC set) GLOSS Core Network (GCN) with approx. 280 stations http: //www. pol. ac. uk/psmsl/programmes/gloss. info. html

GLOSS Activities Regional Developments • Regional networks of gauges with greater spatial density, to serve the particular oceanographic interests of those regions - examples: IOCARIBE (Caribbean), Med. GLOSS (Mediterranean & Black Seas) National Activities • Contribution to the activities of national agencies by improving the standards for sea level recording around the world Training • Annual training courses on the techniques of tide gauge operations, and workshops on special interests e. g. measurements in environmentally hostile areas http: //www. pol. ac. uk/psmsl/programmes/gloss. info. html

Responsibilities of GLOSS Data Providers There are 3 responsibilities of GLOSS data providers: 1. Monthly and annual MSL data to PSMSL by 6 months after the data-year 2. Delayed-mode higher-frequency data (typically hourly values), quality controlled to one of the GLOSS centres (in practice PSMSL again or UHSLC) 4 months after recording 3. ‘Fast’ H-F data (not quality controlled) to GLOSS Fast Centre at UHSLC http: //www. pol. ac. uk/psmsl/programmes/gloss. info. html

GLOSS Data Availability Data from GLOSS tide gauges • Permanent Service for Mean Sea Level http: //www. pol. ac. uk/psmsl/ • University of Hawaii Sea Level Center http: //www. soest. hawaii. edu/UHSLC/ • National Tidal Facility (Australia) Southern Ocean Centre http: //www. ntf. flinders. edu. au GLOSS sea level data and information on each gauge in the GCN are also available from PSMSL on CD-ROM. http: //www. pol. ac. uk/psmsl/programmes/gloss. info. html

GLOSS - The Global Sea Level Observing System Documentation • July 1997: Second Implementation Plan for the GLOSS Program • IOC Manuals on Sea Level Measurement and Interpretation (Manuals and Guides No. 14, 3 volumes) Further Information GLOSS Technical Secretary Intergovernmental Oceanographic Commission (IOC), UNESCO email: t. aarup@unesco. org Permanent Service for Mean Sea Level Proudman Oceanographic Laboratory email: psmsl@pol. ac. uk http: //www. pol. ac. uk/psmsl/programmes/gloss. info. html