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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.

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  1. 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

  2. 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

  3. 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

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

  5. 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

  6. 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 • Regional and global climate changes • Geological processes Maldives Int. Airport http://www.pol.ac.uk/psmsl/programmes/gloss.info.html

  7. 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

  8. 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

  9. 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

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

  11. Responsibilities of GLOSS Data Providers • There are 3 responsibilities of GLOSS data providers: • Monthly and annual MSL data to PSMSL by 6 months after the data-year • 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 • ‘Fast’ H-F data (not quality controlled) to GLOSS Fast Centre at UHSLC http://www.pol.ac.uk/psmsl/programmes/gloss.info.html

  12. 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 inthe GCN are also available from PSMSL on CD-ROM. http://www.pol.ac.uk/psmsl/programmes/gloss.info.html

  13. 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 Permanent Service for Mean Sea LevelIntergovernmental Oceanographic Proudman Oceanographic Laboratory • Commission (IOC), UNESCOemail: t.aarup@unesco.org email: psmsl@pol.ac.uk http://www.pol.ac.uk/psmsl/programmes/gloss.info.html

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