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)
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
Tide Gauge (float)
Bottom Pressure
Gauge
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
trend/acceleration
studies (e.g. for input to IPCC)
secular
• Higher frequency sampling important in
straits
and other areas
• High latitude regions of ice coverage
Acoustic Gauge in
Australia
• Altimeter
‘relative’)
calibrations
(‘absolute’
and
• Coastal applications (GOOS Coastal
http://www.pol.ac.uk/psmsl/programmes/gloss.info.html
Module)
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), MedGLOSS (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
http://www.pol.ac.uk/psmsl/programmes/gloss.info.html
operations,
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