Presentation given by Roland Klees at the symposium on Sea Level Rise by TU Delft Climate Institute http://bit.ly/Y5dPvY

1. Observing Sea Level
R Klees
Department of Geoscience & Remote Sensing
11/29/12University of Technology
Delft
Delft
University of
Technology
Challenge the future

2. What is sea level?
• Distance of water level from some reference point
• Absolute and relative sea level
• (Global) Mean sea level
fixed point on land
relative sea level
absolute sea level
Observing Sea Level 2

3. How is sea level measured?
Floats + satellite
Tide gauge Satellite radar altimetry gravimetry
Observing Sea Level 3

4. Tide gauge measurement system
Basic principle
Ruler edged staff
Observing Sea Level 4

5. Tide gauge technical realizations
Radar gauge @ Liverpool
Acoustic gauge
Classical float gauge
@ Hamburg
(from ~1832)
Observing Sea Level 5

6. 25 well-selected tide gauge records
20
15
10
5
ΔSL (mm)
0
-5
-10
-15
Rate ~ 1.8 ± 0.1 mm/yr
-20
1900 1920 1940 1960 1980 2000 Nerem 2005
Year
Observing Sea Level 6

7. Satellite radar altimetry
Observing Sea Level 7

8. MSL from satellite radar altimetry
10-day coverage of Topex & Jason
North Sea mean sea level
seasonal signals removed
)))
NOAA
))
Change in mean sea level [mm]
trend: 1.7 ± 0.4 mm/year
) )
100
)
Laboratory for Satellite Altimetry
NOAA•NESDIS•STAR
0
Jason-2
-100 Envisat
Jason-1
GFO
Observing Sea Level
ERS-2 8
TOPEX
1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012

9. Observing changes in the volume of
ocean water …
ARGO GRACE
… due to changes in
…due to changes in
ocean water density
+ total ocean water mass
Observing Sea Level 9

10. Observing ocean water temperaturefloats
ARGO
Surface
Pressure
Profile data
Observing Sea Level 10

11. ARGO network
Observing Sea Level 11

12. Changes in the volume of ocean water
RA versus ARGO+GRACE
GRACE versus RA-ARGO
ARGO versus RA-GRACE
ARGO GRACE
Leuliette & Miller 2009
Observing Sea Level 12

13. Some issues with sea level records
• Vertical land movement
GPS
Abs grav
Geology
or GIA models
Observing Sea Level 13
2000-2050

14. Some issues with sea level records
• Uneven geographic distribution
PSMSL stations
Woodworth et al 2011
Observing Sea Level 14

15. Some issues with sea level records
• Uneven geographic distribution
PSMSL stations with record > 60 yrs
Woodworth et al 2011
Observing Sea Level 15

16. Some issues with sea level records
• Uneven geographic distribution
Regional mean sea level trends
(Jan 1993 – April 2012)
Observing Sea Level 16

17. Some issues with sea level records
• Calibration of radar altimeters
Nerem 2005
• ± 0.4 mm/yr tide gauge
calibration error
• dominated by errors in
vertical land movement from
GPS data Sea Level
Observing 17

18. Predicted present-day impact of GIA…
… on relative sea level change … on absolute sea level change
measured by tide gauges measured by radar altimetry
… on change in water mass
Observing Sea Level 18
Tamisiea 2011
measured by GRACE

19. New techniques for sea level measurements
Spar buoy, NOAA
Waverider GPS buoy, University GNSS altimetry
19
Observing Sea Level
of Tasmania (PARIS concept)