Observing Sea Level

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Challenge the future Delft University of Technology Observing Sea Level R Klees Department of Geoscience & Remote Sensing Delft University of Technology

description

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

Transcript of Observing Sea Level

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11/29/12

Challenge the future Delft University of Technology

Observing Sea Level

R Klees Department of Geoscience & Remote Sensing Delft University of Technology

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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

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How is sea level measured?

Tide gauge Satellite radar altimetry Floats + satellite gravimetry

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Tide gauge measurement system Basic principle

Ruler edged staff

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Tide gauge technical realizations

Classical float gauge (from ~1832)

Radar gauge @ Liverpool

Acoustic gauge @ Hamburg

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25 well-selected tide gauge records

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1900 1920 1940 1960 1980 2000

ΔSL

(mm

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Year

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1900 1920 1940 1960 1980 2000

ΔSL

(mm

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Year

Rate ~ 1.8 ± 0.1 mm/yr

Nerem 2005

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Satellite radar altimetry

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MSL from satellite radar altimetry 10-day coverage of Topex & Jason

-100

0

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1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012

TOPEXERS-2

GFOJason-1

EnvisatJason-2

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Ch

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me

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se

a l

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[mm

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1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012

North Sea mean sea level

seasonal signals removedtrend: 1.7 ± 0.4 mm/year

Laboratory for Satellite AltimetryNOAA•NESDIS•STAR

NOAA) ) ) ) ) )))

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Observing changes in the volume of ocean water …

… due to changes in total ocean water mass

…due to changes in ocean water density

+

ARGO GRACE

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Observing ocean water temperature

Profile data

Surface Pressure

ARGO floats

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ARGO network

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Changes in the volume of ocean water

GRACE

RA versus ARGO+GRACE

ARGO versus RA-GRACE

ARGO

GRACE versus RA-ARGO

Leuliette & Miller 2009

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Some issues with sea level records • Vertical land movement

GPS

Abs grav

2000-2050

Geology or GIA models

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• Uneven geographic distribution

Some issues with sea level records

PSMSL stations

Woodworth et al 2011

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• Uneven geographic distribution

Some issues with sea level records

PSMSL stations with record > 60 yrs

Woodworth et al 2011

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Regional mean sea level trends (Jan 1993 – April 2012)

• Uneven geographic distribution

Some issues with sea level records

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• Calibration of radar altimeters

Some issues with sea level records

•  ± 0.4 mm/yr tide gauge calibration error

•  dominated by errors in vertical land movement from GPS data

Nerem 2005

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Predicted present-day impact of GIA…

… on relative sea level change measured by tide gauges

… on absolute sea level change measured by radar altimetry

… on change in water mass measured by GRACE Tamisiea 2011

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New techniques for sea level measurements

Waverider GPS buoy, University of Tasmania

GNSS altimetry (PARIS concept)

Spar buoy, NOAA