Transcript Plotting Altimeter Data: GMT and Google Earth

Is sea level rise larger near the coast?
Remko Scharroo
Altimetrics LLC, Cornish, New Hampshire
Eric Leuliette and Laury Miller
NOAA / Laboratory for Satellite Altimetry, Silver Spring, Maryland
Is sea level rise larger near the coast?
• Not an arbitrary question ...
– Sea level rise in the middle of the ocean is rather academic
– Coastal sea level rise is most important to our society
Remko Scharroo — Is sea level rise larger near the coast? — AGU Fall Meeting, 18 December 2009
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Is sea level rise larger near the coast?
• In support of the affirmative
– Sea surface temperature near the coast rises faster
– Tide gauges show a rate larger than altimeters
Sea surface
temperature change
(2002-2009)
• In support of the contrary
– Drop in sea level expected around Greenland and Antarctica
Remko Scharroo — Is sea level rise larger near the coast? — AGU Fall Meeting, 18 December 2009
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Is sea level rise larger near the coast?
• Probably YES
– Jason-1 (2002-2009)
– Coastal sea level rise clearly and significantly larger
4.8 mm/yr
3.0
Remko Scharroo — Is sea level rise larger near the coast? — AGU Fall Meeting, 18 December 2009
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Is sea level rise larger near the coast?
• Probably …
Pierre Prandi et al. (2009):
– TOPEX/Jason-1 (1993-2007), GIA corrected
Remko Scharroo — Is sea level rise larger near the coast? — AGU Fall Meeting, 18 December 2009
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Is sea level rise larger near the coast?
• Probably NO
Global and coastal sea level rise from satellite altimetry
and tide gauges (Prandi et al., 2009). 12-month running
average. GIA corrected. Values in mm/yr.
1993-2002
1993-2007
Global
3.4 ± 0.2
3.4 ± 0.1
Coastal (<200 km)
4.4 ± 1.0
3.3 ± 0.5
Be wary of claims of a 0.1 mm/yr error bar!
Remko Scharroo — Is sea level rise larger near the coast? — AGU Fall Meeting, 18 December 2009
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EOFs of sea level rise
• Jason-1 (2002-2009) EOF 1 (15% of variance)
– Annual variation
– High energy currents and tropical oscillation
Remko Scharroo — Is sea level rise larger near the coast? — AGU Fall Meeting, 18 December 2009
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EOFs of sea level rise
• Jason-1 (2002-2009) EOF 2 (9% of variance)
– Annual variation, 3 months out of phase with EOF 1
– Tropical and subtropical oscillation
Remko Scharroo — Is sea level rise larger near the coast? — AGU Fall Meeting, 18 December 2009
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EOFs of sea level rise
• Jason-1 (2002-2009) EOF 3 (7% of variance)
– Interannual variation, overall rise
– Strong rise in Western Pacific = Coastal and ENSO
Remko Scharroo — Is sea level rise larger near the coast? — AGU Fall Meeting, 18 December 2009
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Results from 7 altimeters
• Global sea level trend (1992-2009)
– No GIA correction (~0.3 mm/yr)
– 5 mm annual amplitude
– Overall trend 2.75 ± 0.2 mm/yr
Remko Scharroo — Is sea level rise larger near the coast? — AGU Fall Meeting, 18 December 2009
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Results from 7 altimeters
• Coastal (<200 km) sea level trend (1992-2009)
– No GIA correction (~0.2 mm/yr)
– Significantly larger annual amplitude (heating mostly?)
– Slightly but not significantly larger trend (2.90 mm/yr)
Remko Scharroo — Is sea level rise larger near the coast? — AGU Fall Meeting, 18 December 2009
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Conclusion?
• Is sea level rise (significantly) larger near the coast?
–
–
–
–
NO
But it isn’t smaller either!
And … was it really useful to ask the question in the first place?
Don’t we have to worry most about places with a lot of people
living near a shallow coast?
Remko Scharroo — Is sea level rise larger near the coast? — AGU Fall Meeting, 18 December 2009
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Question rephrased…
• What’s the sea level rise in “my backyard”?
Mediterranean
North Sea
GIA: +0.3
GIA: +0.0
Gulf of Mexico
S. China Sea
GIA: +1.9
GIA: -0.4
Remko Scharroo — Is sea level rise larger near the coast? — AGU Fall Meeting, 18 December 2009
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Or rephrased again …
• Where don’t I want to plant my backyard?
• Where is the largest impact of sea level rise?
GIA: +1.9
Remko Scharroo — Is sea level rise larger near the coast? — AGU Fall Meeting, 18 December 2009
GIA: +0.0
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