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

2 Remko Scharroo — Is sea level rise larger near the coast? — AGU Fall Meeting, 18 December 2009 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

3 Remko Scharroo — Is sea level rise larger near the coast? — AGU Fall Meeting, 18 December 2009 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 In support of the contrary –Drop in sea level expected around Greenland and Antarctica Sea surface temperature change ( )

4 Remko Scharroo — Is sea level rise larger near the coast? — AGU Fall Meeting, 18 December 2009 Is sea level rise larger near the coast? Probably YES –Jason-1 ( ) –Coastal sea level rise clearly and significantly larger mm/yr

5 Remko Scharroo — Is sea level rise larger near the coast? — AGU Fall Meeting, 18 December 2009 Is sea level rise larger near the coast? Probably … Pierre Prandi et al. (2009): –TOPEX/Jason-1 ( ), GIA corrected

6 Remko Scharroo — Is sea level rise larger near the coast? — AGU Fall Meeting, 18 December 2009 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 Global3.4 ± ± 0.1 Coastal (<200 km)4.4 ± ± 0.5 Be wary of claims of a 0.1 mm/yr error bar!

7 Remko Scharroo — Is sea level rise larger near the coast? — AGU Fall Meeting, 18 December 2009 EOFs of sea level rise Jason-1 ( ) EOF 1 (15% of variance) –Annual variation –High energy currents and tropical oscillation

8 Remko Scharroo — Is sea level rise larger near the coast? — AGU Fall Meeting, 18 December 2009 EOFs of sea level rise Jason-1 ( ) EOF 2 (9% of variance) –Annual variation, 3 months out of phase with EOF 1 –Tropical and subtropical oscillation

9 Remko Scharroo — Is sea level rise larger near the coast? — AGU Fall Meeting, 18 December 2009 EOFs of sea level rise Jason-1 ( ) EOF 3 (7% of variance) –Interannual variation, overall rise –Strong rise in Western Pacific = Coastal and ENSO

10 Remko Scharroo — Is sea level rise larger near the coast? — AGU Fall Meeting, 18 December 2009 Results from 7 altimeters Global sea level trend ( ) –No GIA correction (~0.3 mm/yr) –5 mm annual amplitude –Overall trend 2.75 ± 0.2 mm/yr

11 Remko Scharroo — Is sea level rise larger near the coast? — AGU Fall Meeting, 18 December 2009 Results from 7 altimeters Coastal (<200 km) sea level trend ( ) –No GIA correction (~0.2 mm/yr) –Significantly larger annual amplitude (heating mostly?) –Slightly but not significantly larger trend (2.90 mm/yr)

12 Remko Scharroo — Is sea level rise larger near the coast? — AGU Fall Meeting, 18 December 2009 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?

13 Remko Scharroo — Is sea level rise larger near the coast? — AGU Fall Meeting, 18 December 2009 Question rephrased… What’s the sea level rise in “my backyard”? MediterraneanNorth Sea Gulf of MexicoS. China Sea GIA: +0.3 GIA: +0.0 GIA: +1.9 GIA: -0.4

14 Remko Scharroo — Is sea level rise larger near the coast? — AGU Fall Meeting, 18 December 2009 Or rephrased again … Where don’t I want to plant my backyard? Where is the largest impact of sea level rise? GIA: +1.9GIA: +0.0