1. Extreme sea level variability due to El Niño Taimasa
Matthew J. Widlansky
Axel Timmermann1,2, Shayne McGregor3, Malte F. Stuecker4, Yoshimitsu Chikamoto1, Wenju Cai5 and Mark Merrifield2
1International Pacific Research Center, University of Hawai‘i at Mānoa
2Dept of Oceanography, University of Hawai‘i at Mānoa
3Climate Change Research Centre, University of New South Wales
4Dept of Meteorology, University of Hawai‘i at Mānoa
5CSIRO Marine and Atmospheric Research-Aspendale

2. taimasa [kai’ ma’sa] Samoan “foul smelling tide”
microatoll Low tide limits upward coral growth
Flat top Porites coral
courtesy National Park of American Samoa

3. Shallow reefs respond to sea level variability
Normal conditions
El Niño Taimasa
depth > height
depth < height
Top portions of coral heads die off, creating microatolls (e.g., Woodroffe and McLean, 1990 Nature)

4. Tide gauges in the tropical western Pacific

5. Very low sea levels, or ‘taimasa’, affect tropical western Pacific islands during strong El Niño
UH Sea Level Center data
Prolonged low sea levels in Southwest Pacific (r = 0.60 at lag 6 months)

6. Meridional sea-level seesaw of El Niño Taimasa
Sea level gradient & PC2 wind stress correlated (r = 0.74 at lag 3 months)

7. Zonal sea level gradient Meridional sea level gradient
Sea level responds to wind-stress variability
Regressions: Sea surface height and wind stress
Zonal sea level gradient
Meridional sea level gradient
Canonical sea level response to El Niño
(e.g., Wyrtki, 1984 JGR)
Most pronounced during strong El Niño
(e.g., Alory and Delcroix, 2002 JGR)
Equatorially symmetric wind stress pattern associated with ENSO
(Stuecker et al., 2013 Nature Geoscience)
Southward shifted westerly wind anomaly east of Dateline
(McGregor et al., 2012 J. Climate)
Vectors: Wind stress (ERA interim)
Shading: Sea surface height (ECMWF ORAs4)
Vectors: Wind stress (ERA interim)
Blue contours: Negative wind-stress curl (SH cyclonic)
Vectors: Wind stress (ERA interim)
Contours: Wind-stress curl (negative, SH cyclonic)
Shading: Sea surface height (ECMWF ORAs4)
Tide Gauge Stations: (UHSLC)

8. SPCZ South Pacific Convergence Zone—
largest rainband in Southern Hemisphere
Zonal SPCZ Equatorward collapse of rainband
Observed rainfall and sea surface temperature during austral summer
(mm day-1)
28°C
26°C
Extreme El Niño
GPCP rainfall
NOAA SST
(Vincent et al. 2011, Climate Dynamics; Cai et al. 2012, Nature)

9. Zonal SPCZ events are associated with prolonged sea level drops in Southwest Pacific
(PC1 & PC2 > 0)
Shading: Rainfall (GPCP)
Blue contours: Pacific rainbands enclosed by 5 mm day-1 rainfall annual climatology

10. Key Points
Extreme low sea levels persist after termination of strong El Niño
Sea level drops are related to interaction of El Niño with seasonal development of the South Pacific Convergence Zone
Hindcasts suggest potential predictability of future extreme sea level drops
(J. Climate 2014)
How will coastal sea levels and shallow reefs respond to the next El Niño?

11. El Niño Update

12. Dynamical forecasts (June initialization)
Blue are most recent forecasts

13. Dynamical sea-level forecasts NOAA CFSv2 (June initialization)
November 2014: Guam 15 cm below normal
Meridional sea-level seesaw (red minus blue)
March 2015: Samoa 15 cm below normal

14. Retrospective forecast of the 1997/98 El Niño

15. Retrospective forecast of the 1997/98 El Niño

16. Strong El Niño phase-locked to annual cycle

17. Climate model data services at IPRC
Serving ocean output from CMIP5 future projections in a user-friendly framework
Key variables are (nearly) complete:
Sea surface temperature
Sea level
Surface currents
Surface salinity
Primary productivity of phytoplankton
*more variables to come
>40 climate models
Poseidon Tripole Grid from NCAR CESM
Jim Potemra, APDRC manager
Sharon DeCarlo, IPRC

18. Climate Model Server

19. Future climate projections

20. Future climate projections