Observations, Impacts, and Paleoclimate Evidence of Pacific Multidecadal Variability

1. Observations, Impacts, and Paleoclimate Evidence of Pacific Multidecadal Variability Nate Mantua University of Washington JISAO Climate Impacts Group November 16, 2006 CLIVAR MDV Workshop, Honolulu, Hawaii

2. Lines of Evidence for Pacific MDV • Historical measurements • Surface temperature, sea level pressure, precipitation, stream flow, ecosystem indicators • Paleoclimate indicators • Tree-ring series, tropical corals, and clam shells

3. “The 1977 Climate Shift”November-April SLP change: (1977-88) - (1965-76)

4. Cool season Aleutian Low variability: (Nitta and Yamada 1989, J. Met. Soc. Japan; Trenberth 1990, BAMS) North Pacific winter sea level pressure field (i.e. the Aleutian Low) “shifted” in 1977

5. Distinguishing tropical interannual ENSO from MDV • interannual SST pattern the tropical ENSO • interdecadal SST pattern has more amplitude in the North Pacific, and a “fat” ENSO-like pattern in the tropics • Zhang et al. 1997: J. Climate

6. The Pacific Decadal Oscillation • EOF analysis of monthly “residual” North Pacific SSTA identifies an El Niño-like pattern of climate variability • 20 to 30 year periods of persistence in North American and Pacific Basin climate (and Pacific salmon production) • indices for ENSO and the PDO are not independent (r=0.58) 1925 1947 1977 1998 Mantua et al. 1997: BAMS

7. 500 mb height anomalies during positive phases of the PDO pattern: the Pacific North America pattern H L H Contour interval = 5 m The cool-season PNA pattern is the mid-tropospheric signature of Aleutian Low sea level pressure pattern

8. Warm phase PDO and Nov-March North American climate temperature precipitation Todd Mitchell, UW/JISAO

9. Regional Indicators for PDO variability(Mantua et al 1997, BAMS) Gulf of Alaska winter air temperature BC Coastal SST Scripps Pier SST 1925 1947 1977 Kenai River Streamflow BC/Washington Streamflow

10. An Interdecadal Production Pattern in Pacific salmon 34% variance Hare et al.1999, Fisheries The leading EOF and PC of annual salmon landings (a proxy for abundance) Chinook Coho Sockeye Pink chum PC scores r(pdo) = .73 r(niño34) = .53

11. Global correlation fields November-April Precipitation November-April Temperature Mantua and Hare, 2002 J. of Oceanography 58: 35-44

12. Pacific Sardines, Anchovies, climate and carbonChavez et al. 2003, Science

13. Wavelet Amplitudes of NPI & PDO index Low frequency variance is concentrated at periods of 15-to-25 and 50-to-70 years Minobe (1999 GRL; 2000 Prog. Oceanogr)

14. Distinct modes of NP SST variability?from a Rotated PC analysis of COADS SST 1945-1993(Nigam et al. 1999, Eos Trans.) Vary the analysis and you vary the resulting patterns and time series

15. Patterns of MDV • Interdecadal (top) and multidecadal (bottom) patterns from an EOF analysis of ENSO and global trend-residual SSTA fields Enfield and Mestas-Nunez, (1999, J. Climate)

16. Patterns of MDV • multidecadal patterns from a rotated EOF analysis of ENSO and global trend residual SSTA fields Mestas-Nuñez and Enfield (1999, J.Climate) • The interhemispheric pattern resembles the “Interdecadal Pacific Oscillation” (IPO) Power et al. 1999 (Clim. Dyn.)

17. Composite IPS SST anomalies A distinct pattern of MDV(?) • CCA between Pacific SST (tropical + N. Pacific) and N. Hemisphere vortex position reveals a distinctly multidecadal mode of ocean-atmosphere variability Interdecadal Pacific Signal (IPS) Frauenfeld and Davis 2002; GRL

18. Amplitude of the IPS SST pattern projected onto Kaplan SST IPS IPS PDO PDO Frauenfeld et al. 2005; J. Climate

19. Spatial patterns of Pacific MDV • Are you feeling confused yet? You should be!

20. Paleoclimate reconstructions of PDV x Paleoclimate perspectives warm PDO cool PDO 1969 1998 1978 Are Strom, 2003 M.Sc., UW School of Fisheries

21. a) Instrumental PDO index (SST) b) China summer rainfall c) US spring temperature (TR) d) SW rainfall (TR) e) SW-NW rainfall (TR) f) NW spring temperature (TR) g) NW spring temperature (TR) Various PDO index reconstructions (N. Am vs Asia) Annual PDO Annual PDO Annual PDO Annual PDO Spring PDO Spring PDO 1500 1600 1700 1800 1900 2000

22. Changing period and amplitude of MDV MTM spectrum • Drifting amplitudes and prominent frequencies are a common property of multi-century NPI and PDO index reconstructions • This PDO index reconstruction is based on proxies of summer rainfall in China (historical drought/flood index) Period (year) Annual PDO Annual PDO Shen et al. 2006: GRL

23. the spatial coherence of Pacific MDV • W. North American versus East Asian perspective of NPI/PDO • Both reconstructions contain MDV, but only the 20th C. shows a close correspondence (overall r = 0.09!) • PDO reconstructions? Regional climate proxies? D’Arrigo and Wilson 2006: Int. J. Clim.

24. Pacific MDV: Summary • 20th C. instrumental data shows prominent ENSO-like pattern of MDV with quasi-periodic variance concentrated ~15-25 and ~50-70 year periods • Some aspects of Pacific MDV appear to be interhemispheric (including the tropics: e.g.IPO/PDO, IPS), while others appear to be isolated in the northern extratropics (e.g.NP) • Paleoclimate evidence suggests that Pacific MDV signals have amplitudes, frequencies, and spatial expressions that drift over time

25. Pacific Decadal Oscillation (PDO) – Leading Mode of N.Pacific SSTA Overland and Bond, unpublished BCCR CGCM3-T63 CGCM3-T47 CCSM3 CSIRO GISS-AOM GISS-EH GISS-ER INM IPSL MIROC-Hi MIROC-Me MRI PCM1 UK-HadCM3

26. Principal Components Black – Observed PDO Overland and Bond unpublished

27. Coherent MDV patterns in the Pacific sector • Multivariate frequency domain SVD of N. Hemisphere SST and SLP reveals a near 20 year oscillatory pattern in North Pacific SST and SLP Mann and Park (1994 JGR; 1996 J Climate)

28. Slowdown of the meridional overturning circulation in the Tropical Pacific~25% decrease in upwelling from 1970’s to 1990’s, rising eq. SSTs and a reduced CO2 flux to the atmosMcPhaden and Zhang, Nature,2002