1. Janelle Fleming Interdisciplinary Seminar September 16, 1998 The 1976-77 North Pacific Ocean event: A unique climate shift, natural decadal variability, or global warming?

2. Outline n Description of Regime Shift n Physical characteristics n Climatological characteristics n Biological characteristics n Interpretations n I. Unique series of events n II. Part of decadal variation n III. Global warming trend n Conclusions

3. The Region Tomczak and Godfrey (1994)

4. The Shift Descriptive Data

5. The Shift Physical Indicators n n Begins during winter months of 1976-1977 n n Altered Patterns of Upper-Ocean SST n n Cooler SST in Central Pacific n n Warmer SST along coast of North America n n Warmer SST in central and eastern tropics n n Altered Temperature Patterns in water column

6. SST anomalies - North Pacific Graham, N.E. (1994)

7. SST anomalies-North Pacific Venrick, et al. (1987) Winters (1980-85) minus (1968-73)

8. SST anomalies-the tropics Graham, N.E. (1994) Difference Map: Epoch 2 - Epoch 1

9. Water Column Temp Anomalies Deser, et al (1996) Temp Difference (1978-89) and (1971-76) at 100m

10. Water Column Temp Anomalies Deser, et al (1996) Temp Difference (1979-90) and (1972-77) at 250m

11. Water Column Temp Anomalies Deser, et al (1996) Temp Difference (1980-91) and (1972-78) at 400m

12. The Shift Climate Indicators n Aleutian Low shifts and intensifies n Increased storminess n Westerly winds shift and intensify n Organized convection over the tropical Pacific shifts

13. 700 hPa heights - North Pacific Graham, (1994)

14. Trenberth (1990) North Pacific Sea Level Pressure

15. The Shift Wind Patterns Deser, et al, (1996)

16. Graham (1994) Organized Convection - OLR Difference Maps: Epoch 2 - Epoch 1

17. Organized Convection - HRC Graham (1994) Difference Map: Epoch 2 - Epoch 1

18. The Shift Biological Indicators n Chlorophyll a concentration n vertically averaged n mean concentration doubles after 1976 n Species Richness on a reef system off California declined by 15-25%.

19. Chlorophyll a Concentrations Venrick, et al, (1987)

20. Species Richness Holbrook, et al (1997)

21. The Shift Broad based evidence n 40 environmental variables n distributed throughout the Pacific basin n Variables include: n Number of Great Basin Canada goose nests n Sea Ice extent n Salinity n upwelling n commercial dungeness crab production n salmon catch

22. The Shift Step-wise change Ebbesmeyer, et al, 1991

23. Interpretations

24. I. Unique Event n Miller et al (1994) n Used a layered ocean GCM n forced with total surface heat flux anomalies n forced with wind stress anomalies n reproduced SST change n Large advective effects n Long term heat flux variations n Caused by “unique atmospheric anomalies”

25. I. Unique Event Miller et al. (1994)

26. I. Unique Event n Graham, et al (1994) n Used evolving general circulation model (GCM) n Forced with observed SSTs n abrupt change in SST in equatorial Pacific lead to the shift

27. I. Unique Event Graham, et al(1994) 700 hPa difference Maps: winters (1977-82)-(1971-76)

28. II. Decadal Variation n Latif and Barnett (1994,1996) n mid-latitude SSTs interact with mid-latitude atmosphere n Drives a decadal cycle of ~20 yrs

29. II. Decadal Variation Latif and Barnett (1996)

30. II. Decadal Variation n Gu and Philander (1997) n Tropical SST affects the mid-latitudes through the atmosphere n Mid-latitudes affect the tropics through the ocean

31. II. Decadal Variation Gu and Philander, (1997)

32. II. Decadal Variation n Mantua et al (1997) n Create a Pacific (Inter-) Decadal Oscillation (PDO) index. n Correlate PDO with salmon catch

33. II. Decadal Variation Mantua et al (1997)

34. Decadal Variability Mantua, et al (1997)

35. II. Decadal Variation n French Frigate Shoals in the Western Hawaiian Islands n Mixed layer depths increase n Response to climate change in higher trophic levels n spiny lobsters (2nd trophic level) n reef fishes (3rd trophic level) n seabirds and monk seals (top trophic level)

36. II. Decadal Variation Polovina, et al (1994)

37. III. Global Warming n California Coastal System n 80% decrease in zooplankton biomass n Correlated linear increase in SST

38. III. Global warming Roemmich and McGowan (1995)

39. III. Global Warming n Pelagic Bird population decline of 40% since 1987 n Correlation with long-term increase in SST

40. III. Global Warming Veit, et al (1996)

41. III. Global Warming n Latif and Barnett (1994) n linear trend in SST in both observation and model data

42. III. Global Warming Latif et al (1997)

43. Conclusions n An “abrupt shift” did occur in the mid-70’s n Shift is part of interaction of cycles: n ENSO cycle in the tropics n Aleutian Low cycle in the extratropics n Inconclusive data as to anthropogenic influence

44. Socio-historical perspective Thank you: Dr. Luettich, Dr. Werner, Dr. Shay, J. Fleming, Dr. McNinch, J. Hench, J. Dyble, C. Conoway, G. Johnson, M. Harrington, D. Whitehall