Response of Fish Population Changes to Climate Events

1. Response of Fish Population Changes to Climate Events James Overland and Nick Bond

2. First Concept - Climate • Decadal Climate Variability more “Event-like” than regular Oscillations • Large and long deviations from averages • Default Model is Stochastic Red Noise- AR1 to Long Memory; Little deterministic predictability

3. SAT anomaly (°C) Year Extended annual mean SAT record for the northern North Atlantic region (TNA). (Wood, et al. 2010). NO 60-80 Year Oscillations in early portion of record.

4. Havsklimatgruppen www.oceanclimate.se Sub-arktisk vinterklassifikation för de senaste 500 åren Perioder 1522-36 Mild 1562-76 Kall 1577-91 Mild 1597-1629 Kall 1630-62 Mild 1663-1706 Kall 1707-50 Mild 1750-1877 Kall - 1803-20 Kall 1878-nu Mild - 1930-40 Mild - 1940-42 Kall - 1971-75 Mild - 1985-87 Kall - 1988-93 Mild No Regular Climate “Cycles” Eriksson et al, in press

5. Low-pass EEMD analysis with a low-pass Butterworth filter applied to the St. Paul air temperature time series. (From Overland et al., 2012)

6. Can Fit a square oscillator to Pacific Decadal Oscillation (PDO) timeseries to give “multiple stable states” BUT: Other simple times series models without multiple stable states (Stochastic Red Noise AR1 and Long Memeory) also fit the PDO data equally well CONCLUSION: Cannot determine underlying process model from data alone for records shorter than 200 years, CANNOT Deterministically Project, only use Statistical Scenarios Overland et al. (2006)

7. George Sugihara: “time series observations of key physical variablesfor the North Pacific Ocean…are best described as linear stochastic. In contrast, we find that time series for biological variableshaving similar properties exhibit a low-dimensional nonlinear signature*.” *Chih-hao Hsieh, Sarah M. Glaser, Andrew J. Lucas & George Sugihara, Distinguishing random environmental fluctuations from ecological catastrophes for the North Pacific Ocean, Nature435, 336-340 (2005) (E) Embedding dimension/Degrees of freedom: how many independent ways a system can vary

8. Distinguishing random environmental fluctuations from ecological catastrophes for the North Pacific Ocean Chih-hao Hsieh, Sarah M. Glaser, Andrew J. Lucas & George Sugihara Nature 435, 336-340(19 May 2005)

9. Second Concept: Ecosystems/Fish Populations The responses to climate shifts by biological systems are direct, but diverse because intervening processes introduce amplifications, time lags, hysteresis, and non-linearities, leading a variety of climate to ecosystem transfer functions

10. But northern North Pacific Ecosystems have a limited number of main interactions for each major species Aydin Coyle et al. Gaichas and Francis

11. Southern Bering Sea Ecosystem Changes Warm temperatures previously favored pollock over Arctic species. But recently, poor preyin very warm period, more predators gave a biomass loss of 50% Now recovery with cold temperatures- but nearly a biological regime shift 2000 2001

12. Photo by W.B. Miller ca. 1920, Alaska Library of Congress Cod in the Bering Sea 1870s- 1930s

13. SUMMARY: Northern North Pacific Ecosystem Response to Climate Variability Temperature C Stochastic Climate Variability Low Dimension on all time scales Ecosystems

14. In the future we can expect large excursions in the climate system that last for multiple years, but there is as yet little predictability for when they will occur or how long they will last. -Low Frequency Red Noise Stochastic System with long AVERAGE return periods • Transitions mechanisms appear more like individual multi-year events rather than multi-decadal oscillations. Minimal decadal (PDO) memory processes. • Biology shows regime shifts in response to random climate forcing. Northern species develop to take advantage of this stochastic structure of extremes. A few dominant species, patchiness, multi-year life spans with highly variable year classes. Conclusions