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Response of Fish Population Changes to Climate Events. James Overland and Nick Bond. First Concept - Climate. Decadal Climate Variability more “Event-like” than regular Oscillations Large and long deviations from averages

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first concept climate
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
slide3

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.

slide4

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

slide5

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

slide6

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)

slide7

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

slide8

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)

slide9
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

slide10

But northern North Pacific Ecosystems have a limited number of main interactions for each major species

Aydin

Coyle et al.

Gaichas and Francis

southern bering sea ecosystem changes
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

slide12

Photo by W.B. Miller

ca. 1920, Alaska

Library of Congress

Cod in the Bering Sea

1870s- 1930s

slide13

SUMMARY:

Northern North Pacific Ecosystem Response to Climate Variability

Temperature

C

Stochastic Climate Variability Low Dimension

on all time scales Ecosystems

slide14

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

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