decades long el niño-like climate variations: the pacific decadal oscillation and its impacts on...

Decades long El Niño-like climate Decades long El Niño-like climate variations: the Pacific Decadal variations: the Pacific Decadal Oscillation and its impacts on Oscillation and its impacts on marine and terrestrial systemsmarine and terrestrial systems

Nate Mantua

Climate Impacts Group

University of Washington, Seattle WA

October 21, 2003, UC Berkeley

OutlineOutline

• PDO signatures in Pacific/N. American climate

• impacts on forests and marine ecosystems

• paleoclimate evidence

• mechanisms and predictability

The Pacific Decadal OscillationThe Pacific Decadal Oscillation

• an El Niño-like pattern of climate variability

• 20 to 30 year periods of persistence in North American and Pacific Basin climate

• PDO fingerprints found in records of temperature, precipitation, snow pack, streamflow, and marine ecosystems

Mantua et al. 1997: A Pacific Interdecadal Climate Oscillation with Impacts on Salmon Production, Bulletin of the American Meteorological Society, Vol 78, p 1069-1079.

1900 1925 1950 1975 2000

1925 1947 1977 1998?

PDO research ...PDO research ...

Both climate and fisheries research are behind this story

– Ebbesmeyer et al’s “1977 Regime Shift”• A step change in 40 environmental parameters in the Pacific

(1991)

• Nitta and Yamata 1989, Tanimoto et al 1993, Graham 1994, Trenberth and Hurrel 1994, Kawamura 1994, Latif and Barnett 1994, Miller et al 1994, Zhang 1996, Zhang et al 1997, Mantua et al 1997, Minobe 1997 ... and many more have followed

“1976 Step in Pacific Climate: 40 environmental changes …”(Ebbesmeyer et al. 1991, PACLIM proceedings)

Large and local scale climate indices, Canadian geese, NW salmon, dungeness crab, Pacific sea birds numbers, Washington Oyster growth … all folded into a 40-member composite variable.(see Kerr, Science Vol 255, 1992)

PDO research at the University of PDO research at the University of WashingtonWashington

• A product of 3 semi-independent streams of research

• Hare and Francis (1992), UW Fisheries Research Institute: North Pacific climate and 20-30 year boom/bust cycles in Alaska salmon

• Zhang and Wallace (1994), UW Atmospheric Sciences: Ocean/Atmos variability in Pacific climate, ENSO vs North Pacific Climate Variations

• Mantua (1995), UW Climate Impacts Group: Pacific Northwest “climate history”, climate impacts on NW salmon

L H

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Oct-March Sea Level Pressure anomalies during warm phases of PDO: an intensified Aleutian Low

Contours every .5 mb

500 mb height anomalies during warm phases of PDO: the Pacific North America pattern

LH

H

Contours every 5 meters

Figures produced by Todd Mitchell, UW/JISAO

October-March PDO Regression fields

Surface Air Temperature Precipitation

Regional Indicators for PDO

variability(Mantua et al 1997, BAMS)

Gulf of Alaska winter air temperature

BC Coastal SST

Scripps Pier SST

Kenai River Streamflow

BC/Washington Streamflow

1925 1947 1977

PDO and North American ClimatePDO and North American Climate

• winter and spring time winter and spring time temperaturestemperatures: relatively warm in northwest North America, and cool in the southeast

• winter and spring time winter and spring time precipitationprecipitation: wet in the southern US and northern Mexico, and dry in the Pacific Northwest and Great Lakes regions

• winter and spring time winter and spring time temperaturestemperatures: relatively cool in northwest North America, and warm in the southeast

• winter and spring time winter and spring time precipitationprecipitation: dry in the southern US and northern Mexico, and wet in the Pacific Northwest and Great Lakes regions

Warm PDO: 1925-46; 1977-1998(?)

Cool PDO: 1900-1924; 1947-1976;

PDO impacts on western forestsPDO impacts on western forests

Snowpack, PDO and tree growthMountain hemlock in the Cascade and Olympic Mountains

From Peterson and Peterson (2001)

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

high elevation OR/WA Mt Hemlock and snowpack

low elevation OR/WA Mt Hemlock and pdo

Cool/wet

warm/dry warm/dry

Low snowpack

Deep snowpack

Years with fires > 80,000 haFires in national forests, 1916-1997

From Mote et al. (1999)

PDO impacts on marine ecosystemsPDO impacts on marine ecosystems

Alaska Commercial Salmon Catches 1878-2001

Alaska Department of Fish and Game http://www.state.ak.us/adfg

Bottom trawl surveys in Pavlov Bay, Alaska(source: Botsford et al. 1997, Science, 277: 509-515)

1960

’s19

70’s

1980

’s

A history of change from a 50 year record of Gulf of Alaska bottom trawl surveys

From: Anderson and Piatt (2000) Mar. Ecol. Prog. Ser 189: 117-123.

Pacific salmon catch data analysisPacific salmon catch data analysis(Hare, Mantua and Francis 1999, (Hare, Mantua and Francis 1999,

Fisheries)Fisheries)• Combine commercial+sport+subsistence catch from 1925-1997

• assume that catch reflects abundancecatch reflects abundance

• apply “regional normalization”• focus on critical period by shifting each

record in time to reflect typical year of ocean entry (chinook & chum 3 years, sockeye 2 years, coho and pink 1 year)

An Inverse Production Pattern An Inverse Production Pattern

PC scores

34% variance

Hare, Mantua, and Francis 1999, Fisheries Vol 24: 6-14

r(pdo) = .73r(niño34) = .53

Why an inverse production response to Why an inverse production response to PDO/ENSO-related variability?PDO/ENSO-related variability?

H1: “optimal stability windowoptimal stability window” and “bottom up” impacts on marine food-webs

Gargett 1997, Fisheries Oceanogr. 6:109-117

Stratification or upwelling

Ph

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lan

kto

np

rod

uct

ion

NN SS

Other coherent patterns in marine ecosystems?

Empirical Evidence for N. Pacific Regime Shifts in 1977 and 1989

Hare and Mantua, Progress in Oceanogr. 2000, 47: 103-145

1976-771988-89

1976-77: PC1 1988-89: PC2

Hare and Mantua, Progress in Oceanogr. 2000, 47: 103-145

Paleoclimate reconstructions Paleoclimate reconstructions

Tree-ring based PDO index reconstructions:Tree-ring based PDO index reconstructions:(ex: Gedalof and Smith 2001, Geophys. Res. Letts. 28: 1515-1518)(ex: Gedalof and Smith 2001, Geophys. Res. Letts. 28: 1515-1518)

Plots courtesy of Torrence and Compo http://paos.colorado.edu/research/wavelets

Geoducks:

“gooey duck”,

Panopea abrupta

geoduck shells may have the tree-rings of the extratropical seas

Thin section of geoduck shell from Protection Island

cool PDO warm PDO

1978

1969

1998

Are Strom, 2003 M.Sc., UW School of Fisheries

QuickTime™ and aGraphics decompressorare needed to see this picture.

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Ocean temperature reconstruction based on Protection Island geoduck growth rates

Are Strom, 2003 M.Sc., UW School of Aquatic and Fishery Sciences

Growing season (March-October) temperatures

xxx

Paleo-salmon abundance

estimates from lakebed

sediment cores

(Finney et al. 2000, Science 290: 795-799)

1700 1800 1900 2000

Using PDO information in Using PDO information in Climate PredictionsClimate Predictions

warm PDO/La Niña

cool PDO/La Niña

ENSO/PDO combined influences on North AmericanClimate (JFM precipitation)

Gershunov, Barnettand Cayan 1999 Eos Transactions

Columbia River summer (April-September) streamflow

Alan Hamlet and Dennis Lettenmaier, UW Civil Engineering

} ~ 20%change

PDO PredictabilityPDO Predictability

PDO mechanisms will define its predictability– best case scenario:

• slow ocean adjustment+air/sea coupling (like El Niño)

– Worst case scenario:• ocean adjustment to surface

fluxes is purely via mixed-layer heat storage -- this would limit predictability to ~ 1 year

atmosphereatmosphere

ocean

Re-emergence in entraining mixed layersDeser et al. 2003, J. Climate 16:57-72

ENSO-forced variability of the PDO ENSO-forced variability of the PDO Newman et al. Newman et al. J. Climate LettersJ. Climate Letters (in press) (in press)

• PDO variability reflects a “reddened” response to atmospheric “white noise” and ENSO forcing (at all time scales)

• The basic model: “the PDO is simply due to reemergencereemergence + ENSO forcingENSO forcing

+ random atmospheric forcingrandom atmospheric forcing”

PDOforecastn = *PDOobservedn-1 +*ENSOn + oisen

Simple model performanceNewman, Compo and Alexander (in press) J. Climate Letters

• 1 year lead time hindcasts hindcasts vs Observed correlations

• Modeled time series power spectra not as “red” as observed PDO

• Prediction for July-June 2004? ~ + .6 to +1

Forecast vs. ObservedAnnual PDO (July-June)

Power Spectra

Period

Full model R = .74

Ignore ENSO R = .53

ENSO only R = .54

Observedforecast

1900 1950 2000

Now-castingNow-casting

– assessing the current status of the PDO is difficult:

what should we be tracking????

• El Niño experience tells us that improved understanding will come with improved measurements, diagnostics and modeling

Keeping track of El Niño/Southern Keeping track of El Niño/Southern Oscillation: the TAO/TRITON arrayOscillation: the TAO/TRITON array

The backbone of today’s ENSO Observing Network • initiated in 1985, completed in 1994 • 70 moored buoys provide real-time in-situ surface and subsurface conditions (winds, temperatures, currents)

ARGO: the latest addition to a ARGO: the latest addition to a global ocean observing systemglobal ocean observing system

SummarySummary• over the past few centuries PDO has been an important pattern of climate variability at periods comparable to a human’s life time

• provides insights into the history of water and fishery resources: can we learn from this history?

• offers another avenue for improving climate predictions at the seasonal and (potentially) multi-year time scales

• fisheries and climate research communities putting lots of effort into learning more about PDO and its impacts

upwelling food webs in our coastal ocean: the California Current

http://www.noaa.gov/

Cool water, weak stratificationhigh nutrients, a productive “subarctic” food-chain with abundant forage fish and few warm water predators

Warm stratified ocean, fewnutrients, low productivity “subtropical” food web, a lack of forage fish and abundant predators

Abundant Krill!

Krill are in short supply