Decades long El Niño-like Decades long El Niño-like climate variations: the climate variations: the Pacific Decadal Pacific Decadal Oscillation and its Oscillation and its impacts on marine and impacts on marine and terrestrial systems terrestrial systems Nate Mantua Climate Impacts Group University of Washington, Seattle WA October 21, 2003, UC
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Decades long El Niño-like climate variations: the Pacific Decadal Oscillation and its impacts on marine and terrestrial systems Nate Mantua Climate Impacts.
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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
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
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.
x
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