janelle fleming interdisciplinary seminar september 16, 1998 the 1976-77 north pacific ocean event:...
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Janelle FlemingInterdisciplinary Seminar
September 16, 1998
The 1976-77 North Pacific Ocean The 1976-77 North Pacific Ocean event: A unique climate shift, event: A unique climate shift, natural decadal variability, or natural decadal variability, or
global warming?global warming?
OutlineOutline Description of Regime ShiftDescription of Regime Shift
Physical characteristicsPhysical characteristics Climatological characteristicsClimatological characteristics Biological characteristicsBiological characteristics
InterpretationsInterpretations I. Unique series of eventsI. Unique series of events II. Part of decadal variationII. Part of decadal variation III. Global warming trendIII. Global warming trend
ConclusionsConclusions
The RegionThe Region
Tomczak andGodfrey (1994)
The ShiftThe Shift
Descriptive DataDescriptive Data
The ShiftThe ShiftPhysical IndicatorsPhysical Indicators
Begins during winter months of 1976-1977
Altered Patterns of Upper-Ocean SST Cooler SST in Central Pacific Warmer SST along coast of North America Warmer SST in central and eastern tropics
Altered Temperature Patterns in water column
SST anomalies - North PacificSST anomalies - North Pacific
Graham, N.E. (1994)
SST anomalies-North PacificSST anomalies-North Pacific
Venrick, et al. (1987)
Winters (1980-85) minus (1968-73)
SST anomalies-the tropicsSST anomalies-the tropics
Graham, N.E. (1994)
Difference Map: Epoch 2 - Epoch 1
Water Column Temp Water Column Temp AnomaliesAnomalies
Deser, et al (1996)
Temp Difference (1978-89) and (1971-76) at 100m
Water Column Temp Water Column Temp AnomaliesAnomalies
Deser, et al (1996)
Temp Difference (1979-90) and (1972-77) at 250m
Water Column Temp Water Column Temp AnomaliesAnomalies
Deser, et al (1996)
Temp Difference (1980-91) and (1972-78) at 400m
The ShiftThe ShiftClimate IndicatorsClimate Indicators
Aleutian Low shifts and intensifiesAleutian Low shifts and intensifies
Increased storminessIncreased storminess
Westerly winds shift and intensify Westerly winds shift and intensify
Organized convection over the tropical Organized convection over the tropical
Pacific shiftsPacific shifts
700 hPa heights - North 700 hPa heights - North PacificPacific
Graham,(1994)
Trenberth (1990)
North Pacific Sea Level North Pacific Sea Level PressurePressure
The ShiftThe ShiftWind PatternsWind Patterns
Deser, et al, (1996)
Graham (1994)
Organized Convection - OLROrganized Convection - OLRDifference Maps: Epoch 2 - Epoch 1
Organized Convection - HRCOrganized Convection - HRC
Graham (1994)
Difference Map: Epoch 2 - Epoch 1
The ShiftThe ShiftBiological Indicators Biological Indicators
Chlorophyll a concentrationChlorophyll a concentration vertically averaged vertically averaged
mean concentration doubles after 1976mean concentration doubles after 1976
Species Richness on a reef system Species Richness on a reef system
off California declined by 15-25%.off California declined by 15-25%.
Chlorophyll a ConcentrationsChlorophyll a Concentrations
Venrick, et al, (1987)
Species RichnessSpecies Richness
Holbrook, et al (1997)
The ShiftThe ShiftBroad based evidenceBroad based evidence
40 environmental variables 40 environmental variables distributed throughout the Pacific basindistributed throughout the Pacific basin Variables include:Variables include:
Number of Great Basin Canada goose nestsNumber of Great Basin Canada goose nests Sea Ice extentSea Ice extent SalinitySalinity upwellingupwelling commercial dungeness crab productioncommercial dungeness crab production salmon catchsalmon catch
The Shift The Shift Step-wise changeStep-wise change
Ebbesmeyer, et al, 1991
InterpretationsInterpretations
I. Unique EventI. Unique Event
Miller et al (1994)Miller et al (1994)
Used a layered ocean GCMUsed a layered ocean GCM forced with total surface heat flux anomaliesforced with total surface heat flux anomalies forced with wind stress anomaliesforced with wind stress anomalies reproduced SST changereproduced SST change
Large advective effects Large advective effects
Long term heat flux variationsLong term heat flux variations
Caused by “unique atmospheric anomalies”Caused by “unique atmospheric anomalies”
I. Unique Event I. Unique Event
Miller et al. (1994)
I. Unique Event I. Unique Event
Graham, et al (1994)Graham, et al (1994)
Used evolving general circulation model Used evolving general circulation model
(GCM)(GCM) Forced with observed SSTsForced with observed SSTs
abrupt change in SST in equatorial abrupt change in SST in equatorial
Pacific lead to the shiftPacific lead to the shift
I. Unique EventI. Unique Event
Graham, et al(1994)
700 hPa difference Maps: winters (1977-82)-(1971-76)
II. Decadal VariationII. Decadal Variation
Latif and Barnett (1994,1996)Latif and Barnett (1994,1996)
mid-latitude SSTs interact with mid-mid-latitude SSTs interact with mid-
latitude atmospherelatitude atmosphere
Drives a decadal cycle of ~20 yrs Drives a decadal cycle of ~20 yrs
II. Decadal VariationII. Decadal Variation
Latif and Barnett (1996)
II. Decadal Variation II. Decadal Variation
Gu and Philander (1997)Gu and Philander (1997)
Tropical SST affects the mid-latitudes Tropical SST affects the mid-latitudes
through the atmospherethrough the atmosphere
Mid-latitudes affect the tropics through Mid-latitudes affect the tropics through
the oceanthe ocean
II. Decadal Variation II. Decadal Variation
Gu andPhilander,(1997)
II. Decadal VariationII. Decadal Variation
Mantua et al (1997)Mantua et al (1997)
Create a Pacific (Inter-) Decadal Create a Pacific (Inter-) Decadal
Oscillation (PDO) index.Oscillation (PDO) index.
Correlate PDO with salmon catchCorrelate PDO with salmon catch
II. Decadal VariationII. Decadal Variation
Mantua et al (1997)
Decadal VariabilityDecadal Variability
Mantua,et al (1997)
II. Decadal Variation II. Decadal Variation
French Frigate Shoals in the Western French Frigate Shoals in the Western Hawaiian IslandsHawaiian Islands
Mixed layer depths increaseMixed layer depths increase Response to climate change in higher Response to climate change in higher
trophic levelstrophic levels spiny lobsters (2nd trophic level)spiny lobsters (2nd trophic level) reef fishes (3rd trophic level)reef fishes (3rd trophic level) seabirds and monk seals (top trophic level)seabirds and monk seals (top trophic level)
II. Decadal VariationII. Decadal Variation
Polovina, et al (1994)
III. Global WarmingIII. Global Warming
California Coastal SystemCalifornia Coastal System
80% decrease in zooplankton biomass80% decrease in zooplankton biomass
Correlated linear increase in SSTCorrelated linear increase in SST
III. Global warmingIII. Global warming
Roemmich andMcGowan (1995)
III. Global WarmingIII. Global Warming
Pelagic Bird population decline of 40% Pelagic Bird population decline of 40%
since 1987since 1987
Correlation with long-term increase in Correlation with long-term increase in
SSTSST
III. Global WarmingIII. Global Warming
Veit, et al (1996)
III. Global WarmingIII. Global Warming
Latif and Barnett (1994)Latif and Barnett (1994)
linear trend in SST in both observation linear trend in SST in both observation
and model dataand model data
III. Global WarmingIII. Global Warming
Latif et al (1997)
ConclusionsConclusions
An “abrupt shift” did occur in the mid-70’sAn “abrupt shift” did occur in the mid-70’s
Shift is part of interaction of cycles:Shift is part of interaction of cycles: ENSO cycle in the tropicsENSO cycle in the tropics Aleutian Low cycle in the extratropicsAleutian Low cycle in the extratropics
Inconclusive data as to anthropogenic Inconclusive data as to anthropogenic
influenceinfluence
Socio-historical perspectiveSocio-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