janelle fleming interdisciplinary seminar september 16, 1998 the 1976-77 north pacific ocean event:...

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