Time scales of physics vs. biology ENSO effects on biology Pacific Decadal Oscillation (PDO)

• Time scales of physics vs. biology

• ENSO effects on biology

• Pacific Decadal Oscillation (PDO)

years

decades

centuries

The problem: multiple time scales of variability

Humans

century

• Generation time: Doubling time for unicellular organisms, or time to first reproduction for animals

• Dominant environmental forcing: Typically the physical process responsible for the greatest amount of variability in a biological response

Tuna

Sardine

Anchovy

Salmon

Krill

Copepods

Jellyfish

Phytoplankton

Bacteria1 hour

1 day1 week

1 month

1 year5 years

10 years

15 years

20 years

Time scales

• Life

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Generation times

Tuna

Sardine

Anchovy

Salmon

Krill

Copepods

Jellyfish

Phytoplankton

Bacteria1 hour

1 day1 week

1 month

1 year5 years

10 years

15 years

20 years

SeasonalCycles

Time scales

• Life

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Tuna

Sardine

Anchovy

Salmon

Krill

Copepods

Jellyfish

Phytoplankton

Bacteria1 hour

1 day1 week

1 month

1 year5 years

10 years

15 years

20 years

ENSO Duration

PDO +/- Duration

SeasonalCycles

ENSO Frequency

Time scales

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Main effects of climate oscillations on pelagic species

• Temperature/nutrients affect primary production

• Food availability affects higher trophic levels

• Temperature affects rates of growth or survival (all trophic levels)

• Larger/faster species move to find preferred temperature, causing range shifts

Top: normal Bottom: El Niño condition

Open University, 1998

Normal

El Nino

Eastern boundary

•Shallow thermocline•Cold, nutrient-rich water•Mixing depth shallower than critical depth•High NPP

•Deep thermocline •Warm, nutrient-poor water•Mixing depth not as much shallower than critical depth•Lower NPP

Major episodes occur every 3-7 years and last 9-18 months

Temperatureanomaly

El Niño La Niña

Equatorial upwelling

Much weaker Much stronger

California Current upwelling

Weaker Stronger

California Current temperature

Warmer Cooler

California Current thermocline

Deeper Shallower

West Pacific warm pool

Spreads east across equator

Compressed in western Pacific

The most notable El Niño events

Note the scale is reversed relative to Southern Oscilation Index, so El Niño is on top, La Niña on bottom

#1: 1997-1998

#2: 1982-1983 #3: 2015-2016????

Jan. 1998 El Niño

July 1998 La Niña

El Niño year looks more like this

La Niña year looks more like this

Weak upwelling Strong upwelling

In El Niño conditions, upwelling is weaker, and the coastal jet (warm water) reconnects with the coast farther north near CA.

In La Niña conditions, upwelling is stronger, and the coastal jet (warm water) reconnects with the coast farther south near Baja.

Normal year

El Niño year

SST distribution in California Current

Shaded area =16 to 17 oC

Lavaniegos and Ohman 2003

California Current-El Niño reduces upwelling -Lower nutrients reduced primary production -Low primary production low zooplankton biomass etc.

Biomass of Zooplankton

>500 μm

Major El Niños (warm)Major La Niñas (cool)

Comparisons of distribution patterns of an eastern tropical Pacific species of krill, Euphausia eximia, between 1962, a typical year, and 1958, an El Niño year. Brinton 1967

El Niño yearNormal year

Some tropical krill follow warm water (population moves in/out of CalCOFI grid)

California Current krill community - response to SST is species-specific

Brinton & Townsend 2003

Euphausia pacifica(cool water, widespread)

Jaime Gomez

Nyctiphanes simplex(subtropical)

ocean.stanford.edu/blsaenz

Ab

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no

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Life span <1 year

Life span ~2 years

El Niños (warm) La Niñas (cool)

Skipjack tunatolerate 15 to 30 oC

Recruitment in PacificEl Niño (average distribution October1982 - March 1983) and La Niña (average distribution October 1988 - March 1989) skipjack recruitment. Biomass distribution of first skipjack age class (0-3 months) in tonnes per degree square.

Lehodey et al. 2003

El Niño

La Niña

Squid: average lifespan ~1 year, juveniles eat zooplanktonAdults vertically migrate to surface at night, eat small fish

Major El Niño

Major El Niño

Mackerel: average lifespan 6-8 years, eat large zooplankton & fish, tropical or sub-tropical

Major El NiñoMajor El Niño

Sardine: lifespan 12-25 years, eat small zooplankton, prefer warm water

Major El Niño

Chavez et al. 2003

Major El Niños

Major El NiñosMajor El Niños

-ENSO weakly affects sardine & anchovy landings in Peru. -Compared to sardines, anchovy have shorter life span and are more negatively affected by El Niños.-ENSO effects are small relative to long-term variability.

Pacific Decadal Oscillation (PDO) ~15 to 30 year cycle

Positive PDO pattern Negative PDO pattern

+ -

•The PDO Index is a spatial average of monthly sea surface temperature (SST) anomaly of the Pacific Ocean north of 20°N. The global average anomaly is subtracted to account for global warming (Mantua, 2000).• Highly correlated with temperature in California Current

El Niño = ENSO warm event La Niña = ENSO cool event

Pacific Decadal Oscillation (PDO)

Positive/warm PDO phase Negative/cool PDO phase

ENSO events: 6-18 month duration2-8 year frequency

ENSO index is based on sea level but has characteristic temperature pattern (Walker circulation affects location and extent of Pacific warm pool)

PDO cycle:15-30 year phase (low-frequency oscillation)

PDO index is based on patterns of temperature anomaly but has sea level patterns like those of ENSO

El Niño, +PDO Pattern La Niña, -PDO Pattern

Sea Surface Temperature Anomalies

-ENSO and PDO index both change continuously. -Their patterns are additive.

Positive PDO Negative PDO

Equatorial upwelling

Weaker Stronger

California Current upwelling

Much weaker Much stronger

California Current temperature

Warmer Cooler

Calif. Current thermocline

Deeper Shallower

West Pacific warm pool

Spreads east across equator

Compressed in western Pacific

warm cool warm

Long positive (warm) and negative (cool) phases of PDO

Biomass of Zooplankton

>500 μm

- PDO (cool) + PDO (warm)

Major El Niños (warm)Major La Niñas (cool)

Lavaniegos and Ohman 2003

California Current-Zooplankton biomass is low during warm phases with weak upwelling-Effects of warm PDO and warm El Niño events are additive

Some krill track PDO better than ENSO

Brinton & Townsend 2003

Euphausia pacifica(widespread)

Jaime Gomez

Nyctiphanes simplex(subtropical)

ocean.stanford.edu/blsaenz

El Niños (warm) La Niñas (cool)

- PDO (cool) + PDO (warm)

Ab

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Life span <1 year

Life span ~2 years

-PDO(cool)

+PDO(warm)

+PDO (warm) is sardine regime -PDO (cool) is anchovy regime (anchovies are also affected by ENSO cycle)

ENSO vs. PDO effects on biology

• El Niño/La Niña and Pacific Decadal Oscillation have similar “fingerprints” but different time scales

• Short-lived species more responsive to ENSO, longer-lived species more responsive to PDO

• BUT effects on abundance and distribution of zooplankton and fish are species-specific

• Tropical species less likely to be negatively impacted by El Niño or +PDO

On top of these cycles there is a global warming trend (Theme 4, up next).