Time scales of physics vs. biology ENSO effects on biology Pacific Decadal Oscillation (PDO)
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Transcript of 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
Sp
an
s• #
Rep
rod
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s• B
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siz
e• S
wim
min
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pee
d• E
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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
Sp
an
s• #
Rep
rod
uctiv
e y
ear
s• B
ody
siz
e• S
wim
min
g s
pee
d• E
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rve
s
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
• Life
Sp
an
s• #
Rep
rod
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e y
ear
s• B
ody
siz
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wim
min
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pee
d• E
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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
un
dan
ce a
no
mal
ies
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
un
dan
ce a
no
mal
ies
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).