Transcript 21-Bio-climate

Marine Ecosystems
and
Climate Variability
Interannual Time Scales:
ENSO
Decadal Time Scales:
Basin Wide Variability
(e.g. Pacific Decadal Oscillation,
North Atlantic Oscillation)
Longer Time Scales:
Warming trend
Marine Ecosystems
and
Climate Variability
Interannual Time Scales:
ENSO
Decadal Time Scales:
Basin Wide Variability
(e.g. Pacific Decadal Oscillation,
North Atlantic Oscillation)
Longer Time Scales:
Warming trend
Mean Sea Level Pressure
Negative Phase
Positive Phase
Mean Sea Level Pressure
Anomaly PDO Negative Phase
Anomaly PDO Positive Phase
SST Anomalies
Anomaly PDO Negative Phase
SST Anomalies
Anomaly PDO Positive Phase
Material on the Pacific Decadal Oscillation connections
to the marine ecosystem is found in:
From anchovies to sardines and back: Multidecadal
change in the Pacific Ocean
Chavez FP, Ryan J, Lluch-Cota SE, et al.
SCIENCE 299 (5604): 217-221 JAN 10 2003
Posted on website (only 7 pages)
Marine Ecosystems
and
Climate Variability
Interannual Time Scales:
ENSO
Decadal Time Scales:
Basin Wide Variability
(e.g. Pacific Decadal Oscillation,
North Atlantic Oscillation)
Longer Time Scales:
Warming trend
Mean Sea Level Pressure
North Atlantic
Iceland Low
Azores High
North Atlantic Oscillation
Iceland Low
Azores High
NAO Index = SLP(Azores High) – SLP(Iceland Low)
measured November through March
The North Atlantic Oscillation Index
NAO Index = SLP(Azores High) – SLP(Iceland Low)
measured November through March
The North Atlantic Oscillation Index
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The NAO index shows large variations from year to year. This
interannual signal was especially strong during the end of the 19th
century.
Sometimes the NAO index stays in one phase for several years in a
row. This decadal variability was quite strong at the beginning and
end of the 20th century.
One might also interpret the recent 30 years as a trend in the NAO
index possibly linked to "global warming".
North Atlantic Oscillation
Iceland Low
Azores High
NAO Index = SLP(Azores High) – SLP(Iceland Low)
measured November through March
The positive NAO index phase
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Wet
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Dry
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The positive NAO index phase
shows a stronger than usual
subtropical high pressure center
and a deeper than normal
Icelandic low.
The increased pressure difference
results in more and stronger
winter storms crossing the
Atlantic Ocean on a more
northerly track.
This results in warm and wet
winters in Northern Europe and in
cold and dry winters in
Mediterranean region.
The eastern US experiences mild
and wet winter conditions.
Martin Visbeck
5 April, 2016
The negative NAO index phase
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Dry
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Wet
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The negative NAO index phase
shows a weak subtropical high
and weak Icelandic low.
The reduced pressure gradient
results in fewer and weaker
winter storms crossing on a more
west-east pathway.
They bring moist air into the
Mediterranean and cold weather
to northern Europe.
The US east cost experiences more
cold air outbreaks and hence
snowy winter conditions.
Martin Visbeck
5 April, 2016
SST Anomalies
Wet
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Positive NAO
Stronger Currents
Dry
Dry
Wet
Weaker Currents
Negative NAO
Impacts of the NAO
Martin Visbeck5 April, 2016
Us East Coast Impacts of the NAO
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The US East coast experiences milder
winter conditions during a positive
NAO index phase.
The amount of snow cover is reduced.
Warmer than usual ocean temperatures
cause more frequent occurrence of
"red tides" in the summer.
Colder than usual tropical ocean
temperatures reduce the number of
hurricanes in the following summer.
Cold ocean temperatures in the
spawning grounds over the Grand
Banks cause less cod reproduction.
Martin Visbeck
5 April, 2016
Impacts of the NAO in Europe
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Northern Europe experiences mild and
wet winter during the positive NAO
index phase.
This has dramatic consequences for
hydro-electric power generation and
heating oil consumption.
South-Eastern Europe receives less rain
and hence causes significant problems
with drinking water supply and
reduced stream flow volume in the
Middle East.
Harvest yield of grapes and olives have
been shown to depend significantly on
the NAO.
Martin Visbeck
5 April, 2016
NAO and significant wave heights
Martin Visbeck 5 April, 2016
NAO and fish catch in the North Atlantic
Topliss, BIO, Canada
Ecological effects of the North Atlantic Oscillation
Geir Ottersen, Benjamin Planque, Andrea Belgrano, Eric Post, Philip C. Reid,
Nils C. Stenseth
Posted on class website (12 pages)
…more than 100 documented
correlation between NAO and marine
ecosystems.
How to make sense?
SST Anomalies
Wet
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Positive NAO
Stronger Currents
Dry
Dry
Wet
Weaker Currents
Negative NAO
The response to NAO is classififed into 3 type:
DIRECT - A direct ecological response to one of the environmental
parameters synchronised with the NAO.
INDIRECT - The indirect effects of the NAO are non-trivial mechanisms
that either involve several physical or biological intermediary steps
between the NAO and the ecological trait and/or have no direct impact
on the biology of the population.
INTEGRATED - The integrated effects of the NAO involve simple
ecological responses that can occur during and after the year of an NAO
extreme. This is the case when a population has to be repeatedly
affected by a particular environmental situation before the ecological
change can be perceived (biological inertia). or when the environmental
parameter affecting the population is itself modulated over a number of
years (physical inertia)
Direct Effects
Temperature Mediated Response
Length of active growing season, Individual growth (size), growth rate,
eggs variability, timing of reproduction, spawning, time of food
availability, larval growth and mortality,
Indirect Effects
Physically induced by changes in oceanic transport
Changes in spatial distribution of phytoplankton and larvae, alteration in
competition between different levels of the trophic chain  alteration
in food web
Effects on Predator-Prey
Through changes/alteration in the food
Flowering
Abbundance (2 year later)
NAO Index
Fecundity (1 year later)
Flowering
Integrated Effects
NAO Index
Phenology to herbivore dynamics (red deer)
Cartoon of Red Deer
correlation with NAO
NAO and Copepods (Calanus Finmarchicus)
Difficult to identify causes of
observed relationships
Calanus Finmarchicus distribution
1) Changes in food availability
2) Alteration of competition
balance
3) Variations in transport of
individuals from North Atlantic
Calanus Helgolandicus distribution
NAO and global warming
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Some scientist argue that
changes in the stratospheric
circulation can influence the
phase of the NAO.
Ozone depletion and increase of
CO2 both result in a strong
polar night vortex which
might cause the NAO to prefer a
positive state.
Will "global warming" cause a
persistent positive NAO phases?
Martin Visbeck
5 April, 2016
Some facts
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The North Atlantic Oscillation is the largest mode of climate variability in
the Atlantic Sector and possibly of the northern hemisphere.
The dynamics of the NAO are not fully understood and in partiuclar its
sensitivity to ocean, land or changes in the sea-ice conditions need more
study.
Its impacts reach from the upper atmosphere to the bottom of the ocean
and reach from N. America over to Europe and far into Asia.
The Ecological Impacts of NAO can be direct, indirect and integrated.
Some scientist argue that the NAO is strongly coupled to the stratosphere
and will be significantly influenced by "global warming".
Other scientist see evidence for coupling with the North Atlantic Ocean.
It has also been suggested that tropical ocean temperatures can influence
the phase of the NAO.
Martin Visbeck
5 April, 2016
Additional Slides
Atlantic Ocean SSTs and the
NAO
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Some scientist have
suggested that the
storage and propagation
of temperature
anomalies by the ocean
gives an important feed
back to the atmosphere
and is responsible for
the decadal signal.
If correct one could
make use of the "slow
ocean dynamics" to
predict aspects of the
NAO.
Martin Visbeck 5 April, 2016
NAO and Energy in Norway
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Norway experience cold
winters during a negative
NAO phase.
Heating Oil consumption in
Norway varies by 30% in
good (anti) correlation with
the NAO.
Correlation with
precipitation results in
variability in hydropower
generation.
Martin Visbeck5 April, 2016
NAO and Water Resources in Turkey and
the Middle East
Precipitation in Turkey is well
correlated with the NAO.
As a result spring stream flow
in the Euphrates River
varies by about 50% with
the NAO.
An upward trend in the NAO
will lead to drought
conditions in the Middle
East.
Martin Visbeck 5 April, 2016
NAO and stream flow in the US
Correlation
Martin Visbeck5 April, 2016
North Atlantic SST connection
Jacob Aaal Bonnevie Bjerknes
1897-1975
NAO related tripole
in sea surface temperatures
Source: Rowan Sutton and D.B. Stephenson
NAO impact on Atlantic Ocean
SSTs
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Ocean surface temperatures (SST) changes with the phase of the
NAO.
During a positive year the ocean warms just east of the US east coast
and cools in the subpolar gyre between England, Newfoundland and
Iceland.
The Gulf stream transports those temperature anomalies downstream
towards Europe.
Martin Visbeck 5 April, 2016
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NAO movie
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Animation of sea level
pressure and surface
winds during an
idealized NAO cycle of
12 year duration.
The lower panel shows
the land temperature
response and the
propagation of SST
anomalies in the ocean.
The ocean is simulated
by the Lamont Ocean
model (LOAM)
All other data are
regressions from the
NCEP/NCAR
reanalysis.
Martin Visbeck 5 April, 2016
NAO forced by Atlantic SST's ?
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Some scientist argue that changes in the
Atlantic Oceans SST can influence the
phase of the NAO.
Others argue that changes in the tropical
Atlantic influence the extratropical
climate.
A (small) number argue that the ocean
plays no role at all.
CLIVAR has decided to make those
issues of high programatic priority.
Martin Visbeck 5 April, 2016
NAO Prediction
Hamilton, University College London
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No robust predictability has
been demonstrated.
Different methods are used:
SST based => 2001 positive
SSA based => negative soon
global warming based =>
stay positive next decades
Martin Visbeck 5 April, 2016