Impact of Climate Change on the Oceans
Ken Denman
Canadian Centre for Climate Modelling and Analysis
Meteorological Service of Canada
University of Victoria
&
Institute of Ocean Sciences-DFO, Sidney, BC
Email: ken.denman@ec.gc.ca
U. Victoria
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Outline of Talk
Global Oceans
– warming, freshening and sea level rise
The Arctic Ocean
– warming, ice extent + secondary impacts
BC Regional Ocean
– trends versus fluctuations
Ocean Biogeochemistry
– ‘anthropogenic’ carbon penetration
– positive feedbacks to climate
– life in a high CO2 ocean and calcifiers:
corals and coccolithophorids
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The Surface Ocean is Warming
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The Deep Ocean is Warming Too
~half the heating is below 700m
Levitus et al., Geophys. Res. Lett., in press.
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The Oceans Have Absorbed 21 x More
Heat than the Atmosphere 1955-1998
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Global Sea Level is Rising
Global
Global Mean Sea Level
1950-2001
100 mm
Reconstruction from Church et al. (2004)
1950
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2000
6
Sea Level is Rising Fastest at Mid-latitudes
Variations in global mean sea
level (1993-2004) computed
from TOPEX and Jason
altimeter data (updated from
Cazenave and Nerem, 2004;
Leuliette et al., 2004)
5
← 4 mm/yr →
1994
2004
∆MSL (mm/year)
4
3
2
1
0
60
60N
50
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30
20
10
0
-10
Latitude
-20
-30
-40
-50
-60
60S
7
The Oceans are Freshening
Linear trends (1955-1998) of the zonally averaged salinity of the
world ocean by one-degree latitude belts. (pss). Negative values
are shaded. (Boyer et al., Geophys. Res. Lett., accepted)
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1963
2002
Most New Fresh Water
is in the North Atlantic
(from the Arctic Ocean)
Salinity (psu)
over the last 40 years
0.05 psu
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People Living in
Arctic Regions
Indigenous People
Others
http://www.acia.uaf.edu/
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The Arctic is Warming and Sea Ice is Melting
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Observed Sea Ice Change 1979 vs 2003
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Projected
Sea Ice
Change
•open for
shipping by
2020?
•ice edge
ecosystems?
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Future Arctic Warming 3 – 6 oC
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Projected Surface Air Temperature
Change 1990s→2090s in °C
(Annual)
(Winter: Dec-Feb)
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Sea Level
Has Risen
~115m in
last 18 Kyr
•Arctic Ocean
was an icecovered deep
basin
•now ~1/3 is
flooded shelf
Next 5 slides courtesy
Robie Macdonald
Institute of Ocean Sciences
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These Shelves are Still Evolving
ISSUES
• Shelves are
depocentres for
riverine
sediments &
contaminants
• More open water
will lead to more
wind waves and
shoreline erosion
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No Sea Ice → No Polar Bears
Courtesy Ian Stirling
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Primary vs Secondary Changes
• Climate changes (Temperature, Hydrology)
– Runoff, precipitation (snow or rain?)
• Important secondary changes include
– Ice (amounts, drift pathways, time scales)
– Ocean structure (currents, convection, mixing)
– Ocean connections (Atlantic, Pacific, Arctic)
– Carbon cycle & ecosystem integrity
– Water storage (sea ice, glaciers, oceans?)
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Arctic Status
• We are monitoring primary change and
modelling it
• The secondary changes are far more
difficult and are being monitored
inadequately → hampers model development
• The secondary changes are likely to contain
within them the serious consequences for
life systems (biota and humans included)
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BC Regional Ocean
from DFO 2003 Ocean Status Report (Chair: W. Crawford, IOS)
http://www.pac.dfo-mpo.gc.ca/sci/psarc/OSRs/Ocean_SSR_e.htm
Line P
Sept. 97 – July 98: Chlorophyll from Ocean Colour Sensor
Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center & ORBIMAGE
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Subarctic NE Pacific
surface mixed layer
Warming →
2000
1995
Shallowing
Year
↓
1990
1985
Depth (m)
Ocean Station P – maximum winter mixed layer depth
1980
1975
1970
OSP
VI
oC
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Subarctic NE Pacific
thermocline stratification
Precursor to
global ocean
changes over
next century ??
Strengthening
↓
Long term average
Ocean Surface Layer
- warmer
- shallower
- stronger
stratification
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Coastal Sea
Level Records
Tofino
1982-83 El Niño
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BC Lighthouse Sampling Stations
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BC Coast T&S
trend +
interannual
variability
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BC Coast Meso-Zooplankton
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Coastal Temperature in 2004
Courtesy H. Freeland, Institute of Ocean Sciences
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Japan / East Sea
warming to depth of 3500m → increased stratification
→ O2 decrease over 65 years (bacterial respiration)
Dissolved Oxygen (µM)
Potential Temperature (oC)
0
0.2
0.4
0.6
0.8
200
240
280
320
0
500
Depth (m)
1000
1500
2000
2500
3000
1932 : Uda, 1934
1954 : USSR AOS, 1957
1969 : Sudo, 1986
1979 : Gamo and Horibe, 1983
1996 : Kim et al., 2001
3500
Changes in temperature and dissolved oxygen during the last
several decades (Kang et al., 2004).
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Ocean Biogeochemistry
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Anthropogenic CO2 in the Ocean
Î ~48% of all emissions have ended up in the ocean, ~ 1/3 of its
potential storage
Î suggests terrestrial biosphere has been a net source of 39±28 PgC
Total
106 ± 17 PgC
Sabine et al. (2004) Science 305: 367-371.
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Positive Ocean Feedbacks
to Warming & Increasing Atmospheric CO2
• Warming decreases solubility of CO2 thereby
increasing ocean pCO2 - for same total DIC
• Adding CO2 to the ocean decreases pH
thereby increasing surface ocean pCO2
K1
K2
CO2 + H2O ↔ HCO3- + H+ ↔ CO32- + 2H+
i.e. it makes the oceans more acidic
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Surface pH is Decreasing
?
Riebesell et al., Pelagic Ecosystem CO2 Enrichment Study
EU Large-Scale-Facilities, University of Bergen, Norway
http://spectrum.ifm.uni-kiel.de/peece/index.htm
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Oceanic Acidity is Not Uniform:
Saturation Depth Patterns
Corals
Coccolithophorids
Feely et al. 2004. Science, 305: 362-366.
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Carbonate (CaCO3) Pump -
Coccolithophorid Emiliania huxleyi
Image courtesy of Southampton
Oceanography Centre, UK
SeaWiFS image
25 April 1998
SEM image
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Phytoplankton Grown Under Different
CO2 Concentrations
~300 ppm
~780 –
850 ppm
Riebesell et al. 2000. Nature, 407, 364-367.
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Saturation Layer in N. Pacific is Shrinking
Present
Preindustrial
Feely et al. 2004. Science, 305: 362-366.
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Lower pH Threatens Cold Water Corals
CaCO3 may start to dissolve
Corals on sill (at ~60m depth) in Knight Inlet BC
(courtesy Verena Tunnicliffe, U. Victoria)
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The Unanswered Question
How Will the Structure and Dynamics of
Marine Communities Change as the Climate
and Biogeochemical Cycles Change?
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Why We Should Do Something Now
RIO DECLARATION ON ENVIRONMENT AND DEVELOPMENT
from the United Nations Conference on Environment and
Development, Rio de Janeiro, 3 to 14 June 1992
Principle 3: ‘Intergenerational Equity’
The right to development must be
fulfilled so as to equitably meet
developmental and environmental needs
of present and future generations
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The End
Thank-you
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