Transcript PRESENTATION NAME

The Oceans and Climate
Change: Modern Pressures
and Lessons from Ancient
Examples
Jennifer Latimer
Department of Earth and Environmental
Systems
Outline
• Current Environmental Issues
Impacting the World’s Ocean
• Lessons from Marine Records
about Ocean Responses to
Climate Change
• Geo-engineering the oceans…
Why are the oceans
important?
• Provide food
• Help regulate planetary
temperatures
• Support coastal economies (i.e.
fisheries and tourism)
• Responsible for ~50% of carbon
fixation (and production of
oxygen) on the planet
Environmental Issues
Along Coasts
• At least 50% of the world’s
population lives near the coast
• Coastal areas already deal with
• Pollution: sewage, agricultural
chemicals, heavy metals,
plastics, etc.
• Storms
• Rising sea levels
• Loss of wetlands and marshes
Plastic Trash
Dead Zones
http://earthobservatory.nasa.gov/
Increased Pressures Resulting
from Climate Change
• Rising sea levels – sovereign
island nations have already been
forced to consider evacuation due
to saltwater intrusion, erosion, and
flooding
• Tuvalo – South Pacific
• Kiribati – South Pacific
• Maldives – Indian Ocean
• Marshall Islands – South
Pacific
• http://flood.firetree.net/
Increased Pressures Resulting
from Climate Change
• Sea Level Rise due to:
• thermal expansion of water
• melting glaciers and ice sheets
• Greenland – 7 m
• West Antarctica – 5 m
• East Antarctica – 55 m
• Estimated over 600 million people live
in areas that are <10m above sea
level
• 2/3 of the world’s cities with
populations over 5 million are in
these same areas
Increased Pressures Resulting
from Climate Change
• Another consequence of ice sheets
melting is a change in thermohaline
circulation – which contributes to heat
transport and weather patterns
• Deepwater today forms at the high
latitudes where water is cold and salty
• If deepwater is not dense enough it will
not sink and disrupt thermohaline
circulation
• Impact continental temperatures in
northern Europe
• Impact carbon fixation in the oceans
(primary productivity)
Increased Pressures Resulting
from Climate Change
• Oceans absorb ⅓ – ½ of
anthropogenic CO2 emitted
• Changes in ocean pH – the oceans
are becoming more acidic
• From ~8.2 to ~8.1 over 250 years
• Geologic and model evidence
suggests this is a larger change in
pH than has occurred in the past
300 million years
• The rate of change is much higher
than due to geologic causes
Increased Pressures Resulting
from Climate Change
• As more and more CO2 is pumped into
the atmosphere, the oceans become
less able to resist changes in pH
• If the rate of change is not slowed, pH
will drop by another 0.5 units this
century changing carbonate chemistry
significantly in the oceans.
• 60% drop in available CaCO3
• Adversely affect primary productivity
in the oceans (carbon fixation)
• Impact most ocean ecosystems
Cenozoic Climate Change
Cretaceous
• Greenhouse World
• High CO2
• High sea levels
ocean…
PETM
• Interval of rapid global warming 55.8
million years ago
• Global temperatures rose over ~20
thousand years
• The event lasted ~180 thousand years
• Deep sea extinctions resulted
• Localized anoxia in the oceans
• Large scale changes in ocean circulation
• Surface waters more acidic
Pleistocene Climate
Kump (2002) after Petit et al. (1999)
• Temperatures and CO2 varied
in a cyclic pattern
Since the LGM…
• Stadial (i.e. Younger Dryas, 8.2 kyr event) and
interstadial events (Bolling-Allerod)
• Younger Dryas – rapid return to glacial
conditions (maybe as few as 10 years) while
recovery lasted 40-50 years
• Mideval warm period and Little Ice Age – not as
severe as previous glaciations
• Holocene climate has been relatively stable
• Studies of abrupt climate change teach us that
climate can change in decades
What we have learned…
• Oceans and marine processes during a
Greenhouse World are fundamentally
different
• Transient climate events are much
shorter than the time it takes for natural
processes to recover
• We have already exceeded the natural
variability in the carbon cycle of the last
million years
• Abrupt climate change can be on
human time scales
Geoengineering the Oceans
• When a major climate change catastrophe
occurs or a series of catastrophes
occurs…people will demand action…
• One of the quickest responses could be
ocean iron fertilization, but…will it work?
• Scientific community says – NO…maybe?
– “Ocean fertilization: Time to Move on” Nature,
October 2009
• Currently UN restrictions on iron fertilization
Geoengineering the Oceans
Boyd et al. (2007)
Geoengineering the Oceans
Boyd et al. (2007)
 Adding soluble Fe to Fe-deficient waters always results
in higher rates of primary productivity!!!
Geoengineering the Oceans
• Rationale…
– Iron is the limiting nutrient in some regions
– “natural” process – artificial iron fertilization
mimics a dust storm
• Iron fluxes in the ocean not controlled
completely by dust
• Lefevre and Watson (1999); Watson et al. (2000);
Latimer and Filippelli (2002); Ridgewell and Watson
(2002); Blain et al. (2007); Latimer and Filippelli
(2007); Meskhidze et al. (2007); Anderson et al.
(2010)
Geoengineering the Oceans
• Instead of buying and selling C credits,
buy Fe and pay someone to “dump” it in
the ocean, which theoretically = C
sequestration
Geoengineering the Oceans
• October 2009 – dust storm in
Australia dumped 3 million tons of
dust (N & P) into Sydney Harbor
and the Tasman Straits
– Phytoplankton
tripled
– Boost fishing
industry and
feed people?
– Slow climate
change
Geoengineering the Oceans
• Original Fertilization Plan: Add iron to iron
depleted areas to stimulate phytoplankton
• Newer Fertilization Plan: Add nitrate and
phosphate to stimulate phytoplankton
• Instead of buying and selling C credits,
buy fertilizer and pay someone to “dump” it
in the ocean, which theoretically = C
sequestration (but probably not…)
Geoengineering the Oceans
• Other consequences…
– Algae associated with HABs along coasts
also thrive in iron fertilized patches of open
ocean (Trick et al. 2010; Silver et al., 2010;
PNAS)
– Pseudonitschia produce domoic acid, a potent
neurotoxin
• Responsible for marine mammal and bird deaths
• In some cases become dominant species and
produce more domoic acid
Geoengineering the Oceans
• Other consequences…
– Extensive ocean anoxia
Potential long-term outcomes
for iron fertilization of the ocean
are unknown, and could include
newly productive fisheries and
reduced atmospheric carbon
dioxide (left) or a polluted
ocean, unenhanced fisheries,
and little effect on atmospheric
carbon dioxide (right).
Credit: Jack Cook, Woods Hole
Oceanographic Institution