The Oceans and Climate Change: Modern Pressures and Lessons from Ancient

ExamplesJennifer 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• High Temperatures

• Very different 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

Adding soluble Fe to Fe-deficient waters always results in higher rates of primary productivity!!!

Boyd et al. (2007)

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