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

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

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 CO 2 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 CO 2 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 CaCO 3 Adversely affect primary productivity in the oceans (carbon fixation) Impact most ocean ecosystems

Cenozoic Climate Change

Cretaceous Greenhouse World High CO 2 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 CO 2 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 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