Geography and Oceanography - Chapter 12 ppsx

Ocean Acidification and the Future Global Carbon Cycle • Rising atmospheric CO2 • Ocean’s role in uptake of atmospheric CO2 • Resulting changes in ocean chemistry • Possible outcomes for

Ocean Acidification and the

Future Global Carbon Cycle

• Rising atmospheric CO2

• Ocean’s role in uptake of atmospheric CO2

• Resulting changes in ocean chemistry

• Possible outcomes for future oceans

• What can we can do to help improve the future?

Jack Barth (barth@coas.oregonstate.edu)

College of Oceanic & Atmospheric Sciences

for further info: “The Future of Ocean Biogeochemistry in a High CO2 World,” Oceanography magazine (Dec 2009)

http://www.tos.org/oceanography/issues/issue_archive/22_4.html

Data from Keeling and Whorf, 2004

David Keeling in the mid 1900s.

Atmospheric CO2 Record

Northern Hemisphere has larger seasonal variability than southern hemisphere

Atmospheric CO2 levels are rising

everywhere in the world This can easily

be seen even with the natural variability

Atmospheric CO2 was steady for at least 1,000 years

before the industrial revolution.

“It is very likely that [man-made]

greenhouse gas increases caused most

of the average temperature increase since the mid-20 century”

- Intergovernmental Panel on Climate Change (IPCC) 4th Assessment

A1B A1T A2 B1 B2

A1B A1T A2 B1 B2

50-year constant growth rates

to 2050 B1 1.1%, A1B 1.7%, A2 1.8%

A1FI 2.4%

Observed 2000-2006 3.3%

2007 2006

Recent emissions have been higher than the worst of the IPCC projected scenarios

Carbon Inventories of Reservoirs that Naturally

Exchange Carbon on Time Scales of Decades to Centuries

Ocean 38,136 PgC

Soil=2300 PgC

Plants=650 PgC Atm.=775 PgC

Preind Atm C

=76%

Ocean Anth

C=0.35%

• Oceans contain ~90% of carbon in this 4 component system

• anthropogenic component is difficult to detect

Anth C=24%

In the 1990s we conducted a global survey of CO2 in the oceans to learn how much fossil fuel is stored in the ocean.

~72,000 sample locations

-1

TA ± 4 µmol kg-1

Penetration of human-caused CO2 into Ocean

•Present-day levels minus

pre-industrial (year 1800)

•Equivalent to about half of all

historical fossil fuel emissions

Sabine et al (Science, 2004)

After Turley et al., 2005

pH

CO2 + H2O H2CO3 HCO32- + H+ CO3- + H+

CO2 is an acid gas so the addition of 22 million tons of

carbon dioxide to the ocean every day is acidifying the

seawater…we call this process “ocean acidification”

Feely et al (2009)

50 100 150 200

0 50

100 150

200 250

300 350

Predictions of Ocean Acidification and the effects on coral reef calcification

p CO2 280-380 ppmv p CO2 780-850 ppmv

Emiliania huxleyi

Gephyrocapsa oceanica

Coccolithophores

Riebesell et al.(2000); Zondervan et al.(2001)

Calcification decreased

- 9 to 18%

- 45%

The shells of living pteropods begin to dissolve

at elevated CO2 levels

C pyramidata Limacina helicina

Potential Effects on Open Ocean Food Webs

Pteropods

Pteropods make up 45% of the pink salmon diet amphipods (likely also affected by OA) make up 32% of diet

Much of our present knowledge stems from

 abrupt CO2/pH perturbation experiments

 with single species/strains

 under short-term incubations

 with often extreme pH changes

Hence, we know little about

 responses of genetically diverse populations

 synergistic effects with other stress factors

 physiological and micro-evolutionary adaptations

 species replacements

 community to ecosystem responses

 impacts on global climate change

What we know about the biological impacts of ocean acidification

CENOZOIC MESOZOIC PALEOZOIC PRECAMBRIAN

Age (Ma)

From Signor (1990)

Number of Genera

Cretaceous/

Tertiary Triassic/Jurassic Permian/Triassic LateDevonian Ordovician/Silurian Era

Coral Reef Gap

Where will the future take us?

But with every major rise there have been mass extinctions

How will these changes affect the global

carbon cycle in the future?

Calcification decrease lower natural CO2 production negativeCaCO3 dissolution-sed higher CO32- increasing uptake negativeCaCO3 dissolution-water higher CO32-/lower org transport Neg./pos.Increasing SST Convert ocean HCO3- to CO2 positiveIncreased stratification Reduced mixing and transport positiveIncreased stratification Lower productivity and uptake positiveIncreased dust input Increased productivity-N fixers negativeEcosystem structure Lower or higher productivity Pos./neg

Acidic waters

brought near the

coast by coastal

upwelling

Possible changes to:

• species composition &

abundances

• food webs

• biogeochemical cycles

Feely et al (2008)

Aug & Sep Courtesy of MI_LOCO

(Barth, Adams, Chan)

Dissolved oxygen

off Oregon

“Spat” on shell, newly

metamorphosed juvenile oysters,

after their larval stage

“Spat” raised in

hatchery, not on shell.

affect oyster hatcheries

Courtesy of George Waldbusser

(COAS/OSU)

Whiskey Creek Hatchery,

Netarts Bay, OR

www.netartsbaytoday.com

From McConnaughey & Gillikin 2008

How a bivalve shell is formed

Calcification in bivalves is an Internal process,

Dissolution is primarily External*

Two sources of Shell Carbonate

-Respired CO2

Two components of shell growth, organic and inorganic

Internal shell surface is used to buffer during

exposure or stress.

Courtesy of George Waldbusser

(COAS/OSU)

2 The ocean has provided a great service to society by helping

to slow the rate of atmospheric increase.

3 The addition of >200 billion metric tonnes of carbon to the

ocean over the last 100 years has lowered ocean pH by 0.1 unit.

4 By the end of this century pH may drop by another 0.3 units

and will likely have dramatic consequences on the ocean

ecosystems.

to adapt to climate change…slowing the rate of growth could determine the structure of the future oceans.

for further info: “The Future of Ocean Biogeochemistry in a High CO2

World,” Oceanography magazine (Dec 2009)

http://www.tos.org/oceanography/issues/issue_archive/22_4.html