Global Climate Change and the OceanJames Barry - Monterey Bay Aquarium Research Institute

Global Climate Change and the Ocean

Road Map for Talk• A short climate change introduction

• Carbon dioxide on Earth – the long and short of it

• Global warming and the oceans• Sea level rise• Effects of climate warming on ocean ecosystems

• The high-CO2 ocean and ocean acidification• How does increased ocean carbon affect ocean

ecosystems?• A glimpse of our research at MBARI on ocean

acidification

• Summary

Climate Change during the last 150 million years(Reconstruction from a carbon

cycle model)Tajika, E. (1998) Earth & Planet. Sci. Lett. 160

• CO2 has declined over the past 150 million years

• Up to ~6 x present atmospheric level (PAL) in the past

• ~1 C change in surface T per PAL

Years Before Present (1,000s)0100200300400

Deg

rees

(C)

-12

-8

-4

0

4C

O2

(ppm

)

200

240

280

320

360

400

CO2

Temperature

What is the link between CO2 and Climate?

Ice ages

Millennial Northern Hemisphere CO2 & Temperature

Source: Mann et al. 1999.

Year1750 1800 1850 1900 1950 2000

Atm

osph

eric

CO

2 (p

pm)

260

280

300

320

340

360

380

Car

bon

Emis

sion

s (G

tC/y

)

0

1

2

3

4

5

6

7Atm. CO2 (Ice Core)Atm. CO2 (Moana Loa)Global CO2 Emissions

WW1

WW2

Stocks Crash

1973Oil Embargo

Peak OPECOil Prices

Iraq War 1Poor US Economy

History of CO2 Emissions & Atmospheric CO2 Levels

Years Before Present (1,000s)0100200300400

Deg

rees

(C)

-12

-8

-4

0

4

CO

2 (p

pm)

200

300

400

500

600

700

800

CO2

Temperature

Climate Response

=1.0 - 4.5 oC

perPAL CO2

PAL = PresentAtmospheric

Level

Warming by ~2090

Temperature

Arctic Ice Cover Sept. 2003

Arctic Ice Cover Sept. 1979

Precipitation

Sea Level Rise and Coastal Flooding

Intergovernmental Panel on Climate Change

Sea Level Rise and Coastal Flooding

Intergovernmental Panel on Climate Change

1 m 2 m

4 m 8 m

Societal Impacts: Effects on California

Source: Union of Concerned Scientists- uscusa.org

Global Warming & Ocean Ecosystems

Warming1900 to 2075

Ecosystem Impacts:Coral Reefs

Mass coral bleaching caused by thermal stress1. 95% correlation with increases in sea

temperature (1-2oC above long-term summer sea temperature maxima) and bleaching.

2. Backed up experimentally 3. Basis for a highly predictive SST program at

NOAA (HotSpots):

1. 95% correlation with increases in sea temperature (1-2oC above long-term summer sea temperature maxima) and bleaching.

2. Backed up experimentally 3. Basis for a highly predictive SST program at

NOAA (HotSpots):

1998

2002

Strong, Hayes, Goreau, Causey and others

Threshold temperature –above which bleaching manifests itself (1-2oC above the long-term summer maximum temperatures

WHAT DOES THE FUTURE HOLD?

Hoegh-Guldberg (1999)

Climate-related shifts in rocky intertidal animals (1932-19Warming of water temperatures over 60 years has been accompanied by a shift in the geographic ranges of species

1932 Abundance19

93 A

bund

ance Southern Species

Northern Sp.Cosmopolitan Sp.

Monterey

Warming prediction: Species ranges should migrate poleward with warming temperatures

Southern Species Increased Northern Species Declined

Barry et al. 1995

Changes in Fish Communities in the Channel Islands, California

Conclusions:Northern Species decreasedSouthern Species increased

Are observed changes a response to short-term climate variation or long-term climate warming?

Holbrook et al. 2002

Scale of Oceanographic Variability

3-12 years

~25 years

Centuries+?

Effects of Ocean Warming on Productivity

warm

low growth

Warming increases stratification of the upper ocean, leading to reduced mixing.

In low latitudes, this reduces growth of phytoplankton, which are the base of the food chain

Behrenfeld et al. 2006

Will global warming affect coastal upwelling ecosystems?

• Spring and summer NW winds (alongshore) move water offshore rather than alongshore• Deeper, cooler, nutrient-rich waters ‘up-well’ to the surface• Phytoplankton communities flourish in these high nutrient waters: = high primary production• The food web (zooplankton to whales) benefits from upwelling

Sea Surface Temperature Ocean Color = Phytoplankton

El Nino and Ocean ProductivityEl Nino• Low upwelling• Warm, unmixed waters• Low ocean productivity • Low zooplankton biomass and growth

La Nina• More wind, greater upwelling• Cool, mixed, nutrient-rich waters• Low ocean productivity • Low zooplankton biomass and growth Ocean color = phytoplankton

Zooplankton Biomass

Pacific Decadal Variation in Ocean “Climate”

Chavez et al. 2004

Potential Changes in Sockeye Salmon Distribution from a Doubling of CO2

Sockeye Salmon spend ~2-3 y in the NE Pacific and Bering Sea• Migrate northward in summer, southward in winter• Food availability greatest in summer, but decreases with warmer temperature• Metabolic costs increase exponentially with temperature.• Net intake drops to <0 (beginning starvation) at warmer temperatures

Winter

Summer

7 deg.boundary

now

12 deg.boundary

Welch et al. 1998

now

~2050

-80-60-40

-200

204060

80100120

0 5 10 15 20

Temperature

Ener

gy

Food LevelMetabolic

cost

Net IntakeStarvation ~2050

Potential Changes in Sockeye Salmon Distribution from a Doubling of CO2

Warming of ocean waters will:• Increase metabolic costs • Decrease food levels• Shift optimal feeding areas northward• Increase starvation rates, thereby reducing both individual size and catch• These effects cascade through the entire food chain (i.e. birds & mammals)

Winter

Summer

7 deg.boundary

now

12 deg.boundary

Welch et al. 1998

now

~2050

-80-60-40

-200

204060

80100120

0 5 10 15 20

Temperature

Ener

gy

Food LevelMetabolic

cost

Net IntakeStarvation ~2050

The High CO2 Ocean

Global Carbon Pools & Fluxes

Values in billions of metric tonnes (Gt C/y)

Atmosphere775

Vegetation& Soils2,190

Global PrimaryProduction

& Respiration Fossil Fuels

Deep Ocean38,100

Shallow Ocean = 1,030

Surface Sediments = 150

AvailableFossil Fuels

4,000

0.51.6

6160

90 92

6

Changesin Land

Use

Ocean CO2 “Disposal” Today

Fossil fuel signal has penetrated to >1000 - 2000m.

• The inventory was 48 Pg C in 1994.

• We have disposed of 118 PgC in the world ocean.

• Global surface ocean CO2 disposal is now about 20-25 million tons per day (61 kg/km2)

Sabine et al. (2004)

Range of Reference Case Fossil Fuel Carbon Emissions

Range of all scenarios in the database

0

10

20

30

40

50

60

1900 1920 1940 1960 1980 2000 2020 2040 2060 2080

Range of all scenarios in the database

0

10

20

30

40

50

60

1900 1920 1940 1960 1980 2000 2020 2040 2060 2080 2100

Glo

bal C

O2

Emis

sion

s (G

tC)

Foss

il &

Indu

stry

Source: IIASA

Median SRES 2100 emission = 14.4 PgC/yOpen literature 2100 emissions ~20 PgC/y

Ocean Carbonate Chemistry

Carbonic Acid Bicarbonate Carbonate

CO2 + H20 H2CO3 HCO3- + H+ CO3

-2 + H+

CO3-2 + Ca2+ CaCO3

CalciumCarbonate

Addition of CO2• Increases acidity• Decreases carbonate ions• Decreases carbonate saturation• Decreases calcification

Future Decrease in Ocean pH

Caldeira and Wickett (2005)

CO2 Air – Sea Exchange

Physiological Stresses Associated with High CO2

Physiological Challenges Respiratory Stress

Reduced pH limits oxygen-binding and transport by respiratory proteins, leading to reduced aerobic capacity.

Acidosis (reduced internal pH)Disruption of acid/base balance impairs function and requires energy to restore or maintain optimal internal pH levels.

Reduced CalcificationDepression in carbonate saturation state increases the difficulty of carbonate deposition, with unknown metabolic consequences

Metabolic Depression (Torpor)Elevated CO2, reduced pH, or both can cause some animals to enter a state of reduced metabolic rate and semi-hibernation

CO2 + H20 H2CO3 HCO3- + H+ CO3

-2 + H+

CO2Carbonic Acid Bicarbonate Carbonate

Air – Sea Exchange

Are CO2-related stresses severe for deep-sea animals?

pH

7.2 7.4 7.6 7.8 8.0 8.2

Dep

th (m

)

0

1000

2000

3000

4000

5000

6000

Central PacificWestern PacificNorth PacificAntarctic PacificEastern Pacific

1. Reduced metabolic rates 2. Reduced enzyme function 3. Evolved in highly stable deep-sea

environment4. Food-limited –

“Living on the edge”

Deep-Sea Animals

Humboldt Squid

pH Variation Among Ocean Basins

Expected Reduction in Coral Reef Calcification due to Reduced Ocean pH

Kleypas et al 1999

Reduced Calcification

Riebesell et al 2000

Normal CO2

High CO2

Pteropod Mollusc

CoralsOcean acidification will effect calcificationfor may species

Clams, Snails, Sea Stars, Urchins, Crabs, Shrimp, Others

The consequences of reduced calcification are not known.

Ocean acidification may affect early life stages more than adults

Impaired development of sea urchin larvae in high CO2 sea water

365 500 1000 2000 5000 10000ppm

7.9 7.8 7.5 7.2 6.8 6.4pH

Kurihara et al. 2004

Tiburon tracks (2000, 2002, 2006)

Deep-sea Corals – Vulnerable to CO2?Deep-sea Corals – Vulnerable to CO2?

MBARI small scale CO2 experiments

CO2 Release System20 liter CO2 pool

ROV Tiburon

RV Western Flyer

Deep-Sea CO2Experiments

CO2 release Time lapse video

Animal cage

Full CO2 corral

Slurp sampler for megafauna

Collecting Megafauna CO2 StationUrchins

Sediment Cores

pH/CTDsensor

Experimental Design

50m

Control

CO2

Controlled-gas Aquarium System for lab-based studies of CO2 tolerance

• Control of temperature, oxygen, carbon dioxide• Use:

• Studies of chronic hypercapnia on marine animals• Growth rates, respiration, physiology

High CO2Low CO2 Average CO2

Nitrogengenerator

GasEx.

CO

2 Ta

nk

O2

Tan

k

Gas Control SystemOxygen , CO2

Regulation

Reservoir: very low O2, CO2

Tank 1 Tank 2 Tank 2 Tanner Crab

Summary of Expected Effects of Ocean Warming

Ocean Warming• Increased stratification of surface waters, reduced primary

productivity, cascading effects throughout the food chain.• Reduced catch for important fishery species• Reduced abundance of marine mammals and birds These phenomena are

known best for short-term events (e.g. El Nino)

• Changes in species distributions, perhaps a disconnect between feeding and breeding grounds

• Warming-related mortality for coral reefs is expected to be severe

• Ocean communities will change with ongoing climate warming, perhaps drastically, but the nature of future ocean ecosystems remains unclear

Summary of Expected Effects of Ocean Warming

• Ocean acidification• Metabolic Stress (respiratory stress, acidosis, reduced

calcification)• Marine calcifiers (from phytoplankton to corals) will be

impaired, with as yet unknown consequences.• Plankton communities will likely change• Water-breathing animals will have higher costs for coping

with CO2-related stress, resulting in lower growth, survival and reproduction• Unclear effects on food webs, but may include a loss of

biodiversity, simplified food webs• Deep-sea organisms are the most sensitive to CO2-related

stress (respiratory stress, acidosis)

• Mitigation of climate warming and ocean acidification is essential