ocean response to global warming/global change
DESCRIPTION
Ocean Response to Global Warming/Global Change. Possible changes in ocean circulation and how they may affect regional climate patterns. William Curry Woods Hole Oceanographic Institution Environmental Defense May 12, 2005. Ocean Response to Global Warming/Global Change. - PowerPoint PPT PresentationTRANSCRIPT
Ocean Response to Global Ocean Response to Global Warming/Global ChangeWarming/Global Change
William Curry
Woods Hole Oceanographic Institution
Environmental Defense
May 12, 2005
Possible changes in ocean circulation and how Possible changes in ocean circulation and how they may affect regional climate patternsthey may affect regional climate patterns
Ocean Response to Global Ocean Response to Global Warming/Global ChangeWarming/Global Change
William Curry
Woods Hole Oceanographic Institution
July 19, 2005
Possible changes in ocean circulation and how Possible changes in ocean circulation and how they may affect regional climate patternsthey may affect regional climate patterns
What is the Ocean’s Role in Climate?What is the Ocean’s Role in Climate?
• the ocean covers 70% of the earth’s surfacethe ocean covers 70% of the earth’s surface• the ocean stores a thousand times more heat the ocean stores a thousand times more heat
than the atmospherethan the atmosphere• seawater stores four times more heat per unit seawater stores four times more heat per unit
mass than airmass than air• it transports 25 to 50% of the energy received it transports 25 to 50% of the energy received
from the sunfrom the sun
What is the Ocean’s Role in Climate?What is the Ocean’s Role in Climate?
• it circulates slowly, on time scales of decades it circulates slowly, on time scales of decades to centuriesto centuries
• it is the major source of heat to some regions it is the major source of heat to some regions like the North Atlanticlike the North Atlantic
• it sets long-term patterns of atmospheric it sets long-term patterns of atmospheric circulation affecting climate systems like circulation affecting climate systems like ENSO, NAOENSO, NAO
How will the Oceans Change How will the Oceans Change as the Earth Warms?as the Earth Warms?
• the oceans will warm, sea level will risethe oceans will warm, sea level will rise
• its salinity balance will be alteredits salinity balance will be altered
• its ability to absorb COits ability to absorb CO2 2 will changewill change
• it will impact atmospheric circulation, storm it will impact atmospheric circulation, storm tracks, severe storms, and the frequency and tracks, severe storms, and the frequency and distribution of droughtsdistribution of droughts
Levitus et al., 2000Levitus et al., 2000
The oceans The oceans have been have been warming for warming for the last 50 the last 50 yearsyears
The net warming above 3000 m is 0.06The net warming above 3000 m is 0.06oo C C
The oceans have absorbed about 30 times more The oceans have absorbed about 30 times more heat than the atmosphere since 1955heat than the atmosphere since 1955
OceansOceans 18.2 x 1018.2 x 102222 J JAtmosphereAtmosphere 6.6 x 10 6.6 x 102121 J J
Indistinguishable from the expected response to Indistinguishable from the expected response to rising COrising CO2 2 – an anthropogenic signal– an anthropogenic signal
Levitus et al., 2001Levitus et al., 2001
The oceans will continue to absorb heat as The oceans will continue to absorb heat as the climate system warmsthe climate system warms
Warming will cause sea water to expandWarming will cause sea water to expand
The effect of heat absorption will be to The effect of heat absorption will be to delay the warming of the atmospheredelay the warming of the atmosphere
The rate and magnitude of global warming The rate and magnitude of global warming will be affected by how the ocean circulates will be affected by how the ocean circulates in the future – when and where will it in the future – when and where will it release the stored heat?release the stored heat?
What are the Implications?What are the Implications?
What about Salinity?What about Salinity?
• Oceans contain 97% of Earth’s waterOceans contain 97% of Earth’s water
• Oceans experience 86% of evaporationOceans experience 86% of evaporation
• Oceans receive 78% of planetary precipitationOceans receive 78% of planetary precipitation
• A 1% increase in Atlantic precipitation equals the annual A 1% increase in Atlantic precipitation equals the annual Mississippi runoffMississippi runoff
• A key element of the global water cycleA key element of the global water cycle
The Water Cycle Will Accelerate With The Water Cycle Will Accelerate With Global WarmingGlobal Warming
• A warmer atmosphere A warmer atmosphere will carry more water will carry more water vapor, because of the vapor, because of the exponential increase of exponential increase of vapor pressure with vapor pressure with temperature.temperature.
• An enhanced water An enhanced water cycle will change the cycle will change the distribution of salinity in distribution of salinity in the upper ocean.the upper ocean.
0 5 10 15 20 25 300
5
10
15
20
25
30
35
40
45
Vap
or P
ress
ure
of W
ater
, m
B
Vapor Pressure of Water as Function of Temperature
Temperature, C
0 5 10 15 20 25 300
5
10
15
20
25
30
35
40
45
Vap
or P
ress
ure
of W
ater
, m
B
Vapor Pressure of Water as Function of Temperature
Temperature, C
Sea surface salinity distributions are determined in large part by E-P patterns
Global Salinity and E-P distributions
Source: R.Schmitt,WHOISource: HydroBase2
Increasing Increasing salinities salinities in the in the tropical tropical AtlanticAtlantic
Over the same 40-year period, salinities have been increasing..
…. a shift in the entire Atlantic hydrological cycle?
Ruth Curry et al., 2003
Surface Water
Tropical Salinities Increasing for last 40 yearsTropical Salinities Increasing for last 40 years
Fresher Saltier
Ruth Curry (pers. comm.)
1967-1972 1980-1984 1995-2000
Summer Arctic Sea IceSummer Arctic Sea Ice
1979197920032003 NASA Goddard Space Flight Center
NY Times June 8, 2004
Greenland is melting
Curry and Mauritzen, in press
Largest effects in the upper 1000 m
Freshwater storage and net flux anomalies
Ruth Curry & Cecile Mauritzen, in press
19000 km3
4000 km3
15000 km3
0.066 Sv
10,000 km3
Large Scale Ocean CirculationLarge Scale Ocean Circulation
Fresher Deep Water Flowing South at 3000 mFresher Deep Water Flowing South at 3000 m
Fresher Saltier
Ruth Curry (pers. comm.)
1967-1972 1980-1984 1995-2000
Two Important Ocean Processes Two Important Ocean Processes will be Affectedwill be Affected
Two Important Ocean Processes Two Important Ocean Processes will be Affectedwill be Affected
• Convection and thermohaline circulation – the large scale ocean circulation
• Air-sea coupling – El Nino and the North Atlantic Oscillation
Large-scale Large-scale Ocean Circulation Ocean Circulation Affects the Heat Affects the Heat
TransportTransport
Large Scale Ocean CirculationLarge Scale Ocean Circulation
Conveyor ON
Conveyor OFF
Manabe and Stouffer, 1997
Temperature ResponseTemperature Response
• Strong cooling in North Atlantic
• Warming everywhere else
• No net global change
Greenhouse models predict a Greenhouse models predict a slowdown in the deep water slowdown in the deep water
circulationcirculation
IPCC Report
Air-Sea InteractionsAir-Sea InteractionsAir-Sea InteractionsAir-Sea Interactions
Ocean surface temperatures set atmospheric circulation
El Nino 1997-1998El Nino 1997-1998
January 1997
November 1997
Goddard Space Flight Center - NASAGoddard Space Flight Center - NASA
Goddard Space Flight Center - NASAGoddard Space Flight Center - NASA
High Phase Low Phase
The North Atlantic OscillationThe North Atlantic Oscillation
The North Atlantic OscillationThe North Atlantic Oscillation
High Index Low IndexHigh Index Low IndexFewer hurricanes More hurricanesFewer hurricanes More hurricanes
North Atlantic Oscillation IndexNorth Atlantic Oscillation Index
NAO and Gulf Stream TransportNAO and Gulf Stream Transport
The Gulf Stream South of Cape Cod
SummarySummary
• The ocean and atmosphere work together to affect The ocean and atmosphere work together to affect climateclimate
• Surface conditions of the ocean set atmospheric Surface conditions of the ocean set atmospheric circulation – the surface conditions are changingcirculation – the surface conditions are changing
• Deep water produced in the Atlantic is exported to Deep water produced in the Atlantic is exported to the worldthe world
• The circulation system is density driven – warm, salty The circulation system is density driven – warm, salty water becomes cold, dense, salty deep waterwater becomes cold, dense, salty deep water
• The salinity balance appears to be changingThe salinity balance appears to be changing
SummarySummary
• Heat released to the atmosphere by the oceans is an Heat released to the atmosphere by the oceans is an important source of heat to the Atlantic regionimportant source of heat to the Atlantic region
• Several models of future greenhouse climate produce Several models of future greenhouse climate produce a significantly altered Atlantic circulationa significantly altered Atlantic circulation
• Some of the changes predicted by the models may Some of the changes predicted by the models may be occurring in the Atlantic todaybe occurring in the Atlantic today
The Ocean andClimate Change
Institute
The Ocean andClimate Change
InstituteWoods Hole Oceanographic InstitutionWoods Hole Oceanographic Institution