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Title: Ocean Response to Global Warming/Global Change


1
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

2
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
  • July 19, 2005

3
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4
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5
What is the Oceans Role in Climate?
  • the ocean covers 70 of the earths surface
  • the ocean stores a thousand times more heat than
    the atmosphere
  • seawater stores four times more heat per unit
    mass than air
  • it transports 25 to 50 of the energy received
    from the sun

6
What is the Oceans Role in Climate?
  • it circulates slowly, on time scales of decades
    to centuries
  • it is the major source of heat to some regions
    like the North Atlantic
  • it sets long-term patterns of atmospheric
    circulation affecting climate systems like ENSO,
    NAO

7
How will the Oceans Change as the Earth Warms?
  • the oceans will warm, sea level will rise
  • its salinity balance will be altered
  • its ability to absorb CO2 will change
  • it will impact atmospheric circulation, storm
    tracks, severe storms, and the frequency and
    distribution of droughts

8
The oceans have been warming for the last 50 years
Levitus et al., 2000
9
The net warming above 3000 m is 0.06o C The
oceans have absorbed about 30 times more heat
than the atmosphere since 1955 Oceans 18.2 x
1022 J Atmosphere 6.6 x 1021 J Indistinguishabl
e from the expected response to rising CO2 an
anthropogenic signal
Levitus et al., 2001
10
What are the Implications?
The oceans will continue to absorb heat as the
climate system warms Warming will cause sea
water to expand The effect of heat absorption
will be to delay the warming of the
atmosphere The rate and magnitude of global
warming will be affected by how the ocean
circulates in the future when and where will it
release the stored heat?
11
What about Salinity?
  • Oceans contain 97 of Earths water
  • Oceans experience 86 of evaporation
  • Oceans receive 78 of planetary precipitation
  • A 1 increase in Atlantic precipitation equals
    the annual Mississippi runoff
  • A key element of the global water cycle

12
The Water Cycle Will Accelerate With Global
Warming
  • A warmer atmosphere will carry more water vapor,
    because of the exponential increase of vapor
    pressure with temperature.
  • An enhanced water cycle will change the
    distribution of salinity in the upper ocean.

13
Global Salinity and E-P distributions
Source R.Schmitt,WHOI
Source HydroBase2
Sea surface salinity distributions are determined
in large part by E-P patterns
14
Increasing salinities in the tropical Atlantic
15
Surface Water
Over the same 40-year period, salinities have
been increasing.. . a shift in the entire
Atlantic hydrological cycle?
Ruth Curry et al., 2003
16
Tropical Salinities Increasing for last 40 years
1967-1972
1980-1984
1995-2000
Fresher
Saltier
Ruth Curry (pers. comm.)
17
Summer Arctic Sea Ice
1979
2003
NASA Goddard Space Flight Center
18
Greenland is melting
NY Times June 8, 2004
19
Largest effects in the upper 1000 m
Curry and Mauritzen, in press
20
Freshwater storage and net flux anomalies
Ruth Curry Cecile Mauritzen, in press
21
Large Scale Ocean Circulation
22
Fresher Deep Water Flowing South at 3000 m
1967-1972
1980-1984
1995-2000
Fresher
Saltier
Ruth Curry (pers. comm.)
23
Two Important Ocean Processes will be Affected
  • Convection and thermohaline circulation the
    large scale ocean circulation
  • Air-sea coupling El Nino and the North
    Atlantic Oscillation

24
Large-scale Ocean Circulation Affects the Heat
Transport
25
Large Scale Ocean Circulation
26
Conveyor ON
27
Conveyor OFF
28
Temperature Response
  • Strong cooling in North Atlantic
  • Warming everywhere else
  • No net global change

Manabe and Stouffer, 1997
29
Greenhouse models predict a slowdown in the deep
water circulation
IPCC Report
30
Air-Sea Interactions
Ocean surface temperatures set atmospheric
circulation
31
El Nino 1997-1998
November 1997
January 1997
Goddard Space Flight Center - NASA
32
Goddard Space Flight Center - NASA
33
The North Atlantic Oscillation
34
The North Atlantic Oscillation
High Index Low Index Fewer
hurricanes More hurricanes
35
North Atlantic Oscillation Index
36
NAO and Gulf Stream Transport
37
The Gulf Stream South of Cape Cod
38
Summary
  • The ocean and atmosphere work together to
    affect climate
  • Surface conditions of the ocean set atmospheric
    circulation the surface conditions are changing
  • Deep water produced in the Atlantic is exported
    to the world
  • The circulation system is density driven
    warm, salty water becomes cold, dense, salty deep
    water
  • The salinity balance appears to be changing

39
Summary
  • Heat released to the atmosphere by the oceans
    is an important source of heat to the Atlantic
    region
  • Several models of future greenhouse climate
    produce a significantly altered Atlantic
    circulation
  • Some of the changes predicted by the models may
    be occurring in the Atlantic today

40
The Ocean and Climate Change Institute
Woods Hole Oceanographic Institution
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