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Southern Hemisphere Climate Change Professor Matthew England Climate and Environmental Dynamics Laboratory School of Mathematics, Faculty of Science The University of New South Wales. Outline. Observed 20 th Century changes in the Southern Hemisphere climate system Temperature Rainfall

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Southern Hemisphere Climate Change

Professor Matthew England

Climate and Environmental Dynamics Laboratory

School of Mathematics, Faculty of Science

The University of New South Wales


Outline
Outline

  • Observed 20th Century changes in the Southern Hemisphere climate system

    • Temperature

    • Rainfall

    • Land ice, ice shelves, and sea-ice

    • Ocean properties

    • Winds and extratropical weather systems

  • Projected changes


  • Increase in Atmospheric CO2 Since the Beginning of the Industrial Era


    Co 2 concentration is rising

    2004

    1959

    290

    190

    CO2 Concentration is Rising

    2000

    1000

    1200

    1600

    1800

    1400




    Is the southern ocean changing
    Is the Southern Ocean changing?

    … observations

    Larsson-B Ice Shelf Collapse 31 January to 7 March 2002

    http://nsidc.org/iceshelves/larsenb2002/animation.html


    West antarctic ice sheet
    West Antarctic Ice Sheet

    Oppenheimer (Nature 1998)


    Twentieth century land ice changes
    Twentieth Century Land-Ice Changes

    Davis et al., Vaughan; Science, 2005



    Arctic sea ice melting
    Arctic Sea-ice melting

    ~10% decrease in sea-ice per decade

    1990

    2000


    Ice Age Climate

    Today’s Climate




    0.017 psu

    Rintoul 2006


    .015

    .008

    .009

    Rintoul 2006


    Causes of fresher shelf water
    Causes of fresher shelf water

    • Increased glacial ice melt?

    • More precipitation?

    • Less sea ice formation?

    • Change in winds and ocean circulation?

    Davis et al., Vaughan; Science, 2005


    Intermediate depth waters in both hemispheres

    have become cooler and fresher in recent decades.

    Wong et al., 1999


    Figure 3 from Gille, S. T., 2002. Warming of the Southern Ocean since the 1950s. Science,295, 1275-1277.

    Temperature trends between 700 and 1100 m depth from ALACE floats.

    Observations of temperature at intermediate depths show a greater than expected warming at high latitudes and a cooling at mid-latitudes of the Southern Ocean over the last 50 years (Gille 2002).




    Southern Hemisphere Jet Stream Ocean since the 1950s.


    Changing Southern Hemisphere climate: Ocean since the 1950s.

    the Southern Annular Mode

    Sen Gupta & England 2006


    Southern annular mode
    Southern Annular Mode Ocean since the 1950s.


    Roaring forties furious fifties
    Roaring Forties / Furious Fifties Ocean since the 1950s.


    Southern annular mode1
    Southern Annular Mode Ocean since the 1950s.


    Southern annular mode2
    Southern Annular Mode Ocean since the 1950s.

    … trend due to ozone delpletion & greenhouse gas increases


    Northern annular mode
    Northern Annular Mode Ocean since the 1950s.


    Regression of the Southern Annular Mode Ocean since the 1950s.

    onto rainfall

    ‘Observed’

    Model

    Sen Gupta & England 2006


    July Zonal Wind (200 hPa) Ocean since the 1950s.

    1949-1968 1975-1994 difference

    Pandora Hope IOCI



    Climate modelling
    Climate Modelling Ocean since the 1950s.

    Governing equations

    Forcing conditions

    Initial conditions

    Model output


    Models of the ocean and atmosphere
    Models of the ocean and atmosphere Ocean since the 1950s.

    • Solve governing equations over a discrete grid

    • Use (sparse) observations in forcing functions

    • Integrate solutions forward in time

    • Assess simulation vs. observed fields


    5.8 Ocean since the 1950s.

    IPCC high

    and low

    projection

    1.4

    Spörer

    minimum

    Maunder

    minimum

    Dalton

    minimum

    2100

    The Past and the Future

    • Instrumental Data

    • Proxy Reconstructions

    • Model Simulations

    ∆T

    0.4

    0.2

    0

    -0.2

    -0.4

    -0.6

    -0.8

    Year

    1500

    2000

    500

    1000


    Climate change appears to be buffered by the Southern Ocean THC

    Annual-mean temperature change predicted for ~ the year 2050 in the GFDL coupled climate model experiment (Manabe et al. 1989).


    Annual-mean temperature change predicted for 2070-2100 THC

    in IPCC Third Assessment Report models

    Annual mean change in temperature (colour shading) and its range (isolines) (Unit: °C) for the SRES scenario A2, showing the period 2071 to 2100 relative to the period 1961 to 1990.



    CONTROL THC

    2050

    Figure 1. Model Simulation of Trend in Hurricanes

    (from Knutson et al, 2004)


    CONCLUSIONS THC

    • The Southern Hemisphere, like the antipodes, have undergone substantial climate change in the past century

    • A manifestation of climate change can be easily found in Southern Hemisphere air temperatures, rainfall, ocean properties, land-ice, sea-level, winds, and storm tracks

    • Models suggest these changes will continue for centuries even with relatively aggressive response strategies


    Southern Hemisphere Climate Change THC

    Professor Matthew England

    Climate and Environmental Dynamics Laboratory

    School of Mathematics, Faculty of Science

    The University of New South Wales


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