Air-Sea Interactions

1. Air-Sea Interactions Martin Visbeck Department of Earth and Environmental Sciences,LDEO, Columbia Universityhttp://www.ldeo.columbia.edu/~visbeck Why Is Europe Warmer than Canada? The Gulf Stream vs. Atmospheric Winds

2. IS EUROPE WARMER THAN CANADA? • Evidence from Global Data • For example you can use http://ingrid.ldeo.columbia.edu • compute zonal mean anomaly

3. Climatological January Temp. Convinced ?

4. Winter Temp. Atlantic

5. Winter Temp. Atlantic (2) Temp.differencebetweenpointsis: 18 Cor32 F Here the zonal mean Temp. is removed

6. WHY? • Where does the energy come from? • What sets the energy balance? • How is it distributed? • Why is the temperature different at the same latitude?

7. Climate Forcing

8. WHY? • Where does the energy come from? • What sets the energy balance? • How is it distributed? • Why is the temperature different at the same latitude?

9. Radiative Energy Balance Short waveradiationcomes in… Long waveradiationgoes out… water vaporis green house gas

10. Radiative Energy Balance (2) Short waveradiationcomes in… Long waveradiationgoes out…

11. Radiative Energy Balance (2) The imbalance of the top of the atmosphere radiation implies that there must be an internal heat transport by the combined action of ocean and atmosphere of ~6 1015 W 30°N/S.

12. WHY? • Where does the energy come from? • What sets the energy balance? • How is it distributed? • Why is the temperature different at the same latitude?

13. Atmospheric Heat Transport

14. Atmospheric Heat Transportsimulation in tank light Cool water

15. Atmospheric Heat Transportsimulation in tank light Cool water Warm Cold

16. Atmospheric Heat Transportsimulation in tank What do we miss? The rotation of the planetintroduces a new force: The Coriolis Force Warm Cold

17. Global Wind System

18. Global Wind System

19. Global Wind and Cloud System

20. WHY? • Where does the energy come from? • What sets the energy balance? • How is it distributed? How much is due to the atmospheric circulation? How much is due to the ocean’s circulation? • Why is the temperature different at the same latitude?

21. Ocean Surface Temperature (SST)

22. Ocean Surface Currents

23. The Gulf Stream / North Atlantic Current

24. Oceanic Temperature Structure

25. Ocean Heat Transportsimulation in tank light Cool water

26. light Cool water Warm Cold Ocean Heat Transportsimulation in tank (2)

27. Oceanic Heat Transport

28. Oceanic Heat Transport Ocean warms Atmosphere Ocean is warmed by Sun Black numbers are ocean heat transport in PW

29. WHY? • Where does the energy come from? • What sets the energy balance? • How is it distributed? • Why is the temperature different at the same latitude?

30. Winter Atmospheric Circulation

31. Winter Atmospheric Circulation Cold Warm

32. Winter Heat Transport The Atmosphere has whatwe call standing waves whichare able to preferentially heat parts of the planet. The current scientific debateis on what causes theirexistence. Either mountainsor air-sea temperature difference or a combinationof both.

33. Winter Heat Transport The Atmosphere transportsabout 5/6 of the heat polewardin the global mean. However, in the Atlantic sectorthe ocean is believed to carryabout 1/2. There is debate about who is most responsible for changesin the poleward heat transport.Weather this is in an ice-ageor global warming context.

34. Some Final Remarks • The atmosphere carries: • 78 percent of the heat transport in the Northern Hemisphere and • 92 percent in the Southern Hemisphere at 35 degrees latitude, where the heat transport peaks. • It would take a million 1,000-megawatt electric power stations - the largest power plants now used - to produce a quantity of energy equivalent to the heat the atmosphere carries on average from the tropics to polar regions.

35. Atmosphere-Ocean Heat Transportsimulation in tank light Cool water Warm Atmosphere Cold Warm Ocean Cold