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Disko Bay, Greenland - 624,000 cubic miles of ice; 10% of Earth’s fresh water.

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Presentation on theme: "Disko Bay, Greenland - 624,000 cubic miles of ice; 10% of Earth’s fresh water."— Presentation transcript:

1 Disko Bay, Greenland - 624,000 cubic miles of ice; 10% of Earth’s fresh water

2 Air temps 9 degrees above normal For example, autumn air temperatures in the Arctic are at a record 9 degrees Fahrenheit above normal. Rising temperatures help melt the ice, which in turn allows more solar heating of the ocean. In addition to global warming there are natural cycles of warming and cooling, and a warm cycle in the 1990s added to the temperature rise.

3 Albedo – percent of incident solar radiation reflected by a surface

4 Air-Sea Interface Air-sea exchanges of heat & freshwater change density thus driving ocean circulation. Air-sea exchange of momentum (mass in motion; wind) causes ocean currents and waves. - exchange of heat - exchange of mass (mostly water/salt; also gases) - exchange of momentum Geography 104 - “Physical Geography of the World’s Oceans”

5 weather vs. climate climate processes contribute to local weather weather – environmental conditions for a specific time and place climate – average environmental conditions for a time and place

6 Hurricane Katrina (2005) – ultimate expression of air-sea interaction

7 ocean “mixed layer” interacts with atmospheric troposphere troposphere contains ~80% of atmospheric mass and ~100% of atmospheric water (vapor)

8 major differences between ocean and atmosphere: density, compressibility

9 Earth’s heat budget (W m -2 ) Earth not a perfect blackbody. Albedo (incoming solar / reflected solar) = 107 W m -2 / 342 W m -2 = ~0.3

10 ocean’s heat budget by % Qsw = Qlw + Qlat + Qsens 100% = 41% + 53% + 6% on average no net heating or cooling

11 changes in overhead position of sun cause variations in Earth’s solar heating

12 solar radiation at Earth’s surface (W m -2 )

13 solar radiation directly heats water beneath the sea surface UV IR ~50% of solar energy attenuated in top 1 m

14 seawater and things in it alter the spectral shape of the solar field (“bio-optics”) seawater and things in it have fairly unique light absorbing and scattering properties solar radiation can be back-scattered to space

15 Most solar energy quickly “attenuated” by seawater and converted to heat. Some wavelengths can penetrate to depths of 100m

16 heat loss terms act at air-sea interface - latent heat flux (Q lat ) energy required to change state (evaporate) of water most important in tropics & midlatitudes largest outflow of heat from ocean - longwave radiation (Q lw ) net thermal IR emission from ocean - sensible heat flux (Q sen ) transfer from high to low temp. to equalize difference typically small

17 net ocean heat gain or loss (“net surface heat flux”) flux – rate of transfer across a surface

18 poleward heat transport via ocean & atmosphere heat gain & loss vs. latitude ocean heat advection: low flow, high heat capacity atmosphere heat advection: high flow, low heat capacity advection - transfer by movement heat advection similar for ocean and atmosphere

19 cumulonimbus cloud rising air & condensing water vapor

20 warm sea surface causes evaporation addition of water vapor decreases air density (N 2 2x14; O 2 2x16; H 2 O 2x1+16) air rises decreasing pressure  decreasing density (more rising) but, temperature in atmosphere decreases with height cooling  condensation and heat release to atmosphere

21 need cloud condensation nuclei

22 water vapor over the oceans

23 global sea surface temperature

24 evaporation vs. precipitation

25 heat flow

26 mean sea surface T & S

27 global sea surface salinity

28 momentum transfer; atmosphere to ocean


30 Readings (Ocean and Atmosphere): Text Chapter 8 (pgs 138 – 147) Reader pgs. 51 – 61 HW #2 assigned; Due Friday 31 Oct 2008 Midterm on Wednesday 5 Nov 2008

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