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Air temps 9 degrees above normalFor 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.
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”
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
ocean “mixed layer” interacts with atmospheric troposphere
troposphere contains ~80% of atmospheric mass and ~100% of atmospheric water (vapor)
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
ocean’s heat budget by %
Qsw = Qlw + Qlat + Qsens100% = 41% + 53% + 6%
on average no net heating or cooling
solar radiation directly heats water beneath the sea surface
UV IR
~50% of solar energy attenuated in top 1 m
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
Most solar energy quickly “attenuated” by seawater and converted to heat. Some wavelengths can penetrate to depths of 100m
heat loss terms act at air-sea interface
- latent heat flux (Qlat) energy required to change state (evaporate) of
watermost important in tropics & midlatitudeslargest outflow of heat from ocean
- longwave radiation (Qlw)net thermal IR emission from ocean
- sensible heat flux (Qsen)transfer from high to low temp. to equalize
differencetypically small
poleward heat transport via ocean & atmosphere
heat gain & loss vs. latitude
ocean heat advection: low flow, high heat capacityatmosphere heat advection: high flow, low heat capacity
advection - transfer by movementheat advection similar for ocean and atmosphere
warm sea surface causes evaporation
addition of water vapor decreases air density (N2 2x14; O2 2x16; H2O 2x1+16)
air rises
decreasing pressure decreasing density (more rising)
but, temperature in atmosphere decreases with height
cooling condensation and heat release to atmosphere