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

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.

Albedo – percent of incident solar radiation reflected by a surface

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

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

ocean “mixed layer” interacts with atmospheric troposphere

troposphere contains ~80% of atmospheric mass and ~100% of atmospheric water (vapor)

major differences between ocean and atmosphere: density, compressibility

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

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

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

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

net ocean heat gain or loss (“net surface heat flux”)

flux – rate of transfer across a surface

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

cumulonimbus cloud

rising air & condensing water vapor

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

need cloud condensation nuclei

water vapor over the oceans

global sea surface temperature

evaporation vs. precipitation

evaporation vs. precipitation

heat flow

mean sea surface T & S

global sea surface salinity

momentum transfer; atmosphere to ocean

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