Important oceanic features Flashcards
Normal conditions in equatorial Pacific
trade winds pile up warmer water in W
50 cm slope in sea level between E and W
W - strong precip due to rising warm air and condensing
El Nino - Southern Oscillation (ENSO)
anomaly due to changes in atm pressure and associated with warm water and anomalous precip in E Pacific
Every 2-7 years
El Nino (warm episode)
trade winds weaken or reverse due to atm pressure change
ocean responds
- eastward return of warm water
sea level drops in W Pacific and rises in E Pacific
surface slope and thermocline decrease
rain shifts to center of Pacific - droughts in N Australia and Indonesia
Impacts of El Nino
last about a year but up to 3
Off of Peru, a warm current from N flows over upwelling regions and anchovy fishery collapses
W of Peru, high precip in normally dry areas
La Nina (cold episode)
trade winds become stronger than average
accumulation of warm surface water in W
In W, sea level and precip rise in Indonesia
Off of Peru, sea level drops and upwelling intensifies
In C and E Pacific, upwelling increases and temp is low
climate index
simple diagnostic quantity used to characterize an aspect of a geophysical system such as a circ pattern
Oceanic Nino index
sea surface temp anomalies in Nino 3.4 region surpassing a threshold of plus or minus 0.5 deg C
Intertropical Convergence Zone (ITCZ)
equatorial area where trade winds converge
zone of rising air near equator associated with equatorial low - a little S equator in winter, N in summer
coriolis effect
- trades reverse direction
ADD
monsoon
pattern of wind circulation that changes with the season
intensified due to land
in summer, air over land is heated more than over oceans and ITCZ shifts toward land regions
Open ocean polynyas
form due to upwelling of water above freezing temp
water at subsurface is warm
when brought to the surface, this warm water transfers heat to ice and melts it/prevents the formation of new ice
Importance of polynyas
intense exchanges between warmer ocean and very cold atm
Polynyas general info
major source of bottom waters - influences thermohaline circ
ventiliation of deep ocean e.g. O2
carbon etc sequestration
source of heat and moisture to atm
important for wildlife - access between ocean and atm, water rich in nutrients
eddy
swirling of a fluid associated with a turbulent flow regime
ocean mesoscale eddies ar ethe ‘weather’ of the ocean
10-100 km, 1-several months, reach down into pycnocline, different props tahn surroundings
instabilities in strong currents cause large eddies, and transfer of PE into KE forms smaller eddies
key role in heat and nutrient transport
