Lecture 3 Flashcards
What is radiative forcing?
the difference between radiant energy received by the earth and the energy radiated back to space.
typically quantified as the tropopause in units of watts per square meter of earths surface.
What is Tropopause?
The difference between the troposphere and the stratosphere varying in altitude from approx 8km at the poles to approx 18 km at the equator
How does positive forcing impact the system?
More incoming energy warms the system
How does negative forcing impact the system?
More outgoing energy cools the system
What are some causes of radiative forcing?
Changes in insolation (incident solar radiation)
Concentrations of radiatively active gases and aerosols
What is ENSO?
The El Nino-southern oscillation. A natural see-saw in oceanic sea surface temperatures and surface air pressure between the east and west tropical Pacific Ocean
How does the rotation of the earth impact ENSO?
Rotation causes trade winds from E to converge on the equator in Tropical Pacific.
Pushes warm surface water into the western tropical pacific. (snow plow)
How does ENSO impact Temperature in the west?
Warm water pools up in west pacific, works with solar rays to heat surrounding air
Hot air rises and creates a zone of low air pressure
as air ascends, it cools and condenses, forming rain clouds
How does ENSO impact temperature in the east?
Warm pacific air then travels east to the coast of peru n ecuador. forms a high pressure (vice like) zone which squeezes air in the east, over to the west to fill the void created by hot, rising air
What is the name for this ENSO cycle?
The walker circulation
How is EL Nino different from La Nina?
El Nino -trade winds slacken -eastward migration of warm water -rainfall increases further east (peru/ecuador) El Nina (opposite) -trade winds intensify -stack warm surface water in the west -Australia waters often 1.5 m higher - intense rainfall pushed towards australia
Why do El Nino and La Nina events flip-flop?
The air and oceans respond to each other at different speeds
The atmosphere reacts to warming or cooling sea surface temperatures within days, but the ocean takes months to react to changes in the atmosphere
What is the Thermocline?
a temperature boundary which separates deeper, cold water from warmer, surface water.
What determines the interval between El Nino and La Nina?
the speed of subsurface waves (cold under thermocline)
What are normal conditions for trade winds?
blow from east along the equator pushing warm water into the pacific ocean.
- West sea surface ~8 degrees higher
What impact does sea surface temp on primary productivity?
Cold water is nutrient rich, high levels of PP, diverse marine ecosystems and major fisheries.
Warmer temperatures drastically decline PP, Which affects trophic levels of the food chain, including commercial fisheries
What are some characteristics of El Nino weather?
- Rain/flooding pacific coast
- Warm water disrupts food chains
- tornadoes and thunderstorms South US
- Fewer than normal hurricanes in the atlantic
What are some characteristics of La Nina Weather?
- Snow and rain on west coast
- Unusually cold in alaska
- Unusually warm in the rest of US
- Drought in the SW
- Higher than normal number of hurricanes in Atlantic
What is the Pacific Decadal Oscillation?
Long term fluctuation of the Pacific ocean that waxes and wanes between cool and warm phases approx every 5-20 years
Long lived El Nino/Nina pattern of pacific climate variability
What are 2 main distinctions between PDO and ENSO?
- 20th century PDO “events” persisted for 20-30 yers, while typical ENSO events persisted for 6-18 months
- The climatic fingerprints of the PDO are more visible in the North Pacific/NA sector, while secondary signatures exist in the tropics- opposite is true for ENSO
During La Nina events, in which direction do the trade winds blow strongly in the tropical pacific ocean?
Towards indonesia (
During La Nina events, is the sea surface higher in the tropical pacific near australia or ecuador?
Australia by 1.5m
During La Nina events, is th relative depth of the ocen thrmocline near ecuador deeper or shallower when compared to the ocean thermocline depth near indonesia?
shallower
How does PDO impact ecosystem productivity?
Warm PDO eras have seen increased coastal ocean biological productivity in Alaska and inhibited productivity off the west coast of the contiguous US.
Cold PDO eras have seen the opposite N-S pattern of marine ecosystem productivity
What is a Polar vortex?
Is a persistent, large-scale cyclone located near either of a plantes geographic poles.
(AKA polar cyclone, polar low, or circumpolar whirl)
What are 4 main results of Polar vortex?
- tropics expanding, increasing desertification of large areas of the earths surface
- extreme droughts (Aus, Cali, Argentina)
- Climate warming causes polar vortexes to wobble, and send extreme cold air south
- if CO2 concentrations to reach the 450-600 ppm range we will most likely have condemned the planet to 1,000 years of drought and desertification of 1/3 of planets surface
What are positive feedback mechanisms?
When the driving force of a reacting force is positively accelerated by the reacting force, thus exponentially accelerating one another
What are the 6 Climate changes wild cards?
Ocean acidification North Atlantic Circulation Methane releases from thawing arctic permafrost Loss of tropical rainforests Rapid Melting of arctic ice
Ocean acidification
Emissions of CO2 from humans over past 200 years have already led to a reduction in the average pH of surface seawater of .1 units and could fall by .5 units by the year 2100
What impacts would ocean acidification have?
Disrupts the process of calcification used by marine organisms to build shells, carapaces and coral reefs.
North Atlantic Circulation
Heat conveyor belt controlled by the sinking of dense (cold and salty) water at high latitudes
Atlantic is the only ocean where heat is transported north across the equator. warm tropics surface water reaches further north.
What impact does North atlantic circulation have?
-the heat released by this warm water makes the climate in regions bordering the North atlantic warmer than at similar latitudes elsewhere
Global warming could create precisely this effect. increased rainfall, melting of sea ice, glaciers and the greenland ice sheet could reduce north atlantic surface salinity sufficiently to slow down or even stop the formation of deep water
shutting down the THC, cooling northwest europe
Methane releases from thawing arctic permafrost
Methane (Ch4) has at least 20x the heat-trapping effect of CO2.
as warmer air thaws arctic soils, as much as 55 billion metric tons of methane could be released from beneath siberian lakes alone.
Loss of tropical rainforests
Amazon rainforest is suprisingly sensitive to drought. releasing massive amounts of carbon in the atmosphere. reversing decades of carbon absorption. carbon sink to carbon source.
How much carbon does Amazon absorb?
Nearly 2 billion tonnes of CO2 per year
2005 drought caused a release of over 3 billion
total impact of the drought +5 billion tonnes. more than the annual emissions of Europ and Japan combined
Rapid Melting of arctic ice
As ice disappears from the arctic, the darker ocean below absorbs more radiation from the sun, exacerbating warming in wat is known as the ice-albedo feedback effect.
Ocean release of methane hydrates
Methane molecules are trapped in cages of water molecules in the deep sea. they appear as ice-like crystals. only seen in areas of high pressure and low temperature.
