Lecture 6 Flashcards
Explain the earths energy budget
Energy surplus at low latitudes are equal to energy deficits at high latitudes = balanced heat budget.
As the heat is then transferred from the equator regions to the polar through wind and ocean currents.
What drives ocean circulation?
Temperature
Salinity
(Cool, salty water = most dense)
Explain thermohaline circulation
Warm water = lower density than cold
Cold regions - cold salty water sinks (heavy)
Evaporation increases salinity of water in warm regions
During journey to cold regions, salty water cools and sinks toward ocean floor
In contrast, diffuse upwelling occurs in warm regions
Therefore, temperature and salinity gradients drive an overturning circulation
The North Atlantic current is responsible for…
The relatively mild climates of Western and Northern Europe
What forms over the Gulf Stream?
Clouds, as water vapour evaporates from the ocean surface
What probe is dropped 3500m and produces low frequency tones once a day for tracking currents?
SOFAR
An example of meridonal overturning circulation:
Atlantic.
Being denser, Antarctic bottom water slips beneath North Atlantic deep water. The water then gradually rises across a very large area in the tropical zones, then flows poleward to repeat the cycle
Water salinity is affected by:
Precipitation, run off, melting of ice + snow (decrease)
Evaporation (increase)
Input of dissolved ions is balanced by removal to sediments - global oceans in steady state
Seawater solution =
Dissolved salts
Dissolved gases
Dissolved organic material
Large range of particles in suspension
Meridonal overturning circulation is part of thermohaline circulation which can be called the:
‘Ocean conveyor belt’
Thermohaline circulation
Driven by temperature and salinity
Contributes to the global distribution of energy in heat form
El Niño southern oscillation
Abnormal weather pattern - caused by the warming of the Pacific Ocean near the equator.
Occurs when the normal trade winds weaken (or even reverse), which lets the warm water that is usually found in the western Pacific flow instead towards the east.
This warm water displaces the cooler water that is normally found near the surface of the eastern Pacific, setting off atmospheric changes that affect weather patterns in many parts of the world.
Happens usually every 2-7 years
Has to be a 0.5 degrees c change to be considered an El Niño year
The tropical Pacific Ocean and atmosphere act as…
A giant heat engine that converts solar energy to kinetic energy of winds
Walker circulation (walker cell)
Normal: trade winds blow towards the west across tropical Pacific = pile up of warm water in W Pacific
cold-nutrient rich water, wells up in S. American coast - supports diverse marine ecosystems, dry climate conditions
High water temperatures = extensive convection near Indonesia
Forms convective loop (important part of Hadley cell)
= formation of a zonal gradient in water temperatures
El Niño conditions
Trade winds relax in central and western Pacific
Consequently, thermocline in Eastern Pacific gets depressed, W. Pacific elevated
Warm surface water moves eastwards followed by rainfall
Causes change in atmospheric circulations affecting weather even at great distances from Pacific
Example of effects from El Niño
Flooding in South America
Drought in Indonesia and Australia
La Niña conditions
Unusually cold sea temperatures
Trade wins strong
Sometimes follows El Niño
Opposite to El Niño (hot phase) - El Niña = cold phase
Anthropogenic activities increasing CO2
Emissions from transport Energy generation (e.g. Coal, oil) Industrial and domestic heating Cement production Deforestation (land use change)
Natural sources of atmospheric CO2
Volcanoes (1/150th compared to anthropogenic)
Combustion processes (e.g. Wildfire)
Respiration of aerobic organisms (animals, humans)
The average incoming solar radiation exceeds the average annual outgoing infrared radiation, emitted by the earth, between what latitudes?
40 N and 35 S
What does the CO2 concentration depend on in the ocean?
Depends on amount of Co2 in atmosphere and temperature of water
As water temperature increases, it’s ability to dissolve co2…
Decreases
How much did CO2 increase in the atmosphere from the pre-industrial stage?
It doubled, which meant the oceans co2 doubled also
Global warming reduces the oceans ability to absorb co2 leaving more in the atmosphere this will cause…
Higher temperatures
Colder areas of water temp generally represent regions of…
Net co2 uptake
Warmer water regions = positive sea-air flux
What is ocean acidification?
Uptake of increased co2 reduces surface ocean PH values, which increases the acidity of ocean water
Increase in ocean acidification affects:
Coral reefs (declining calcification)
Cold water corals
Ecosystems where aragonite is essential (shell building)
Temperature increase results in coral bleaching
