L9 - SLR and Corals Flashcards
importance of oceans?
- 1/3 global population relies on the ocean (economic)
- SLR - 40% of world lives within 100 km coast
- Heat absorption - absorb 90% of excess heat from global warming
- CO2 absorption - biogeochemical processes (but causes acidification, reducing ability)
Why does the pycnocline strengthen (stratification)/ why will climate change increase mixing in upper ocean?
Because surface water reacts faster than deep ocean to climate change. Exchange between atmosphere and mixed layer is between 10-100 years (compared to 1000 years). Also due to freshwater input from glacial melt, or seasonal changes
How does climate change heat up the globe?
Heat transfer by oceans and greenhouse effect - Convection at poles causes advection, redistributing heat and nutrients
How will atmospheric temperature changes affect thermohaline circulation?
AMOC will be affected by freshwater input from glacier melting. Circulation will be slower and less deep (due to reduced density) and Europe will become colder.
response time to warming for atmosphere, mixed ocean layer and deep ocean?
Atmosphere = months
Mixed layer = years
Deep ocean = 100s years
What happens if we stop co2 emission now?
Ocean warming will continue to due lag time. CO2 uptake and SLR will continue until equilibrium.
Major threats of climate change for cold water corals?
- Ocean acidification
- Ocean warming
- Decreased food supply
Explain how ocean acidification takes place?
CO2 is absorbed by seawater and reacts to form carbonic acid (H2CO3). Most dissociates into H+ ions, lowering ocean pH
How do cold water corals differ to tropical corals?
No photosynthesis and form in deep sea (below 200m)
Why is it extraordinary that cold water corals are highly productive and biodiverse?
Because little food from primary productivity reaches this deep
How is there a positive energy balance in the deep sea?
Vertical mixing brings food from primary productivity, and there is nutrient recycling. Species here have lower metabolic rates (due to cold water), thus preserving energy. Also can store energy for long periods of time (food pulses).
Pycnocline
Boundary separating layers of different densities
Changes with season and latitude (temp differences)
What determines buoyancy?
Change in density with depth (N2)
Steeper density gradient, higher buoyancy frequency
How can transfer of heat, gasses, solutes and particles occur?
- Diffusion - over gradient (warm to cold or salty to fresh)
- Convection - vertical mixing
- Advection - horizontal movement (from currents)
What is convection driven by?
Differences in temperature and salinity. Convection will decrease due to climate change as there is less difference - thus decreased food and nutrient supply (for cold water corals)
