Marine Systems Flashcards
How have sea-level changed since 1993-2010
+3.2 mm yr⁻¹
Changes relative corresponding averages (1961-1990)
This has almost doubled fromt the 100yr average
There some spatial patterns in sea level trends
What factors will cause this?
- Sea temperature
- Density (salinity)
- Ocean currents and regional freshwater inputs to the ocean
How do sea surface temperatures and sea levels link
Where we have an increase in sea surface temperature, there is an increase in sea-levels
Water moves around the globle through…
…thermohaline circulation
Warming oceans causes the water to expand is known as….
…thermal expansion
Name 6 contribuitors to sea level rise
- Terrestrial water storage, extraction of groundwater, building of reservoirs, changes in runoff, and seeping into aquifers
- Subsidence in river delta regions, land movements, and tectonic displacement
- Suface and deep ocean circulation changes and storm surges
- Warming ocean causes the water to expand
- Land can lift when glaciers melt
- Exchange of water stored on land as glaciers and icecaps with ocean water
Oceans have experienced around a 0.6°C rise in temperature
How much has thermal expansion contributed to sea-level rises
30-40%
The earth has gained 274 ZJ of energy since 1971
What substituents of the earth’s surface absorb this additional energy?
- Oceans (93%)
- Melting of ice and glaciers (3%)
- Warming of the contients (3%)
- Warming the atmosphere (1%)
The ocean dominated the changes in the energy balance because of its?
- Large mass
- High heat capacity
- Low albedo
What is the second biggest input to sea-level rise apart from thermal expansion?
Water from melting glaciers
(~30%)
with 25% coming from Greenland and Antarctic ice sheets
What are the two factors which have caused the net-loss to the ice sheets
- Loss of ice cover through sublimation, melting and iceberg calving
- And increase ablation - low-latitude area of a glacier or ice sheet below solidfied snow where there is a net loss in ice mass
Future patterns of sea levels trends are expected to be affected by….
- Changes in ocean density (e.g. fresh water inputs)
- Circulation changes (e.g. weaker ocean currents)
If we reduce emissions by 2100 what will we expect to happen to sea level rise?
Due to thermal expansion sea level rise will continue beyond 2100 irrespective of reduction in emissions
Oceans have absorbed 155 PgC since 1750 corresponding to increasing atmospheric CO₂ from 280 to 392ppm
What affect has this had on the oceans?
This has lowered ocean pH
And further decreases as expected to occur
Where has most of the CO₂ been absorbed by the oceans
More CO₂ will dissolve in colder oceans due to greater solubility of gases
Which is predominately the north Atlantic and southern ocoean
Dissolution of CO₂ in sea water produces ….
….carbonic acid
H₂CO₃
Oceanic pH changes, affects the saturation state with respect to…
…Aragonite (CaCO₃)
Due to lowering the amount of carbonate (CO₃²⁻) ions
Hence limits the formation of aragonite - affecting calsifying organisms and subsequent food webs
What ocean structure is highly affected by increasing ocean acidity?
Corals
Affect reef development
What affect does acidifying ocean have on seagrass
- Lower pH results in lower calcification of leaves
- and higher shoot density
- (also affecting algae + other marine fauna)
It is suggested that we are getting more short-duration stoms while the climate warms
As well as the storms increasing in power too
What is the reason behind this?
Tropical storm intensity is linked to sea surface temperature (SST) which provides increasing energy to the storm
Warming seas also reduces the shear stress of increasing wind speed
What impacts of rising oceanic temperatures is there on marine biology?
- Shifts in ranges and changes in algal, plankton and fish abundance in high latitude oceans - has actually resulted in higher productivity
- Coral bleaching linked to higher temperature
Each species has an optimum temperature range
If climate change alters the sea temperature in an area this may affect ….
… fitness of animals
Why may it be hard to conclusively say what will happen to fish with temperatures rises
- Growth increases with temperature up to a certain point
- then declines as temperature continues to rise
- differences between northern and southern species
- implications for fish productivity in warmer species
- Implication for different trophic interactions (food chain)
To combat warming oceans, organism may move to deep parts
What is the issue however?
If the organism is dependent on light penetration
Or prey are still existing in warmer parts of the oceans (sea urchines/corals etc cannot swim)
Coastal Mangroves have experienced a…..
Expansion in their distribution polewards due to climate change
Observed in the Gulf of Mexico and New Zealand
(may lead to increased sediment accretion)
Corals have a symbiotic relationship between…
Why does bleaching occur?
photosynethetic algae and host organism (polyp)
Bleachings is a loss of colour due to expulsion or death of algae
Why is bleach of corals not all bad
Because when the corals recover the symbiont moved to thermo-tolerant corals
Most marine systems are based on the net primary productivity of….
….marine phytoplankton
Where are we expecting to see increases/decreases in net primary productivity due to climate change?
- Increase NPP in the Arctic and Southern Ocean
- Reduced NPP in warm tropical seas (reduced oxygen levels, heat stress and reduced pH)
Coast are experiencing hazards related to climate change
including….
- Storms in combination with sea level rise: erosion, inundation, ecosystem losses
- More frequently coral bleaching and mortality
