A&O SCI 1 Lecture Notes - Lecture 17: Crustacean, Radiative Forcing, West Antarctic Ice Sheet
8 Jun 2018
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Ecosystem impacts on the Oceans
Ecosystem services - benefit that is provided to humans in a direct or indirect way
Among ecosystem services provided by the ocean ecosystem are:
• Food production (fish)
• Absorption of excess heat caused by anthropogenic forcings in atmosphere
• Absorption of CO2 from atmosphere (ocean carbon sink)
• Reservoir of biological diversity (Coral reefs)
• Cultural, recreational services (tourism, recreational fishing)
Climate change is altering the ocean ecosystem in profound ways --> some will be felt for decade or
centuries b/c of committed climate change
Adaptation to and mitigation of anthropogenic climate change needs to consider services of ocean
ecosystem provides to humankind
RECALL: stressors by humans
• Pollution of air, water, and soil
• Deforestation and land use change - agriculture
• Fragmentation of habitats, loss of biodiversity
Ocean are affected by a range of stressors, many are projected to increase over nxt decades under
climate change:
• Overfishing, increase in bycatches, ecological extinctions
• Habitat degradation in coastal regions
• Invasive species
• Sea level rise threats to coastal ecosystems
• Loss of sea-ice habitats
• Ocean acidification
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OCEAN WARMING
Most of ocean surfacing is warming up….
• Warming is stronger in North Atlantic Ocean
• Leads to increases in stratification b/c surface warms more than deep oceans, so surface get less
dense
o Makes harder to mix ocean and bring nutrients up
o Productivity of at surface declines with warming
o Polar regions --> positive effects (reduce mixing, increasing light availability) and
productivity may in fact increase
• RCP8.5 --> +3oC by end of century (2100)
o Productivity decrease over most tropical and mid-latitude regions
o Productivity increases (phytoplankton) in high latitudes and polar regions
Decline in productivity means less food available for ecosystem and food webs
• Negative effects on fisheries, many of which are already affect by overfishing, by-catches, and
habitat degradation
Changes in Ocean Oxygen
• Warm water holds less oxygen --> warming will decrease oxygen in ocean
• Also, oxygen is consumed in ocean interior b/c of decomposition of phytplankton and other
organic materials that sink from the surface
o Deficit is constantly replenished by mixing and currents that bring in oxygen from the
surface (thermohaline circulation)
• Ocean warms --> more stratified --> transport of oxygen from atmosphere to ocean interior will
decrease
• Deoxygenation - decline in ocean oxygen
Changes in temp, productivity and oxygen cause a shift in habitat of many species
• Much migration is similar to temp change son earth (poleward), BUT some species can’t move any
further north (Gulf of Mexico) so they sink deeper!!
o Expected to continue in the future
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COMING SEA LEVEL RISE
• Contribution from thermal expansion is fairly straightforward to calculate, since it can be inferred
from the simulated warming of the ocean
o Roughly seawater expands by 0.02% for every K of warming
o Does have uncertainty, due to uncertainty in warming
• Contribution from mountain glaciers is provided by models of their responses to projected
warming --> also has uncertainty
• Contribution from Greenland and Antarctic ice sheets are more complex
o Includes direction contribution from enhanced melting of ice sheets and internal changes in
ice sheets as they warm
• RCP8.5 --> 0.65m (~2 feet) change
Document Summary
Ecosystem services - benefit that is provided to humans in a direct or indirect way. Among ecosystem services provided by the ocean ecosystem are: Food production (fish: absorption of excess heat caused by anthropogenic forcings in atmosphere, absorption of co2 from atmosphere (ocean carbon sink, reservoir of biological diversity (coral reefs, cultural, recreational services (tourism, recreational fishing) Climate change is altering the ocean ecosystem in profound ways --> some will be felt for decade or centuries b/c of committed climate change. Adaptation to and mitigation of anthropogenic climate change needs to consider services of ocean ecosystem provides to humankind. Recall: stressors by humans: pollution of air, water, and soil, deforestation and land use change - agriculture. Ocean are affected by a range of stressors, many are projected to increase over nxt decades under climate change: overfishing, increase in bycatches, ecological extinctions, habitat degradation in coastal regions, ocean acidification.
