climate topic 2

Question 1

rise in atmospheric & global sea surface temp

Answer 1

• excess heat trapped by GHGs absorbed by oceans, cause rise in temp
• over last century, rose by 1 degrees celsius
• incr not evenly distributed
  + eastern coast of south america
  + western coast of central africa
  + western coast of northeast asia

Question 2

changes in ocean circulation (slowing down)

Answer 2

• warm surface water moves from equator to poles due to wind
• water cools, become denser & sinks
• cold water spreads along bottom of ocean, form cool subsurface flows,eventually rises back towards surface of ocean
  [climate change]
• water at surface gains heat due to rising atmospheric temps
• water become less dense, reduces sinking of water at poles, slows down flow of water
• ocean circulation in Atlantic Ocean slowed by 15%

Question 3

disruption of marine food webs

Answer 3

• ocean circulation transports heat from tropics to poles, allows for exchange of oxygen & nutrients bet surface & deep waters
• sinking of water is reduced at poles , warm surface waters mix less w cooler, deeper water, slowing down flow of water
• warming oceans result in rapid changes in aquatic env: some species unable to adapt -> at risk of going extinct
• species dependent on one another for food, a decline in one or more species can cause the entire ecosystem to collapse

Question 4

changes in geographic distribution of aquatic species

Answer 4

• aquatic species migrate to areas where temperatures r more favourable (poleward, into cooler, deeper waters)
  eg Atlantic Cod
  => decr in biodiversity in equatorial regions, & incr in biodiversity at poleward regions

Question 5

changes in population density of species & composition of ecosystems due to species migration

Answer 5

• as geographic distribution of species changes, the mix and population density of prey, predator & competitors in ecosystem oso changes
  + some species might find abundance of food sources -> incr in pop; species they feed on decline
  + some species unable to migrate/move fast enough may not be able to adapt to higher sea temps, face local or global extinction (env unsuitable, habitats & food sources disappear)

Question 6

threat to coral reefs

Answer 6

• coral reefs: structures that develop on rocks or dead coral remains slightly below sea level on seabed
  + fragile & sensitive to env, natural or artificial conditions affect their life forms
  + expected to decline by 90% if ocean temp increases by 1.5
  + up to 2/3 of corals died in northern section of great barrier reef in Australia in 2016 & 2017
• reef structures created by coral, provide habitat , protection & source of food for thousands of marine species
• coral reefs home to estimated 830,000 species, 25% marine species

Question 7

ocean acidification

Answer 7

• reduction of pH of ocean, chased by CO2 for atmosphere
• coral reefs eroding faster than new corals can form, coral skeletons shrink, species that depend on them for food, habitat & shelter from predators may oso potentially go extinct
• average coral cover in great barrier reef has dropped about 30% of what it was in the 1960s