Climate Change Ocean & Marine Systems 3

Question 1

Under high-emissions scenarios (SSP5-8.5), what range of global mean sea level rise does the IPCC AR6 project by 2100?

Accepted Answer

63–101 cm (25–40 inches)

Answer

10–20 cm (4–8 inches)

Answer

28–55 cm (11–22 inches)

Answer

150–200 cm (59–79 inches)

Question 2

Why are methane hydrates (clathrates) on the ocean floor considered a climate risk under continued warming?

Accepted Answer

Destabilization by warming could release vast quantities of methane, a potent greenhouse gas, creating a feedback loop

Answer

They dissolve and directly acidify deep ocean water when ocean temperatures rise

Answer

They block oxygen exchange between the deep sea and the atmosphere

Answer

Mining them for energy produces toxic byproducts that further warm coastal waters

Question 3

Kelp forests are declining in many coastal regions primarily due to which climate-related mechanism?

Accepted Answer

Ocean warming weakens kelp predators while fueling sea urchin population explosions that overgraze kelp

Answer

Increased nitrogen fixation by bacteria in warmer water fertilizes competing algae

Answer

Reduced cloud cover and greater sunlight penetration bleaches kelp fronds

Answer

Ocean acidification dissolves the calcium carbonate holdfast anchoring kelp to the seafloor

Question 4

Compared to pre-industrial levels (~8.18), what is the approximate surface ocean pH today?

Accepted Answer

About 8.1—representing roughly a 26% increase in acidity

Answer

About 8.5—slightly more alkaline than pre-industrial

Answer

About 7.8—a major shift approaching neutral pH

Answer

About 7.5—approaching mildly acidic conditions

Question 5

Which groups of marine organisms are most directly threatened by ocean acidification due to their reliance on carbonate ions for shell or skeleton formation?

Accepted Answer

Oysters, mussels, sea urchins, and reef-building corals

Answer

Jellyfish and sea anemones

Answer

Cetaceans (whales and dolphins)

Answer

Sharks, rays, and large pelagic fish

Question 6

What fraction of all marine species is estimated to depend on coral reef ecosystems despite reefs covering less than 1% of the ocean floor?

Accepted Answer

About 25%

Answer

About 5%

Answer

About 10%

Answer

About 50%

Question 7

How does the loss of Arctic sea ice create a positive (self-reinforcing) climate feedback loop?

Accepted Answer

Reflective white ice is replaced by dark ocean water that absorbs far more solar radiation, accelerating warming

Answer

Melting sea ice releases trapped CO2 and methane that were frozen in the ice for centuries

Answer

Reduced ice cover increases wind-driven evaporation, which cools the Arctic and moderates the feedback

Answer

Sea ice loss redistributes cold air to lower latitudes, increasing global cloudiness and reducing warming