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

IPCC AR6 projects 0.63–1.01 m of global mean sea level rise by 2100 under SSP5-8.5, with low-likelihood but high-impact scenarios exceeding 1.5 m if ice-sheet instabilities occur.

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

Methane hydrates store enormous amounts of methane in solid form; if ocean warming destabilizes seafloor deposits, rapid methane release could significantly amplify greenhouse warming.

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

Warmer oceans stress kelp directly and decimate sea urchin predators (like sunflower sea stars), allowing urchin populations to explode and graze kelp forests into barren wastelands.

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

Surface ocean pH has dropped from ~8.18 to ~8.08–8.10 today; because pH is logarithmic, this represents roughly a 26% increase in hydrogen ion concentration.

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

Calcifying organisms like bivalves, echinoderms, and corals build calcium carbonate structures; as pH drops, carbonate ion concentration falls, making shell and skeleton formation energetically costly or impossible.

Climate Change Practice Test

Climate Change Practice Test

Climate Change Ocean & Marine Systems 3