Climate Change Ocean & Marine Systems 1 â Questions and Answers
Question 1: What chemical process primarily causes ocean acidification as atmospheric CO2 levels rise?
- CO2 reacts with seawater to form carbonic acid, releasing hydrogen ions (Correct answer)
- UV radiation breaks down salt compounds in seawater, lowering pH
- Increased evaporation concentrates existing acids already present in the ocean
- Nitrogen runoff from agriculture introduces acids into coastal ocean zones
Correct answer: CO2 reacts with seawater to form carbonic acid, releasing hydrogen ions
When CO2 dissolves in seawater it forms carbonic acid, which dissociates to release hydrogen ions, directly lowering ocean pH.
Question 2: Approximately what percentage of human-caused CO2 emissions have the world's oceans absorbed since the industrial era?
- About 10%
- About 25-30% (Correct answer)
- About 50%
- About 70%
Correct answer: About 25-30%
Oceans have absorbed roughly 25-30% of anthropogenic CO2 emissions, making them one of Earth's most important carbon sinks.
Question 3: What is coral bleaching?
- The natural death cycle that occurs when coral reefs reach old age
- A stress response in which corals expel their symbiotic zooxanthellae algae, turning white (Correct answer)
- A process where algal blooms coat coral surfaces and block sunlight
- Whitening caused by increased UV radiation penetrating the water column
Correct answer: A stress response in which corals expel their symbiotic zooxanthellae algae, turning white
Bleaching occurs when thermally stressed corals expel the zooxanthellae algae living in their tissues, removing their color and primary food source.
Question 4: What is thermohaline circulation?
- The seasonal surface temperature cycle driven by solar radiation
- The global ocean conveyor belt driven by density differences from temperature and salinity variations (Correct answer)
- The upwelling of cold, nutrient-rich water along continental coastlines
- The mixing of surface and deep water layers by wind action alone
Correct answer: The global ocean conveyor belt driven by density differences from temperature and salinity variations
Thermohaline circulation is the planet-wide ocean circulation driven by density contrasts created by water temperature (thermo) and salinity (haline) differences.
Question 5: Since approximately 1870, global mean sea level has risen by roughly how much?
- About 5 cm (2 inches)
- About 20-23 cm (8-9 inches) (Correct answer)
- About 50 cm (20 inches)
- About 1 meter (39 inches)
Correct answer: About 20-23 cm (8-9 inches)
Global mean sea level has risen approximately 20-23 cm since 1870, with the rate of rise accelerating significantly in recent decades.
Question 6: Which statement about the effect of ocean warming on marine primary productivity is most accurate?
- Warming uniformly increases phytoplankton productivity across all ocean regions
- Warming increases stratification in tropical zones, reducing nutrient upwelling and lowering productivity (Correct answer)
- Warming has no significant effect on phytoplankton because they adapt rapidly
- Warming only affects productivity in polar seas while tropical productivity remains stable
Correct answer: Warming increases stratification in tropical zones, reducing nutrient upwelling and lowering productivity
Increased warming strengthens ocean stratification in tropical and subtropical regions, cutting off the supply of deep nutrients to surface waters and reducing primary productivity.
Question 7: What term describes hypoxic coastal ocean areasâoften worsened by nutrient runoff and rising temperaturesâwhere dissolved oxygen is insufficient to support most marine life?
- Thermal vents
- Dead zones (Correct answer)
- Benthic layers
- Abyssal plains
Correct answer: Dead zones
Dead zones are hypoxic coastal regions where excess nutrient input fuels algal blooms; their decomposition consumes oxygen, and warming further reduces oxygen solubility.
Climate Change Ocean & Marine Systems 1
What chemical process primarily causes ocean acidification as atmospheric CO2 levels rise?