Oceans & Currents — Set 3

Correct Answer: A. Irminger Current

• **Irminger Current** = a warm ocean current in the North Atlantic, branching from the North Atlantic Drift, keeping waters off southwest Iceland warmer than expected for its latitude. • **North Atlantic Drift branch** — the Irminger Current moderates the climate of Iceland and parts of southern Greenland by delivering warm North Atlantic water. • 💡 Wrong-option analysis: Labrador Current: cold current flowing south from the Arctic along eastern Canada; Canary Current: cold current flowing south along northwestern Africa; East Greenland Current: cold current flowing south along Greenland's east coast.

Correct Answer: A. The Sun, Moon, and Earth are in a straight line

• **Spring Tides** = occur during full moon and new moon when the Sun, Moon, and Earth align in a straight line (syzygy), producing the highest high tides and lowest low tides. • **Syzygy alignment** — combined gravitational pull of Sun and Moon maximizes tidal force; occurs twice monthly at new moon and full moon. • 💡 Wrong-option analysis: Sun and Moon at right angles: produces Neap tides (weaker), not Spring tides; Moon in third quarter: this is when Neap tides occur; Moon in first quarter: also produces Neap tides as Sun and Moon are perpendicular.

Correct Answer: B. Bathymetry

• **Bathymetry** = the science of measuring underwater depths of lakes and oceans, the aquatic equivalent of topography for land surfaces. • **Sonar technology** — Sound Navigation And Ranging (SONAR) is the primary tool for bathymetric surveys, sending sound pulses to measure ocean floor depth. • 💡 Wrong-option analysis: Altimetry: measurement of altitude above a reference level; Topography: study and mapping of land surface features; Hypsometry: measurement of land elevation above sea level.

Correct Answer: B. Guyot

• **Guyot** = a flat-topped seamount (submerged volcanic island) that was once an active volcanic island eroded flat by waves, then submerged below sea level. • **Pacific Ocean prevalence** — guyots are most common in the Pacific Ocean; named after Swiss geographer Arnold Guyot. • 💡 Wrong-option analysis: Trench: deep narrow depression in ocean floor at subduction zones; Atoll: ring-shaped coral reef remaining after a volcanic island subsides; Ridge: underwater mountain range at divergent plate boundaries.

Correct Answer: C. Pacific Ocean

• **California Current (Pacific Ocean)** = a cold ocean current flowing southward along the western coast of North America, cooling California's coastal climate. • **Eastern boundary current** — California Current is the eastern boundary of the North Pacific Gyre, equivalent to the Canary Current in the North Atlantic. • 💡 Wrong-option analysis: Indian Ocean: no California Current; Arctic Ocean: too far north; Atlantic Ocean: Canary Current is the equivalent cold eastern boundary current in the North Atlantic.

Correct Answer: A. Red Sea

• **Red Sea** = one of the world's saltiest water bodies with salinity exceeding 40 ppt, due to high evaporation, low rainfall, and minimal freshwater river input. • **40+ ppt** — Red Sea salinity is significantly higher than the average ocean salinity (35 ppt); its restricted connection to the Indian Ocean limits salt dilution. • 💡 Wrong-option analysis: Hudson Bay: receives abundant freshwater from rivers, lower salinity; Baltic Sea: very low salinity (~7-8 ppt) due to many rivers and limited ocean exchange; Black Sea: low salinity (17-18 ppt) due to freshwater from Danube and other rivers.

Correct Answer: C. Africa

• **Mozambique Current (Africa)** = a warm western boundary current of the Indian Ocean, flowing through the Mozambique Channel between Madagascar and the African continent. • **Mozambique Channel** — the ~1,700 km strait between Madagascar and Mozambique (Africa) through which this warm Indian Ocean current flows southward. • 💡 Wrong-option analysis: Asia: Mozambique Channel is on Africa's east side; South America: far from Madagascar; Australia: Madagascar is in the western Indian Ocean, far from Australia.

Correct Answer: C. Upwelling

• **Upwelling** = the process where deep, cold, nutrient-rich water rises to replace warm surface water pushed away by winds, supporting high biological productivity. • **Fishery richness** — upwelling zones along Peru (Humboldt Current), California, and West Africa are among the world's most productive fishing areas. • 💡 Wrong-option analysis: Tsunami: large ocean waves caused by earthquakes or landslides; Downwelling: opposite of upwelling, when surface water sinks; Subduction: tectonic process where one plate slides under another, not an ocean water process.

Correct Answer: A. Atlantic Ocean

• **Falkland Current (South Atlantic)** = a cold ocean current flowing northward along the Patagonian coast, a branch of the Antarctic Circumpolar Current. • **Malvinas Current** — Falkland Current is also called the Malvinas Current; it meets the warm Brazil Current near Rio de la Plata, creating productive waters. • 💡 Wrong-option analysis: Arctic Ocean: Falkland is in South Atlantic, far from Arctic; Indian Ocean: no Falkland Current here; Pacific Ocean: Peru/Humboldt Current serves equivalent role on South America's Pacific coast.

Correct Answer: D. Brazil Current

• **Brazil Current** = a warm ocean current flowing southward along the coast of Brazil in the South Atlantic, eventually meeting the cold Falkland Current. • **Rio de la Plata convergence** — Brazil Current (warm) meets Falkland Current (cold) near the Rio de la Plata, creating biologically rich waters off Argentina. • 💡 Wrong-option analysis: Peru Current: cold current flowing north along South America's Pacific coast; Benguela Current: cold current flowing north along Africa's west coast; Canary Current: cold current flowing south along Northwest Africa.