Tema 2.1-4 Flashcards
How much salt do rivers contribute to oceans annually?
2.5-4 × 10¹⁵ g/year.
How old are the oceans, and what caused significant changes over 1500 million years?
3400+ million years old; changes due to imbalances in sources and sinks.
What percentage of dissolved salts in seawater are major constituents, and why are they stable?
99%; they are conservative and barely reactive.
What is salinity?
Weight of dissolved salts (g) in 1 kg of seawater; measured in psu (e.g., 35 psu = 35‰).
What is the Principle of Constant Proportions?
Relative amounts of major ions in seawater are always consistent.
Why are oceans chemically well-mixed?
Mixing time (< 1000 years) is much shorter than major ion residence times.
How is salinity determined?
Evaporation: Weighing salts left after water removal.
Chlorinity: Measuring halogens in g/kg.
Electrical Conductivity (EC): Measured using a salinometer.
What is the typical salinity distribution in oceans?
Open ocean: 33-37‰.
1000 m depth: 34.5-35.0‰.
Neritic zones/partially enclosed seas: Varies (e.g., Amazon 5 × 10¹² m³ freshwater/year).
How does surface salinity vary?
Subtropics: Low precipitation → high salinity.
Equator: High precipitation → low salinity.
What is a halocline, and where is it found?
A layer where salinity changes rapidly with depth (100-300 m); it affects mixing and circulation.
How does temperature affect the ocean surface?
Tropics: >25°C; Poles: <0°C.
Isotherms show temperature gradients (tropical = uniform; high latitudes = rapid change).
What is a thermocline, and what are its types?
Permanent: 200-1000 m, separates warm surface from cold deep water.
Seasonal: 40-100 m, forms in summer, may vanish in winter.
Diurnal: <12 m, changes daily due to sunlight.
How does pressure influence the ocean?
Increases with depth, affecting gas-filled structures and organism distribution.
How do temperature, salinity, and pressure interact with density?
Density increases with salinity, decreases with temperature, and rises with pressure.
What are pycnoclines, and why are they important?
Density layers caused by salinity/temperature changes; contribute to stratification.
How are ocean temperatures measured?
Thermometers, Niskin bottles, and electronic sensors (CTDs) for large areas.
What affects gas saturation in seawater?
Temperature, salinity, and pressure determine how much gas can dissolve at equilibrium.
What are the main sources and losses of oxygen in oceans?
Sources: Atmospheric exchange and photosynthesis.
Losses: Respiration, decomposition.
What is the oxygen minimum layer?
Layer (150-1500 m) with lowest O₂ levels due to limited mixing and high respiration.
How is CO₂ distributed in oceans?
50x more than in the atmosphere; exists as CO₂, HCO₃⁻, and CO₃²⁻, depending on pH.
What is the Calcite Compensation Depth (CCD)?
Depth where CaCO₃ dissolves as quickly as it accumulates; influenced by CO₂, pH, T°, and P.
What role does DMS play in the atmosphere?
Produced by algae, oxidized to SO₂ → forms SO₄²⁻ → contributes to acid rain/cloud formation.
What is H₂S, and why is it important?
Produced by anaerobic decomposition; indicates ecosystem health and nutrient cycle changes.
