Temperature, Salinity & Density

This set of flashcards covers key concepts related to ocean water properties, including temperature, salinity, and density, aimed at preparing for an extreme difficulty examination.

Why does the highest surface ocean temperature lie slightly north of the equator?

Due to higher insolation in the northern hemisphere and prevailing trade winds that push warm water northward.

How does the thermocline act as a barrier in oceanic vertical mixing?

The sharp temperature gradient restricts vertical movement between warm surface water and cold deep layers.

Why do polar oceans exhibit uniform vertical temperature profiles?

Low surface temperatures cause minimal gradient with depth, preventing thermocline formation.

Why does temperature distribution show longitudinal variation along the same latitude?

Ocean currents, prevailing winds, and proximity to landmasses alter temperature patterns even at similar latitudes.

How do seasonal changes affect the vertical structure of ocean temperature layers in mid-latitudes?

In summer, stratification increases due to surface heating, creating a prominent thermocline that weakens in winter.

Why are eastern margins of oceans generally cooler than western margins at the same latitude?

Cold currents from higher latitudes flow along eastern margins, while warm equatorial currents dominate western margins.

What role do prevailing winds play in ocean surface temperature distribution?

Winds push surface water, redistributing heat laterally and vertically through upwelling and downwelling.

How does vertical temperature gradient affect nutrient availability in surface waters?

Steep gradients prevent mixing, limiting nutrient-rich deep water from reaching the surface.

Why does the Southern Ocean exhibit the least seasonal temperature variation?

Its vast expanse and consistent westerlies distribute heat evenly, reducing seasonal contrasts.

Why are shallow tropical seas more prone to coral bleaching?

Higher surface temperatures and poor vertical mixing increase thermal stress on corals.

Why is salinity lower near equatorial regions despite high evaporation rates?

Heavy rainfall and river discharge outweigh evaporation, diluting surface salinity.

How does the Mediterranean Sea achieve high salinity levels?

High evaporation, limited freshwater inflow, and restricted exchange with the Atlantic concentrate salt.

Why is salinity higher in subtropical high-pressure zones?

Low precipitation and strong evaporation due to descending dry air increase salt concentration.

How does sea ice formation affect surrounding water salinity?

When ice forms, salt is excluded (brine rejection), increasing salinity and density of nearby waters.

Why are landlocked seas like the Caspian and Red Sea saltier than open oceans?

Minimal freshwater inflow and high evaporation without outflow raise salinity levels.

How does thermohaline circulation originate from polar regions?

Cold, saline water becomes dense and sinks, initiating deep ocean currents driving global circulation.

Why does increasing salinity raise ocean water density?

Dissolved salts increase the mass of water without significantly changing its volume.

How do temperature and salinity jointly control water stratification?

Warm, fresh water stays atop denser cold, salty layers, resisting vertical mixing.

Why do tropical cyclones lead to temporary changes in salinity?

They mix upper layers and bring rain, reducing surface salinity while deepening mixed layers.

How can salinity patterns help trace water mass origins?

Each water mass has a unique salinity-temperature profile, helping identify its formation zone.

Which of the following seas exhibits the highest surface salinity: Red Sea, Baltic Sea, Arabian Sea, or Caribbean Sea?

Red Sea.

Arrange the following in decreasing order of salinity: Mediterranean Sea, Bay of Bengal, North Pacific, North Atlantic.

Mediterranean Sea > North Atlantic > North Pacific > Bay of Bengal.

Identify the oceanic zone with most pronounced thermocline: Equatorial, Polar, or Mid-latitude?

Equatorial zone.

Which currents are responsible for maintaining low salinity along Peru and Namibia coasts?

Peru Current and Benguela Current.

Which of the following regions is a known source of deep water formation: Labrador Sea, Arabian Sea, Sargasso Sea, or Black Sea?

Labrador Sea.

What are the three major vertical layers of ocean water based on temperature?

Surface mixed layer, thermocline layer, and deep cold layer.

Why is the deep ocean layer nearly isothermal?

Lack of sunlight and mixing causes uniformly cold temperatures below the thermocline.

How does the pycnocline relate to ocean stratification?

It's the layer where density increases rapidly with depth due to combined temperature and salinity changes.

Why is the Arctic Ocean more stratified than the Antarctic?

Higher freshwater inflow from rivers and less deep mixing lead to sharper density gradients.

How does density-driven circulation differ from wind-driven circulation?

Density-driven flows occur at depth due to temperature-salinity contrasts, while wind affects surface layers.

Why are El Niño years associated with weakened thermocline gradients?

Warm surface water spreads eastward, flattening the thermocline and suppressing upwelling.

How does ocean salinity influence regional climate patterns?

It affects evaporation, heat storage, and latent heat flux, influencing humidity and precipitation.

What is the role of ocean heat content in intensifying tropical storms?

Warm upper ocean layers provide energy for storm development and rapid intensification.

Why do heat anomalies in western Pacific drive rainfall in eastern Indian Ocean?

Shifts in SST alter convection zones, pushing rain belts toward the east.

How does polar amplification relate to ocean stratification in the Arctic?

Warming increases surface freshwater, intensifying stratification and reducing deep heat mixing.

Why is the Arabian Sea saltier than the Bay of Bengal?

Lower river inflow and high evaporation in the Arabian Sea contrast with heavy freshwater discharge into Bay of Bengal.

How does monsoon influence salinity in Indian coastal waters?

Rainfall and runoff reduce salinity during SW monsoon, while NE monsoon increases evaporation.

Why is temperature-salinity structure more complex in the Andaman Sea?

Influence of freshwater from rivers, tides, and oceanic inflow creates high spatial variation.

Which Indian coastal region shows strongest seasonal variation in salinity?

Eastern coast (Bay of Bengal) due to river discharge and monsoon rainfall.

How does Lakshadweep’s location in tropical waters affect salinity and SST?

High SST and limited runoff result in relatively stable and saline surface waters.

Why is CTD profiling crucial in oceanographic surveys?

It provides simultaneous measurements of Conductivity (salinity), Temperature, and Depth, helping map water column structure.

How do Argo floats detect subsurface thermocline changes?

They drift at depth and periodically ascend, recording vertical temperature and salinity profiles.

Why is salinity data critical for submarine navigation?

It affects sound propagation speed and buoyancy, which influence sonar performance and depth control.

How do ocean temperature anomalies trigger marine heatwaves?

Persistent warming in upper layers disrupts ecological balance, causing bleaching and species displacement.

Why are polar regions considered key in global climate sensitivity studies?

They respond rapidly to temperature changes and control deepwater formation affecting global thermohaline circulation.

Why is the Bay of Bengal prone to strong vertical stratification?

High river runoff and rainfall create a fresh surface layer that resists mixing with denser saline water below.

How does salinity affect sound speed in submarine warfare strategy?

Higher salinity increases water density and sound speed, influencing sonar accuracy and detection range.

Why are thermocline depths useful for predicting El Niño and La Niña events?

Anomalies in thermocline depth signal changes in heat distribution and ocean-atmosphere coupling in the Pacific.

How do seasonal thermoclines differ from permanent thermoclines?

Seasonal thermoclines form in summer and mix away in winter, while permanent thermoclines persist in tropical oceans.

Why is mixed layer depth important for primary productivity in oceans?

Shallower mixed layers allow more light but limit nutrients, while deeper layers enhance mixing but reduce light availability.