The atmosphere and ocean are in constant communication, exchanging energy, moisture, and momentum. This dynamic interplay shapes our climate through processes like evaporation, precipitation, and heat transfer. Understanding these interactions is key to grasping how Earth's climate system functions.

Ocean temperatures greatly influence atmospheric circulation patterns, affecting weather worldwide. El Niño and La Niña are prime examples of how ocean-atmosphere coupling can lead to far-reaching climate impacts. These interactions play a crucial role in maintaining Earth's energy balance and climate stability.

Atmosphere-Ocean Interactions

Air-sea interaction processes

• Exchange energy, moisture, momentum between atmosphere and ocean at interface
  • Driven by differences in temperature, humidity, wind speed between environments
• Heat exchange involves ocean absorbing solar radiation, releasing heat to atmosphere
  • Sensible heat flux: direct conduction of heat from ocean to atmosphere
  • Latent heat flux: heat transfer through evaporation of water from ocean surface (evaporative cooling)
• Moisture exchange occurs as evaporation adds moisture to atmosphere
  • Atmospheric moisture can condense, return to ocean as precipitation (rain, snow)
• Momentum exchange transfers momentum from atmosphere to ocean via wind stress
  • Drives ocean currents (Gulf Stream), waves (tsunamis), mixing in upper ocean layer

Evaporation and precipitation cycles

• Evaporation occurs when water molecules gain kinetic energy, escape liquid phase, enter atmosphere as vapor
  • Rate depends on ocean surface temperature, air temperature, humidity, wind speed
  • Cools ocean surface, adds moisture to atmosphere (humidification)
• Condensation occurs when atmospheric water vapor cools, condenses into liquid water droplets
  • Releases latent heat into atmosphere, warming surrounding air
  • Leads to formation of clouds (cumulonimbus) and fog (advection fog)
• Precipitation occurs when water droplets in clouds grow large enough to fall back to Earth's surface
  • Transfers moisture, freshwater from atmosphere to ocean surface
  • Affects ocean salinity, density, influencing circulation patterns (thermohaline circulation)

Ocean temperature vs atmospheric circulation

• Ocean surface temperature anomalies (El Niño, La Niña) significantly impact atmospheric circulation
• El Niño: warmer eastern equatorial Pacific Ocean temperatures
  1. Weakens Walker circulation, east-west atmospheric circulation in tropics
  2. Increases rainfall in eastern Pacific, decreases in western Pacific (drought in Australia)
• La Niña: cooler eastern equatorial Pacific Ocean temperatures
  1. Strengthens Walker circulation
  2. Decreases rainfall in eastern Pacific, increases in western Pacific (flooding in Indonesia)
• Anomalies influence position, intensity of Intertropical Convergence Zone (ITCZ), jet streams (polar jet stream)
  • Affects global weather patterns via teleconnections (Pacific-North American pattern, North Atlantic Oscillation)

Atmosphere-ocean coupling in climate

• Crucial for maintaining Earth's energy balance, climate stability
• Positive feedbacks amplify changes
  • Warm ocean temperatures increase evaporation, atmospheric moisture, enhancing greenhouse effect
  • Melting sea ice reduces ocean surface albedo, allows more solar radiation absorption (Arctic amplification)
• Negative feedbacks mitigate changes
  • Increased evaporation from warmer ocean leads to more cloud formation, reflecting solar radiation, cooling atmosphere
  • Enhanced upwelling of cold, deep ocean waters due to stronger winds cools ocean surface, atmosphere (La Niña)
• Coupled processes (El Niño-Southern Oscillation, Indian Ocean Dipole, Atlantic Multidecadal Oscillation) influence regional, global climate patterns
• Long-term climate change (global warming) amplified or mitigated by atmosphere-ocean interactions
  • Crucial to understand coupled processes for accurate climate projections (climate models)