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NORTHERN HEMISPHERE CLIMATE Ocean circulation & greenhouse warming -…
NORTHERN HEMISPHERE CLIMATE
Ocean circulation & greenhouse warming
Ocean heat transport
Warm surface water flows north.
Heat is released to the atmosphere.
This helps warm Europe.
Cold deep water returns south.
Deep water formation
Cold + salty water is dense and sinks.
2 main convection sites:
Labrador Sea + Greenland Sea.
Sinking supports Atlantic overturning.
Greenhouse warming
More precipitation + meltwater can freshen the North Atlantic.
Lower salinity → lower surface density.
Less sinking → weaker overturning.
Thresholds + feedback
Convection can switch “on” or “off”.
Crossing a threshold can cause abrupt change.
1 convection site may stop before the whole circulation collapses.
Climate + ecosystem effects
Weaker currents change northward heat transport.
Regional climate can change.
Mixing and nutrient supply can change.
Marine ecosystems + seabirds may be affected.
Evidence + uncertainty
Models showed roughly 25% weaker overturning.
The highlighted model stopped Labrador convection.
Rainfall, eddies and freshwater inputs were uncertain.