Gulf Stream at its weakest in over 1,000 years

Context

A new study suggests that the Gulf Stream is weaker now than at any point in the last 1,000 years.

What is Gulf Stream?

• The Gulf Stream is a part of the Atlantic Meridional Overturning Circulation (AMOC).
• The giant ocean circulation influences the climate of the east coast of North America from Florida to Newfoundland, and the west coast of Europe.
• In 20 to 30 years it is likely to weaken further, and that will inevitably influence weather, so there would be an increase in storms and heatwaves in Europe, and sea level rises on the east coast of the U.S.

Importance of AMOC

• Distributing heat around the planet
• Aids to achieve less harsh conditions during winters in Western Europe (Gulf Stream and North Atlantic Drift are warm ocean currents)

How global warming is weakening AMOC?

• The Atlantic overturning is triggered by the differences in the density of the ocean water, warm and salty water moves from the south to the north where it cools down and thus gets denser. When it is heavy enough the water sinks to deeper ocean layers and flows back to the south.
• Global warming disturbs this mechanism.
• Increased rainfall and enhanced melting of the Greenland Ice Sheet add fresh water to the surface ocean.
• This reduces the salinity and thus the density of the water, inhibiting the sinking and thus weakening the flow of the AMOC.

How sea level will rise at US East Coast?

• The northward surface flow of the AMOC leads to a deflection of water masses to the right, away from the U.S. east coast.
• This is due to Earth’s rotation that diverts moving objects such as currents to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.
• As the current slows down, this effect weakens and more water can pile up at the U.S. east coast, leading to an enhanced sea level rise.