North Atlantic Drift

Also called: North Atlantic Current · Topic: Movements of Ocean Water: Waves, Tides and Currents · NCERT: Class 11, Ch 8 "Solar Radiation, Heat Balance and Temperature"; Class 11, Ch 12 "Water (Oceans)"; Class 11, Ch 13 "Movements of Ocean Water"

Meaning

The North Atlantic Drift (also called the North Atlantic Current) is a warm ocean current. It continues the Gulf Stream east and north-east across the Atlantic towards north-west Europe, and the westerly winds drive it. It matters because it gives Britain and Norway mild winters and keeps their ports open in winter. It is the main exception to the rule that the eastern side of an ocean basin has cold currents.

Explanation

Basic ideas

• Ocean current: a large, steady flow of seawater in one direction, like a river inside the ocean.
• Warm current: flows from low latitudes (near the equator) towards the poles. It warms the coasts it passes.
• Drift: a slow surface flow pushed by the wind. The North Atlantic Drift gets this name because the westerlies (winds that blow from the west in the middle latitudes) push it across the ocean.

How it forms (cause → process → result)

• Cause: the Gulf Stream moves away from the American coast
• The Gulf Stream leaves the Gulf of Mexico through the Florida Strait.
• It runs north along the US east coast to Cape Hatteras.

• It then turns north-east towards Newfoundland.

• Process: the westerlies take over

• Beyond Newfoundland, the westerly winds push this warm water east and north-east across the Atlantic.

• The flow becomes wider and slower. This slow, wind-driven part is the North Atlantic Drift.

• Result: tropical heat reaches high latitudes

• Warm water from the tropics reaches the seas off Britain and Norway.

Its place in the current system

• Part of the North Atlantic gyre: a gyre is a large ring of currents that goes round an ocean basin.
• The North Atlantic gyre is clockwise. This is because of the Coriolis force (the turning effect of the earth's rotation, which pushes moving water to the right in the Northern Hemisphere) and the planetary winds.
• The order of the loop is Gulf Stream → North Atlantic Drift → Canary Current → North Equatorial Current → back to the Gulf of Mexico.

• The North Atlantic Drift is the northern edge of this loop.

• Part of the subpolar loop (beyond NCERT)

• The Irminger Current is a warm branch of the North Atlantic Drift. It flows west past south and west Iceland.
• The Irminger Current, the East Greenland Current (cold), the Labrador Current (cold) and the North Atlantic Drift form a smaller anticlockwise loop north of the main gyre.

Its effects on north-west Europe

• Mild winters
• Warm tropical water reaches high latitudes.
• The westerly winds blow over this warm water and pick up heat and moisture.
• The winds carry the heat onto land, so winters are mild and wet.

• So Britain and Norway are much warmer than other places at the same latitude, such as Labrador in Canada.

• Ice-free ports

• The warm water stops the sea from freezing.

• Ports stay open all winter, even north of the Arctic Circle.

• Isotherms bend north

• Isotherms are lines on a map that join places with the same temperature.

• Over the north-east Atlantic, they curve towards the pole. This is because the water there is warmer than usual for that latitude (NCERT Class 11, Ch 8).

• Higher North Sea salinity

• Salinity is the amount of dissolved salt in seawater.
• Salty water from the tropics flows into the North Sea and raises its salinity (NCERT Class 11, Ch 12).

Where it occurs

• Ocean: the North Atlantic. It flows from the waters off Newfoundland (Canada), across the ocean, to north-west Europe.
• Coasts it warms:
• Britain: mild, wet winters.
• Norway: Hammerfest (about 70°N) and Narvik stay ice-free in winter.
• Russia: Murmansk, on the Kola Peninsula, stays open all winter.

• North Sea: has higher salinity because of the tropical water.

• Sargasso Sea: the North Atlantic Drift is its northern edge. The other edges are the Gulf Stream (west), the Canary Current (east) and the North Equatorial Current (south).

• Iceland: its branch, the Irminger Current, flows past south and west Iceland.
• India: it has no direct effect on India. It is a North Atlantic feature.

Don't confuse with

• Gulf Stream: the Gulf Stream is the source. It runs from the Florida Strait along the US coast to Cape Hatteras and Newfoundland. The North Atlantic Drift is the part that crosses the ocean and warms Europe. Ice-free Norwegian ports are credited to the North Atlantic Drift, not to the Gulf Stream itself.
• Labrador Current: this is a cold current. It flows south from the Arctic past Labrador and Newfoundland. Labrador's ports freeze in winter, while Norwegian ports at higher latitudes stay open because of the North Atlantic Drift.
• Canary Current: this is a cold current on the eastern side of the same gyre. It flows south from Spain to Senegal and makes the coastal Sahara dry. The North Atlantic Drift flows north-east and makes the coast warm and wet.
• Irminger Current: this is a branch of the North Atlantic Drift. It flows west past Iceland. It is not a separate source of warm water.

Prelims Hooks

• Hammerfest, Narvik and Murmansk stay ice-free in winter because of the North Atlantic Drift, not the Gulf Stream itself.
• The currents across the North Atlantic, from west to east, are: Gulf Stream → North Atlantic Drift → Canary Current.
• The Sargasso Sea, the only sea with no land boundary, has the North Atlantic Drift as its northern edge [2].
• It is a warm current on the eastern side of a basin. This is the exception to the "western side warm, eastern side cold" rule.
• Over the north-east Atlantic, isotherms bend towards the pole because of the North Atlantic Drift.
• The westerlies drive the North Atlantic Drift. The trade winds drive the North Equatorial Current. Mixing these up is a common trap.

Mains Points

• Climate on western and eastern coasts (GS-I):
• Usually, warm currents run along the western sides of ocean basins (Gulf Stream, Brazil), and cold currents run along the eastern sides (Canary, Benguela), which helps create coastal deserts.

• The North Atlantic Drift breaks this pattern. With the westerlies, it carries tropical heat to north-west Europe. This gives Britain and Norway mild, wet winters and makes them much warmer than Labrador at the same latitude.

• Economy and transport (GS-I/GS-III):

• Ice-free ports such as Hammerfest, Narvik and Murmansk stay open all winter, even north of the Arctic Circle.

• This keeps shipping and fishing going all year. The frozen Labrador ports, cooled by the Labrador Current, show the opposite effect.

• Ocean heat transport and climate (GS-I/GS-III):

• The Gulf Stream–North Atlantic Drift system carries heat towards the pole, bends isotherms north and raises North Sea salinity.
• Any change in this flow would affect Europe's climate. This shows why ocean monitoring matters; India's INCOIS plays a similar role for the Indian Ocean.

Related concepts

• Gulf Stream
• Canary Current
• Sargasso Sea
• Labrador Current
• Brazil Current
• Falkland Current
• Benguela Current

Read more

• Currents of the Atlantic Ocean