According to researchers from University College London (UCL) and Woods Hole Oceanographic Institution North Atlantic Ocean Circulation which is a key cog in global ocean circulation system hasn't been running at highest strength since the mid-1800 and is currently working at it lowest point in the past 1600 years.
Image Credit: https://www.pmfias.com/atlantic-ocean-currents-sargasso-sea-gulf-stream-north-atlantic-drift-benguela-current/
What Is Atlantic Ocean Circulation:
It is an ocean current flowing NE towards the British Isles, formed by the convergence of the Gulf Stream and the Labrador current SE of Newfoundland.
The relatively warm waters of the North Atlantic drift are responsible for moderating the climate of western Europe .
Because of this in winters season the climate of UK and others places of Europe is not colder like Canada because of same latitude.
Otherwise British Isles winters are estimated to be 5°C more coller from the present temperature.
Because of constantly moving global ocean current circulation warm, salty Gulf stream water flowing into the North Atlantic and releases its heat to the atmosphere and warms Western Europe.
As density of cooler and less salty water is higher is sinking into great depth and travels all the way to Antarctica and later circulates back to Gulf Stream.
What Happened If North Atlantic Drift Current Is Going To Weak More:
1)Present Weather Pattern of the United States and Europe and African Sahel will be changed.
2)It can cause rapid increase in sea level on the US East Coast.
How Scientists Came To The Conclusion:
Scientists examined the size of sediment of ocean grains in the region. According to them the higher the grain size higher the ocean current.
Source Of Information:
https://www.sciencedaily.com/releases/2018/04/180411131642.htm