Gulf Stream System currently weaker than it has ever been in the past 1,000 years

A group of international scientists have concluded that over the past few decades the Gulf Stream System, also known as the Atlantic Meridional Overturning Circulation (AMOC), has been at its weakest state in over 1,000 years.

The researchers used data from ocean sediments and ice cores to reconstruct the flow history of the AMOC. The team determined that this weakening trend or slowdown of the circulation is likely the result of human-induced climate change.

Northern portion of the AMOC. Image courtesy Wikipedia.

Earlier research found that the AMOC has slowed down by as much as 15 percent since the middle of the 20th century.

This new study found that the AMOC was relatively stable up through the middle of the 19th century followed by a decline and a second, more pronounced decline after that, according to Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research PIK and lead author of the study.

This slowdown is not all that surprising as climate models have long predicted that this outcome due to the steady, long-term increase in man-made greenhouse gases.

Key excerpts from the Potsdam news report......

The AMOC weakening has also been linked to a unique substantial cooling of the northern Atlantic over the past hundred years. This so-called ‘cold blob’ was predicted by climate models as a result of a weakening AMOC, which transports less heat into this region.

Ocean surface temperature trend since 1880. Note cooling trend blob south of Greenland and warming trend off Northeast U.S. and Atlantic Canada coasts.

"The northward surface flow of the AMOC leads to a deflection of water masses to the right, away from the US 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 US east coast, leading to an enhanced sea level rise.”

The report also explains that the continued slowdown of the AMOC may also lead to more extreme weather, heat waves and lower summer rainfall over Europe.

If it remains "business as usual" in terms of global greenhouse gas emissions, the AMOC may weaken by as much as 34-45 percent by the end of the century and become permanently unstable.