Kristin Richter and Elaine McDonagh, senior researchers at NORCE and the Bjerknes Centre, brought together experts to investigate major knowledge gaps about the fate of the overflows in the North Atlantic Ocean.
Examinations of the Atlantic Meridional Overturning Circulation, where deep water is a vital component, show that the flow of cold-water returning southwards is reducing. Meanwhile, the dense overflows coming from the Nordic seas over the Greenland-Scotland ridge, seem to be unaffected.
"You would think that once the AMOC is reduced in strength, it would also somehow affect the overflows. But recent measurements show that the overflows are surprisingly stable, in terms of transport. What the measurements do show is that the water gets warmer – slowly," Richter says.
Many potential reasons
Whether it’s an internal variability or a long-term signal caused by human activities, is still uncertain, according to Richter. And with no reduction observed in the overflow waters, the observations seem to be contradicting.
"There are many potential reasons behind this accumulation. There is no direct pipe of flow from the Greenland-Scotland ridge, which means that the water can take many years to move southwards. The water could also be stored, in ocean gyres," Richter adds.
Understanding these deep-water formations are of great importance because they contribute to the long-term storage of heat and carbon.
"Continuing observations and network are crucial to better understand what is happening in the North Atlantic Ocean," Richter says.
The podcast is produced by Stephen Outten and Ingjald Pilskog. Stephen Outten is a researcher at Nansen Environmental and Remote Sensing Center and Bjerknes Centre for Climate Research. Ingjald Pilskog is an associated professor at Western Norway University of Applied Sciences and connected to the Bjerknes Centre for Climate Research.