New Research: Could North Atlantic Current be Slowing? March 22, 2018

I took some heat for the above video from some who questioned whether the slowdown of the North Atlantic current, discussed here, was still a live issue in climate science. My take evolved, having heard from heavy hitting scientists like J.P. Steffensen,(above) and Mike Mann, Stefan Rahmstorf and Jason Box (below) that a persistent “cold spot” in the North Atlantic was suggestive of a slowdown in the Atlantic Meriodonal Overturning Circulation (AMOC).

A continued slowdown of that current would divert warm ocean water from Northern Europe, with potentially severe consequences for agricultural production, among other impacts.

Guardian:

Global floods and extreme rainfall events have surged by more than 50% this decade, and are now occurring at a rate four times higher than in 1980, according to a new report. Other extreme climatological events such as storms, droughts and heatwaves have increased by more than a third this decade and are being recorded twice as frequently as in 1980, the paper by the European Academies’ Science Advisory Council (Easac) says. The paper, based partly on figures compiled by the German insurance company Munich Re, also shows that climate-related loss and damage events have risen by 92% since 2010. Prof Michael Norton, Easac’s environmental programme director, said that greenhouse gas emissions were “fundamentally responsible for driving these changes”. “Trends towards extremes are continuing,” he said. “People have experienced extreme weather already – big switches [between] warm and cold winters – but the frequency of these shifts may be changing.” “Some of the underlying drivers of extreme weather which were speculative four years ago are now looking less speculative and [more like] credible hypotheses. That is the weakening of the Gulf Stream and the meandering behaviour of the jet stream.” The Easac study, Extreme weather events in Europe: Preparing for climate change adaptation, looked at new data and models focused on a potential slowdown of the Atlantic Gulf Stream, due to an influx of freshwater from melted ice sheets in Greenland. It was compiled by experts from 27 national science academies in the EU, Norway and Switzerland, although the data was not peer-reviewed.

The UN’s Intergovernmental Panel on Climate Change (IPCC) has assessed the probability of a slowdown before 2100 at more than 90% – or “very likely”. However, a complete “switch off of the gulf stream – or Atlantic Meridional Overturning Circulation (AMOC) – is increasingly thought possible by some scientists. Some studies say this could lower land temperatures in the UK, Greenland, Iceland and Scandinavia by up to 9C. UK arrays positioned in the north Atlantic measured a 30% drop in AMOC strength between 2009-10, the Easac study says. And while uncertainties persist about the pace and scale of possible future changes, the decline in Gulf Stream strength itself has now been “confirmed”.

Science Daily:

Is a contemporary shutdown of the Gulf Stream (AMOC) possible? The update also reviews evidence on key drivers of extreme events. A major point of debate remains whether the Gulf Stream, or Atlantic Meridional Overturning Circulation (AMOC), will just decline or could ‘switch off’ entirely with substantial implications for Northwest Europe’s climate. Recent monitoring does suggest a significant weakening but debate continues over whether the gulf stream may “switch off” as a result of the increased flows of fresh water from northern latitude rainfall and melting of the Greenland icecap. EASAC notes the importance of continuing to use emerging oceanographic monitoring data to provide a more reliable forecast of impacts of global warming on the AMOC. The update also notes the recent evidence which suggests an association between the rapid rate of Arctic warming and extreme cold events further south (including in Europe and the Eastern USA) due to a weakened and meandering jet stream.