By Dr. Sebastian Lüning and Prof. Fritz Vahrenholt
(German text translated/edited by P Gosselin)
The horror scenario from the movie The Day After Tomorrow keeps getting presented as a real plausible scenario for our future: Falling salt content of the upper Gulf Stream due to melting ice flowing into the Arctic is slowing down the North Atlantic Current (NAC), and so doom and gloom is about to sweep across the North Atlantic.
However a team of researchers led by Carina Bringedal from the University of Bergen recently studied the northern end of the North Atlantic ocean circulation (Bringedal & Eldevik 2018). The result: the inflow of warm water and the overflow of denser deep water are in good sync. And since 1998 we do not see any long-term divergence of the sort we would expect to observe when adding more fresh water that would slow the “pump” down.
On shorter timescales the currents are influenced by the winds and the NAO. On longer timescales the currents are influenced by the AMOC.
In short: There’s no sign of a “collapsing Gulf Stream” due to the anthropogenic warming of the Arctic and the associated melting of the ice:
Figure 1: Transported water volume in the North Atlantic during the past 25 years. Chart: Bringedal & Eldevik 2018
Observed rainfall contradicts doom & gloom claims
In the published paper that concerns the doom and gloom forecasts related to the weakening Gulf Stream (Caesar et al. 2018), there’s a second reason that gets named: anthropogenic impacts are causing more rainfall over the North Atlantic.
Yet, the following chart shows this as well is not being observed:
Figure 2: Chart depicting rainfall in the North Atlantic over the past 35 years. Source: KNMI Climate Explorer. Data: NOAA.