TLDR: "Golfský proud (nejen) - the end is near"Almost all the non-linearly detrended sea surface temperature (SST)-
and salinity-based Atlantic Meridional Overturning Circulation (AMOC
indices show highly significant increases in the three considered EWS
indicators, providing evidence that the AMOC is approaching a
bifurcation-induced transition. Statistical sig-
nificance of positive trends is determined from a test based on
phase surrogates that preserve both variance and autocorrelation
, and the results are not sensitive to changing the size of
the sliding windows. The possibility
of false alarms due to rising variance or AC1 of the high-frequency
forcing can be ruled out since the corrected restoring rate λ has been
considered here.
...
As expected for a system approaching
a bifurcation-induced transition, the time evolution of the restoring
rate λ is strongly correlated with the inverse of the estimated model
sensitivity dx*/dt, which provides strong evidence that the AMOC is
indeed approaching a critical, bifurcation-induced transition.
...
these findings still raise
concern regarding whether state-of-the-art climate models would
be skilful in predicting a forthcoming AMOC collapse. This is in
agreement with previous results showing that the present AMOC
mode is too stable in state-of-the-art models9, most likely due to an
underestimation of the freshwater export from the northern Atlantic
Ocean, caused by errors in the salinity fields and insufficient model
resolution12. The high-resolution, eddy-permitting HadGEM3-GC2
model, which was used to establish the suitability of the SST-based
AMOC indices employed here51, constitutes a major step forward
concerning a more accurate representation of the AMOC and its
stability
...
The results presented here hence show that the recently discov-
ered AMOC decline during the last decades is not just a fluctuation
related to low-frequency climate variability or a linear response to
increasing temperatures. Rather, the presented findings suggest that
this decline may be associated with an almost complete loss of sta-
bility of the AMOC over the course of the last century, and that the
AMOC could be close to a critical transition to its weak circulation
mode.
Observation-based early-warning signals for a collapse of the Atlantic Meridional Overturning Circulation | Nature Climate Changehttps://www.nature.com/articles/s41558-021-01097-4fulltext
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