Drop In Solar Activity And AMOC

  • Date: 18/02/15
  • Frank Bosse and Fritz Vahrenholt, No Tricks Zone

Last month the sun reached a sunspot number of 67.0 and thus was once again below normal in activity: It reached 85% of what is normal for the particular cycle month.

Fig. 1: The mean activity of the sun since systematic observations have been conducted is shown in blue and the current cycle (24th cycle, red), along with the relatively similar Cycle No. 1 of 260 years ago.

The red curve shows that the sunspot maximum is now over. Up to now that was not so easy to identify because instead of the usual pronounced maximum (compared to the mean curve in Fig. 1), there have been two peaks with a pronounced dip between them.

Observation of the sun’s polar magnetic fields brings certainty rather than guesses. We reported on this in detail before the end of the year. In short the polar fields have a zero polarity during the solar sunspot maximum. The difference of north polar field and south polar field is zero, yet it can occur often when the fields do not reverse at the same time. During the current cycle the fluctuation about the zero line was quite intense:

Figure 2: The difference between the polar fields of the sun, source: leif.org.

The zero value was first approached in fall 2012, in early summer 2013, and again at the beginning of 2014. The maximum dragged on for some 15 months. But now the trend appears to be clearly away from zero and the maximum to be behind us for good. The month with the highest activity was month no. 63 of the cycle, February 2014, with a SSN= 102.8. […]

North Atlantic harboring a bitter surprise?

As some readers may recall, we reported earlier here on the North Atlantic and we suspected that a relatively significant reduction in the Atlantic Meridional Overturning Circulation (AMOC) could be in the pipeline. Since then there have been additional mesurements of this near surface warm current, which impacts the Atlantic part of the Northern Hemisphere and to some extent other large regions of the Northern hemisphere. Our earlier prognoses are now confirmed:

Fig. 4: The AMOC strength between 2004 and spring 2014. Source: climate-lab-book.ac.uk.

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