Fig. 4: Contributions of modulators to change in variability of SNUW and SNMD modes.

a SNUW standard deviation during 1984–2003 and 2004–2023, attached with relative change after signal removal (last column), and relative change between two sub-periods (last row). b Same as (a) but for SNMD standard deviation. c Correlation coefficient between north (SNMD-N) and south (SNMD-S) poles of SNMD during 1984–2003 (blue) and 2004–2023 (green), with SIC signal and remove SIC signal, respectively. Dashed lines are the 90% confidence level threshold. In (b, c), SIC signal is removed based on corresponding periods because the correlation between SIC and SNMD is insignificant after 2004.