Fig 1.
Bathymetry of the Red Sea and topography of Africa and Arabian Peninsula that surround the basin (GEBCO Compilation Group (2021) GEBCO 2021 Grid [
49]). Black line denotes the 250 m isobath (determined from MITgcm bathymetric layers). Dashed lines set the boundaries of the sub-regions.
Fig 2.
Annual cycle of MLD (grey) and CHL (green) 4-day composites of the Red Sea sub-regions.
(A) Climatological seasonal cycle of average ± standard deviation of MLD (grey) and CHL (green line) composites with their corresponding Pearson correlation coefficients at the 5% significance level (n = 96, p < .000) for each sub-region for 2002–2013 and (B) scatter plots of MLD vs. CHL 4-day seasonal cycle composites. Note that the diamond marking represents the winter, and the circle the summer. Filled data points indicate composites that their relative changes share the same sign (co-vary), accompanied by their percentage over the whole seasonal cycle. The grey line represents the fitted linear regression model during the winter (S1 Table).
Table 1.
Relative positive (negative) change between consecutive MLD climatological 4-day composites appearing with simultaneous positive (negative) relative change in the CHL climatological 4-day composites in the five Red Sea sub-regions. The relative changes of each variable are calculated with respect to their previous value and expressed as a percentage.
Fig 3.
Seasonal climatological fields of mean MLD(m) and median CHL(mg/m3) for OND (A and B) and JFM (C and D) in the Red Sea.
Dashed lines set the boundaries of the sub-regions.
Fig 4.
Maps of Pearson correlation coefficients between MLD and CHL standardised anomaly 4-day composites.
(A) October-November-December for 2002–2012 and (B) January-February-March for 2003–2013 (significance level 5%, n: at least 100 out of the total n = 253). Orange colour scale depicts increasing positive correlation, purple depicts negative and grey colour marks insignificant correlations, where p > .05). Dashed lines set the boundaries of the sub-regions.
Fig 5.
Time series of MLD (grey) and CHL (green) standardized anomaly 4-day composites in the five Red Sea sub-regions.
The time series present the months October to March from 2002 to 2013 for each sub-region with their corresponding Pearson correlation coefficients.
Fig 6.
Temporal averages of daily standardised anomaly maps during compound events of MLD (left column) and CHL (right column).
(A) Positive compound event (deep ML/ high CHL) and (B) negative compound event (shallow ML/ low CHL) in the NCRS respectively, while (C) and (D) positive and negative compound events in the SCRS-S respectively.