Fig. 1.
Spatial sea level statistics from satellite altimetry: (A) annual mean absolute dynamic topography (shading, in cm) over the 1993–2014 period, (B) linear trend (cm/year), (C) range of the seasonal cycle of the sea level anomaly (cm), and (D) standard deviation of the winter-mean sea level anomaly, after removing the linear trend and the seasonal cycle (cm). Mean depth-averaged current from the TOPAZ4 reanalysis (arrows, in m s−1) over the 1993–2014 period (A). The solid/dashed/dotted black/white lines indicate the 500 m/100 m/50 m isobaths, respectively. In B, C and D, the grid points over the open ocean are masked and the continental shelf is delimited by the thick black line.
Fig. 2.
Frequency (in days) of the jet clusters for each winter between December 1979 and February 2014.
Table 1.
Frequency of occurrence of each jet cluster over the entire period considered (December 1979–February 2014), between December 1979 and February 1993 and over the period covered in the paper (December 1993 and February 2014).
Fig. 3.
Composite maps of daily mean sea level pressure anomaly (shading, in hPa) and 10 m zonal winds (black contours, 3 m s−1 intervals from 3 m s−1) for each jet cluster: (N) Northern jet cluster, (C) Central jet cluster, (S) Southern jet cluster, (M) Mixed jet cluster.
Fig. 4.
Composite maps of daily sea level anomaly (shading, in cm) and 10 m wind anomaly (arrows, in m s−1) for each jet cluster: (N) Northern jet cluster, (C) Central jet cluster, (S) Southern jet cluster, (M) Mixed jet cluster. The black dots denote regions where the sea level anomaly composite is significantly different from zero at a 0.05 significance level. The grey line shows the location of the continental slope, depicted by the 500 m isobath.
Fig. 5.
Standardised maps of the composite of the daily sea level anomaly for each jet cluster: (N) Northern jet cluster, (C) Central jet cluster, (S) Southern jet cluster, (M) Mixed jet cluster. To standardise the maps in Fig. 4, we divide them by the standard deviation of the daily sea level anomaly over the 21-winter record. The grid points over the open ocean are masked and the continental shelf is delimited by the thick black line (the 500 m isobath).
Fig. 6.
Maps of jet clusters most strongly associated with anomalously high (A) and with anomalously low (B) sea level anomaly. Colours correspond to: Northern jet cluster (blue), Central jet cluster (black), Southern jet cluster (yellow), Mixed jet cluster (red), Northern and Central jet clusters (light blue), Northern and Southern jet clusters (lilla), Northern and Mixed jet clusters (purple), Central and Southern jet clusters (green), Central and Mixed jet clusters (brown), Southern and Mixed jet clusters (orange), otherwise (‘no jc’, grey). The grid points over the open ocean are masked and the continental shelf is delimited by the thick black line (i.e. the 500 m isobath).
Table 2.
Magnitude of the depth-averaged Coriolis force, of the depth-averaged pressure gradient force and, of the depth-averaged force exerted by the winds, all averaged over the entire northern European continental shelf (more precisely, over the region of the shelf delimited by the coordinates 3°W–30°E and 51°N–66°N). Units are m s-2.
Fig. 7.
Ekman transport associated with each jet cluster (arrows, 1 Sv = 10–6 m3 s−1) and rate of change of the sea level anomaly as a result of Ekman transport (m day−1) for each jet cluster: (N) Northern jet cluster, (C) Central jet cluster, (S) Southern jet cluster, (M) Mixed jet cluster. Positive values indicate regions of convergence, whereas negative values indicate regions of divergence.
Fig. 8.
Composite maps of daily sea level anomaly (shading, in cm) and 10 m wind anomaly (arrows, in m s−1) over the first days (left column) and the fifth days (right columns) of persistence of each jet cluster: (N) Northern jet cluster, (C) Central jet cluster, (S) Southern jet cluster, (M) Mixed jet cluster. The black dots denote regions where the sea level anomaly composite is significantly different from zero at a 0.05 significance level. The grey line shows the location of the continental slope, depicted by the 500 m isobath.
Table 3.
Number of cases when each jet cluster persists at least five consecutive days.
Fig. 9.
At each grid point, fraction of the monthly mean sea level anomaly variance in winter that is explained by the multiple linear regression model.