Fig. 7: North American snow cover extent (SCE) variability and its relationship with Greenland blocking.

Panels a–c show the 1979–2022 frequency of weekly snow cover at each grid point during a May, b June, and c July. Panel d presents grid point Pearson correlation coefficients relating the total number of weeks with snow cover from April to June of each year and the monthly mean Greenland Blocking Index for the following July. Note that negative values are shaded red to reflect an increase in blocking associated with a decrease in snow cover duration. Snow cover is represented using the National Oceanic and Atmospheric Administration SCE Climate Data Record64. Stippling indicates statistical significance at the 95% confidence level. Hypothesis tests conducted individually for each grid cell without multiple testing or spatial autocorrelation correction.