Table 1: Contingency table tallying the count of December–January warm and cold events as a function of the phase of the November–January Southern Annular Mode in idealized CAM4 model simulations.

From: January 2016 extensive summer melt in West Antarctica favoured by strong El Niño

 Type of temperature anomaly*
 WarmColdRow totals
+SAM3 (7.82)8 (3.18)11
Neutral SAM14 (13.51)5 (5.49)19
−SAM15 (10.67)0 (4.33)15
Column totals321345
  1. *The temperature anomalies are December–January means, spatially averaged over the 75°–90°S, 180°–90°W sector of West Antarctica, and calculated with respect to the 15-year mean of the control simulation. The warm and cold columns correspond to positive and negative temperature anomalies, respectively.
  2. The SAM index represents the November–January average. The positive (+SAM), neutral, and negative (−SAM) phases are defined based on the ±0.5 standard deviation of the SAM index.
  3. Expected counts (which assume independence between the two variables) are given in parentheses. The chi-square statistic is 14.67. The P value is 0.00065.