The Arctic Sea Ice Extent (SIE) and the associated Ice Surface Temperature (IST) are highly correlated variables. The SIE increases during the Arctic cooling period and decreases during warming period. This interaction was for many years a rather stabile hysteresis system, where the SIE assumes 2 states for the same mean temperature, depending on whether the IST is increasing (in spring) or decresing (in autumn). Since 2007, where the largest loss of multy-year ice in recent time occurred, the earlier rather predictable hysteresis loop has changed significantly.
The SIE-IST hysteresis is illustrated in the animated figure, where monthly pairs of SIE and IST since 1982 are plotted.
The temperature axis in the hysteresis plot has been changed. Previously, it was the average surface temperature of the grid points with >30% sea ice concentration. Now, it is the average of all sea surface grid points north of the polar circle.
