Results of heat and sea ice budget analyses. Seasonal evolutions of (a) heat input through the open water fraction (Qu, red line), ice melt volume (Qm, black line), and the volume of ice export (Adv, green line), and (b) mean ice thickness calculated from the surface melt by heat input at the ice surface. The volume of ice is converted to the heat required for the equivalent amount of ice melt. (c) Interannual variations in Qu, Qm, and Adv accumulated from May to August. (d) Interannual variations of ice divergence (Div) averaged from mid-May to early-June (blue line) and yearly Qm. (e) Scatter plot of Qu and Qm. Monthly means (May to August) for each year are plotted. (f) Scatter plot of Div averaged from mid-May to early-June versus yearly Qm. Blue crosses and red circles indicate values before and after 2000, respectively. Dashed lines indicate the regression line for both periods. Uncertainties due to errors in the satellite observations are shown as shaded envelopes (see Methods).