...winter weather which will arguably have a bigger impact on the 2020 outcome than the current high pressure environment.
The 2020 winter gave an extra 20 cm average thickness to CAB ice (some of which was in the form of extra-thick ice near the Fram exit), partly at the price of too-thin ice on the Siberian side. 10 cm of this extra CAB thickness was already gone by the end of June, according to PIOMAS data.
Posts made on the melting season thread, which I am unable to personally verify, mentioned possible losses of several cm and up to 10cm
per day, resulting from the heat dome and clear skies during peak insolation period - while the ice is at very low albedo thanks to its preconditioning in May and June.
Additional cold winter days contribute less and less to ice thickening due to the thermodynamics involved - freezing occurs at the bottom of the ice and is impeded by the insulation of the ice and snow layer - thus there is a negative feedback loop. Not that winter is unimportant, but there is a limit to its effect. On the other hand, additional sunny summer days contribute directly to ice thinning, as melting occurs at the top. In addition, continuous insolation reduces ice albedo (and also warms the water below the ice) and thus there is a positive feedback loop. This makes summer-induced variability potentially higher than winter-induced variability, should a stuck weather pattern come along. Note the above description does not include transport and export, which further complicates the issue.
So which can have the bigger impact, winter weather or summer weather? I think it's both. And when an unprecedented HP sits over the CAB at peak insolation, maybe it's best to wait for its outcome and only then reassess what we know of variabilities.
Some charts and statistics of past years, click to enlarge. Each line starts at day 266 (late Sep). All units in 1000s of km3. Will 2020 break volume loss records for late summer? We will know soon.