Very nice, Archimid! The map definitely helps visualize this.

I've been messing around with this some more, and thought this was a useful comparison:

The first day of refreeze is calculated as before. The first week represents the start of the first seven-day period of continuous increases in volume after the last day at the minimum.

The graph shows the means, but medians are probably better, and they're what Archimid used on the map, so here they are:

Okhot: first week = 336 (02-Dec) first day = 311 (07-Nov)

Berng: first week = 336 (02-Dec) first day = 312 (08-Nov)

Beauf: first week = 276 (03-Oct) first day = 266 (23-Sep)

Chukc: first week = 289 (16-Oct) first day = 273 (30-Sep)

ESS: first week = 272 (29-Sep) first day = 269 (26-Sep)

Laptv: first week = 277 (04-Oct) first day = 268 (25-Sep)

KaraS: first week = 276 (03-Oct) first day = 265 (22-Sep)

Baren: first week = 297 (24-Oct) first day = 270 (27-Sep)

GrnLS: first week = 249 (06-Sep) first day = 237 (25-Aug)

CAB: first week = 264 (21-Sep) first day = 256 (13-Sep)

CAA: first week = 268 (25-Sep) first day = 258 (15-Sep)

Baffn: first week = 280 (07-Oct) first day = 250 (07-Sep)

Hudsn: first week = 304 (31-Oct) first day = 274 (01-Oct)