Ambitious. 31,5 km/day is plenty even in good weather. It's likely they have to navigate ice at Barrow Strait (270 km), this will diminish the daily distance by (an estimate) a factor of three so if 18 km/day for this section so it'll take some 15 days off the planned 80. Add the odd storms too rough for small boats taking some 10 days off the remaining time. So the remaining 2730 km should be traversed in 55 days making the daily distance of ~50 km. On a sea-worthy rowing boat with good rowers in good condition (think f.e. a bicycle tourer making 80 km/day) in fairly easy weather this takes at least 5 hours/day, so an estimate of 8-10 hours of rowing every day might be a good one. Then there's the extra weight from equipment for survival (or do they have a supporting vessel providing meals and such) so 12 hours/day might be a reasonable estimate. They will likely have to eat in the boat on many days. I'd say the success depends on the winds and currents helping them, and who knows which way they'll go. Hopefully none of them get sick (even a stomach-ache preventing rowing would be too much). Good equipment helps a lot in rowing in cold conditions, f.e. water-proof gloves/upper torso cover (for the moist cold wind) are essential for health, so a very fit group with a support vessel should succeed. Don't know about this one though. In short, I think it's more the distance than the environment.
Oh, they're planning 24/7 rowing with shifts every 4 hours, haven't seen a proper image of the boat, hopefully they have more than two seats for rowing, on brisk head/sidewind two men on oars won't be enough. But at least three of them are physically fit for such an adventure.
