Is there a way to access the trunk from the backseat?

Try pouring some cold water around the trunk lid where the lid meets the body of the vehicle. This should loosen it up enough for you to open the trunk lid. Once you get it open, dry the gasket and the underside of the trunk lid where it meets the gasket. Don't use warm or hot water! If the water gets on the back window, warm or hot water will crack the glass! Hope that helps! Jim

OP here: Thanks Jim, i ended up being angry enough i used a kitchen scraper and hacked away at the 3in thick ice around the windshield to get it open. Although i did loosen it up with an isopropyl alcohol/water mix as straight water would’ve froze on contact.

You're welcome. Glad to help. Thanks for letting us know you got it open! Very glad to hear that!! Jim