She completed grammar school with a matriculation exam from the physics line of Menntaskólinn á Akureyri in spring 1991.

During the summers of 1993 and 1994 and winter 1994–1995, she worked at the Science Institute, University of Iceland, with Helgi Björnsson and the glaciology group processing radio-echo sounding measurements, and she participated in expeditions on Vatnajökull ice cap.

[6][7] Each spring she goes with the students in the glaciology course at the University of Iceland to Sólheimajökull to put wires into the ice with a steam drill to measure the summer ablation of this glacier.

She, her supervisor Keith Echelmeyer, and glaciologists at University of Alaska Fairbanks flew a laser altimeter in a Piper PA12 airplane over 67 glaciers to measure how their volume had changed since 1957.

[20][21] She has supervised PhD students and postdoctoral researchers at the University of Iceland, in Copenhagen in Denmark, Birmingham in UK and Bordeaux in France in projects on Vatnajökull, the Greenland ice sheet and smaller Icelandic glaciers (Virkisjökull, Drangajökull, eastern outlet glaciers of Vatnajökull and others).

One project uses a Bayesian hierarchical framework to compute the viscosity and flow of Langjökull and another maps how the groundwater in catchments headed by temperate glaciers evolves due to climate change.

Guðfinna was selected to be one of the lead authors of the Sixth Assessment Report (AR6)[34] of the Intergovernmental Panel on Climate Change.

This report is written to inform the governments of the world on anthropogenic climate change, and what impact it has on nature and society.