Photo of Alexandra Jahn

Alexandra Jahn

We use climate models to provide insights into changes in the Arctic Ocean and its sea ice cover as well as into changes in the ocean in past climates.

Learn about the Polar & Paleoclimate Modeling Group




  • August 2021: Congratulations and goodbye to Hannah Zanowski, who left to start as Assistant Professor at the University of Wisconsin Madison.
  • August 2021: Congratulations to Dr. Patricia DeRepentigny, for officially graduating from CU with her PhD and starting at NCAR as ASP Postdoctoral Fellow.
  • August 2021: Alexandra was awarded tenure and promoted to Associate Professor
  • July 2021: Welcome to Jed Lenetsky, who joined the group as PhD student
  • July 2021: Welcome to Ivonne Martinez, who joined ATOC and INSTAAR to work on a summer REU project on our NSF project "Paleoceanographic Impacts of the onset of Arctic-Baffin Bay throughflow" and was co-mentored by Patricia, Hannah and me, in addition to her main mentor Prof. Julia Moriarty.
  • June 2021: Congratulations to Patricia DeRepentigny, for being awarded the 2021 CESM graduate student award
  • June 2021: Congratulations to Patricia DeRepentigny for being awarded the 1st Place Outstanding Student Oral Presentation at the 2021 Polar AMS meeting and to Chris Wyburn-Powell for being awarded the 2nd Place Outstanding Student Oral Presentation at Polar AMS.
  • May 2021: Congratulations to Dr. Abigail Smith, for officially graduating from CU with her PhD.
  • May 2021: Goodbye to Sara Reinelt, and all the best for the summer REU at Rutgers
  • April 2021: Congratulations to Chris Wyburn-Powell for successfully passing his COMPS2 exam and advancing to PhD candidacy
  • April 2021: Congratulations to Dr. Patricia DeRepentigny for successfully defending her PhD dissertation "Assessing the Future of the Arctic Sea Ice Cover: Processes, Variability and Implications"
  • April 2021: Congratulations to Jed Lenetsky for defending his Master thesis in Geography and on accepting the offer for entering the ATOC PhD program later in 2021 and joinig this group. Welcome Jed!
  • March 2021: Hannah published a new article in JGR-Oceans on "Arctic Ocean freshwater in CMIP6 Ensembles: Declining Sea Ice, Increasing Ocean Storage and Export"
  • March 2021: Congratulations to Patricia DeRepentigny, who was awarded a ASP Postdoctoral Fellowship at NCAR, starting in fall 2021.
  • March 2021: Welcome to Jed Lenetsky, who will join the group as PhD student in fall 2021.
  • January 2021: Goodbye and Congratulations to Abigail Smith, who started a new position at NCAR as Associate Scientist II in RAL.



  • September 2019: Welcome to the group, Hannah Zanwoski. Hannah joins us as a Postdoctoral Researcher.
  • June 2019: Alexandra was awarded a NSF CAREER award on "Reducing the projection uncertainty for Arctic sea ice loss"
  • June 2019: Congratulations to Abigail Smith who was awarded a NASA Future Investigator Award
  • May 2019: Congratulations to Abigail Smith and Patricia DeRepentigny for winning the Most Outstanding and Oustanding presentation awards at the Polar AMS conference
  • April 2019: A new article on the "Non-uniform contribution of internal variability to recent Arctic sea ice loss" by Mark England, Alexandra Jahn, and Lorenzo Polvani was published in the Journal of Climate:
  • January 2019: Congratulations to Abigail Smith, who published her first paper in the Cryosphere:


  • December 2018: Congratulations to Patricia DeRepentigny and Abigail Ahlert for winning the ESSS Poster Conference overall poster conference award (Patricia) and the Snow and Ice Poster category poster award (Abigail)!
  • November 2018: A new article by postdoc Yafang Zhong was published in GRL, on "Asymmetric Cooling of the Atlantic and Pacific Arctic During the Past Two Millennia: A Dual Observation‐Modeling Study"
  • August 2018: Congratulations to Patricia DeRepentigny, who passed the ATOC COMPS1 exam!
  • April 2018: Congratulations to Patricia DeRepentigny, who was awarded NSERC and FQRNT PhD fellowships and the CMOS student supplement award!
  • April 2018: A new article by A. Jahn was published in Nature Climate Change, on the "Reduced probability of ice-free summers for 1.5 °C compared to 2 °C warming"
  • February 2018: Kerrie Dochen graduated from CU and now works at Ball Aerospace. Congrats!
  • January 2018: Welcome to Clara Burgard, who is visiting the Polar and Paleoclimate Modeling Research Group for 2 month.


  • December 2017: Congratulations to Rory Laiho and Abigail Ahlert who were awarded a non-thesis ATOC Masters degree
  • November 2017: Congratulations to Abigail Ahlert, who passed the ATOC COMPS2 exam! 
  • August 2017: Congratulations to Aaron Schroeder and Rory Laiho, who passed the ATOC COMPS1 exam! 
  • August 2017: Graduate Student Patricia DeRepentigny joined the Polar and Paleoclimate Modeling Research Group. Welcome Patricia!
  • May 2017: Kerrie Dochen joined the Polar and Paleoclimate Modeling Research Group as undergraduate researcher. Welcome Kerrie!
  • January 2017: Graduate Student Aaron Schroeder joined the Polar and Paleoclimate Modeling Research Group. Aaron will be working on isotope modeling of the ocean for the LGM and the more recent past. Welcome Aaron!


  • December 2016: A new article co-authored by A. Jahn on the impact of Arctic gateway closure during the warm climate of the Pliocene 3 million years ago was published in GRL: Otto-Bliesner, B. L., A. Jahn, R. Feng, E. C. Brady, A. Hu, M. Löfverström (2016), Arctic Gateways and a stronger Atlantic Ocean conveyor during the Pliocene, Geophys. Res. Lett., 44, doi: 10.1002/2016GL071805
  • August 2016: A new Arcticle by A. Jahn and co-authors on the predictability of an ice-free Arctic has been published in GRL:
  • August 2016: Congratulations to Abigail Ahlert, who passed the ATOC COMPS1 exam!
  • April 2016: Congratulations to Abigail Ahlert, who was awarded a NSF Graduate Research Fellowship!
  • January 2016: Graduate Student Rory Laiho joined the Polar and Paleoclimate Modeling Research Group. Rory will be working on Arctic freshwater dynamics. Welcome Rory!