Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder

NSIDC Cryosphere Seminar

NSIDC’s Cryosphere Seminar with Dr. Åsa Rennermalm on “Decreasing density and ice layer volume in near-surface firn in southwest Greenland’s percolation zone, 2012-2019”

Refreezing of meltwater in firn is a major component of the Greenland ice sheet’s mass budget, but in-situ observations are rare. Here, we compare the firn density and ice layer volume in the upper 15 m of nineteen new and twenty seven previously published firn cores extracted at fifteen locations in southwest Greenland between 1989 and 2019. Between 1989 and the 2010s, bulk density and ice layer volume increased in the top 15 m of ice sheet firn,. However, following several years with above median surface melt starting in 1998 and culminating with the extreme melt in 2012, density and ice layer volume decreased in the top 3.75 m between 2013 and 2019. This decline co-vary with local surface melt conditions, which remained at or below median values after 2012. This decline in density and ice layer volume is robust across all sites between elevations from 1895 m a.s.l to 2355 m a.s.l. Only the lowest elevation site at 1840 m a.s.l. diverge from the other sites where density and ice layer volume were rather constant in the top 3.75 m between 2013 and 2019. This study shows that temporary buildup in firn pore space and meltwater infiltration capacity is possible despite the long-term increase in Greenland ice sheet melting that started in the early 1990s and is projected to continue in the coming decades.  

Brief Bio:  Åsa Rennermalm is an associate professor at the Department of Geography at Rutgers, The State University of New Jersey. Her research interest is hydrology and glaciology of the Arctic region. Currently, she is studying the Greenland ice sheet to understand how much meltwater escapes to the ocean where it affects marine environments and raise global sea levels. Her work centers around field data collection and analysis, but also involves models and satellite data. She has participated in several Arctic field expeditions.  Åsa joined Rutgers faculty in 2009. Before coming to Rutgers, she was a postdoctoral researcher at Department of Geography at University of California Los Angeles. Her Ph.D is from Civil and Environmental Engineering at Princeton University, and she has a master and undergraduate degree from the University of Copenhagen in Denmark. 

Note: Åsa [pronounced aw-suh] is a female first name in Sweden and Norway.




Wednesday, February 24, 2021
11:00 am to 12:00 pm





  • CIRES employees
  • CU Boulder employees
  • General Public
  • NOAA employees
  • Science collaborators


  • Seminar
  • Open to Public



Mistia Zuckerman