My research is centered around the interaction between the fast changing atmosphere and the integrating snowpack below. I am fascinated by snow in all its varieties and study the processes affecting it such as snow metamorphism, surface energy fluxes and wind drift. Snow is archiving climatic information and I am particularly interested in how the climate signal is formed in the snow. This signal can be preserved for thousands of years and is retrieved by scientist in the form of ice cores. My work of studying present cryospheric processes will help to improve climate reconstruction efforts from such ice core climate proxy records.

Currently, I am the PI of the SnowDOGS project with collaborators at the University of Washington in the US and Le Laboratoire des Sciences du Climat et de l'Environnement in France. 

2023

• Sonja Wahl; Laura Dietrich; Mathieu Casado et al. (2023). C33E-1443 What can we learn from d-excess in polar snow?. (external link)
• Laura Jasmin Dietrich; Hans Christian Steen-Larsen; Sonja Wahl et al. (2023). On the importance of the humidity flux for the surface mass balance in the accumulation zone of the Greenland Ice Sheet. (external link)
• Alexandra M. Zuhr; Sonja Wahl; Hans Christian Steen-Larsen et al. (2023). A Snapshot on the Buildup of the Stable Water Isotopic Signal in the Upper Snowpack at EastGRIP on the Greenland Ice Sheet. (external link)
• Romilly Harris Stuart; Anne-Katrine Faber; Sonja Wahl et al. (2023). Exploring the role of snow metamorphism on the isotopic composition of the surface snow at EastGRIP. (external link)
• Harald Sodemann; Pål Tore Mørkved; Sonja Wahl (2023). FLIIMP - a community software for the processing, calibration, and reporting of liquid water isotope measurements on cavity-ring down spectrometers. (external link)
• Laura Jasmin Dietrich; Hans Christian Steen-Larsen; Sonja Wahl et al. (2023). Snow-Atmosphere Humidity Exchange at the Ice Sheet Surface Alters Annual Mean Climate Signals in Ice Core Records. (external link)

2024

• Sonja Wahl (2024). Atmosphere-Snow interactions through the lens of stable water isotopes — impact for ice core records. (external link)
• Laura Jasmin Dietrich; Hans Christian Steen-Larsen; Sonja Wahl et al. (2024). On the importance of the humidity flux for the surface mass balance in the accumulation zone of the Greenland Ice Sheet. (external link)
• Sara Akiba; Sonja Wahl; Lindsey Davidge et al. (2024). Characterizing Stable Water Isotope Signals in Modern Snow from the Allan Hills. (external link)
• Andrea Oviatt; Sonja Wahl; Noah Brown et al. (2024). Characterizing the memory of a water isotope CFA system using laboratory-grown ice samples of different isotopic compositions. (external link)
• Alexandra M. Zuhr; Sonja Wahl; Hans Christian Steen-Larsen et al. (2024). Spatial and temporal stable water isotope data from the upper snowpack at the EastGRIP camp site, NE Greenland, sampled in summer 2018. (external link)
• Michel Stephen Town; Hans Christian Steen-Larsen; Sonja Wahl et al. (2024). Post-depositional modification on seasonal-to-interannual timescales alters the deuterium-excess signals in summer snow layers in Greenland. (external link)
• Sonja Wahl (2024). Atmosphere-Snow interactions through the lens of stable water isotopes; the impact for ice core records. (external link)
• Benjamin Walter; Hagen Weigel; Sonja Wahl et al. (2024). Wind tunnel experiments to quantify the effect of aeolian snow transport on the surface snow microstructure. (external link)
• Sonja Wahl (2024). The isotopic fingerprint of snow processes and their effect on the climate signal stored in ice cores. (external link)
• Sonja Wahl; Benjamin Walter; Franziska Aemisegger et al. (2024). EGU24-6861 Aeolian snow transport induces airborne snow metamorphism with implications for snowpack physical properties. (external link)
• Sonja Wahl; Laura Dietrich; Benjamin Walter et al. (2024). Post-depositional modification of the snow isotopic composition and the implication for paleoclimate reconstructions from ice core water isotope records. (external link)
• Sonja Wahl; Benjamin Walter; Franziska Aemisegger et al. (2024). Identifying airborne snow metamorphism with stable water isotopes. (external link)
• Sonja Wahl; Benjamin Walter; Hans Christian Steen-Larsen et al. (2024). Using stable water isotopes to improve our understanding of snow processes across scales. (external link)
• Sonja Wahl (2024). Investigating airborne snow metamorphism during blowing snow events with stable water isotopes and implications for different cryo-related scientific communities. (external link)

2025

• Ida Haven; Hans Christian Steen-Larsen; Laura Jasmin Dietrich et al. (2025). On the accuracy of the measured and modelled surface latent and sensible heat flux in the interior of the Greenland Ice Sheet. (external link)
• Sonja Wahl (2025). The isotopic fingerprint of snow processes and their effect on the climate signal stored in ice core water isotope records. (external link)
• Shaakir Shabir Dar; Eric Klein; Pertti Ala-aho et al. (2025). Isotopic Stratification and Non-Equilibrium Processes in a Sub-Arctic Snowpack. (external link)
• Hans Christian Steen-Larsen; Sonja Wahl (2025). SNOWISO – what did we learn at EastGRIP, and where do we go from here?. (external link)

2022

• Sonja Wahl; Paul Lucas Halas; Lars Henrik Smedsrud (2022). Popular Science Talks at Climate Park within Ice Music Festival. (external link)
• Daniele Zannoni; Hans Christian Steen-Larsen; A.J. Peters et al. (2022). Non-Equilibrium Fractionation Factors for D/H and ¹⁸O/¹⁶O During Oceanic Evaporation in the North-West Atlantic Region. (external link)
• Sonja Wahl; Hans Christian Steen-Larsen; A.G. Hughes et al. (2022). Atmosphere-Snow Exchange Explains Surface Snow Isotope Variability. (external link)
• Lars Henrik Smedsrud; Sonja Wahl; Paul Lucas Halas (2022). Science at Ice Music Festival - Norway. (external link)

2021

• Sonja Wahl; Hans Christian Steen-Larsen; Joachim Reuder et al. (2021). Quantifying the Stable Water Isotopologue Exchange Between the Snow Surface and Lower Atmosphere by Direct Flux Measurements. (external link)
• Kevin S. Rozmiarek; Bruce H. Vaughn; Tyler R. Jones et al. (2021). An unmanned aerial vehicle sampling platform for atmospheric water vapor isotopes in polar environments. (external link)
• Abigail G. Hughes; Sonja Wahl; Tyler R. Jones et al. (2021). The role of sublimation as a driver of climate signals in the water isotope content of surface snow: Laboratory and field experimental results. (external link)
• Sonja Wahl; Alexandra Zuhr; Maria Hörhold et al. (2021). The Effect of Surface Sublimation on the Snow Isotope Signal. (external link)

2026

• Sonja Wahl; Amy R. Macfarlane; Nicolas Stoll et al. (2026). From Cloud to Ice: A Snowflake’s Tale. (external link)
• Ida Haven; Hans Christian Steen-Larsen; Laura Jasmin Dietrich et al. (2026). On the accuracy of the measured and modelled surface latent and sensible heat flux in the interior of the Greenland Ice Sheet. (external link)

2020

• Sonja Wahl; Hans Christian Steen-Larsen; Alexandra Zuhr et al. (2020). A novel method for directly obtaining the water vapor isotope surface flux for evaluating snow-atmosphere exchange processes. (external link)

2019

• Alexander Kokhanovsky; Maxim Lamare; Olaf Danne et al. (2019). Retrieval of snow properties from the Sentinel-3 Ocean and Land Colour Instrument. (external link)
• Joachim Reuder; Andrew Seidl; Pablo Andres Saavedra Garfias et al. (2019). Nansen Legacy Project - Task 1-2.3: Atmospheric Processes. (external link)

2018

• Hans Christian Steen-Larsen; Sonja Wahl; Maria Hörhold et al. (2018). Revisiting how Water Isotopes in Ice Cores Record the Climate Signal. (external link)

See a complete overview of publications in Cristin.

SnowDOGS - Snow D-excess Origin Study

December 2023 - November 2026

Ice core water isotope records from the polar areas are invaluable climate proxies providing information about the relationship between the climate mean state and it's variability. The secondary ice core water isotope "excess" parameters, d-excess and 17O-excess, are especially useful for climate reconstruction since they presumably contain climatic information from the precipitation source regions. However, when simulating excess records with state-of-the-art isotope-enabled climate models, simulated and observed records disagree in seasonal to decadal signal variability.

Strikingly, the ability to simulate isotope variability in precipitation and isotope variability in ice cores is distinct, which suggests d-/17O-excess signal formation processes after deposition. Recently, it was demonstrated that post-depositional processes (PDP) can influence the snow isotopic composition, yet the impact of PDP on the ice core signal has not been quantified. Thus, PDP could be the missing link in our understanding of the transfer function between climate and ice core signal. SnowDOGS' hypothesis is thus that PDP, which are currently not implemented in climate models, define the ice core d-/17O-excess signals and overprint the original precipitation source region information.

SnowDOGS aims to quantify the impact of PDP on ice core excess signals by implementing multiple PDP in the existing Community Firn Model. Simulated d-/17O-excess records will be compared against observed ice core records from various locations on the Greenland and Antarctic Ice Sheet. SnowDOGS will clarify i) if PDP help in aligning simulated and observed isotope records, ii) to what extent PDP overprint the original source signal, and iii) what role PDP played in generating the high-frequency variability in d-/17O-excess records observed in different climate states. SnowDOGS will thus combine modeling and proxy records to improve the reconstruction and prediction of climate variability.