From seismic signals to calving drivers: Assessing twelve years of glacial earthquakes in Greenland using Random Forest models

Quantifying iceberg calving is important for understanding ice mass loss of the Greenland Ice Sheet and its subsequent impact on sea level rise, and for refining calving laws that currently represent a major source of uncertainty in global climate models. These calving events, particularly those involving capsizing icebergs, exert time-varying forces on the edge of marine-terminating glaciers that produce distinct seismic signals known as glacial earthquakes.

By processing twelve years of continuous seismic data and employing a Random Forest classifier to distinguish these glacial earthquakes from tectonic events, we generated a comprehensive catalogue of 6263 previously undocumented glacial earthquakes occurring between 2013 and 2024. The detected events are located along the Greenland coast with surface wave magnitudes ranging from M_SW 4.1 to 5.4. They cluster at nine major calving glaciers, though the vast majority of activity is concentrated at Sermeq Kujalleq (Jakobshavn Isbræ) and Helheim Gletsjer.

To investigate the driving mechanisms behind these events, we analysed the correlation between calving activity and various environmental variables, including glacier velocity, air temperature, sea ice fraction, sea surface temperature, and wind speed. We train a second Random Forest model to predict monthly calving events and evaluate the relative importance of these environmental features, while applying statistical analyses to investigate correlations on a yearly basis where data points are limited. Our results indicate that the relationship between calving and the environment is highly complex and site-specific, as no single variable serves as a universal driver for all glaciers.

This complexity is further highlighted by scale-dependent correlations between calving events and environmental variables. For instance, while the glacier velocity shows a strong correlation with cumulative yearly calving at Sermeq Kujalleq, its importance diminishes on a monthly scale. Conversely, Helheim Gletsjer exhibits no clear yearly correlation with the glacier velocity, highlighting the site-specific nature of calving dynamics. We will present the spatio-temporal evolution of the detected events and discuss how these diverse environmental correlations quantify the varying sensitivity of individual glaciers to environmental forcing across different temporal scales.