C034-06
Evaluating Greenland Surface Mass Balance and Firn Density Models with ICESat-2 altimetry differences
Thursday, 10 December 2020: 17:50
Virtual
Benjamin Eaton Smith1, Tyler C Sutterley2, Patrick Alexander3,4, Marco Tedesco3,5, Brooke Medley6 and Xavier Fettweis7, (1)University of Washington Seattle Campus, Seattle, WA, United States, (2)Applied Physics Laboratory University of Washington, Polar Science Center, Seattle, WA, United States, (3)NASA Goddard Institute for Space Studies, New York, NY, United States, (4)Lamont -Doherty Earth Observatory, Columbia University, Palisades, NY, United States, (5)Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, United States, (6)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (7)University of Liège, Liège, Belgium
Abstract:
Elevation changes measured on glaciers and ice sheets by altimeters reflect a combination of processes:for example, ice-column thinning or thickening due to ice flow, surface accumulation and ablation, and changes in the air content in the firn can all contribute to increases or decreases in surface height. To understand the relative contribution of changes in surface mass balance and changes in ice flow to the ice sheets’ contributions to sea level, glaciologists often use surface-mass-balance and firn-densification models to estimate the contribution of these quantities to observed ice-elevation changes. A variety of models with different spatial and temporal resolutions, with different representations of firn processes, driven by different reanalysis data are available for this task, and the choice of which model provides the most accurate correction is often unclear.
With the start of ICESat-2 data collection in October, 2018, we now have a set of data that can directly measure elevation changes at quarter-annual temporal resolution, 10-20-meter spatial resolution, and centimeter vertical resolution. In this presentation, we use elevation-difference data from ICESat-2 collected from the first 1.5 years of the mission to evaluate the performance of several estimates from the MAR (Modèle Atmosphérique Régional) model and FD (Firn Density) model, and from a hybrid model derived from MERRA-2 (Modern-Era Retrospective analysis for Research and Applications, version 2) reanalysis data. We restrict the analysis to regions of the ice sheet where we do not expect large contributions to elevation change from dynamic signals. Because the altimetry data span the anomalous 2019 summer melt event, we can evaluate background model performance before and after this event, when atmospheric conditions were relatively typical, as well as the ability of the models to represent this event.
