The Greenland ice sheet runoff limit; simulated by RCMs and detected by MODIS

• Main Authors: Machguth, H., Andrew, T., Nicole, C., Peter, K., Xavier, F., Max, B., Michiel, v., Brice, N.
• Format: Conference Object
• Language: English
• Published: 2023
• Subjects: Greenland; Ice Sheet
• Online Access: https://gfzpublic.gfz-potsdam.de/pubman/item/item_5020757

Streams and lakes develop each summer over the marginal regions of the Greenland ice sheet. These hydrological features reach into the accumulation area and confirm that surface runoff of meltwater is an important component of the mass balance of the ice sheet. Here we map daily visible runoff limits using MODIS data (500 m resolution). Our automated algorithm relies, among other parameters, on spatial variability of surface albedo. The algorithm is applied to all of Greenland for the years 2000 to 2021. Retrievals are adjusted based on hydrological in situ measurements and modelling of the runoff limit. Albeit MODIS' spatial resolution is too coarse to resolve streams or lakes, the results highly agree to surface runoff mapping from Landsat imagery. The data document significant increasing trends in runoff limits until the year 2012, but not thereafter. The visible runoff limit typically rises quickly early in the melt season, but upward migration halts before melting ceases.We utilize the high temporal resolution of the data to compare with state-of-the-art regional climate models (RCMs). The comparison of MODIS and RCM runoff limits reveals a complex pattern, where one of the RCMs well replicates temporal variability while another accurately reproduces the long-term average elevation of the runoff limit. Validating RCMs using visible runoff limit elevations has the potential to further improve regional climate models and estimates of Greenland’s future sea level contribution. We emphasize that the comparison is challenged by the different characteristics of modelled and “real-world” runoff.