Benchmarking Accumulation Rates across the Greenland Ice Sheet using its Shallow Radiostratigraphy

Abstract:

A comprehensive record of the Greenland Ice Sheet’s recent surface accumulation rates can help improve modeling of this ice sheet’s present dynamics and constrain its future evolution. Regional climate models (RCMs) resolve this record over the last few decades across the entire ice sheet and can be evaluated at ice cores, but the latter are sparse. Hence, a significant gap exists in our knowledge of the recent spatial pattern of Greenland Ice Sheet accumulation rates, particularly at centennial scales. To address this gap, we comprehensively traced the shallow (< ~500 m) radiostratigraphy detected during four years (2011–2014) of airborne UHF “accumulation radar” data collection by the Center for the Remote Sensing of Ice Sheets, as part of Operation IceBridge. These traced reflectors are typically ~20–1,050 years old and hence suitable for inferring benchmark centennial-scale accumulation-rate patterns across the Greenland Ice Sheet. We compared these patterns with those from a similar analysis of an existing deeper radiostratigraphy of the ice sheet and with outputs from multiple RCMs. This analysis reveals regions of the ice sheet where accumulation rates vary significantly over time, presumably due to the influence of synoptic-scale climatic variability. These results can also improve modeling efforts for regions where RCM-estimated modern accumulation rates are biased compared to long-term patterns.