Attribution of industrial-era glacier retreat, globally and in the high northern latitudes.

University Of Washington, Seattle WA

Investigators

Abstract

This research aims to provide a comprehensive evaluation of the human contribution to the industrial-era retreat of mountain glaciers around the world. The result will be a stronger foundation for future assessments by the Intergovernmental Panel on Climate Change (IPCC). Although glacier retreat is widely touted as some of the clearest evidence of the impacts of anthropogenic climate change, formal scientific statements attributing the cause remain surprisingly weak. Hesitancy to make stronger statements stems from: i) uncertainty about the natural variability of glaciers; ii) the potential retreat of glaciers from a preceding Little Ice Age; and iii) a dearth of specifically targeted research on a global scale. The research will apply a previously developed attribution methodology to newly available global datasets of glacier geometry, combined with reconstructions and numerical simulations of the climate of the past millennium. The results will be immediately impactful for researchers working on high-mountain surface processes and hazards, ecologists, and all those who study and interpret periglacial environments; including sociologists, geographers, and economists who study societal impacts. The current unclear attribution of glacier retreat is also playing a role in precedent-setting lawsuits seeking to establish the legal principles of climate justice, to which the work contributes. The IPCC needs new research in order to update its assessments, and so to cement prior analyses (or disprove them), it is proposed to: i) use multi-century ensemble simulations from ~20 global climate models to properly initialize simulated glaciers to a pre-industrial climate, and to provide pairs of simulations with-and-without anthropogenic forcing; ii) use real glacier-catchment geometries and flowlines obtained from the Open Global Glacier Model initially with ~50 globally dispersed glaciers, with subsequent expansion to a larger network; and iii) use process-based numerical models of flowline glacier dynamics. This will put theoretical and synthetic analyses onto real landscapes and ice-flow dynamics, in combination with a full range of estimated natural climate variability. The research will maintain a particular focus on anthropogenic attribution for glaciers in the northern high latitudes, which experience large natural climate variability; strong low-frequency variability; a later emergence of the signal of anthropogenic climate change; a strong response to solar and volcanic forcing; and in maritime settings, large variability in wintertime mass balance. This award is co-funded by the Geomorphology and Land-use Dynamics, Arctic Natural Sciences, and Climate and Large-scale Dynamics programs, which cross the Division of Earth Sciences, Division of Atmospheric and Geospace Sciences, and Polar Programs at the NSF. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.