Quantifying the range of future glacier mass change projections caused by differences among observed past-climate datasets

Megumi Watanabe,Yukiko Hirabayashi,Aki Yanagawa,Satoshi Watanabe,Shinjiro Kanae

doi:10.1007/s00382-019-04868-0

Abstract

Observed past climate data used as input in glacier models are expected to differ among datasets, particularly those for precipitation at high elevations. Differences among observed past climate datasets have not yet been described as a cause of uncertainty in projections of future changes in glacier mass, although uncertainty caused by varying future climate projections among general circulation models (GCMs) has often been discussed. Differences among observed past climate datasets are expected to propagate as uncertainty in future changes in glacier mass due to bias correction of GCMs and calibration of glacier models. We project ensemble future changes in the mass of glaciers in Asia through the year 2100 using a glacier model. A set of 18 combinations of inputs, including two observed past air temperature datasets, three observed past precipitation datasets, and future air temperature and precipitation projections from three GCMs were used. The uncertainty in projected changes in glacier mass was partitioned into three distinct sources: GCM uncertainty, observed past air temperature uncertainty, and observed past-precipitation uncertainty. Our findings indicate that, in addition to the differences in climate projections among GCMs, differences among observed past climate datasets propagate fractional uncertainties of about 15% into projected changes in glacier mass. The fractional uncertainty associated with observed past precipitation was 33–50% that of the observed air temperature. Differences in observed past air temperatures and precipitation did not propagate equally into the ultimate uncertainty of glacier mass projection when ablation was dominant.

Highlights

Worldwide, glaciers have reacted sensitively to recent changes in climate forcing and are expected to experience continued mass loss throughout the twenty-first century (Stocker 2014)
The uncertainty was partitioned into three distinct sources: general circulation models (GCMs) uncertainty, observed past air temperature uncertainty, and observed past precipitation uncertainty
Previous global glacier model studies have often discussed the uncertainty in projecting future changes in glacier mass caused by the range of future air temperature and precipitation projections among GCMs (Giesen and Oerlemans 2013; Hirabayashi et al 2013; Huss and Hock 2015; Radic et al 2014), but none have considered the uncertainty caused by differences in climate datasets used for bias correction of GCMs and calibration of glacier models

Summary

Introduction

Glaciers have reacted sensitively to recent changes in climate forcing and are expected to experience continued mass loss throughout the twenty-first century (Stocker 2014). Several studies have attempted to predict future changes worldwide (Marzeion et al 2012; Hirabayashi et al 2013; Radić et al 2014; Huss and Hock 2015). To simulate such changes, glacier models use climate projections as input such as future air temperature and precipitation from general circulation models (GCMs). The climate projections of the various GCMs differ markedly, even among those using the same emissions scenarios (Stocker 2014). Such ranges are defined as “uncertainties” in the present study.

Methods

Results

Discussion

Conclusion