Abstract

Abstract. The ice sheet model intercomparison project for CMIP6 (ISMIP6) effort brings together the ice sheet and climate modeling communities to gain understanding of the ice sheet contribution to sea level rise. ISMIP6 conducts stand-alone ice sheet experiments that use space- and time-varying forcing derived from atmosphere–ocean coupled global climate models (AOGCMs) to reflect plausible trajectories for climate projections. The goal of this study is to recommend a subset of CMIP5 AOGCMs (three core and three targeted) to produce forcing for ISMIP6 stand-alone ice sheet simulations, based on (i) their representation of current climate near Antarctica and Greenland relative to observations and (ii) their ability to sample a diversity of projected atmosphere and ocean changes over the 21st century. The selection is performed separately for Greenland and Antarctica. Model evaluation over the historical period focuses on variables used to generate ice sheet forcing. For stage (i), we combine metrics of atmosphere and surface ocean state (annual- and seasonal-mean variables over large spatial domains) with metrics of time-mean subsurface ocean temperature biases averaged over sectors of the continental shelf. For stage (ii), we maximize the diversity of climate projections among the best-performing models. Model selection is also constrained by technical limitations, such as availability of required data from RCP2.6 and RCP8.5 projections. The selected top three CMIP5 climate models are CCSM4, MIROC-ESM-CHEM, and NorESM1-M for Antarctica and HadGEM2-ES, MIROC5, and NorESM1-M for Greenland. This model selection was designed specifically for ISMIP6 but can be adapted for other applications.

Highlights

  • Introduction and objectivesThe Greenland and Antarctic ice sheets represent the largest and most uncertain contributions to global sea level rise over multidecadal to millennial timescales

  • As part of the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6), ice sheet models will be forced with climate model-derived time series of basal melt, front retreat, and surface mass balance

  • CSIRO-Mk3-6-0 middle to high low IPSL-CM5A-M low high strong warming in Baffin Bay extreme warming in Baffin Bay strong warming in the Greenland–Iceland–Norwegian region (GIN) seas been selected for intercomparison project for CMIP6 (ISMIP6) Antarctic future projection runs, including three for the core experiments (CCSM4; MIROCESM-CHEM; NorESM1-M) and three for the additional targeted experiments (CSIRO-Mk3-6-0; HadGEM2-ES; IPSLCM5A-M)

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Summary

Introduction

Introduction and objectivesThe Greenland and Antarctic ice sheets represent the largest and most uncertain contributions to global sea level rise over multidecadal to millennial timescales. In the future, increased water vapor transport in a warmer atmosphere may lead to increased surface accumulation in Antarctica (Frieler et al, 2015; Palerme et al, 2017) together with increased melting over Greenland (Franco et al, 2013) and the Antarctic ice shelves (Trusel et al, 2015). Besides this general pattern, the spatial distribution and magnitudes of atmospheric and oceanic contributions to the mass balance of both ice sheets vary greatly and depend on synopticscale climate variability and physical processes at regional and smaller scales

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