Arctic temperature and precipitation extremes in present-day and future storyline-based variable resolution Community Earth System Model simulations

Abstract. Over the last few decades, the Arctic region has warmed up at a greater rate than elsewhere on the globe, partly resulting from the on-going loss of sea ice and seasonal snow over land. It is projected that the amplified warming of the surface will continue in the future. In addition, the intensity and frequency of temperature and precipitation means and extremes are projected to change, which may pose serious threats for human infrastructure and livelihoods. To assess (future) climate extremes, advanced modelling approaches with (regionally) refined resolution could be helpful. In this study, we use the variable-resolution Community Earth System Model version 2.2 (VR-CESM) to evaluate and assess present-day and future temperature and precipitation extremes, such as heat waves and heavy precipitation, over the Arctic. Applying a globally uniform 1° grid and a VR grid with regional grid refinements to 28 km over the Arctic and Antarctica, we run 30-year present-day (1985–2014), 10-year present-day (2005–2014), and future (2090–2099) simulations with interactive atmosphere and land surface models, and prescribed sea ice and sea surface temperatures. We use the 30-year simulation to evaluate the ability of the VR grid to simulate climate extremes by comparison with gridded outputs of the globally uniform 1° grid, reanalysis-based datasets, and a regional climate model. The 10-year simulations follow two storylines of Arctic climate change representing a combination of strong/weak Arctic tropospheric warming and weak/strong sea surface warming in the Barents-Kara Seas and are used to assess future climate extremes by focussing on temperature and precipitation extremes. The outcomes show that the VR grid generally performs better in simulating precipitation extremes, while the globally uniform 1° grid generally performs better in simulating temperature extremes, which is mainly related to larger negative temperature differences in the VR grid. Future projections suggest that high temperature extremes will generally increase both in intensity and duration, whereas low temperature extremes will decrease in intensity and duration, especially over regions dominated by sea surface warming and large sea ice loss. Further, wet precipitation extremes are projected to increase in intensity and frequency. The outcomes of this study may contribute to an improved understanding on future climate extremes and its implications.