Arctic climate change in 21st century CMIP5 simulations with EC-Earth

Abstract

The Arctic climate change is analyzed in an ensemble of future projection simulations performed with the global coupled climate model EC-Earth2.3. EC-Earth simulates the twentieth century Arctic climate relatively well but the Arctic is about 2 K too cold and the sea ice thickness and extent are overestimated. In the twenty-first century, the results show a continuation and strengthening of the Arctic trends observed over the recent decades, which leads to a dramatically changed Arctic climate, especially in the high emission scenario RCP8.5. The annually averaged Arctic mean near-surface temperature increases by 12 K in RCP8.5, with largest warming in the Barents Sea region. The warming is most pronounced in winter and autumn and in the lower atmosphere. The Arctic winter temperature inversion is reduced in all scenarios and disappears in RCP8.5. The Arctic becomes ice free in September in all RCP8.5 simulations after a rapid reduction event without recovery around year 2060. Taking into account the overestimation of ice in the twentieth century, our model results indicate a likely ice-free Arctic in September around 2040. Sea ice reductions are most pronounced in the Barents Sea in all RCPs, which lead to the most dramatic changes in this region. Here, surface heat fluxes are strongly enhanced and the cloudiness is substantially decreased. The meridional heat flux into the Arctic is reduced in the atmosphere but increases in the ocean. This oceanic increase is dominated by an enhanced heat flux into the Barents Sea, which strongly contributes to the large sea ice reduction and surface-air warming in this region. Increased precipitation and river runoff lead to more freshwater input into the Arctic Ocean. However, most of the additional freshwater is stored in the Arctic Ocean while the total Arctic freshwater export only slightly increases.

A new pattern of the moisture transport for precipitation related to the drastic decline in Arctic sea ice extent

“…changes in heat and moisture fluxes in the Arctic; Tjernström et al, 2015;Ding et al, 2017) factors. Among these effects, change in moisture transport has emerged as one of the most important with respect to the greenhouse effect (Koenigk et al, 2013;Graversen and Burtu, 2016;Vihma et al, 2016), and is related to SIE decline through hydrological mechanisms such as changes in Arctic river discharges (Zhang et al, 2012), radiative mechanisms such as anomalous downward longwave radiation at the surface (Woods et al, 2013;Park et al, 2015a;Mortin et al, 2016;Woods and Caballero, 2016;Lee et al, 2017), or meteorological mechanisms such as changes in the frequency and L. Gimeno-Sotelo et al: A new pattern of the moisture transport for precipitation intensity of cyclones crossing the Arctic (Rinke et al, 2017). Because the effects of enhanced moisture transport on Arctic ice are diverse, there is no direct relationship between enhanced transport and SIE decline.…”

Regional Arctic sea ice variations as predictor for winter climate conditions

“…Global and regional future model simulations indicate an accelerated Arctic climate change in the next decades (Chapman and Walsh 2007;Vavrus et al 2012;Koenigk et al 2011Koenigk et al , 2013) with a potential total loss of Arctic sea ice in late summer until the middle of the twenty first century (Holland et al 2010;Massonnet et al 2012;Wang and Overland 2013).…”

21st-century climate change around Kangerlussuaq, west Greenland: From the ice sheet to the shores of Davis Strait

“…When compared to other coupled models with similar complexity, the model performs well in simulating tropospheric fields and dynamic variables (Hazeleger et al 2012). However, EC-Earth has a 2°C cold bias over the Arctic with an overestimation of sea-ice extent and thickness (Koenigk et al 2013).…”