Climate State Dependence of Arctic Precipitation Variability

Abstract

Arctic precipitation is projected to increase more rapidly than the global mean in warming climates. However, warming-induced changes in the variability of Arctic precipitation, which are related to surface evaporation and poleward moisture transport (PMT), are currently largely unknown. This study compares the precipitation variability in different quasi-equilibrium climates simulated by a global climate model (EC-Earth) and studies the underlying mechanisms. Five quasi-equilibrium simulations of 400 years length forced with a broad range of CO 2 concentrations (0.25, 0.5, 1, 2, and 4 times the current global mean) were analyzed. PMT is the dominant source of Arctic precipitation variability in colder climates when the ocean in the Arctic basin is completely covered by sea ice year-round. Arctic precipitation variability increases from colder to warmer climates, primarily in summer. In summer, the increasingly stronger relation between Arctic sea level pressure variability and precipitation variability toward warmer climates enhances variability. In winter, the severe increase in mean precipitation (due to enhanced evaporation) exerts a comparatively small increase in variability, and precipitation variability is modulated by both PMT and evaporation, which oppose each other as they both affect the vertical and meridional moisture gradients.

Impact of Atmospheric Rivers on Future Poleward Moisture Transport and Arctic Climate Variability

“…In order to discuss climate-related AR-changes in the context of increased PMT, we first identify the spatial mean changes of moisture transport across 70°N. We note an increase in annual mean PMT towards warmer climates (Figure 4a), consistent with previous studies (Bintanja et al, 2020;Bogerd et al, 2020;P. Zhang et al, 2021).…”

“…It decreases most over Greenland and the Pacific sector of the Arctic Ocean (following the r3C mean -Figure 6d), however also over the Atlantic sector. While mean changes in the Arctic climate (for example increased PR and SAT) are mainly caused by local processes such as evaporation in response to sea ice loss, the IAV of Arctic climate variables is more sensitive to changes in atmospheric dynamics and lower latitudes (Bintanja et al, 2020;Higgins & Cassano, 2009;Bogerd et al, 2020;Gimeno-Sotelo et al, 2019).…”

“…Liu & Barnes, 2015), which could be severely affected by fluctuations of annual AR occurrences. The simulated increase in Arctic precipitation IAV has previously been linked to the respective increase in the IAV of poleward moisture transport (PMT) (Bintanja et al, 2020;Bogerd et al, 2020;Skific et al, 2009a,b).…”

“…Studies on future Arctic AR activity based on GCMs mainly address changes in the mean state of AR characteristics instead of drivers of IAV, focus on a particular season, or do not cover the entire Arctic region (Gao et al, 2015;Shields & Kiehl, 2016;Warner et al, 2015;Warner & Mass, 2017;Payne et al, 2020). Non-AR related Arctic studies discussing future climates point towards a considerable increase in the IAV and number of extreme rainfall and melt events over the Arctic (Bogerd et al, 2020;van der Wiel & Bintanja, 2021;C. Liu & Barnes, 2015), which could be severely affected by fluctuations of annual AR occurrences.…”

“…While the increase in mean PMT was found to mainly occur due to enhanced atmospheric moisture levels following atmospheric warming, the precise causes of the IAV increase are still uncertain (Bintanja et al, 2020;X. Zhang et al, 2013;Bogerd et al, 2020). Similar to the lack of knowledge concerning future AR-IAV, one of the main reasons for this is that PMT-IAV is largely effected by dynamic changes of the atmosphere and therefore sensitive to changes of the location of the jet stream and characteristics of storms reaching the Arctic.…”