Moisture origin, transport pathways, and driving processes of intense wintertime moisture transport into the Arctic

Abstract

Abstract. A substantial portion of the moisture transport into the Arctic occurs in episodic, high-amplitude events with strong impacts on the Arctic's climate system components such as sea ice. This study focuses on the origin of such moist-air intrusions during winter and examines the moisture sources, moisture transport pathways, and their linkage to the driving large-scale circulation patterns. For that purpose, 597 moist-air intrusions, defined as daily events of intense (exceeding the 90th anomaly percentile) zonal mean moisture transport into the polar cap (≥70∘ N), are identified. Kinematic backward trajectories combined with a Lagrangian moisture source diagnostic are then used to pinpoint the moisture sources and characterize the airstreams accomplishing the transport. The moisture source analyses show that the bulk of the moisture transported into the polar cap during these moist-air intrusions originates in the eastern North Atlantic with an uptake maximum poleward of 50∘ N. Trajectories further reveal an inverse relationship between moisture uptake latitude and the level at which moisture is injected into the polar cap, consistent with ascent of poleward-flowing air in a baroclinic atmosphere. Focusing on intrusions in the North Atlantic (424 intrusions), we find that lower tropospheric moisture transport is predominantly accomplished by two types of airstreams: (i) cold, polar air warmed and moistened by surface fluxes and (ii) air subsiding from the mid-troposphere into the boundary layer. Both airstreams contribute about 36 % each to the total transport. The former accounts for most of the moisture transport during intrusions associated with an anomalously high frequency of cyclones east of Greenland (218 intrusions), whereas the latter is more important in the presence of atmospheric blocking over Scandinavia and the Ural Mountains (145 events). Long-range moisture transport, accounting for 17 % of the total transport, dominates during intrusions with weak forcing by baroclinic weather systems (64 intrusions). Finally, mid-tropospheric moisture transport is invariably associated with (diabatically) ascending air and moisture origin in the central and western North Atlantic, including the Gulf Stream front, accounting for roughly 10 % of the total transport. In summary, our study shows that moist-air intrusions into the polar atmosphere result from a combination of airstreams with predominantly high-latitude or high-altitude origin, whose relative importance is determined by the underlying driving weather systems (i.e., cyclones and blocks).

Polar Aerosol Atmospheric Rivers: Detection, Characteristics, and Potential Applications

“…The aerosol transport occurring higher up also connects to the findings from Papritz et al. (2022), who found that air subsiding from the mid‐troposphere into the boundary layer is as important an airstream as surface fluxes for the transport of moisture to the Arctic in wintertime. Using similar algorithms for heat transport as developed for ARs and p‐AARs, and cross comparing ARs, p‐AARs and heat transport events could allow the community to understand how moisture, aerosols, clouds, latent heat release and heat advection interact during these events, and quantify how these interactions impact the heat budget at high latitudes.…”

Surface impacts and associated mechanisms of a moisture intrusion into the Arctic observed in mid-April 2020 during MOSAiC

“…The required wind fields are retrieved from ERA5 reanalysis on 137 model levels and its native spatiotemporal resolution. ERA5 wind fields have been used in many recent studies relying on trajectory analysis in the Arctic (e.g., Ali and Pithan, 2020;You et al, 2021;Papritz et al, 2022). Notably, during the WAI period in mid-April 2020, 4 radiosondes were launched daily at different locations upstream of RV Polarstern, and additional 7 radiosondes daily directly from RV Polarstern.…”

“…Our trajectory analyses show that the corridor during 2020 is initially positioned over Greenland, and only later shifts to the Fram Strait/Iceland region (Section 3.2). In springtime, the North Atlantic WAI corridor is climatologically favored and has been reported to yield the most intense events (e.g., Mewes and Jacobi, 2019;Nygård et al, 2020;Papritz et al, 2022).…”

“…In fact, 60%-90% of poleward moisture transport occurs during only 10% of the time (Johansson et al, 2017;Nash et al, 2018;Pithan et al, 2018). WAIs take place throughout the year, move along season-dependent pathways, and are associated with specific large-scale atmospheric circulation patterns and individual weather events (Henderson et al, 2021), such as synoptic cyclones and the occurrence of atmospheric blocking (e.g., Binder et al, 2017;Fearon et al, 2021;Murto et al, 2022;Papritz et al, 2022).…”

Cloud Characteristics during Intense Cold Air Outbreaks over the Barents Sea Based on Satellite Data

“…Temperature changes are accompanied by reductions in sea ice area and thickness [3,4], increases in air humidity [5], changes in cloud cover [6][7][8], and changes in circulation regimes [3,9]. Changes in the characteristics of marine cold air outbreaks (MCAOs) over the Arctic Ocean are particularly indicative of circulation changes [5,10], which are critical for atmospheric interactions between the Arctic and midlatitudes [11]. In the Arctic, MCAOs occur when relatively cold and dry air masses from the sea ice regions move over the comparatively warmer ocean surface, triggering turbulent heat and moisture fluxes and promoting cloud formation [12][13][14].…”